ASHS 2025 Conference

Grafting is an effective management strategy in watermelon crop against soil borne pathogens. Carolina strongback (SB) rootstock used for grafting, is resistant to both fusarium wilt and root knot nematodes which are devastating soil borne pest of watermelon. Recent experiments have shown that SB grafted plant have higher plant vigour and bear fruits 7-10 days later than regulate plants leading to farmers losing early profitable watermelon market. Similarly, grafted watermelon nursery is 4-5 times more expensive than regular nursery which leads to reluctance among growers for adoption of this effective management strategy. To fill these gaps for informed adoption of SB grafted nursery, a field experiment was conducted at Blackville SC. The experiment comprised of three transplanting times (April 1, 10 and 20) and four transplant densities (1800 non-grafted, 1800, 1550 and 1300 grafted plants/acre) in a split plot design. The highest plant vigour rating was observed in SB grafted nursery at 1800, 1550 and 1300 plants/acre as compared to 1800 non-grafted plants/acre. April1 and April 10 recorded the highest fruit yield at first harvest as compared to April 20 transplanting. Similar fruit yield was observed for different transplanting times and density at second, third and fourth picks. Transplanting of SB grafted plants at 1300 plants/acre recorded the highest total fruit yield as compared 1800 and 1550 grafted and 1800 non-grafted plants/acre. Highest gross and net returns were observed in 1300 grafted plants/acre as compared to 1800, 1550 grafted and 1800 non-grafted plants/acre. The experiment will be repeated in 2025 to collect two years of data.

Evaluating Rootstock for Fresh Market Tomato Yield, Quality and Sustainability Tsedeniya Getahun, Harlene Hatterman-Valenti, Collin Auwarter Department of Plant Science, North Dakota State University Fresh market tomatoes are widely grown by specialty crop producers in North Dakota due to their profitability in the fresh market/local foods segment. However, with North Dakota's short growing season, growers often use high-tunnels for season extension to protect the crop from early and late frost events. Unfortunately, tomato plants often face numerous soil and disease challenges due to limited growing space in the high tunnel. Inadequate leaching of soluble salts in the soil and limited crop rotation contributes to salt and disease inoculum buildup in the soil that threatens the health of tomato plants and may cause serious losses in high tunnels. This two-year project with the first year completed in 2024, aims to evaluate the improvement of tomato production by grafting an heirloom, fresh market and paste tomato cultivar with excellent fruit quality characteristics onto rootstocks that are resistant to various abiotic/biotic stresses under high tunnel production. Tomato scion ‘Bigboy’, ‘Brandywine’ and ‘San Marzano’ (indeterminate), and ‘BHN 589’ (determinate) were grafted on to six rootstocks: ‘Arnold’ (generative), ‘DR0141TX’ (generative and vegetative), ‘Estamino’ (generative), ‘Fortimino’ (vegetative), ‘Maxifort’ (generative) and ‘Multifort’ (generative). Scion selection significantly influenced marketable yield, whereas rootstock had no significant impact. This effect was observed in ‘Big Boy’ but not in ‘San Marzano’ or ‘Brandywine’. ‘Big Boy’ grafted onto ‘Multifort’ or ‘Fortamino’ produced the highest marketable yield, followed by ‘Arnold’, Maxifort’, and ‘DR014TX’, with the lowest yield observed in non-grafted Big Boy’. ‘DR0141TX’ and ‘Multifort’ increased stem diameter and San Marzano tomatoes grafted onto Maxifort, Multifort, and Fortamino had the tallest plants. The trial will continue for another year to further evaluate the benefits of grafting for high tunnel tomato production in North Dakota.

The goal of the project is to understand the suitability of different scions when grafted onto commonly used watermelon rootstocks in California. This scion variety trial was conducted in 2024 within a commercial watermelon field near Stockton, California. Six different scions (Captivation, Fascination, Citation, Embasy, Melody, and Summer Breeze), categorized by horticultural characteristics such as maturity, fruit size, and color, were grafted onto three widely used watermelon rootstocks in California (Camelforce, Cobalt, and Carolina Strongback). The three rootstocks are grouped into interspecific hybrid squash (Cucurbita maxima x Cucurbita moschata) and Citron (Citrullus amarus). The field experiment was arranged as a randomized block design including eighteen treatments replicated three times. Each plot was 60 ft long and contained 10 triploids and 3 grafted pollenizers (Sentinel). The field was mechanically transplanted on May 14, 2024. In-season plot maintenance included vine separation multiple times to ease data collection and harvest. Canopy coverage was measured using a handheld crop sensor starting at 10 days after transplanting and thereafter at an approximate interval of two weeks for a total of eight measurements. With the help of farm crew, three harvests were conducted on August 5, 12, and 26. Total yields from each harvest and fruit quality taken from the first harvest were recorded and compared among the rootstock-scion combinations. For quality assessment, fruit length and width were measured by yardstick. Fruit flesh firmness was measured using a fruit penetrometer at the spots 1/3 and 2/3 distance from the blossom end after a melon was cut in half. Rind thickness at the blossom and stem ends were measured with a caliper. Sugar content (⁰Brix) was measured by scooping the center flesh of each half and reading the results through a portable reflectometer. Canopy coverage showed no significant differences among the treatments. For yield, four out of six scions (Fascination, Citation, Embasy, and Melody) produced the highest total yield (ton/acre and no/acre) when they were grafted onto Camelforce, while Captivation and Summer Breeze resulted in higher total yield when grafted with Carolina Strongback. A notable difference was observed in fruit quality for ⁰Brix and firmness that Carolina Strongback produced the lowest firmness and highest ⁰Brix when grafted with all six scions. These results provide a helpful advantage for growers in California who are considering grafting in their production. Continuous assessments will be conducted to further aid in the understanding of field performances from different rootstock-scion combinations.

New Mexico green chile is a labor-intensive crop, with harvesting posing increasing challenges due to labor shortages and rising costs. To meet growing consumer demand, farmers are transitioning to mechanical harvesting, traditionally reliant on direct seeding, which promotes strong taproots and minimizes uprooting. However, transplant seedling establishment, which allows multiple harvests, produces a root system less suitable for mechanical harvesting. This study evaluated transplant sowing methods to develop taproots compatible with efficient mechanical harvest. In 2024, ‘NuMex Odyssey’ was planted using three methods, direct seeding, ihort® Q plugs, and paperpots®, at the NMSU Agricultural Science Center in Los Lunas, NM. The study employed a randomized complete block design with five replications. Plant architecture, root, and yield data were collected. Preliminary findings show no statistical difference in marketable green fruit yield among the planting methods during mechanical harvest. However, taproot lengths of ihort Q plugs and direct-seeded plants were significantly longer than those of paper pot transplants. These results suggest that taproot length did not impact marketable green fruit yield during mechanical harvest. The findings indicate that ihort Q plugs and paper pot transplanting methods have potential for efficient mechanical harvesting of New Mexico green chile.

Bare-root transplants are the primary planting material used in strawberry production. They are grown in open-field conditions and dug up at maturity before shipment to fruit production sites. Delayed digging exposes transplants to different amounts of winter chilling (

Consumers seek locally grown tomatoes for their superior flavor, making them a valuable crop for local vegetable growers. Tomato production can be difficult with the temperature requirements for fruit set, development, and ripening. Optimum growing conditions are available for a short period in Oklahoma, causing a distinct decline in production during late July and August. A field experiment was designed to investigate the success of late planted, heat tolerant tomatoes in Oklahoma field conditions, as well as explore the relationship between physiological responses and season-long temperatures. The experiment utilized a split plot design with three transplanting dates as whole plot and five cultivars as subplot. ‘Red Snapper’ and ‘Laguna Red’ were selected as potential heat sensitive cultivars. ‘Bella Rosa’, ‘Volante’, and ‘Florida 91’ were selected as heat tolerant cultivars, based on previous trial information. Planting occurred on April 23, May 9, and May 23 to represent early, mid, and late plantings dates, respectively. Physiological measurements were collected every two weeks and included electrolyte leakage, net photosynthetic rate, stomatal conductance, leaf temperature, and chlorophyll fluorescence. Plants were harvested routinely from June to the end of August. Cultivars were not found to be significantly different in the trial for yield or physiological responses. The early planting date was the most productive, compared to mid and late. Yield dropped dramatically for all planting dates in August. There was a strong positive correlation between electrolyte leakage and temperature and a moderate negative correlation between photosynthetic rate and average daily temperature. These correlations indicate that physiological parameters may be able to provide insight into late season thermotolerance. Future research will involve cultivar screenings in controlled environments to promote a wider range of responses to temperature.

Blueberries (Vaccinium sect. Cyanococcus) are prone to drought due to their shallow root system and limited ability to uptake water from the soil. Previous research has shown rabbiteye (Vaccinium virgatum) blueberries to be more tolerant than highbush varieties (Vaccinium corymbosum L.) to abiotic stresses. However, little is known about their response to drought and whether there are ecotype- or cultivar-specific responses. In order to breed for more drought-tolerant cultivars, this study aims to identify drought tolerant mechanisms within existing cultivars of both southern highbush (SHB) and rabbiteye (RE) blueberries. We evaluated seven cultivars of southern highbush and rabbiteye blueberry for physiological response and fruit quality characteristics under water deficit and recovery across two consecutive years. Overall, drought was found to decrease photosynthesis, stomatal conductance, electron transport rate, leaf relative water content, specific leaf area, chlorophyll content, maximum rate of Rubisco carboxylation (Vcmax) and maximum rate of RuBP regeneration (Jmax). Additionally, drought treatment was found to significantly decrease yield and average berry weight while increasing total soluble solids and berry firmness. Misty (SHB) was identified as the most drought tolerant cultivar due to maintenance of CO2 assimilation, stomatal conductance, and yield under drought conditions across both years, while Suziblue (SHB), Powderblue (RE), and Vernon (RE) were found to be more sensitive to water deficit. Star (SHB) was tolerant of drought in the short term but performed worse under repeated drought events.

Regional recommendations for blueberry irrigation exist, but few studies report the actual amount of water needed. The goal of this multiyear project was to determine the water requirements for growing northern highbush blueberry (Vaccinium corymbosum) in the U.S. Pacific Northwest. Weighing lysimeters were used to measure crop evapotranspiration (ETc) of three cultivars with various ripening seasons, including ‘Duke’ (early season), ‘Top Shelf’ (mid-season), and ‘Aurora’ (late season). Each lysimeter was constructed from steel and included a large soil tank (1.5-m wide × 0.9-m long × 1.0-m deep) positioned on four hermetically sealed, shear-beam load cells, housed inside an underground chamber. Plants were spaced 0.9 × 3.0 m apart in the lysimeters (one plant/lysimeter) and surrounding field (0.4 ha) and managed using standard industry practices, including raised planting beds mulched with Douglas fir (Pseudotsuga menziesii) sawdust, grass alleyways between the beds, irrigation with two lines of drip tubing per row, and fertigation with nitrogen and other nutrients as needed. During the first year after planting, ETc totaled 94–104 mm, depending on the cultivar, or 18–19% of total potential evapotranspiration (ETo) from initiation of the measurements on 1 June to when irrigation was turned off for the season on 23 September 2023. That year, crop coefficients (Kc), calculated by dividing ETc by ETo obtained from a nearby agricultural weather station, averaged 0.11, 0.15, 0.27, and 0.41 each month from June through September, respectively. The following year, the plants were lightly cropped (0.2–0.8 kg of marketable fruit per plant), and ETc totaled 175–343 mm, or 30–59% of total ETo. At that point, Kc averaged 0.31, 0.34, 0.45, 0.61, and 0.61 each month from 14 May to 30 September, which was the entire timeframe in which the plants were irrigated. This project is ongoing and will continue until the plants reach full production. Once the study is finished, a set of seasonal Kc curves will be developed for each cultivar and uploaded to regional websites called AgriMet and AgWeatherNet, where they will be used to automatically calculate irrigation water requirements using meteorological data from local weather stations.

The southeastern United States is a major producer of blueberries (Vaccinium corymbosum), however extreme weather events pose significant threats to blueberry production. On September 24, 2024, Hurricane Helene made landfall in Georgia, causing substantial damage to commercial blueberry fields, including uprooted or leaning plants, broken branches, and defoliation. Our project examines the effectiveness of staking leaning plants and humic acid application to enhance the recovery of blueberry plants after hurricane damage. Trials were conducted in five commercial sites with three different cultivars: ‘Farthing’, ‘Legacy’, and ‘Optimus’. Treatments included staking of leaning plants and the application of humic acid alone or in combination. Plant physiological responses were assessed using SPAD (chlorophyll content), leaf area index (LAI), chlorophyll fluorescence, and stomatal conductance (Gsw). Preliminary data indicate that staking leaning plants improved light interception, chlorophyll content, and photosynthetic efficiency in damaged blueberries. The application of humic acid did not result in enhanced plant recovery beyond staking alone. Root and canopy assessments are ongoing and will help determine whether the practice of staking damaged plants and the incorporation of humic acid contributes to long-term plant recovery. Our study will help blueberry producers implement evidence-based strategies to increase the resilience of blueberry fields following extreme weather events.

Substrate production in pots has emerged as a popular method for growing highbush blueberry (Vaccinium corymbosum). However, there is limited knowledge on the best strategies for irrigation in substrate. To address this issue, a multiyear study was conducted in a retractable-roof greenhouse using ‘Legacy’ blueberry to determine an optimal combination of drip emitters (two, four, or eight emitters per pot) and irrigation set point (-2 or -4 kPa) and frequency (a single continuous pulse of up to 45 minutes or short 3-minute pulses every 15 minutes to reach container capacity). The plants were grown in 25-L pots filled with a mix of peat, coir, and perlite. Tensiometers were installed horizontally into the center of the pots to monitor the matric potential and to determine when to trigger irrigation. Irrigation was triggered automatically using a data logger and applied until the pots reached container capacity determined by small weighing lysimeters. Yield was highest in plants with eight emitters in the second year (first year of fruit production), but this difference diminished in year 3. A similar relationship was observed for aboveground biomass. Root size was also highest with eight emitters. Leachate pH and EC were mostly similar among treatments, but EC was more uniform throughout the pot with eight emitters. In contrast, the lower set point and shorter irrigation frequency decreased the ability of the pots to reach container capacity, particularly when the plants were irrigated with only two emitters per pot. Overall, the plants grew best when irrigation was triggered at -2 kPa and applied in single continuous pulses with four or eight emitters per pot.

Day length and temperature interactively influence flower bud initiation in blueberry (Vaccinium corymbosum interspecific hybrids) plants. When days are short and temperatures are low, blueberry plants initiate flower buds rather than vegetative buds. Night interruption and/or warmer temperatures limit flower bud initiation. Once differentiated, flower buds enter endodormancy, restricting reproductive development to specific times of the year. Some genotypes in the University of Florida Blueberry Breeding and Genomics program have been observed to bloom in the middle of the summer under long days and warm temperatures. To investigate this phenomenon, we conducted a controlled-environment experiment to assess flower bud initiation and dormancy responses in a summer-blooming genotype, ‘FL16-64’, compared to the standard southern highbush cultivar ‘Arcadia’. Plants were grown in growth chambers with factorial combinations of temperature and photoperiod treatments. Temperature regimes mimicked Florida field conditions: warm (28 °C day / 20 °C night) and cool (18 °C day / 10 °C night). Photoperiods included short (8 hours), neutral (12 hours), long (16 hours), and interrupted (8 hours 1 hour of night interruption) day lengths. There were 6 plants of each genotype per temperature-photoperiod combination. Results showed that warm temperatures promoted vegetative growth in both genotypes. ‘Arcadia’ developed flower buds primarily under short days and cool temperatures, and these buds entered endodormancy after differentiation. In contrast, ‘FL16-64’ initiated flower buds across all temperature and photoperiod treatments. Moreover, flower bud development was enhanced under warmer temperatures and neutral day lengths. Notably, these buds bypassed dormancy and progressed directly to bloom. These findings indicate that ‘FL16-64’ exhibits day-neutral flower bud initiation and some of its flower buds lack endodormancy, characteristics consistent with an everbearing growth habit. Everbearing blueberry genotypes could be used to produce blueberries during the domestic off season in Florida.

Crop protection measures, cultural practices, nutrient and irrigation management, rootstock selection, and other studies have been conducted to alleviate the devastating bacterial disease of huanglongbing (HLB, aka citrus greening) in recent years. However, there is no single cure for HLB caused by Candidatus Liberibacter asiaticus, which is spread by the Asian citrus psyllid, Diaphorina citri Kuwayama. The objectives of the study were to assess whether tree growth, soil and leaf tissue nutrient concentrations, fruit yield, and postharvest quality can be improved through improved nutrient management using selected rootstocks. The study was conducted on ‘Hamlin’ citrus trees [Citrus sinensis (L.) Osbeck] budded on Cleopatra mandarin (Citrus reshni) or Swingle rootstocks [Citrus paradisi Macf. Poncirus trifoliata (L.) Raf.] from 2019 – 2021. The study was conducted in a split plot design with two rootstocks as main plots, three nitrogen rates (168, 224, and 280 kg ha-1) as sub-plots, and secondary macronutrients (control, Ca or Mg-thiosulfates at 45 kg ha-1 each, and a combination of Ca and Mg at 22.5 kg ha-1 each) replicated four times. Results indicated that soil ammonium nitrogen (NH4-N) and nitrate nitrogen (NO3-N) were significantly accumulated in an oscillating (between spring and summer seasons) pattern for soil NH4-N and persistent accumulation of NO3-N on both rootstocks. Leaf Ca and Mg nutrient concentrations were significantly greater in Cleopatra than Swingle rootstocks. Trees on Swingle rootstocks react greater than those on Cleopatra rootstocks. Control trees had a lower LAI than those that received either Ca and/or Mg treatments, and the impact is significantly prevalent on Swingle than on Cleopatra rootstocks. Trees on Cleopatra had greater canopy volumes than Swingle rootstocks. However, the impact of secondary macronutrients manifested only after the third year of the study. Fruit yield significantly increased with a magnitude of 1.8× in the trees that received combined Ca and Mg treatments than a control tree. Greater fruit total soluble solids were detected in trees that received Mg or combined Ca and Mg treatments. Hence, nutrient management can enhance tree growth, fruit yield, and postharvest quality and can be used as an immediate solution until the HLB can be permanently eradicated.

Huanglongbing (HLB), a.k.a. citrus greening, is an endemic disease significantly impacting Florida and Texas citrus production. HLB-affected trees are compromised in the canopy and root health, often found with heavy loss of root mass that impairs water and nutrient uptake, leading to nutrient deficiencies. The prevalent presence of the suspected causal organism of HLB, Candidatus Liberibacter asiaticus (CLas) bacterium, in the citrus phloem leads to a cascade of active defense responses triggered by plant-pathogen interactions. One of the crucial outcomes of the interactions is the production of reactive oxygen species, leading to excessive oxidative stress that, over time, weakens tree health. Therefore, this research investigated the therapeutic strategies to mitigate nutrient deficiencies and HLB symptoms, attenuate reactive oxygen species load, and improve the production of premium grapefruits in trees affected by HLB by combining an integrated approach of micronutrient applications with antioxidants. The experiment design consisted of the foliar application of micronutrients, zinc (Zn), iron (Fe), and manganese (Mn) varied in two rates: 2 quarts/acre (control) and 3 quarts/acre that were conducted alone or in combination with gamma-aminobutyric acid (GABA), uric acid, and gibberellic acid (GA). The micronutrients, GABA, and uric acid applications were conducted at an interval of three months, while GA sprays were limited between blooming to the pre-harvest period in the HLB-affected mature grapefruit grove with a tree density of 104 trees/acre in the Lower Rio Grande Valley of Texas. The results demonstrated that merely increasing micronutrient application to 3 quarts/acre improved canopy health, with healthy (non-HLB-symptomatic) canopy quadrants reaching an average of 30% compared to 16.7% in the control treatment. Moreover, the standalone 3-quarts/acre significantly improved the yield of premium-size grapefruit to 25% compared to 6.2% in 2-quarts/acre only. The combination of GA (10 Fl.Oz/acre) and GABA (8 gm/tree) with control micronutrient treatment enhanced healthy canopy quadrants to 33% and 38%, respectively, compared to 19% in the micronutrient-only control. In 3 quarts/acre, GA and GABA showed synergistic effects in improving the canopy health by alleviating HLB severity. This applied research provides a practical framework for translating laboratory findings into field applications for managing HLB-affected trees. The integrated approach of combining enhanced micronutrient applications with antioxidants and phytohormones shows promise in mitigating HLB symptoms and improving fruit yield, particularly in the premium size category.

Nitrogen (N) is an essential nutrient required to support citrus yield and fruit quality. Its bioavailability to the tree must be continuous to support adequate biomass production, especially at key phenological stages such as vegetative flush and fruit setting. However, most commercial nutrition programs in southern Texas deliver synthetic fertilizer on average twice per year when not drip-irrigated. Although adoption of fertigation strategies continues to gain ground, the rate of transition is of low velocity, and a percentage of orchards is still flood-irrigated. In these systems, trees rely on the soil storage capacity to meet permanent nutrient demand. This field study investigated the effects of traditional N management practices on two orchards with different rootstock * scion combinations. We evaluated the effects of different N fertilization rates on fruit growth and postharvest traits such as brix, and size-class distribution. Our preliminary data indicates that despite trees growing in similar soil properties, they exhibited differences in fruit growth rate, and size-class distribution of fruits. Moreover, certain rootstocks * scion combinations exhibited superior fruit yield and quality. Continue refinement of nutrient management practices, especially N application is imperative to support tree long-term productivity under the constant pressure of pathogens in commercial settings.

Soil organic matter (SOM) is a key determinant of soil health, directly influencing structure, moisture retention, nutrient availability, and microbial activity. Among soil amendments, biochar has gained attention for its potential to enhance soil fertility and support plant productivity. However, its influence on citrus root system architecture and nutrient uptake across different rootstocks remains underexplored. This study evaluated the effects of four biochar concentrations (0%, 10%, 20%, and 30% v/v) mixed with native field soil on four citrus rootstocks: ‘Sour Orange’, ‘Swingle’, ‘US-802’, and ‘US-942’. Plants were grown under controlled greenhouse conditions for 16 weeks. Root system architecture traits: total root length, surface area, root volume, and number of forks, were quantified using WinRHIZO™ analysis. Soil parameters, including pH, cation exchange capacity (CEC), moisture content, and SOM, were assessed post-harvest, alongside plant tissue nutrient concentrations (P, K, Ca, Mg, Mn). The 20% biochar treatment significantly enhanced root morphological traits across all rootstocks, with increases of up to 35% in total root length and 40% in surface area compared to the control. Plant tissue analysis revealed elevated macro- and micronutrient concentrations in the 20% treatment, particularly for P, K, Ca, and Mg. Soil analysis showed progressive improvements in pH, SOM, CEC, and moisture content with increasing biochar concentration, with the highest values recorded at 30%. While higher biochar rates improved soil physicochemical properties, the 20% concentration provided the most balanced benefits, optimizing both root development and nutrient uptake. These findings suggest biochar, particularly at moderate rates, may be an effective amendment for improving soil fertility and citrus root system performance in nutrient-limited soils.

The origin of the cultivated strawberry traces to the 1700s, when representatives of the octoploids F. chiloensis and F. virginiana – previously brought to Europe from South and North America, respectively – were grown in proximity in European horticultural gardens. Cross-pollination produced hybrids that were quickly recognized for their unique and desirable combinations of morphological and fruit characteristics and were brought into cultivation and breeding (Hancock 1999). Traditional breeding objectives are the following (Rosati 1993): a production of relatively large berry size in order to limit the cost of harvest, a firmer fruit with regular shape and long shelf life, which is easy to harvest, an increase in the total yield, an improvement in fruit appearance (color, shape, brightness), and disease resistances. The recent origin makes F. ananassa one of the youngest of contemporary crop species. Bottle neck existing in strawberry traditional breeding is that it is difficult to manipulate single genes to control strawberry characteristics, modern genetic transformation and genome editing technology provide promising ways for single gene control in strawberry. Diploid strawberry transformation has been reported, limited report was available for transformation of octoploid cultivated strawberry. We report an efficient Agrobacterium mediated strawberry transformation system with the aid of GFP visual selection. First three open leaves from 4 weeks old in vitro plants were harvested, and leaflets were separated from each other and inoculated with Agrobacterium tumefaciens GAV3101 contains a binary vector with GFP and hygromycin resistance genes. Transgenic callus and shoots obtained with GFP visual selection with high efficiency. PCR double check proved transgenes in transgenic plants. Transgenic plants are phenotyping in the greenhouse.

Flowering plays a crucial role in blueberry production since fruits develop from flowers. In plants, FLOWERING LOCUS T (FT) and TERMINAL FLOWER 1 (TFL1), which interact with the bZIP transcription factor FD, are central regulators of flowering. This study investigates the roles of their homologs in blueberries, VcTFL1 and VcFD, using RNA interference (RNAi) to silence these genes. Two RNAi constructs, VcFD-RNAi and VcTFL1-RNAi, were introduced into the northern highbush blueberry (Vaccinium corymbosum) cultivar ‘Aurora’ via Agrobacterium tumefaciens-mediated transformation. Phenotypic analysis of first-generation (T0) transgenic plants accessed flowering time, architecture, fruit and leaf bud development, plant height, and branching. Preliminary results revealed that VcFD-RNAi plants produced fewer shoots, while VcTFL1-RNAi plants exhibited reduced branching per shoot compared to nontransgenic ‘Aurora’ controls. Significant differences in leaf bud number were also observed between nontransgenic and transgenic lines. VcFD-RNAi plants were smaller than nontransgenic ‘Aurora’ plants, whereas no significant size difference was detected between VcTFL1-RNAi and wild-type plants. Transcriptomic comparisons between nontransgenic ‘Aurora’ and transgenic lines revealed differentially expressed genes (DEGs). The VcFD-RNAi vs. nontransgenic ‘Aurora’ identified 2,108 DEGs, including 49 flowering-related genes, 116 genes hormone pathway genes, and 57 sugar metabolism genes. Similarly, the VcTFL1-RNAi vs. nontransgenic ‘Aurora’ uncovered 2,030 DEGs, with 52 flowering-related, 111 hormone-related, and 55 sugar-metabolism-associated genes. Ongoing analyses of these DEGs aim to elucidate the molecular mechanism underlying VcFD- and VcTFL1-mediated flowering regulation of flowering and development in blueberry. This study will reveal the functional roles of VcFD and VcTFL1, offering potential targets for genetic improvement of blueberry architecture and yield.

Botrytis cinerea is the second most economically important fungal phytopathogen causing gray mold disease. Multiple fungicide-resistant B. cinerea strains have also been reported, especially in strawberries, raspberries, grapes, and tomatoes. RNA interference (RNAi) is a post-transcriptional gene silencing mechanism in all known eukaryotes. The exogenous application of dsRNAs to knock down the target organism's essential genes is called spray-induced gene silencing (SIGS). This non-transgenic SIGS-based approach has emerged as an appealing alternative biofungicide. Despite the great potential of sprayable RNAi-based pesticides, this innovative technology encountered challenges. The low stability and the limited uptake efficiency of dsRNA are significant challenges facing SIGS. Nanomaterials-based delivery systems and structured modification of dsRNA molecules could be innovative SIGS approaches for improving its stability, uptake efficiency, and biofungicidal efficacy. This study aims to develop sprayable RNAi (SIGS) solutions by modifying dsRNA structure and using chitosan-based nanoparticles to control fungicide-resistant B. cinerea. Chitosan nanoparticles (CNPs) were generated using ionic gelation, and different forms of double-stranded RNA (dsRNA), either linear or secondary-structured, were loaded into them. The positive charges from the amine groups present in chitosan facilitated the self-assembly of the CNPs-dsRNA complex through electrostatic attraction. The stability of CNPs-dsRNAs complexes was evaluated ex-vivo by incubating naked-dsRNAs and complex-dsRNAs with the RNase A. Gel retardation assay revealed that CNPs-dsRNA complex of either linear or secondary structured-dsRNAs exhibited substantial protection of dsRNA from RNase A degradation for up to 72 hours, suggesting its potential for improving stability and long-lasting efficacy. The CNPs-dsRNAs significantly reduced the mycelial growth of wild-type and fungicide-resistant B. cinerea isolates. The results from this study indicated that chitosan-based polymer could be an effective delivery technology for both linear and secondary-structured dsRNA and hold great promise for the management of gray mold diseases.

Bacterial wilt (BW), caused by the soil-borne vascular bacterium Ralstonia solanacearum (Rs) species complex (RSSC), is one of the most devastating diseases affecting tomato and many other economically important crops. Rs infection leads to quick wilting and eventually plant death. Unfortunately, tomato bacterial wilt resistance genes have not been identified yet. Our previous study identified a candidate resistance gene from Hawaii 7996, a highly resistant tomato cultivar, that appears to be associated with qualitative resistance to bacterial wilt. Overexpression of the allele from Hawaii 7996 resulted in enhanced resistance in Heinz 1706, a model bacterial wilt susceptible cultivar. Gene editing-assisted gene knockout of the allele in Hawaii reduced bacterial wilt resistance. Yeast two-hybrid assay revealed a potential kinase that interacts with this resistance gene. The identification of the resistance gene and its interacting partner provide a better understanding of the resistance mechanisms and can be used for tomato bacterial wilt resistance breeding.

Manipulating the expression of flowering pathway genes holds potential for regulating tomato fruit productivity. SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1) is a MADS-box gene that serves as a key integrator in the flowering pathway. In this study, two full-length SOC1 genes cloned from maize (ZmSOC1) and soybean (GmSOC1), along with a partial SOC1 gene from blueberry (VcSOC1K, containing the K-domain), were individually transformed into tomato for constitutive expression. Phenotypically, the expression of VcSOC1K and ZmSOC1, but not GmSOC1, led to early flowering. Most transgenic lines for all three constructs exhibited a significant increase in fruit number per plant. More importantly, compared to non-transgenic plants, all three constructs resulted in varying degrees of increased fruit production per plant, primarily through enhanced branching. At the transcriptomic level, comparative analysis of GmSOC1 revealed the broader impact of the transformed genes. The increased expression of CLF and EZA1 appears to explain the unchanged flowering time of the GmSOC1 transgenic plants, while the repressed expression of DWARF genes likely contributes to enhanced branching. Additionally, numerous genes associated with biotic and abiotic stress tolerance displayed differential expression. These findings demonstrate that constitutive expression of either full-length or partial SOC1 has the potential to enhance tomato fruit production.

Flowering dogwood (Cornus florida) is a native tree species to the Eastern US that is susceptible to powdery mildew fungus. Genetic transformation of somatic embryogenic tissue in conjunction with gene editing are molecular methods used to breed pathogen-resistant cultivars. This research investigates the most effective germination treatment in regenerating plantlets from genetically transformed somatic embryos of flowering dogwood. From somatic embryogenic callus cultures containing the reporter transgene ß-glucuronidase (GUS), we grew tissue in liquid suspension and size fractioned using sterile metal sieves of different pore sizes. We collected pro-embryogenic masses (PEMs) from the small mesh size sieve, plated PEMS onto nylon supports using vacuum, and placed the nylon supports to semi-solid maturation media for embryo development. We chose somatic embryos elongating beyond the torpedo stage with the best quality and appearance and placed them across the four germination treatments. The germination experiments evaluated four different treatment concentrations of four different plant growth regulators (PGRs), gibberellic acid (GA3), abscisic acid (ABA), 6-benzylaminopurine (BAP), and melatonin. The environmental conditions for the first experiment included fluorescent lighting (10 μmol/m²/sec), temperature at 23 ºC (±1), and a photoperiod of 16h light:8h dark. Somatic embryos growing in germination media supplemented with GA3 (1, 2mg/L) had a higher percentage of embryos showing emergence of the apical shoot meristem between the cotyledons. The next highest percentage of somatic embryos with emerging apical meristems occurred using BAP at the concentrations 0.5 and1mg/L. The second germination experiment assessed the same treatments above except used early- stage torpedo somatic embryos and the light intensity increased to 35 μmol/m²/sec. BAP at 0.5 and 1mg/L showed the highest percentage of greening cotyledons and rooting rates. However, in 60 days, all the somatic embryos died in the GA3, ABA, melatonin, and BAP germination treatments. Although we successfully developed healthy transgenic somatic embryos, converting them into plants was a major challenge. The furthest germination stage we reached was the emerging of apical shoots, where the meristem elongates and continues to primary leaf formation. The difficulty in obtaining complete conversion to plants from these transgenic somatic embryos suggests there may be unintended impacts on growth or germination based on the location of the GUS transgene in the genome. Additionally, the original transgenic embryogenic culture was eight years old prior to the germination experiments, which could have influenced embryo conversion to plants.

Spring frost is a major environmental stressor caused by sub-zero temperatures (≤ 0 °C), often accompanied by freezing dew points, and poses a substantial economic threat to fruit crops. While the frequency of spring frost events may be influenced by climate change, the severity of damage has increased in recent years. This is largely due to elevated early spring temperatures that induce precocious bloom, making developing flower buds more vulnerable to subsequent frost events. Although no bloom-delay plant growth regulator (PGR) has been fully established to date, the use of PGRs to postpone flowering and mitigate frost risk remains a highly sought-after strategy in horticultural production. Our previous research demonstrated that fall applications of ethephon can delay bloom by 3–6 days in peach (Prunus persica). However, this treatment has also been associated with severe gummosis, necrosis, and branch damage. In the present study, we employed a plant hormonomics approach to investigate the relative abundance of endogenous hormones in flower buds of ethephon-treated versus untreated peach trees. Our analysis revealed dynamic profiles of abscisic acid (ABA), auxins (e.g., indole-3-acetic acid, indole-3-acetamide, 2-oxo-indole-3-acetic acid), brassinosteroids (e.g., 28-norcastasterone), cytokinins (e.g., zeatin, kinetin, N6-isopentenyladenosine), jasmonate-related compounds (e.g., cis-12-oxo-phytodienoic acid, dinor-12-oxo-phytodienoic acid, jasmonic acid [JA], JA-phenylalanine), salicylic acid, gibberellins (e.g., GA1, GA3, GA4, GA6), and strigolactones, with distinct accumulation patterns related to chilling and heat accumulation during dormancy and in response to ethephon treatment. Among these, jasmonates exhibited a unique pattern: levels remained low during dormancy and spiked sharply near bud break, but this spike was significantly suppressed in ethephon-treated trees. Based on this observation, we hypothesized that JA biosynthetic inhibitors could serve as effective bloom-delay agents. Indeed, over two consecutive seasons (2023 and 2024), we tested two JA inhibitors—propyl gallate and antipyrine—in two peach cultivars, ‘Sunhigh’ and ‘Redhaven’. Both compounds significantly delayed bloom progression compared to untreated controls. Furthermore, in 2025, antipyrine treatment resulted in a marked reduction in flower mortality following a killing freeze, which caused 100% damage in untreated trees versus approximately 90% in antipyrine-treated trees. To the best of our knowledge, this study represents the first hormonomics-driven translational approach aimed at regulating bloom time in perennial fruit trees to enhance their resilience to climate-related frost events.