ASHS 2025 Conference: Full Schedule

1:44pm CDT

POM 1 - Oral Session

Tuesday July 29, 2025 1:44pm - 1:45pm CDT

Foster 1

Presiding/Moderator

Edgar Vinson

Auburn University

Tuesday July 29, 2025 1:44pm - 1:45pm CDT
Foster 1

Oral presentation, Pomology 1

Subject Pomology

1:45pm CDT

POM 1 - Application Timing and Efficacy of Bacteriophage Treatment for Managing Xanthomonas-Induced Bacterial Spot in Peach

Tuesday July 29, 2025 1:45pm - 2:00pm CDT

Foster 1

Bacterial spot, caused by Xanthomonas arbicola pv. pruni, is considered an economically important disease of peach and other stone fruit. In peaches, bacterial spot can affect leaves, twigs, and fruit. The disease can cause slight to nearly complete defoliation of infected trees. When significant defoliation occurs early in the season, fruit size can be reduced. In more severe cases, fruit may become infected. Small water-soaked spots can develop on the fruit at any time during fruit development. Early infection is the most concerning because unsightly cratering or pitting on the fruit can occur. Copper based fungicides are the main product used to manage bacterial spot in peaches and are associated with the potential for elevated phytotoxicity. This damage to the leaves resembles the actual disease and can cause defoliation in severe cases. Bacteriophage technology employs viruses that specifically infect bacteria offering a targeted approach to managing bacterial spot without the risk of phytotoxicity. The efficacy of these products have not been widely tested in the southeastern United States. The objective of this study was to determine the optimal timing during the growing season for applying a bacteriophage product in Central Alabama to achieve control of bacterial spot that is comparable to or better than a traditional copper-based spray program. A study was conducted at the Chilton Research and Extension Center in Clanton, AL. Treatments were applied to single tree replications and each treatment was replicated four times. The study followed a randomized complete block design. The control treatment (standard protocol) consisted of a copper-based product applied at each phenological stage. Bacteriophage treatments consisted of applications of the bacteriophage at select phenological stages in place of the copper-based product. Treatments were applied weekly. The entire canopy of each treatment tree was rated for incidence of bacterial spot every two weeks. At harvest, fruit were separated by degree of bacterial spot infection, counted, and weighed. Applications of bacteriophage during specific phenological stages—such as from pink to open bloom, delayed dormant to early bud swell, and from petal fall to early shuck split—were associated with the lowest incidence of foliar bacterial spot. Across all bacteriophage treatments, most fruit exhibited only mild symptoms and remained marketable. These findings suggest that targeted application timing may improve bacteriophage efficacy, though additional studies are needed to validate and optimize these strategies.

Speakers

Edgar Vinson

Auburn University

Co-authors

Elina Coneva

Auburn University

Kassie Conner

Auburn University

Tanzeel Rehman

AUBURN UNIVERSITY

Wendiam Sawadgo

Auburn University

Tuesday July 29, 2025 1:45pm - 2:00pm CDT
Foster 1

Oral presentation, Pomology 1

Subject Pomology

2:00pm CDT

POM 1 - Profiling Sweet Cider Apple Cultivars for the U.S. Midwest

Tuesday July 29, 2025 2:00pm - 2:15pm CDT

Foster 1

Sweet cider serves as both a fresh juice product and a precursor for hard cider production and is an important facet of agrotourism within the apple industry in the U.S. In this study, juice characteristics and physiological traits of apple cultivars developed by the Midwest Apple Improvement Association (MAIA) and apple cultivars bred at Iowa State University (ISU) by Spencer Ambrose Beach were compared to an industry-standard cultivar for sweet cider quality from 2022 to 2024. Given the historical and economic significance of apple production in Iowa during the early 1900s and its subsequent decline due to multiple factors, including a devastating winter storm that killed thousands of apple trees, this research examines the potential for regionally bred cultivars to compete with established industry standards. Juice quality parameters were analyzed, including pH, Brix, titratable acidity (TA), sorbitol content, nutritional composition, and oxidation rates. Flowering and harvest dates were assessed to determine the impact of climatic risks like spring and fall freezes, which are typical weather occurrences and concerns for apple growers in the Midwest during bloom and harvest periods, respectively, on production timing and feasibility. Preliminary findings indicate that Secor (ISU) demonstrated comparable juice quality metrics to the industry standard GoldRush and ranked highest in sensory preference evaluations. Sweet Zinger (MAIA) also received high consumer preference scores, suggesting promise as a regionally bred apple that is marketable both as a fresh-eating or cider apple. One cultivar, the Original Delicious (Iowa), scored the lowest consistently in consumer preference. While having relatively high Brix, it lacked acidity, with a pH of 4.0. GoldRush, a preferred cultivar, had a pH value of 3.2, suggesting the need for blending with more acidic cultivars to optimize cider quality. These findings provide insight into the quality and economic viability of regionally bred cultivars and their potential role in strengthening the cider industry in the U.S. Midwest.

Speakers

Olivia Meyer

Iowa State University

Co-authors

Abigail Knight

Iowa State University

Emma Frederick

Iowa State University

Kellie Walters

University of Tennessee-Knoxville

Suzanne Slack

Iowa State University

Tuesday July 29, 2025 2:00pm - 2:15pm CDT
Foster 1

Oral presentation, Pomology 1

Subject Pomology

2:15pm CDT

POM 1 - From GWAS to Glass: Genetic Insights into Cider Apple Quality

Tuesday July 29, 2025 2:15pm - 2:30pm CDT

Foster 1

Traditional cider apples are typically classified by their sugar, acid, and phenolic composition and concentration, which all impact the sensory profile and fermentation characteristics of the final beverage. Despite the practical importance of these traits, the genetic basis underlying cider apple fruit quality remains poorly understood and few functional genetic markers have been successfully adapted for cider apple breeding. Using a genome-wide association study (GWAS) on 253 cider apple accessions from the USDA-Plant Genetic Resources Unit Malus collection held in Geneva, NY, we found 19 significant marker-trait associations for titratable acidity, pH, total polyphenols, and non-structural carbohydrates. Notably, we identified a distinct marker on chromosome 15 strongly associated with total polyphenols, a key determinant of bitterness and astringency. A major association on chromosome 16, near the Ma1 locus, explained a substantial proportion of the phenotypic variance for titratable acidity and pH, confirming the importance of this region. Significant marker-trait associations were detected for sugar concentration on chromosomes 1, 6, 8, and 10. Further analysis confirmed identification of favorable alleles for titratable acidity, total polyphenols, glucose and sucrose concentration. These results provide a foundation for identifying apple cultivars with desirable phenotypic traits for cider production from germplasm collections and for making marker assisted selections within breeding programs.

Speakers

Pierre Bouillon

Cornell University

Co-authors

David Zakalik

Cornell University, Horticulture

Gregory M. Peck

Cornell University, Horticulture

Michael G. Brown

Cornell University, Horticulture

Tuesday July 29, 2025 2:15pm - 2:30pm CDT
Foster 1

Oral presentation, Pomology 1

Subject Pomology

2:30pm CDT

POM 1 - The Foraged Fruit Project: Explorations into Foraging Apples for Hard Cider Production

Tuesday July 29, 2025 2:30pm - 2:45pm CDT

Foster 1

The Foraged Fruit Project began in 2021 and involves researchers from Cornell and Rutgers Universities, with support from the New York Cider Association and funding from the David M. Einhorn Center for Community Engagement. The aim of this project was to better understand the practice of foraging in New York through a transdisciplinary lens, which includes ethnographic interviews, genetic identification of apple trees, and fruit quality assessments of the foraged apples. Over 30 commercial cider producers were interviewed for this study and we analyzed fruit samples from nearly 50 different trees. Seventy-eight percent of the submitted samples were unique apple genotypes, meaning there was no match among the thousands of samples in the MyFruitTree reference panel managed by Washington State University. According to the Long Ashton Research Station’s cider apple classification, 45% of the apple samples were bittersharp, 14% were bittersweet, 35% were sharp, and 6% were sweet. Based on these data, New York cider producers are largely foraging for high tannin and high acid apples which are difficult to procure from commercial apple producers in the region. Common themes revealed through the ethnographic interviews related to climate change resiliency, reparation for indigenous groups, intellectual property control, discovering unique genetics, and access to public and private lands. By studying these factors, we sought to better support the practice of foraging, unlock unique apple genetics that can benefit growers in a rapidly changing climate, and increase the profitability and uniqueness of New York cider.

Speakers

Gregory Peck

Cornell University

Co-authors

Andrew James

Cornell University

Maria Kennedy

Rutgers University

Victoria Broughton

Cornell University

Tuesday July 29, 2025 2:30pm - 2:45pm CDT
Foster 1

Oral presentation, Pomology 1

Subject Pomology

2:45pm CDT

POM 1 - UAV Remote Sensing for Diagnosing Rapid Apple Decline

Tuesday July 29, 2025 2:45pm - 3:00pm CDT

Foster 1

Modern apple production has moved from traditional open orchard formats to that of high-density trellised plantings. As industry has shifted, the number of trees in commercial apple orchards typically reaches 1,500 per acre, making the management of these orchard blocks on a per-tree basis impractical. The use of unmanned aerial vehicles (UAVs) in the form of portable drones offers a method for collecting image data for thousands of trees in a matter of minutes. Combining these UAVs with multispectral cameras, which collect visual data on spectra that the human eye cannot perceive, allows for the calculation of vegetation indices (VIs) such as the normalized difference vegetation index (NDVI) for individual trees. Many VIs correlate with important orchard management considerations such as tree vigor, nutrient status, and disease severity. Multiple challenges hinder the incorporation of VIs into orchard management: parsing data on a per-tree basis is challenging in high-density systems, there is no comprehensive understanding of how VIs vary across a growing season and between cultivars, and at what magnitude deviation from expected norms is indicative of a weak tree is uncertain. This experiment aimed to classify this variation in VIs by examining a large cohort of cultivars at multiple timepoints and sites. A DJI Mavic 3M equipped with a 4-channel (green, red, red edge, and near infrared) multispectral camera was used to perform flights at both commercial and research orchards in upstate New York. Orthomosaics of each site were created using Agisoft Metashape and analyzed in QGIS and R (using the FIELDimageR package). Results showed statistically significant differences in VI values between cultivars and timepoints. These differences increased in intensity later in the growing season- in September, differences in cultivar explained 40% of the observed variance in NDVI at one orchard site, compared to only 19% in July.

Speakers

Kenneth Buck

Cornell University

Co-authors

Jason Londo

Cornell University

Tuesday July 29, 2025 2:45pm - 3:00pm CDT
Foster 1

Oral presentation, Pomology 1

Subject Pomology

3:00pm CDT

POM 1 - Role of Oxidative Stress in Strawberry (Fragaria x ananassa) Fruit Development

Tuesday July 29, 2025 3:00pm - 3:15pm CDT

Foster 1

Understanding the dynamics of oxidative stress during the growth of strawberry fruits is essential for optimizing fruit yield, quality, and shelf life. By strategically targeting reactive oxygen species (ROS) generation and the antioxidant defense mechanisms across various developmental stages, researchers and producers can refine cultivation practices, resulting in healthier and more flavorful strawberries. Strawberry fruits were categorized into six distinct developmental and ripening stages: small-size green fruits (S1, indicating the early stage of development), medium-size green fruits (S2, characterized by continued growth and elongation), full-size green fruits (S3, where the fruit attains its final size), white fruits (S4), turning-stage pink fruits (S5), and fully matured red fruits (S6). To evaluate the influence of oxidative stress and antioxidant defenses throughout the growth phases, several parameters were analyzed. These included hydrogen peroxide (H2O2), malondialdehyde (MDA), superoxide dismutase (SOD), lipoxygenase (LOX), catalase (CAT), guaiacol peroxidase (GPOD), ascorbate peroxidase (APOD), glutathione reductase (GR), and glutathione-S-transferase (GST). The levels of H2O2 and MDA exhibited variation across the different developmental stages. SOD and POD activities demonstrated an initial increase followed by a decline, while CAT and APOD levels showed a decrease in the later stages of fruit development. Additionally, LOX activity was elevated in the early developmental stages and declined as maturation progressed. The intricate role of oxidative stress in strawberry fruit growth highlights its significance for improving cultivation methods and post-harvest management. This understanding not only contributes to delivering superior-quality strawberries to consumers but also promotes sustainable agricultural practices.

Speakers

Naveen Dixit

University of MD Eastern Shore

Tuesday July 29, 2025 3:00pm - 3:15pm CDT
Foster 1

Oral presentation, Pomology 1

Subject Pomology
Poster # csv
Funding Source USDA Evans-Allen

3:15pm CDT

POM 1 - Physiological Responses of Flordaguard and MP-29 Peach Rootstocks to Soil Salinity

Tuesday July 29, 2025 3:15pm - 3:30pm CDT

Foster 1

Many low-lying coastal areas worldwide, including Florida, experience soil salinization due to tropical rainstorms, storm surges that cause superficial flooding with saline water, and groundwater salinization from saltwater intrusion. Additionally, excessive fertilizer applications can increase soil salinization, which can reduce the productivity of soil and affect crop growth. This study evaluated the response to salinity stress of two peach rootstocks: 1) Flordaguard, the current recommended rootstock in Florida, and 2) MP-29, a peach-plum hybrid rootstock with the potential to be recommended in the state. A total of 60 plants were distributed in five blocks and exposed to three salinity levels (0, 75, and 150 µM NaCl) for 24 days in a greenhouse. Photosynthetic rate (A), stomatal conductance (gs), and efficiency of photosystem II (ΦPSII) were recorded every other day. Stem water potential (Ψs) and foliar nutrient concentrations were assessed at the end of the experiment. A decline in A level was observed in all plants over time, with a higher reduction under salinity treatments. Starting 16 days after treatment, gs was significantly lower in plantlets exposed to 150 µM NaCl compared to controls. Interestingly, ΦPSII was more stable in Flordaguard plants during the experiment. Moreover, ΦPSII response suggested higher sensitivity to salinity in MP-29 plants. Similarly, Ψs in salinity stressed plants was at least 33% lower compared to the control group. On the other hand, Ψs in ‘MP-29’ was 11% lower compared to ‘Flordaguard’, indicating higher water stress in the hybrid rootstock. Foliar nutrient concentrations were influenced by treatment (N), cultivar (Ca, B, Mn, Zn), or their interaction (Mg, S), while P, K, Fe, and Cu remained unchanged. These results suggest that MP-29 rootstock is more sensitive to salinity stress than Flordaguard, which may have implications for rootstock selection in saline-prone soils.

Speakers

Jonathan Clavijo Herrera

Postdoctoral Associate, University of Florida

Co-authors

Ali Sarkhosh

University of Florida

Jonathan Lainez

University of Florida

Tuesday July 29, 2025 3:15pm - 3:30pm CDT
Foster 1

Oral presentation, Pomology 1

Subject Pomology
Poster # csv

3:30pm CDT

POM 1 - Evaluation of Effects of ACC and Tree Architecture on Mechanical Trunk Shaking Harvest Efficiency in Table Olives in California

Tuesday July 29, 2025 3:30pm - 3:45pm CDT

Foster 1

Table olives in California have historically been hand-harvested. Hand labor crews are increasingly difficult to attract to small acreage orchards and are often prohibitively expensive when available. Mechanical harvesting equipment is available; however, harvest efficiencies typically range from 55-65%, leaving 35-45% of the crop on the tree. While much less expensive than hand-harvesting, the harvest efficiency is not adequate and leaves growers to decide whether to glean the remaining crop or forfeit the income from that portion of the crop. This low efficiency is partially due to the inherent architecture and physiology of olive trees. Additionally, the force required to remove an olive fruit from the tree is relatively high because table olives are harvested before their physiological maturity. In 2024 we conducted a study to evaluate the effects of altering tree architecture by skirting trees in May, removing lower limbs up to 4 feet from the ground to avoid any contact with the harvest machinery. This led to a 15.5% increase in harvest efficiency over trees where lower limbs were left, without affecting total yield. In addition, we examined the effect of a foliar application of 1-aminocyclopropane-1-carboxylic acid (ACC, commercially available as Accede®), an ethylene precursor, at 100 gallons per acre of 1500ppm solution a week before harvest. ACC applications reduced the amount of force required to remove fruit from the tree by 26% and increased harvest efficiency by up to 10.7%. The combination of both removing the skirts of the trees and applying ACC improved harvest efficiency by 23%. These strategies provide clear pathways to improving the economic sustainability of the table olive industry in California.

Speakers

Becky Wheeler-Dykes

UCCE Glenn

Co-authors

Georgia Drakakaki

University of California Davis

Louise Ferguson

University of California Davis

Minmin Wang

University of California Davis

Tuesday July 29, 2025 3:30pm - 3:45pm CDT
Foster 1

Oral presentation, Pomology 1

Subject Pomology
Poster # csv
Funding Source California Olive Committee

12:15pm CDT

POM 1 - Effect of Cellulose Nanofiber (CNF) as a Potential Cryoprotectant to Reduce Spring Frost Damage in Pear and Apple Cultiv

Wednesday July 30, 2025 12:15pm - 1:00pm CDT

Empire AB

Ongoing climate change has resulted in unusually high winter temperatures and earlier spring warming, which have caused major fruit trees to bloom earlier than in previous years. This shift is increasing the risk of spring frost damage, emphasizing the urgent need for eco-friendly, sustainable and cost-effective protective strategies. Considering these, this present study, cellulose nanofiber (CNF), a nanomaterial extracted from plant cell wall cellulose from wood and pulp via mechanical (RE) and chemical (TEMPO) processes, was combined with sodium alginate (AG), a natural substance extracted from seaweed. It was applied as a coating material to provide thermal insulation and assess its effectiveness in protecting pear cultivars ‘Niitaka’ and ‘Wonhwang’ and apple cultivars ‘Hongro’ and ‘Fuji’. As frost damage was forecasted to occur on March 30, 2025, cryoprotectants were applied to apples on March 28, 2025, and pears on March 29, 2025. In pears, treatments were applied to ‘Niitaka’ and ‘Wonhwang’ trees in an orchard in Jinju, Gyeongsangnam-do, South Korea. Five treatments (control, 1.0% RE-CNF, 1.1% TEMPO-CNF, RE:AG=8:2, and TEMPO:AG=8:2) were applied to five trees per cultivar. Spraying was conducted once at the early flower cluster visibility stage (Stage 4) for ‘Niitaka’ and at the half-inch green stage (Stage 3) for ‘Wonhwang’. For apples, treatments were applied to 15 trees each of ‘Hongro’ and ‘Fuji’ cultivars located in an orchard in Hamyang-gun, Gyeongsangnam-do, South Korea. The flower bud stage for both ‘Hongro’ and ‘Fuji’ was at the half-inch green (Stage 4) when a single spray was applied. The study established that in ‘Niitaka’ pears the TEMPO:AG=8:2 treatment achieved the lowest pistil and stamen damage rates at 64% and 83%, respectively, reducing damage by 17% and 11% compared to the control. In ‘Wonhwang’ pears, the pistil damage rate was lowest as 11% with RE-CNF, and the combined pistil and stamen damage rate was lowest as 56% with TEMPO-CNF, showing reductions of 14% and 9% compared to the control. In both ‘Hongro’ and ‘Fuji’ apples, the combined pistil and stamen damage rate was 18% and 7%, respectively, with the TEMPO:AG = 8:2 treatment, showing 12% and 21% reductions compared to the control. In conclusion, the CNF mixtures revealed effective frost protection by significantly reducing frost damage rates in pears and apples. Thus, it is considered the most suitable material for developing cryoprotectants to mitigate spring frost damage in these major fruit crops.

Speakers

HYUNSUK SHIN

Gyeongsang National University

Co-authors

HYO JEONG KIM

Gyeongsang National University

PANDIYAN MUTHURAMALINGAM

Gyeongsang National University

SUJEONG PARK

Gyeongsang National University

YEONJU PARK

Gyeongsang National University

YERIM RYU

Gyeongsang National University

Wednesday July 30, 2025 12:15pm - 1:00pm CDT
Empire AB

Poster, Pomology 2

Subject Pomology
Poster # csv
Funding Source The author(s) declare financial support was received for the research, authorship, and/or publication of this article. This work was carried out with the support of the “Cooperative Research Program for Agricultural Science and Technology Development (Project No. RS-2025-02183070)” funded by the Rural Development Administration, Republic of Korea.
Funding Option OREl or ORG funded all or part of the research associated with this abstract

12:15pm CDT

POM 1 - Evaluation of Select Plant Growth Regulators on Improving Fruit Set in Apricot (Prunus armeniaca)

Wednesday July 30, 2025 12:15pm - 1:00pm CDT

Empire AB

Apricot (Prunus armeniaca L.) production in Texas is limited by inconsistent and overall poor yields due to spring frost and loss of hardiness in buds associated with erratic temperature swings in late winter/early spring. Several plant growth regulators (PGRs) were evaluated for improving yields. PGRs were applied in the fall and spring to assess their potential for mitigating floral bud injury, improving bud hardiness, enhancing fruit set, and improving fruit retention rates. Two-year-old ‘Wenatchee Moorpark’ trees on ‘KRYMSK-1’ rootstock, spaced at 1.33 by 3.33 meters were used with a randomized complete block design with five single-plant replications. Fall applications were made at approximately 50% natural leaf fall of Ethephon at rates of 100, 200, and 300 mg/L-1, Accede (ACC) at rates of 500, 1000, and 1500 mg/L-1, and ProTone (S-ABA) at rates of 500 and 1000 mg/L-1. Following defoliation of the trees, white latex paint was also applied as a treatment to the entire canopy and trunk of dormant trees. Spring treatments aimed at improving fruit set were applied during full bloom and included Promalin (GA4+7, 6-BA) at rates of 1.17 and 2.34 L/ha-1, and ReTain (AVG) at rates of 889 and 1,778 mg/L-1. Additionally, evaluations were conducted on combination treatments of fall and spring applications. These treatments included Ethephon+Promalin+Latex; Ethephon+ReTain+Latex; Accede+Promalin+Latex, and Accede+ReTain+Latex, which were applied at the highest concentrations for each product evaluated individually in this study. Differential Thermal Analysis (DTA) was carried out on the 15th and 16th of February 2025 using 5 floral buds per tree as sub-samples. LT50 found Accede at 1500 mg/L-1 significantly improved bud hardiness by 4.67°C relative to the control. Additionally, treatments of Accede+Latex, Accede+Promalin+Latex, and all three combination treatments of Ethephon delayed floral bud development relative to control. However, Ethephon produced significant gummosis and visible injuries, whereas Accede produced negligible gummosis. Fruit set, as assessed by counting fruit on 50.8cm lengths of standard sample shoots, was improved using the highest concentration of ReTain (AVG). The mean fruit number increased from 1.2 for the control, to 5.0 for AVG, at P= 0.0002, occurring after exposure to temperatures below -4°C on March 19th. The results from this and future years of this trial are anticipated to assist in improving the feasibility of commercial apricot production within Texas and similar environments.

Speakers

Allison Love

Texas A

Co-authors

Amit Dhingra

Texas A

Patrick O'Brien

Texas A

Thayne Montague

Texas A

Tim Hartmann

Texas A

Wednesday July 30, 2025 12:15pm - 1:00pm CDT
Empire AB

Poster, Pomology 2

Subject Pomology
Poster # csv
Funding Source USDA Specialty Crop Block Grant Program
Funding Option SCRI funded all or part of the research associated with this abstract

12:15pm CDT

POM 1 - Fruit Weights, Percent Seed, and Soluble Solids Content of Six Advanced Selections from Kentucky State University’s Pawp

Wednesday July 30, 2025 12:15pm - 1:00pm CDT

Empire AB

The North American Pawpaw (Asimina triloba) is a tree fruit native to the Eastern U.S. which is being produced in commercial orchards across the U.S. and internationally, with an increasing market and interest. There are approximately 50 pawpaw cultivars available, but many of these varieties have low yields with fruit sizes below the threshold of 120 grams needed for commercial sale and processing. New high yielding cultivars with excellent fruit quality would further assist in the development of the pawpaw industry. Kentucky State University serves as the National Clonal Germplasm Repository for Pawpaw. Two goals of the Repository research efforts are germplasm acquisition and evaluation. The repository contains over 2000 accessions from 16 different states; additionally, both open pollinated seedlings from superior genotypes and crosses of superior selections have been incorporated into the repository collection. Fruit weights, percent seed by weight, and soluble solids content from six of KSU’s advanced selections (Hi 1-4, Hi 7-1, G4-25, G6-120, G9-109, and G9-111) were compared to the cultivars ‘KSU-Atwood’, ‘KSU-Chappell’, and ‘Ralph’s Whopper’. All advanced selections had average fruit weights over 120 grams with Hi 1-4 having the highest fruit weight (229.8 g). ‘KSU-Chappell’ had the lowest percent seed (4.7%), with Hi 1-4 having the second lowest (5.9%). Hi 1-4 had the highest soluble solids content at 25.9 Brix and all selections examined were above 21 Brix. Several selections including Hi 1-4 and Hi 7-1 show potential to be promising new releases and have been budded onto seedling rootstock for further evaluation.

Speakers

Jeremy Lowe

Kentucky State University

Co-authors

Kirie Broberg

Kentucky State University

Kirk Pomper

Kentucky State University

Dr. Kirk W. Pomper is the Professor of Horticulture in the College of Agriculture, Community, and the Sciences at Kentucky State University in Frankfort, Kentucky. As Horticulture Research Leader, his program is focused on research and Extension efforts toward developing pawpaw as... Read More →

Page Barker

Kentucky State University

Sheri Crabtree

Kentucky State University

Wednesday July 30, 2025 12:15pm - 1:00pm CDT
Empire AB

Poster, Pomology 2

Subject Pomology
Poster # csv
Funding Source Evans Allen

12:15pm CDT

POM 1 - Hawk238: A Unique Pawpaw Selection for Kentucky Production?

Wednesday July 30, 2025 12:15pm - 1:00pm CDT

Empire AB

The North American pawpaw (Asimina triloba (L.) Dunal) is a native tree fruit that is in the early stages of commercial production. According to the 2022 Census of Agriculture, there are over 90 commercial pawpaw growers in Kentucky. Pawpaw fruit has fresh market appeal for farmers' markets, community-supported agriculture, and organic markets, as well as processing potential for frozen pulp production. There are approximately 50 pawpaw cultivars commercially available. Kentucky State University has already released three pawpaw cultivars: KSU-Atwood™ in 2009, KSU-Benson™ in 2016, and KSU-Chappell™ in 2018. However, additional high-quality cultivars are needed. Pawpaw varieties with fruit weights over 120 g per fruit are considered to have a large enough fruit size for commercial sale and processing. New high-yielding cultivars with excellent fruit quality would further assist in the development of the pawpaw industry. Kentucky State University serves as the National Clonal Germplasm Repository for Pawpaw. Two goals of the Repository’s research efforts are germplasm acquisition and evaluation. The selection Hawk238 was identified by a private grower as having a unique fruit type and promising characteristics as a potential new cultivar. In 2024, the fruit size and quality of the pawpaw cultivars Susquehanna and Shenandoah were compared to Hawk238. Fruit size was similar among ‘Susquehanna,’ ‘Shenandoah,’ and Hawk238, averaging 190 g, 155 g, and 154 g, respectively. The Brix of ripe fruit pulp was significantly lower in ‘Shenandoah’ (17.7 Brix) compared to ‘Susquehanna’ (25.4 Brix) and Hawk238 (24.3 Brix). The selection Hawk238 has a pleasing orange flesh with a mild banana-mango flavor and a large fruit size that would be excellent for processing. This selection, Hawk238, will be included in additional trials.

Speakers

Kirk Pomper

Professor-College of Agriculture, Kentucky State University

Co-authors

Jeremy Lowe

Kentucky State University

Sheri Crabtree

Kentucky State University

Wednesday July 30, 2025 12:15pm - 1:00pm CDT
Empire AB

Poster, Pomology 2

Subject Pomology
Poster # csv
Funding Source USDA Evans Allen Capacity Funding

12:15pm CDT

POM 1 - Hi1-4 and Hi7-1: Yield Data on Two Promising New Selections from Kentucky State University’s Pawpaw Breeding Program

Wednesday July 30, 2025 12:15pm - 1:00pm CDT

Empire AB

The North American pawpaw (Asimina triloba) is a tree fruit native to North America, and is being produced on a small scale commercially across the U.S. and internationally, with over 90 pawpaw growers in Kentucky alone. There are approximately 50 pawpaw cultivars available, but some of these varieties tend to be poor quality, low yielding, have small fruit size, or exhibit poor flavors. Kentucky State University’s pawpaw breeding program is striving to develop new improved pawpaw cultivars with good flavor and high yields. A pawpaw variety trial was established at the Kentucky State University Harold R. Benson Research and Demonstration Farm in Frankfort, KY, in 2017 consisting of two commercially available cultivars (‘KSU-Benson’ and ‘KSU-Chappell’) and two KSU advanced selections (Hi1-4 and Hi7-1). Data on number of fruit and clusters per tree and fruit weights were collected to compare advanced selections Hi1-4 and Hi7-1 to KSU-Benson and KSU-Chappell. The advanced selections Hi1-4 and Hi7-1 had large average fruit weights of 213 g (Hi1-4) and 167 g (Hi7-1). The cultivars KSU-Benson (179 g) and KSU-Chappell (234 g) also had large marketable fruit. Pawpaw fruit over 120 g are generally considered to be large enough for commercial sale and processing. Hi1-4 and Hi7-1 had an average yield of 12.8 kg and 12.0 kg per tree respectively in 2024, compared to KSU-Benson and KSU-Chappell with average yields of 16.9 kg and 27.2 kg respectively. Advanced selection Hi1-4 (1.7) and cultivar KSU-Benson (1.8) averaged under 2 fruit per cluster, while Hi7-1 (2.1) and KSU-Chappell (2.5) averaged slightly over 2 fruit per cluster. It is desirable for pawpaws to have fewer fruit per cluster and more single fruit, for ease of harvesting. Hi1-4 and Hi7-1 have large, flavorful fruit and high yields, and are planned to be released as new cultivars from the KYSU pawpaw breeding program in Fall 2025.

Speakers

Sheri Crabtree

Horticulture Research and Extension Associate, Kentucky State University

Co-authors

Jeremy Lowe

Kentucky State University

Kirk Pomper

Kentucky State University

Wednesday July 30, 2025 12:15pm - 1:00pm CDT
Empire AB

Poster, Pomology 2

Subject Pomology
Poster # csv
Funding Source USDA Evans-Allen Research

12:15pm CDT

POM 1 - Influence of propagation method and irrigation level on coarse root system architecture of Prunus rootstocks

Wednesday July 30, 2025 12:15pm - 1:00pm CDT

Empire AB

Root system development in perennial crops is critical for the long-term survival of trees. Long lived coarse roots form the rigid structure that supports the dynamics of the absorptive fine root system. The woody root scaffold developed early in a tree’s life can shape lasting aspects of mature root system structure and function, including the extent of soil exploration. Research on early root scaffold development under different propagation and field management conditions has untapped potential for orchard system improvement. Rootstock propagation method significantly influences root system architecture (RSA). Seed propagation in Prunus species produces a vertically oriented taproot at germination, with lateral roots developing along this main axis. In contrast, clonally propagated rootstocks (e.g., cuttings, tissue culture) develop adventitious roots from a wound site or callus, often resulting in shallower, clustered root systems emerging from a concentrated point of origin. While clonal propagation exhibits trait uniformity and a high rate of initial root production, excessive root crowding and limited vertical distribution could lead to structural deformities, increased susceptibility to soil-borne disease, and reduced soil exploration for water and nutrients as trees mature. Studies have shown that a greater number of roots increases initial transplanting success, but a profusion of scaffold roots may result in competition for space, leading to permanent changes in RSA detrimental to long-term tree health. This study examines RSA traits (the spatial configuration of roots, including distribution, morphology, and topology) for coarse roots in commercial almond rootstock cultivars that were either seed or clonally propagated and subjected to full or deficit irrigation regimes. We evaluate how propagation method influences root angle (deep water access), scion growth (survival and vigor), root crowding (potential disease risk), and root distribution (soil exploration) in this 3-year common garden experiment. We found that rootstock significantly influenced traits like mean root diameter and convex hull (p < 0.05), suggesting genotypic differences in root vigor and extension into the soil profile. Propagation method did not significantly affect root angle after the first season, but prolonged exposure to deficit irrigation conditions in succeeding years will be important to understanding the adaptive capacity of these traits over time. As climate variability intensifies, understanding how rootstock propagation impacts RSA traits–particularly those relevant for accessing water stores, such as deeper root systems, elevated root vigor, and greater root length density at depth–will be essential for improving almond production in drought conditions, suboptimal soils, and other marginal environments.

Speakers

Rachel Noone

UC Davis

Wednesday July 30, 2025 12:15pm - 1:00pm CDT
Empire AB

Poster, Pomology 2

Subject Pomology
Poster # csv

12:15pm CDT

POM 1 - Phenological Modeling of Pollinizing Crabapple Cultivars (Malus spp.) and Commercial Apple Cultivars (Malus X domestica Borkh.) in Kentucky

Wednesday July 30, 2025 12:15pm - 1:30pm CDT

Empire AB

Apple (Malus X domestica Borkh.) cultivars require a pollinizer for cross-pollination to ensure fruit set when planted in contiguous blocks found in modern apple orchards. The overlap of bloom time between pollinizing crabapples (Malus spp.) and commercial cultivars is a critical component for adequate fruit set to occur. Bloom time and duration is correlated with temperature, suggesting this relationship could be influenced by climate change. Understanding the influence temperature has on bloom phenology of these pollinizing crabapples is important to ensure proper cultivar and pollinizer combinations are made by growers. 4 commercially available pollinizing crabapple cultivars (‘Indian Summer’, ‘Mt. Blanc™’, ‘Mt. Evereste™’, ‘Snow Drift’) were replicated 5 times in completely randomized design. In spring of 2024 and 2025, pollinizers were analyzed 1-2 times per week for developmental stages from silver tip to petal fall. These two years represented one of the warmest and then coldest springs on record in Kentucky, respectively. Commercial apple cultivars were also analyzed for comparison. The stage progression data for each pollinizer cultivar was modeled using growing degrees days (GDD) base 6.6°C. In both observed years, the first crabapple to bloom was ‘Indian Summer’ and the final crabapple to bloom was ‘Mt. Blanc™’. In the first year, ‘Indian Summer’ bloomed on Julian Day (JD) 88 at 166.4 GGD and in the second year bloomed on JD 92 at 179.8 GDD. 'Mt. Blanc™’ bloomed on JD 104 at 250.1 GDD and 244.9 GDD in years one and two, respectively. In year one, ‘Gold Rush’ began bloom on JD 97 at 199.4 GDD, which overlapped with ‘Mt. Evereste™’ and ‘Snow Drift’, whereas in the second year ‘Gold Rush’ began bloom on JD 93 at 179.4 GDD and stopped blooming on JD 108 at 279.8 GDD, which overlapped with ‘Mt. Evereste™’, ‘Snow Drift’, and ‘Mt. Blanc™’. There was little bloom overlap in 2024, with the earliest crabapples blooming earlier and more rapidly than the cultivars. In 2025, bloom overlap improved but little overlap occurred with more than two pollinizers at a time. These results show bloom overlap can be influenced by different temperature patterns during winter and spring, and pollinizer selection needs to be carefully considered. It can be concluded that using growing degree-days can help predict bloom time for pollinizers. In Kentucky, limited bloom overlap of apples and pollinizers could indicate a concern for northern apple growing regions as spring temperatures become more variable with climate change.

Speakers

Elayna Stirn

University of Kentucky

Co-authors

Brent Arnoldussen

University of Kentucky

Miranda Woodcock

University of Kentucky

Wednesday July 30, 2025 12:15pm - 1:30pm CDT
Empire AB

Poster, Pomology 2

Subject Pomology

2:00pm CDT

Pomology Interest Group Meeting

Wednesday July 30, 2025 2:00pm - 3:00pm CDT

Strand 3

Wednesday July 30, 2025 2:00pm - 3:00pm CDT
Strand 3

Meetings Committee/Division/Interest Groups

Subject Pomology, American Pomological Society

10:14am CDT

POM 2 - Oral Session

Thursday July 31, 2025 10:14am - 10:15am CDT

Foster 1

Presiding/Moderator

Ashley Sorrow

University of Georgia

Thursday July 31, 2025 10:14am - 10:15am CDT
Foster 1

Oral presentation, Pomology 2

Subject Pomology

10:15am CDT

POM 2 - Effects of intermittent warm temperature exposure on progression of chill accumulation during peach floral bud dormancy

Thursday July 31, 2025 10:15am - 10:30am CDT

Foster 1

Dormancy is an important strategy in perennial plants such as the tree fruit peach (Prunus persica), to protect them from damage during harsh environmental conditions such as winter weather. As day length and temperature decrease in the fall, floral and vegetative buds enter a state of endodormancy where they remain unresponsive to growth promoting environmental signals (Nilsson, 2022). Exposure to cold temperatures (typically ≤ 7° C) during the winter allows for chill accumulation and upon sufficient such chill accumulation, release from endodormancy occurs. This is followed by exposure to warmer temperatures in the spring leading to the end of eco- dormancy and bud break. In the field, low winter temperatures are often interspersed with periods of substantially warm weather thereby interrupting or negating the progression of chill accumulation and affecting bud break in the spring. Understanding responses of peach buds to intermittent warm temperature exposure is needed to mitigate crop loss due to temperature fluctuations. Experiments were conducted to determine the effects of such intermittent warm temperature exposure on chill accumulation in ‘Contender’ peach. Potted trees were maintained at ambient conditions in the field until around 50% of chill requirements (100 % = 1050 chill hours) were met. Following this, trees were subjected to one of three treatments: Control, Chill break I, and Chill break II, with 4 replicates per treatment. The Control group of peach trees were maintained under ambient conditions to reach their chill requirement. Chill break I and Chill break II were exposed to intermittent warm temperatures of continuous 14 °C in a growth chamber for 7 and 14 days, respectively. Following the treatment, trees were returned to ambient conditions. Peach buds were collected from each treatment at three stages and remaining buds were monitored to track floral bud break progression. Additionally, we determined the metabolite and phytohormone concentrations in ‘Contender’ peach buds that naturally accumulated their chilling requirements. Results indicate that as chilling progression increases, starch concentration increases. Concentration of the phytohormone ABA (abscisic) acid appeared to decrease upon completion of endodormancy. Together, these analyses are expected to help us gain a better understanding of dormancy progression in peach.

Speakers

Ashley Sorrow

University of Georgia

Co-authors

Anish Malladi

University of Georgia

Dario Chavez

University of Georgia

Savithri Nambeesan

University of Georgia

Thursday July 31, 2025 10:15am - 10:30am CDT
Foster 1

Oral presentation, Pomology 2

Subject Pomology

10:30am CDT

POM 2 - Comparative evaluation of phytochemicals in low-chill peach, nectarine, and plum cultivars grown in Florida

Thursday July 31, 2025 10:30am - 10:45am CDT

Foster 1

Peaches, nectarines, and plums are among the most popular and valuable stone fruits from the Rosaceae family. Their fruit are rich in bioactive compounds, including flavonoids, anthocyanins, carotenoids, phenolic compounds, vitamins, and antioxidants. In this study, the chemical attributes, bioactive compound content, and antioxidant activity of 18 peach cultivars (‘UFOne’, ‘UFGlo’, ‘UFBeauty’, ‘UFSun’, ‘Flordaprince’, ‘Gulfcrismon’, ‘UFBlaze’, ‘TropicSnow’, ‘TropicBeauty’, ‘UFGem’, ‘UFBest’, ‘Flordaglo’, ‘Flordabest’, ‘UFO’, ‘Flordaking’, ‘Flordacrest’, ‘UFSharp’, and ‘Flordabelle’), four nectarine cultivars(‘UFRoyal’, ‘Sunraycer’, ‘Sunmist’, and ‘Sunbest’), and four plum cultivars (‘Gulfrose’, ‘Gulfgold’, ‘Gulfblaze’, and ‘Scarlet Beauty’) were evaluated. Total soluble solids (TSS), titratable acidity (TA), TSS/TA ratio, and juice pH presented significant variations among cultivars. The highest TSS content was recorded in ‘Sunmist’ nectarine, while plum cultivars had the highest TA levels, particularly ‘Scarlet Beauty’. The TSS/TA ratio was highest in ‘UFSun’ peach. ‘Gulfrose’ plum showed the highest total anthocyanin concentration (TAC) level. Total phenolic content (TPC) varied significantly, with plum cultivars, particularly ‘Scarlet Beauty’, having the highest amount. Similarly, total antioxidant activity (TAA) was highest in ‘Scarlet Beauty’ and ‘Gulfrose’ plums, while ‘TropicSnow’ peach and ‘SunBest’ nectarine had the lowest TAA. Multivariate statistical analyses revealed clear separations among cultivars based on chemical and bioactive parameters. These findings provide valuable insights into the biochemical diversity of peach, nectarine, and plum cultivars, emphasizing the superior bioactive and antioxidant properties of plum cultivars.

Speakers

Fariborz Habibi

University of Florida

Co-authors

Ali Sarkhosh

University of Florida

Jeffrey Brecht

University of Florida

Jose Chaparro

University of Florida

Thursday July 31, 2025 10:30am - 10:45am CDT
Foster 1

Oral presentation, Pomology 2

Subject Pomology

10:45am CDT

POM 2 - Identifying Low-Chill Blackberry Cultivars for Optimal Performance in Florida

Thursday July 31, 2025 10:45am - 11:00am CDT

Foster 1

The successful cultivation of blackberries in subtropical regions like Florida depends on selecting low-chill cultivars capable of withstanding high temperatures, disease pressure, and minimal chilling hours. This study evaluates the performance of 17 breeding lines alongside four commercial cultivars ('Freedom', 'Ponca', 'Horizon', and 'Osage') to determine their adaptability to Florida’s climate. The goal is to identify blackberry germplasm with the potential for high yields, good fruit quality, and post-harvest stability under these challenging conditions. Field trials were established in late June 2023 at the Citra Research Center, Central Florida, using three-month-old greenhouse-grown plants successfully transplanted into the field. Data collection focused on key production parameters, including total yield, single berry weight, and marketable fruit percentage. Fruit quality was assessed through pH, Brix, and organic acid composition (tartaric, citric, and malic acid). Subjective evaluations of firmness, flavor, and seed content were also conducted. Additionally, post-harvest performance was analyzed by monitoring decay, leakage, and red druplet reversion after seven days of cold storage at 5°C. Preliminary results indicate considerable variation among the evaluated cultivars. 'BLB', 'BLH', 'BLA', and 'Freedom' exhibited the highest yields, whereas 'BLG', 'BLP', and 'BLI' were among the lowest-yielding selections. Berry size ranged from 8.98 g in 'BLB' to 5.27 g in 'Osage'. Acidity levels varied significantly, with 'BLC' (pH 4.01) and 'BLJ' (pH 3.99) displaying the mildest flavor profiles, while 'BLP' (pH 3.60) and 'BLQ' (pH 3.62) exhibited higher acidity. Beyond fruit evaluations, plant vigor and structural characteristics were documented. Prior to last year’s harvest, primocane count and height were recorded, and this season, plants were rated based on vigor, overall health, and the proportion of green versus brown canes. Ongoing data analysis will further clarify cultivar performance in relation to plant growth and long-term productivity. This research provides valuable insights into selecting blackberry cultivars best suited for Florida’s subtropical environment. The findings will contribute to optimizing cultivar recommendations for growers looking to enhance yield, fruit quality, and marketability in sub-tropical climate production systems like Florida.

Speakers

Nurjahan Sriti

University of Florida

Co-authors

Guodong Liu

University of Florida

Jeffrey Williamson

University of Florida

Steven Sargent

University of Florida/IFAS

Professor and Extension Postharvest Specialist

Zhanao Deng

University of Florida

Thursday July 31, 2025 10:45am - 11:00am CDT
Foster 1

Oral presentation, Pomology 2

Subject Pomology

11:00am CDT

POM 2 - Cold Hardiness of Apple Scions and Rootstocks

Thursday July 31, 2025 11:00am - 11:15am CDT

Foster 1

The current understanding of apple stem cold hardiness is very broad- there are certain cultivars generally accepted to be cold hardy or tender. There has been no comprehensive study of cold hardiness of apples at multiple timepoints over multiple years. In this study, cold hardiness was evaluated for 21 rootstock and 23 scion genotypes monthly throughout the dormant season over 4 years. Cold hardiness was measured using the electrolyte leakage method and the temperature at which 25% tissue damage occurs (LT25) was used as the cold hardiness phenotype. The four study winters varied drastically in intensity and had a significant effect on genotype cold hardiness. Contrasting phenotypic responses in cold versus mild winters demonstrated clear environmentally driven differences between inferior and superior genotypes. Another major finding from the study is the rapid deacclimation of rootstocks compared to scions in late winter/early spring- we observed that differences in mean hardiness between groups exceeded 6 °C in some years. Overall, this study represents the largest apple cold hardiness experiment to date in terms of cultivars used and timepoints examined, resulting in both novel implications for how grafted apples navigate cold hardiness during dormancy and which cultivars are best suited for unusual but increasingly common winter conditions.

Speakers

Kenneth Buck

Cornell University

Co-authors

Hanna Martens

Cornell University

Jason Londo

Cornell University

Thursday July 31, 2025 11:00am - 11:15am CDT
Foster 1

Oral presentation, Pomology 2

Subject Pomology
Poster # csv

11:15am CDT

POM 2 - ‘King’ Florets of an Apple Cyme Freeze at Higher Temperatures Than Lateral Florets Prior to Visible Changes in Bud Pheno

Thursday July 31, 2025 11:15am - 11:30am CDT

Foster 1

Cold hardiness and dormancy are critical physiological adaptations enabling woody perennials to endure low temperatures in winter and initiate growth in spring. Hardiness in apple (Malus domestica) is genotype dependent, however maximum hardiness level gained by the buds is strongly regulated by environment. Understanding the relationship between dormancy progression and cold hardiness is essential for predicting plant responses to winter and spring freeze events, as well as optimizing breeding efforts for resilience and orchard decisions for frost management. Information on hardiness mechanism is becoming more crucial given the impact of global climate change in apple growing regions where earlier bloom dates have inherently greater risk of crop loss due to episodic spring frost events. The existing lethal temperature chart for apple floral buds is limited to the visible development stages and lacks critical temperature thresholds for the freeze resistance of floral buds during their transition out of ecodormancy. Further, there is no information distinguishing positional effects of individual florets of the apple cyme inflorescence with respect to their hardiness status. Because the ‘King’ floret is developmentally advanced compared to laterals and has the highest fruit growth and economic potential, the development of lethal temperature limits to inform its protection seems prudent. Thus, we evaluated the difference in LT50 between ‘King’ and ‘Lateral’ florets in ‘Gala’ on ‘Bud9’ rootstock during the transition phase from ecodormacy to growth resumption in 2022 and 2023. Our results demonstrated that cold hardiness is lost at early stages of, or transitions out of, ecodormancy; notably, this occurs prior to visible changes in bud phenology. Moreover, the ‘King’ florets are markedly less hardy than the ‘Laterals’ by approximately 6°C. The magnitude of difference in lethal temperatures between ‘King’ and ‘Lateral’ florets differed between years but remained significant. Increasing susceptibility to freeze mortality at higher temperatures was commensurate with an increase in the relative water content (RWC) of the buds and a marked decrease in sorbitol and sucrose concentration. In both years, an RWC of approximately 60% coincided with the visible green stage of bud burst. Our data indicate that decreasing sorbitol concentration can act as a potential biochemical marker for cold hardiness loss and inform protection measures of the ‘King’ fruit. Further study incorporating multiple commercially important apple cultivars will be beneficial in understanding the cold hardiness in apples.

Speakers

Sangeeta Sapkota

Michigan State University

Co-authors

Todd Einhorn

Michigan State University

Thursday July 31, 2025 11:15am - 11:30am CDT
Foster 1

Oral presentation, Pomology 2

Subject Pomology
Poster # csv
Funding Source Martin and Judith Bukovac Professorship in Tree Fruit Physiology Endowment

11:30am CDT

POM 2 - Dissecting Frost Tolerance in Apple: Rootstock Effects on Gene Networks and Metabolite Profiles

Thursday July 31, 2025 11:30am - 11:45am CDT

Foster 1

Late spring frosts pose a recurrent threat to apple production, particularly under climate change scenarios that promote earlier bloom and heightened exposure to frost events. Recent evidence from our investigations on different apple-rootstock combinations suggested that rootstock genotype may influence scion resilience to frost, yet the underlying molecular mechanisms remain poorly understood. Field trials were conducted from 2021–2023 on 12-year-old ‘Gala’ and ‘Fuji’ trees grafted onto ten rootstocks, including ‘B.9’ and ‘M.26’, representing extremes of frost tolerance. Following three naturally occurring frost events, we have shown that ‘B.9’ rootstock consistently conferred lower bud mortality relative to ‘M.26’, independent of bloom timing. To dissect the molecular and biochemical mechanisms underlying the differential responses of these scion-rootstock combinations to frost, tissue-specific RNA-Seq analysis and untargeted metabolic profiling were conducted on floral buds, scion leaves, and rootstock sucker leaves from ‘Gala’-grafted trees. Samples were collected 12 h before and 6 h after the 2021 frost. Weighted gene co-expression network analysis (WGCNA) was employed to identify frost-responsive modules, and hub genes were validated via qRT-PCR in both ‘Gala’ and ‘Fuji’. Transcriptomic analyses revealed extensive gene regulation following frost exposure, including over 10,000 differentially expressed genes (DEGs). WGCNA identified three frost-correlated gene modules. Key hub genes were implicated in cold acclimation, ABA signaling, and cellular stress tolerance. GO and KEGG enrichment analyses highlighted significant representation of pathways associated with ABA response, cold response, and water deprivation stress. Metabolomic profiling of different tissues and genotypes further supported the transcriptomic findings and provided metabolic signatures associated with the identified gene networks. This work establishes a foundation for integrative omics approaches to dissect physiological cold tolerance mechanisms in apples and guides rootstock selection and germplasm improvement strategies.

Speakers

Sherif M. Sherif

Associate Professor, Virginia Tech

Dr. Sherif M. Sherif is an Associate Professor at Virginia Tech, where he channels his fervent zeal for life sciences and educational outreach into his specialization in tree fruit physiology and molecular biology. His career is defined by a dedication to overcoming the biological... Read More →

Co-authors

Amolpreet Kaur Saini

Viginia Tech

Clay Wright

Viginia Tech

Khalil Jahed

Virginia Tech

Thursday July 31, 2025 11:30am - 11:45am CDT
Foster 1

Oral presentation, Pomology 2

Subject Pomology
Poster # csv
Funding Source 2022-67013-36293

12:15pm CDT

POM 2 - Apple Orchards of Sonoma County - UC Cooperative Extension

Thursday July 31, 2025 12:15pm - 1:00pm CDT

Empire AB

Sonoma County, California is home to many small- to mid-scale apple orchards with diverse cultivars, management approaches and sales outlets. This poster will outline recent UC Cooperative Extension apple programming that responds to high-priority needs identified by apple growers, orchardists, and processors in this region. The new UCCE Specialty Crops Advisor based in Sonoma, Marin, and Napa Counties conducted a Needs Assessment that identified key issues and challenges for sustainable apple orchard system management. This poster will summarize key findings from the Needs Assessment. Stakeholders asked for educational programming on key topics to improve apple orchard health and yield. In response, outreach and Extension education activities focused on science-based sustainable apple orchard management strategies to accelerate practice implementation. This poster will outline these Extension efforts that responded to the Needs Assessment findings and will present evaluation survey results. For instance, stakeholders specifically asked for apple orchard management webinars, so the CE Advisor worked with local and UC partners to deliver a 5-part educational apple webinar series covering key aspects of sustainable apple orchard management. Findings showed that webinars increased attendees’ knowledge (100% of 35 respondents) and 97% reported they will use knowledge gained to manage apple orchards more sustainably. The CE Advisor worked closely with commercial apple growers to address tree health challenges in the orchard on a case-by-case basis. The most common pest issues in the region include codling moth, a suite of diseases, and rodents. Many apple orchards are managed as low-input systems, so tree water stress and nutrient deficiencies are common. The CE Advisor used science-based information and strategies to help growers address these issues. With grower permission, local apple orchard growers’ “Success Stories” are included in Extension educational presentations and materials to highlight examples of sustainable apple orchard management. This poster will include several of these “Success Stories” highlights. This poster will present findings outlining apple growers’ needs for Extension education and applied research in Sonoma County, California. It will outline UCCE activities implemented to increase growers’ practical knowledge and skills to guide sustainable decision making, increase orchard health and yield, and promote grower-to-grower knowledge sharing. Findings will help guide future work to enhance apple orchard sustainability and apple supply for the local food system.

Speakers

Ellie Andrews

Specialty Crops Advisor for Sonoma, Marin, and Napa Counties, UC ANR

Thursday July 31, 2025 12:15pm - 1:00pm CDT
Empire AB

Poster, Pomology 1

Subject Pomology
Poster # csv
Funding Source UC ANR

12:15pm CDT

POM 2 - Evaluation of 4-Vita Biostimulant and Promalin in Mitigating Green Spot in ‘WA 38’ Apple

Thursday July 31, 2025 12:15pm - 1:00pm CDT

Empire AB

With more than 20 million of trees planted in Washington State, ‘WA 38’ apple, commercialized as ‘Cosmic Crisp®’, is channeling the interest of the apple industry. Since the variety hit the market in 2019, consumers reported positive eating experiences and appreciation for its crispiness and juiciness. In suitable growing conditions, ‘WA 38’ can achieve high red coloration and satisfactory pack-out. One of the causes of loss is the ‘green spot’ (GS) disorder that impacts mainly the stem-hemisphere of the apple displaying skin discolored areas that might degenerate affecting the cortex. The onset of the GS occurs at the end of July, and the disorder incidence at harvest fluctuates year to year. Several mitigations approaches were investigated, but only bagging fruit at early stage of development provided positive results. Because the bagging practice is not economically sustainable on commercial scale, the application of a new foliar biostimulant (Plants for Plants 4-Vita) and Promalin (GA4 7 BA) were tested against untreated control. 4-Vita aims to protect the trees by abiotic stressors like drought and heat, stimulating water use efficiency and productivity. On the other hand, Promalin is known to improve fruit shape and size and reduce russeting by increasing epidermis cell elasticity. Our hypothesis focused on the potential positive effects of a biostimulant and a PGR in mitigating the GS in ‘WA 38’. The products were tested in season 2023 on a Granny Smith/M9-T337 orchard top-grafted in 2015 with ‘WA/38’ scions and trained to spindle, by applying them separately on distinct rows, bi-monthly, starting at 4 weeks AFB for 4 times. Productive parameters, pack out and GS incidence GS were assessed for each treatment. Results showed that Plants for Plants 4-Vita and Promalin did not improve yield and did not significantly mitigate the incidence of GS in comparison to untreated control.

Speakers

Stefano Musacchi

Washington State University

Co-authors

Sara Serra

Washington State University

Thursday July 31, 2025 12:15pm - 1:00pm CDT
Empire AB

Poster, Pomology 1

Subject Pomology
Poster # csv
Funding Source WSU Endowment

12:15pm CDT

POM 2 - Field Evaluation of Six Grafted Cherry (Prunus avium) cultivars under Northwest New Mexico Growing Conditions

Thursday July 31, 2025 12:15pm - 1:00pm CDT

Empire AB

RELEVANCE Sweet cherries (Prunus avium) have some historical production in the Four Corners area with renewed interest for fresh eating, baking, juicing and distilling. RESPONSE Six grafted cultivars were planted March 2014 as bare-root, 3-year old tree seedlings on a high mesa location at the NMSU Agricultural Science Center at Farmington at 5,640 feet above sea level (36°4’ N by 108° W). Cultivars ‘Bing’, ‘Skeena’, ‘Rainier’, ‘Benton’, ‘Santina’ and ‘Coral’ were grafted onto either Krymsk 5 or Krymsk 6 rootstock. Yield data was collected for 2019 and 2021 growing seasons. Trees were pruned during winter dormancy beginning in 2020 to control height. Lower yields in 2021 compared to 2019 are attributed to extensive pruning and to bird damage that was noticeably more impactful in 2021 compared to 2019. In all other years since planting, killing spring frosts reduced or eliminated flower production resulting in little to no fruit yield. When harvested, fruit sugar content (measured in °brix; the higher the °brix, the sweeter) ranged from 15.3° to 22.1° brix in 2019 and 13.3° to 24.6° in 2021. Sugar content is acceptable for any number of post-harvest fresh market to fermentation applications. IMPACT Cherry trees are among the first fruit trees to break dormancy on a high mesa site in Northwest, NM and have been prone to damaging spring frosts resulting in flower death and reduced fruit yields. When cherry have yielded, post-harvest metrics have favorable sugar content. Growers can expect to have non-bearing years related to spring frost risk and are advised to have cherry plantings as part of a diversified cropping system to lessen risk during non-fruitful years. PUBLIC VALUE STATEMENT The work is helping to support northwest New Mexico fruit growers.

Speakers

Kevin Lombard

New Mexico State University

Kevin Lombard is a Professor of Horticulture and Research Director of the New Mexico State University Agricultural Science Center at Farmington, a 250 acre research farm uniquely located on the Navajo Nation. His research encompasses specialty crop evaluations including grapes, fruit... Read More →

Co-authors

Bernd Maier

Amaro Winery and Taproom

Ciro Velasco-Cruz

New Mexico State University

Thursday July 31, 2025 12:15pm - 1:00pm CDT
Empire AB

Poster, Pomology 1

Subject Pomology
Poster # csv
Funding Source New Mexico Attorney General’s Office (GR0007668) through the Northwest New Mexico Agriculture Restoration Project

12:15pm CDT

POM 2 - High tunnel stone fruit production in northern New Mexico

Thursday July 31, 2025 12:15pm - 1:00pm CDT

Empire AB

Late spring frost is a major challenge to stone and pome fruit production in northern New Mexico. In this study, three cultivars of peach (Prunus persica)—Challenger, China Pearl, and Contender on Nemaguard rootstocks were planted at 4x10ft planting density with three replications in a 30x72ft high tunnel in April 2017, but severe leaf chlorosis appeared later in the season. We kept the better west row and removed the central and east row. In 2018, tissue-cultured GF677 and Rootpac® R were planted in May and budded in August 2018. Trees were trained to open vase system. Thermostat-controlled propane heaters and fans were employed for frost protection. In 2021, we began securing the sidewalls and the doors of the high tunnel and setting up heaters. In 2022 and 2023, the high tunnel system plus heating system was sufficient to protect blooms and fruitlets from late frosts, and yields averaged 15.8 kg/tree in 2022 and 12.3 kg/tree in 2023, respectively. There was no significant difference among cultivars in either year. However, there were significant differences between rootstocks in 2022, with trees on Nemaguard averaging 24.3 kg/tree across cultivars, while trees on GF677 and Rootpac® R averaging 11.2 and 11.8 kg/tree, respectively. The nearly two years older in age for trees on Nemaguard could contribute to this difference in 2022. There was also a reasonable crop in 2024. By the end of 2024, Trees on Nemaguard with 1-2ft new growth were smaller than plants on GF677 and Rootpac® R, with 1.5-4 ft new growth. There were limited replications in this high tunnel study but GF677 and Rootpac® R were more suitable than Nemaguard rootstock for the high pH soil conditions in New Mexico. Cherry had limited fruit set during this study. In 2022 and 2023, we observed deformed flowers without petals and some flowers with blackened pistils. Only handfuls of cherries were harvested in both 2022 and 2023. The high temperatures inside the high tunnel in summer could affect the floral bud initiation/ development. More studies are needed to clarify the deformed flowers. Growers should be cautious with sweet cherry production in high tunnels in northern New Mexico.

Speakers

Shengrui Yao

New Mexico State University

Co-authors

Robert Heyduck

New Mexico State University

Steven Guldan

New Mexico State University

Thursday July 31, 2025 12:15pm - 1:00pm CDT
Empire AB

Poster, Pomology 1

Subject Pomology
Poster # csv

12:15pm CDT

POM 2 - Irrigation And Foliar Fertilization Effects On Yield And Fruit Quality Of Peaches.

Thursday July 31, 2025 12:15pm - 1:00pm CDT

Empire AB

Previous studies in the southeastern United States have reported benefits of irrigated vs non irrigated orchards, including no major effects of soil-applied fertilizers on fruit yield and quality. However, the benefits of irrigation systems and foliar fertilization effects on yield, and fruit nutrient profiles and quality are limited. This study was conducted in a nine-year-old peach orchard using a split-plot randomized complete block design with two irrigation systems, drip vs micro-sprinkler as whole-plots, and foliar treatments as split plots. Preharvest foliar applications included water (control), nanocellulose crystals (CNC 3%), Calcium (Ca 6%), Potassium Silicate (K2SiO3), plus the combination of CNC with Ca and K2SiO3. Trees received no soil-applied fertilization, and irrigation was managed using the Peach Smart Irrigation App recommendations (https://smartirrigationapps.org/peach-app/). Even though no significant differences were observed in irrigation systems or foliar treatments for fruit weight or perimeter, all foliar treatments resulted in higher total yield compared to the control under drip irrigation. Under micro-sprinkler irrigation, only K2SiO3 and CNC increased total yield relative to the control. Regarding texture, control fruit showed decreased firmness after two weeks of storage at 2 °C and 90% relative humidity. There were main effects of irrigation in total soluble solids (TSS), where micro-sprinkler (10.27%) had higher TSS than drip irrigation (9.67%). Overall, these findings suggest that drip irrigation and foliar applications, particularly with CNC and K2SiO3, may enhance yield in peaches.

Speakers

Selvin Carrillo Ramos

University of Georgia

Co-authors

Dario Chavez

University of Georgia

Thursday July 31, 2025 12:15pm - 1:00pm CDT
Empire AB

Poster, Pomology 1

Subject Pomology
Poster # csv

12:15pm CDT

POM 2 - Visualization of Regional Fruit Growth Rate in Persimmons Using 3D Phenotyping

Thursday July 31, 2025 12:15pm - 1:00pm CDT

Empire AB

Understanding fruit growth and developmental patterns is crucial, as they directly influence fruit size, morphology, and ultimately, yield. While conventional models describe fruit growth and development based on parameters for the whole fruit, how tissue growth in different fruit regions is coordinated to drive overall fruit growth and development remains unclear. Here, we investigated the relationship between the spatial variation of growth rates and fruit morphology in persimmon (Diospyros kaki), a fruit tree species with highly diverse fruit morphology. Starting two weeks after blooming, fruits from four cultivars were marked with dotted lines routinely. Those fruits were sampled and used for the reconstruction of 3D fruit models. The relative positions and distances between points marked were used as parameters for the local growth. All cultivars exhibited more active growth near the calyx than near the apex, particularly during the early stages of fruit development. However, the extent of these spatial differences varied among cultivars. In flattened fruits, growth was highly concentrated near the calyx, with remaining minimal in other portions. In contrast, elongated fruits exhibited a gradual growth gradient from the calyx toward the apex, with high growth even near the apex. These findings provide a foundation for fruit shape regulation and elucidation of physiological disorders in persimmon.

Speakers

Akane KUSUMI

Graduate school of Agriculture, Kyoto University

Co-authors

Ryutaro Tao

Kyoto University

Soichiro Nishiyama

Kyoto University

Thursday July 31, 2025 12:15pm - 1:00pm CDT
Empire AB

Poster, Pomology 1

Subject Pomology
Poster # csv
Funding Source Japan Society for the Promotion of Science KAKENHI grant no. 24KJ1497 to AK

12:30pm CDT

Fruit, Vegetable, and Edible Crops Collaboration Session

Thursday July 31, 2025 12:30pm - 1:30pm CDT

Collaboration Center, Empire AB

A forum for discussion of potential collaborations with regards to fruit, vegetable, and edible crops – i.e. citrus, breeding, production systems, postharvest, pomology, crop management, viticulture, etc.

Thursday July 31, 2025 12:30pm - 1:30pm CDT
Collaboration Center, Empire AB

Hort Theater & Collaboration Center, Collaboration Center

Subject Citrus Crops, Postharvest, Pomology, Produce Quality Safety and Health Properties, Viticulture and Small Fruits, Horticulture Industry, Organic, vegetable Breeding, Vegetable Crops Management, Temperate Tree Nut Crops, Fruit Breeding, Commercial Horticulture, Growth

9:59am CDT

POM 3 - Oral Session

Friday August 1, 2025 9:59am - 10:00am CDT

Foster 2

Presiding/Moderator

Franz Niederholzer

University of California Cooperative Extension

Friday August 1, 2025 9:59am - 10:00am CDT
Foster 2

Oral presentation, Pomology 3

Subject Pomology

10:00am CDT

POM 3 - Phosphorus Uptake and Partitioning in Young Peach Trees

Friday August 1, 2025 10:00am - 10:15am CDT

Foster 2

Phosphorus (P) is an essential plant nutrient required for growth. However, it is a finite natural resource that can cause environmental issues when overused in agriculture. Due to challenging soil relationships, the availability and uptake of P can be challenging to predict. Furthermore, soil tests can be misleading for guiding management decisions regarding P fertilizer applications. The objective of this study was to evaluate the influence of soil P levels on the uptake and partitioning of P in young peach trees. We planted a new peach orchard at the Musser Fruit Research Center near Clemson, SC. This orchard contained a widely variable range of P in the soil. Representative trees were removed in August and January and all plant parts were subjected to P analysis. Soil test P levels had no clear relationship with total plant P uptake or partitioning patterns and are likely a poor reference point for P fertilizer management decisions in peach orchards.

Speakers

Noah Willsea

Clemson University

Co-authors

Juan Carlos Melgar

Clemson University

Friday August 1, 2025 10:00am - 10:15am CDT
Foster 2

Oral presentation, Pomology 3

Subject Pomology
Poster # csv

10:15am CDT

POM 3 - Understanding the Role of Nutrient Leaching in Young Peach Trees: Implications for Growth and Development in Orchard Man

Friday August 1, 2025 10:15am - 10:30am CDT

Foster 2

Nutrient leaching remains a significant environmental concern due to its adverse effects on soil quality, groundwater contamination, human health, and the eutrophication of aquatic ecosystems. The urgency of addressing this issue has escalated with the increasing frequency and intensity of climate variability and extreme weather events, which exacerbate nutrient losses from agricultural systems. For this study, three peach cultivars (Prunus persica L.), including 'Crimson Joy', 'Liberty Joy', and 'Rich Joy', were planted at Auburn University's Research and Extension Center in Chilton, Clanton, Alabama, on February 23, 2024, using a Randomized Complete Block Design (RCBD) with four blocks. Each block consists of 9 peach trees, totaling 36 trees. The aim of this study is to evaluate the extent of nutrient leaching on the growth of three distinct young peach cultivars, using recommended fertilization rate (by The Southeastern peach guide). A soil sampling method is used to compare the nutrient levels at selected depths. The soil depths are 25.4 and 50.8 cm within and 76.2 and 101.6 cm below the peach tree root zone. The collected soil samples are analyzed for Nitrate Nitrogen (NO3-N (mg/kg)), Ammonium nitrogen (NH4-N (mg/kg)) and pH. Additionally, the young peach trees are assessed by measuring plant height (cm), trunk cross-sectional area (cm2) and annual leaf nitrogen analysis (%). The preliminary results of this study, which is still in progress indicate that both depth and cultivar significantly influence NH4-N concentrations over time, while rainfall events and cultivar interactions affect NO3-N leaching dynamics. Although pH levels changed, they did not differ statistically. Each cultivar exhibited TCSA increases and height growth, with all cultivars maintaining leaf nitrogen levels within the optimum range. This study will help the Alabama peach growers to understand the impacts of nutrient leaching and utilize better alternatives that can help to not only get maximum profit economically but also ensure that the environment is safe and sound for the current and future generations.

Speakers

Winfred Nziku

Auburn University

Co-authors

Audrey Gamble

Auburn University

Bernardo Chaves-Cordoba

Auburn University

Dario Chavez

University of Georgia

Edgar Vinson

Auburn University

Juan Carlos Melgar

Clemson University

Melba Ruth Salazar Gutierrez

Auburn University

Friday August 1, 2025 10:15am - 10:30am CDT
Foster 2

Oral presentation, Pomology 3

Subject Pomology
Poster # csv

10:30am CDT

POM 3 - Rapid and quantitative analysis of leaf calcium using X-ray fluorescence scanning

Friday August 1, 2025 10:30am - 10:45am CDT

Foster 2

Development of control measures for nutrient-related apple fruit disorders like bitter pit requires a better understanding of calcium metabolism in the tree. Limiting this understanding is a rapid and accurate method for measuring the concentration of calcium in various plant organs including the leaves. Optimally, measuring calcium levels could be done at the single leaf level, or better yet for whole leaves at a resolution of sub-millimeter dimensions. We report on the use of X-ray fluorescence for apple leaf tissue to quantitatively measure leaf calcium tissue. Using 7-mm diameter discs taken from Granny Smith apple leaves mid-season, we were able to demonstrate that the emission data from a scanning Bruker X-ray fluorescence instrument could be easily transformed to predict accurate and precise calcium levels in apple leaf tissue. If similar relationships can be determined for other minerals, this type of analysis will enable the quantitation of multiple minerals within minutes. Provided software analysis of the samples can be automated, the turn-around time for tissue analysis would be on the order of one or two hours for hundreds of samples

Speakers

Randolph Beaudry

Michigan State University

Dr. Randolph Beaudry, Professor, MSU Department of Horticulture (MSc, PhD, University of Georgia). His appointment is 50% MSU Extension and 50% AgBioResearch. His research program includes both regional and international projects and focuses on the physiology of plant responses to... Read More →

Co-authors

Claudia Moggia

University of Talca

Gustavo Lobos

University of Talca

Marcelo Pirinoli

University of Talca

Ricardo Cabeza

University of Talca

Sebastian Romero-Bravo

University of Talca

Friday August 1, 2025 10:30am - 10:45am CDT
Foster 2

Oral presentation, Pomology 3

Subject Pomology
Poster # csv
Funding Source FONDECYT

10:45am CDT

POM 3 - Horticultural Performance and Physiological Responses of a Mature Peach Orchard to Mulch and Poultry Litter Application.

Friday August 1, 2025 10:45am - 11:00am CDT

Foster 2

Plant nutrient acquisition and responses to different fertilization programs in fruit orchards oftentimes depend on many biotic or abiotic factors or a combination of both, including tree or orchard age and nutrient source. This study aims to evaluate the effect of topically applied, slow-release source of essential nutrients from mulch mixed with poultry litter (PLM) or without (M) and fast-release growers’ standard rate of mineral fertilizer on an eight-year-old replanted orchard containing ‘Juneprince’ and ‘Scarletprince’ peach trees in South Carolina. Soil health indicators such as soil moisture and nutritional status, and tree health parameters, including yield and fruit quality (specifically on the incidence of diseases and physiological disorders), were evaluated over two years. The results showed that soil organic matter and cation exchange capacity were significantly higher in PLM across both years of this study when compared with other treatments. Both PLM and M treatments had higher moisture retention than the grower’s standard. However, yields between the two cultivars used in this study varied considerably in response to treatment and years. Yield of ‘Juneprince’ trees treated with GS was significantly higher in the first year of this study when compared with PLM and M but did not significantly differ in the second year. In contrast, yield of ‘Scarletprince’ trees treated with PLM and M were consistently higher numerically when compared with GS in both years. PLM significantly reduced bacterial spot incidence and severity in both cultivars across the study years. This result suggested that amending the soil through surface covering with mulch mixed with poultry litter provides the nutritional requirement, increases yield and significantly lower disease pressure and improves the quality of the marketable fruit in a mature orchard.

Speakers

Ayodeji Idowu

Clemson University

I am a third-year Ph.D. student working on improving soil health and ecosystem conservation through rigorous enhancement of soil organic matter and strategic soil nutrient management for agricultural and environmental sustainability. To achieve this, I am testing different soil amendment... Read More →

Co-authors

Juan Carlos Melgar

Clemson University

Friday August 1, 2025 10:45am - 11:00am CDT
Foster 2

Oral presentation, Pomology 3

Subject Pomology
Poster # csv
Funding Source United States Department of Agriculture - Sustainable Agriculture Research and Education (USDA-SARE)

11:00am CDT

POM 3 - Cutting Propagation of Southwest Peach Seedlings

Friday August 1, 2025 11:00am - 11:15am CDT

Foster 2

Southwest Native American Tribes, such as the Navajo, Hopi, and other Pueblo, have grown peaches since at least the early 1600’s, making them a nutritionally and culturally important food source. Historically, peach propagation was primarily done by seed, with only one written account of stem cutting propagation occurring within the Zuni Pueblo. Little is known about the effectiveness of different propagation methods for rapidly replicating Southwest seedling accessions and maintaining parent tree genetics. The purpose of this study was to evaluate the rooting success of softwood and hardwood cuttings taken from Southwest peach seedling accessions originating from five locations within the Navajo and Hopi Tribal communities. All cuttings were collected from mature trees established in Thatcher, UT. Two trials of cuttings were conducted in July and November of 2024. Each seedling tree had 18 cuttings per trial. Trial one had softwood and hardwood cuttings and trial two had only hardwood cuttings. Each cutting was measured 12 cm long, had at least three nodes planted into the potting media. Trial one cuttings had the first 3 node leaves cut in half, with all other leaves removed. Cutting treatments included a control (no treatment), Hormodin 1, and Hormodin 2, with six replications for each treatment. All cuttings were placed under a mist system with controlled temperature and relative humidity. Rooting success was assessed over three months by visually evaluating live tissue and new growth. Rooting success was dependent upon seedling parent location, treatment, time of year, as analyzed by analysis of variance. Cuttings from Canyon del Muerto had greater rooting success compared with those from Navajo Mountain. The Hopi and Navajo Mountain cuttings had decreased rooting success as the Hormodin concentrations increased. Canyon del Muerto cuttings benefited from Hormodin 1 treatment. The results of this study will help determine the potential of Southwest peach seedlings for replication as a viable rootstock for the fruit industry.

Speakers

Reagan Wytsalucy

Utah State University

Native American food crops of the Southwest.

Co-authors

Bud Lopez

New Mexico State University

Kevin Lombard

New Mexico State Univeristy

Youping Sun

Utah State University

Friday August 1, 2025 11:00am - 11:15am CDT
Foster 2

Oral presentation, Pomology 3

Subject Pomology
Poster # csv
Funding Source San Juan County Extension with Utah State University and New Mexico State University Agriculture Science Center

11:15am CDT

POM 3 - Root-to-leaf ratio contributes to drought recovery and resilience in northern highbush blueberry genotypes

Friday August 1, 2025 11:15am - 11:30am CDT

Foster 2

Plant canopy and root architecture characteristics play a crucial role in water uptake and plant growth. Blueberry roots are shallow and lack dense root hairs, making them more susceptible to drought than most fruit crop species. In northern highbush blueberry (Vaccinium corymbosum), differences in root size, root architecture, and root-to-leaf balance may impact drought resilience, particularly in maintaining photosynthesis (A) under limited soil moisture. However, this has not yet been examined in this species. This study evaluated drought resilience in two V. corymbosum genotypes with contrasting canopy and root architecture characteristics (Bluecrop, low root-to-leaf ratio; Draper, high root-to-leaf ratio). During the pre-drying period, both genotypes exhibited similar A and stem water potential (Ψ stem). Irrigation water was withheld to initiate drought conditions. By day 4 of withholding water, Bluecrop showed a decline in A, but its Ψ stem did not significantly change until day 6. In contrast, Draper did not show a decline in A or Ψ stem until day 6 of withholding water. Both cultivars reached a critical threshold of stomatal conductance (gs) (90% reduction from well-watered conditions) on day 10 of withholding water. Following re-watering, Ψ stem recovered immediately in both cultivars on day 2 of re-watering (day 12 of withholding water). However, the recovered Ψ stem of Bluecrop did not correspond with any increase in gs until day 14 of rewatering (day 24 of withholding water). Meanwhile, Draper exhibited a much higher gs and A than Bluecrop throughout the post-rewatering period, suggesting that Bluecrop is more sensitive to drought conditions than Draper. Post-experiment analysis confirmed that Draper had a larger root-to-leaf ratio than Bluecrop, which likely enhanced water absorption and supported faster recovery following rehydration. No significant difference in root architecture characteristics were found between these two cultivars, considering the number of root tips, root length, and surface area per root diameter at different levels (< 0.25 mm, 0.25- 0.5 mm, and >0.5 mm). These results suggest that root-to-leaf ratio and root-to-leaf hydraulic conductance play a central role in determining drought resilience in V. corymbosum genotypes. Future studies will be carried out to confirm this finding across a greater number of genotypes.

Speakers

Sheng-yang Li

Michigan State University

Co-authors

Josh VanderWeide

Michigan State University

Friday August 1, 2025 11:15am - 11:30am CDT
Foster 2

Oral presentation, Pomology 3

Subject Pomology
Poster # csv

11:30am CDT

POM 3 - A review of progress and obstacles on a path towards consistent production of high quality ‘Improved French’ prune crop

Friday August 1, 2025 11:30am - 11:45am CDT

Foster 2

Consistent production (CP) of quality crops supports economic sustainability of individual farms and maintains market share for a larger industry. For the last 30 years, annual prune production in California has been highly variable, ranging from < 1 to >3 dried tons per acre. ‘Improved French’ is the primary cultivar grown in California. This variety, like most plums, often requires thinning to maintain CP and grower income where fruit size (count per pound) is positively correlated to fruit quality and price to the grower. Mechanical shaking at reference date, ~45 days after full bloom, is now a common thinning practice although questions have been raised regarding the potential benefit to earlier thinning a phantom practice that would have to be chemical thinning. However, in the last two decades, extreme bloom weather can virtually eliminate a prune crop if warm weather precedes bloom. This talk reviews work by University of California researchers towards improving CP through 1) better understanding of the weather related factors contributing to very low fruit set in prunes, 2) testing ‘Improved French’ prune fruit growth development to determine if and when source limited fruit growth occurs, and 3) identifying chemical thinning practices, materials, and rates to remove flowers before fruit set. Early bloom years are those with risk of crop loss due to extended and wet or extremely warm (>27oC) bloom weather conditions. [The risk of freezing damage is relatively low for prunes in CA given usual March bloom timing.] Relative prune fruit growth rate studies revealed resource limited fruit growth occurs ahead of current thinning timings (reference date), so earlier thinning may improve fruit growth and possibly yield compared to the current thinning practice. Finally, potassium thiosulfate (KTS) applied 2x at 1-2% (v/v) shows promise in thinning prunes. Lime sulfur and fish oil can be effective but is inconsistent in bloom thinning. Obstacles to CP of ‘Improved French’ prune include difficulty identifying practices to quantify bloom strength and help grower with the decision to thin or not. In addition, no ‘rescue’ spray has been found to improve fruit set in years with early, risky, bloom. Grower testing of the current research results awaits successful overcoming of the two obstacles listed above.

Speakers

Franz Niederholzer

University of California Cooperative Extension

Co-authors

Katherine Jarvis-Shean

UC ANR

Luke Milliron

University of California Agriculture Natural Resources

N. Jamie Ott

UC ANR

Richard Rosecrance

California State University, Chico

Sara Castro

UC Davis

Ted DeJong

UC Davis

Friday August 1, 2025 11:30am - 11:45am CDT
Foster 2

Oral presentation, Pomology 3

Subject Pomology
Poster # csv
Funding Source California Prune Board

1:44pm CDT

POM 4 - Oral Session

Friday August 1, 2025 1:44pm - 1:45pm CDT

Foster 2

Presiding/Moderator

Brent Black

Utah State University

Friday August 1, 2025 1:44pm - 1:45pm CDT
Foster 2

Oral presentation, Pomology 4

Subject Pomology

1:45pm CDT

POM 4 - Adjusting the carbohydrate balance sub-models for use in Washington State

Friday August 1, 2025 1:45pm - 2:00pm CDT

Foster 2

Precision crop load management is important for increasing yield, fruit size, and quality of apple production, particularly for the ‘Honeycrisp’ variety, which is highly susceptible to biennial bearing and difficult to thin. The MaluSim model, developed at Cornell University, can be used to guide crop load management by modeling carbohydrate balance to optimize fruitlet thinning. However, this model was developed using tree performance in New York and may not account for higher temperatures in Washington State, which may affect canopy growth and development. The objective of this study was to assess early season canopy growth and evaluate carbon partitioning of Honeycrisp apples grown in Washington state climatic conditions. The first experiment compared the canopy growth of Honeycrisp topworked in 2016 onto a ‘Granny Smith’ planting with M.9T337 as a rootstock. The topworked trees were trained to single, double, or triple-axis trees. The second experiment assessed carbon partitioning of Honeycrisp trees conducted under single, double, and triple leader(s) training systems. Training systems significantly impacted shoot length and the number of shoots. Single-axis trees had significantly longer shoot lengths and higher shoot numbers than the double and triple-axis training systems. Canopy imaging was also used to assess canopy infill and light interception. The second experiment weighed the biomass partitioning of the various tree parts (spurs, 1-year growth, leaves, branches, roots, rootstock, inter-stem, and fruits). Below-ground portions of all training systems accounted for more biomass than above-ground portions. There was smaller wood and a greater proportion of spur buds in the double and triple-axis trees compared to single-axis trees. The differences in carbon partitioning and canopy development among different training systems compared to the types of trees used when developing the MaluSim model may affect how the MaluSim model performs.

Speakers

Harriet Ampofo

Washington State University-TFREC

Co-authors

Lee Kalcsits

Washington State University-TFREC

Friday August 1, 2025 1:45pm - 2:00pm CDT
Foster 2

Oral presentation, Pomology 4

Subject Pomology
Poster # csv
Funding Source USDA-SCBGP

2:00pm CDT

POM 4 - Improving Apple Crop Load Management Using Digital Tools: Matching Data Collection With Accurate Treatment Application

Friday August 1, 2025 2:00pm - 2:15pm CDT

Foster 2

Multiple digital imaging companies can gather apple orchard data to map flower bud load, flower cluster number and fruitlet number at the tree level. However quickly matching photographic survey data to maps which can accurately guide management decisions remains challenging. Over the past year, Cornell University has partnered with several companies which can collect and apply survey data to guide precision pruning, precision blossom thinning, and precision fruitlet thinning in high density apple orchards of Western New York. Photographs and surveys from companies which collect single tree information provided the highest resolution information to guide precision sprayers. Precision sprayers were able to successfully apply treatments to the tree level, but the survey data first needed to be transformed into task maps which defined unique tree positions using the same GPS system used to collect the data and then control the sprayer to avoid an offset. Improving orchard management using digital tools may help improve crop load management but the success of this effort depends on the treatment resolution (section of row vs individual tree) as well as when crop load was modified, such as pruning, blossom, and or fruitlet timing.

Speakers

Brian Lawrence

Cornell University

Co-authors

Terence Robinson

Cornell University

Yu Jiang

Cornell University

Friday August 1, 2025 2:00pm - 2:15pm CDT
Foster 2

Oral presentation, Pomology 4

Subject Pomology
Poster # csv

2:15pm CDT

POM 4 - High relative growth rates during early fruit development in apple are facilitated by processes that promote cell produc

Friday August 1, 2025 2:15pm - 2:30pm CDT

Foster 2

Fruit growth across various stages of development determines the extent of final fruit size, and is therefore of high economic value. The two main processes that mediate growth, cell production and cell expansion, contribute differentially to growth across various stages of fruit development. In apple, growth during early fruit development is largely facilitated by cell production. Mid and late stages of fruit development display growth mediated mostly by cell expansion. Mechanisms that regulate these processes and consequently the growth rates of fruit are not well understood. The objective of this study was to determine the molecular processes associated with higher relative growth rates (RGR) in the apple fruit during different stages of development. To address this objective, we exploited the inherent natural variation in RGR within a population of ‘Empire’ fruit. These evaluations were performed during early and mid-fruit development stages. At each stage, change in fruit size (volume) was determined across a 4 d interval to obtain the RGR. The population of fruit was grouped into two classes based on their RGR values: High and Low RGR. RNA-sequencing analyses were performed to compare the transcriptomes of the two classes of fruit. During early fruit development, the High RGR class fruit displayed 1.46-fold greater growth rates than the Low RGR fruit. Transcriptome analysis indicated that genes associated with cell division processes such as HISTONES, CYCLINS and CYCLIN DEPENDENT KINASES were more abundant in fruit with higher RGR. During mid-fruit development, fruit displayed relatively lower RGR. Yet the High and Low RGR fruit classes differed by 1.76-fold. However, only a limited set of genes, mostly associated with oxidation-reduction processes, were differentially expressed across these two groups. Overall, these data suggest that processes that regulate cell division control the growth rates of apple fruit during early fruit development.

Speakers

Anish Malladi

University of Georgia

Co-authors

Bayleigh Roussel

University of Georgia

Friday August 1, 2025 2:15pm - 2:30pm CDT
Foster 2

Oral presentation, Pomology 4

Subject Pomology
Poster # csv

2:30pm CDT

POM 4 - Rethinking Pollination and Crop Load Management: Multi-Year Evaluation of Insect-Exclusion Netting in Apple Orchards

Friday August 1, 2025 2:30pm - 2:45pm CDT

Foster 2

Thinning remains a critical yet challenging practice in apple production, especially for organic systems where chemical tools are limited. Since 2017, our research has evaluated the use of insect-exclusion netting as a sustainable, non-chemical strategy to simultaneously manage crop load and reduce pest pressure. What began as small-scale trials has expanded to commercial-scale implementation in Michigan, supported by USDA funding. Over the course of eight years, we evaluated netting on a diverse suite of cultivars including 'Gala', 'Fuji', 'SweeTango’, Liberty’ and 'Honeycrisp' in multiple locations. Canopies were enclosed at varying bloom stages, and results consistently demonstrated that netting significantly reduced fruit set in proportion to the amount of open bloom at the time of application. Cultivar-specific responses were observed: Gala’ and 'Fuji' achieved optimal crop loads when netted between 25% and 50% bloom, while ‘SweeTango’ and 'Honeycrisp' often required higher percentage of open bloom. In several trials, netted trees yielded commercial fruit numbers without requiring hand or chemical thinning. Fruit size and quality remained similar to conventional treatments, while seed content was reduced without negatively impacting fruit development. In many cases, trees netted at the ‘pink’ phenology stage produced adequate fruit set of low seed-content fruit despite the exclusion of pollinators. Importantly, molecular genotyping using 16 SNP markers revealed that seed parentage in netted canopies overlapped with known pollinizer genotypes. This ruled out self-pollination and suggested that wind, rather than insects, facilitated cross-pollination under netted conditions. Additionally, fruit retention was linked to seed content at the population level, not the individual fruit level, further supporting the viability of non-insect pollination under netting. In 2024, we implemented nets in commercial orchards in Michigan to validate scalability. Netting treatments at 30% and 60% King Bloom produced yields and fruit quality metrics comparable to conventional thinning. Pest monitoring confirmed male codling moth exclusion and reduced San Jose scale captures, though woolly apple aphid and flower thrips populations increased under nets given the exclusion of natural predators Collectively, our results indicate that exclusion netting is a promising, multifunctional tool for organic and sustainable apple production. Beyond thinning and pest control, netting systems enable effective crop set through wind-mediated pollination, challenging traditional assumptions of insect dependency. Adoption of this system may require revised orchard design to optimize pollen flow, but offers significant environmental benefits, including reduced chemical inputs, support for pollinator conservation, and improved climate resilience in Midwestern apple orchards.

Speakers

Mokhles Elsysy

Michigan State University

Co-authors

Todd Einhorn

Michigan State University

Friday August 1, 2025 2:30pm - 2:45pm CDT
Foster 2

Oral presentation, Pomology 4

Subject Pomology
Poster # csv
Funding Source SARE

2:45pm CDT

POM 4 - Fruit Doubling in Montmorency Tart Cherry (Prunus cerasus)

Friday August 1, 2025 2:45pm - 3:00pm CDT

Foster 2

Heat or drought stress during critical stages of bud differentiation can result in the formation of double pistils in many stone fruits. If these flowers are pollinated, the resulting malformed “double” or “twin” fruit are not marketable. The frequency of double fruit in Utah tart cherry orchards has increased in recent years. To determine the critical time of flower bud formation for doubling, whole-tree treatments of induced heat stress were imposed for one-week intervals from July to September in 2022 and 2023. The resulting doubling incidence was observed in the following spring and at harvest. There were seasonal differences in the frequency of doubled fruit between years, but the highest incidence of doubling in both years resulted from induced heat stress at 4 to 6 weeks after harvest. Understanding this timing is important in targeting alleviation strategies such as evaporative cooling or spray-on orchard protectants.

Speakers

Brent Black

Utah State University

Co-authors

Josette Moon

Utah State University

Friday August 1, 2025 2:45pm - 3:00pm CDT
Foster 2

Oral presentation, Pomology 4

Subject Pomology
Poster # csv
Funding Source Utah Department of Agriculture and Food Specialty Crop Block Grant

3:00pm CDT

POM 4 - Diversity and Abundance of Insect Pollinators in Pawpaw (Asimina triloba), an Emerging Commercial Fruit Crop

Friday August 1, 2025 3:00pm - 3:15pm CDT

Foster 2

Pawpaw (Asimina triloba) is a temperate, deciduous fruit tree native to North America and a member of the custard apple family (Annonaceae). It produces unique, flavorful fruit with a taste resembling mango, banana, and pineapple, making it valuable for various value-added products such as jams, bread, ice cream, and brandy. Pawpaw fruits are also rich in nutrients, vitamins, and antioxidants, contributing to their increasing commercial potential. However, fruit sets in some cultivars may be limited due to the protogynous and self-incompatible nature of pawpaw flowers, which require external pollinators for successful fertilization. Unlike many fruit-bearing species, pawpaw has been thought to be pollinated by beetles and flies rather than bees. However, their abundance and role in pollination remain understudied. This study aims to identify and quantify insect visitors to flowering and non-flowering branches of two pawpaw cultivars, ‘Sunflower’ and ‘Susquehanna’. Ten trees of each cultivar were selected, and a completely randomized design was implemented setting up 20 wire cage traps coated with tangle-trap adhesive (The ORTHO Group, Marysville, OH 43040) on flowering and 20 on non-flowering branches. After an 18-day flowering period, the traps were collected, and captured insects were identified to the level of order and their abundance recorded. In 2024, 20 traps were placed at control sites outside the orchard (roadsides and fields), and nine days of direct observations were conducted to document insect activity on male and female flower stages. Data were analyzed using RStudio v.2023.09.1 (Posit, PBC, Boston, MA) and subjected to an ANOVA, with flowers, cultivars, and years as treatment factors, followed by Least Significant Difference (LSD) means separation. Results from 2023 indicate a significantly higher abundance (p-value< 0.0001***) of Coleopteran insects on both flowering and non-flowering branches of ‘Sunflower’ and ‘Susquehanna’ compared to 2024. In 2023 Coleoptera was significantly higher in the flowering branch (p-value 0.0255*) and had an interaction of cultivar and flowers (p-value 0.04767*) while in 2024 Diptera was substantially higher in the non-flowering branches (p-value 0.04009 *) This study provides valuable insights into the pollination ecology of pawpaw, aiding in the development of strategies to enhance fruit set and improve commercial production as the species transitions into broader commercialization.

Speakers

Subas Thapa Magar

Kentucky State University

A major change happened when the tragedy of Corona hit the world. Hi, I am Subas Thapa Magar, a graduate research assistant under the supervisor Dr. Kirk Pomper. I am currently working on Pawpaw (Asimina Triloba), the native fruit tree of the United States of America, and my research... Read More →

Co-authors

Oral presentation, Pomology 4

Subject Pomology
Poster # csv