ASHS 2025 Conference

Alternative Oxidase Interacts with SNF1 Kinase to Modulate Energy Metabolism During Pear Fruit Ripening Adwaita Prasad Parida and Amit Dhingra1 Correspondence: Amit Dhingra, Professor, Department of horticultural sciences, A

Pawpaw (Asimina triloba), a North American tree fruit, belongs to the Annonaceae family and is the only temperate member of this family. Pawpaw is emerging as an alternative high-value niche crop for small farms in Kentucky and surrounding states; however, due to its highly perishable nature, the marketing window for fresh fruit is currently limited. Pawpaw fruit can only be stored for 3-5 days at room temperature or for about 1 month under cold storage at 4 °C. The objective of this study was to examine the efficiency of modified atmosphere with plastic packaging in cold storage to increase the shelf-life of pawpaw fruit and its impact on the quality attributes of fruit. This experiment was conducted with fruit from the pawpaw cultivar Sunflower. Fruits were harvested and stored in three treatments of modified atmosphere in 2.5-gallon plastic container bags, with the treatments of 1) plastic bag with ambient air (Control), 2) plastic bag with an additional ethylene absorber, and 3) plastic bag with modified atmosphere of low oxygen and high carbon dioxide gas mix (12% O2 and 10% CO2 and balance nitrogen). There were three replicate bags per treatment with each bag containing three fruits. Fruits were stored at 6 °C. Data on gas composition in bags and quality parameters of fruit such as firmness, brix, color (L*, a*, b*), and weight were taken on 5, 10, 20, 40, and 80 days of storage. The ethylene absorber and gas mix treatments maintained lower ethylene concentrations inside the bags as compared to the control. The gas mix treatment resulted in reduced fruit weight loss and maintained the lightness of fruit pulp significantly. However, firmness in all fruits significantly declined after 20 days of storage in all treatments. These data suggest that the ethylene absorber and gas mix treatments during cold storage have at least some potential for extending shelf-life of pawpaw, with additional modifications or harvest times.

Several apple cultivars are susceptible to lenticel breakdown including but not limited to ‘Honeycrisp’, ‘Red Delicious’, ‘Gala’, and ‘SweeTango’. ‘Honeycrisp’ in particular has received considerable scrutiny by apple growers and packers due to its low percentage of packable fruit. ‘Honeycrisp’ in Michigan are put into storage with little to no disorders and, in 3-5 months, are pulled out of storage achieving less than 50% pack-outs of quality fruit in severe cases. These low pack-outs are a result of internal disorders, a physiological disorder ‘bitter pit’, lenticel breakdown, advanced decay, and some unknown light brown spotting that can be similar or smaller in size than lenticels. Investigations into the mechanisms behind these various ‘spots’ and discriminating between them is an essential first step in understanding the disorders and the discovery of solutions for growers and storage operators. In this study, three preliminary assessments were made to resolve the ambiguity behind lenticel breakdown and associated ‘spots’: 1) apple lenticels were imaged by light and scanning electron microscopy and characterized, 2) ‘Honeycrisp’ and ‘SweeTango’ apples were wrapped in paper and mesh bags on the tree as a field chemical spray exclusion assessment, and 3) a preliminary look at the microbiome of healthy and unhealthy lenticels. The latter effort revealed that ‘Alternaria’ species dominate the fungal community of unhealthy lenticels.

The interspecific pear cultivar ‘Greensis’ has become a highly demanded pear cultivar due to its unique flavor of sweetness, crispness and juiciness. This study evaluated the postharvest storage quality of ‘Greensis’ pear at two maturity levels, treated with the 1 µL L-1 1-methylcyclopropene (1-MCP), pre-storage conditioning (PSC), and the combination treatment of 1-MCP and PSC before long term cold storage at 0.5 °C for 6 months. Both the incidence and severity of physiological disorders, such as cortex and core browning, were significantly reduced in PSC treatments, meanwhile, the severity levels of cavity were notably lower in treated fruit compared to untreated (control) fruit. Among the targeted metabolites, soluble carbohydrates and organic acids particularly, sucrose and shikimic acid were lower in mature fruit than immature fruit. Moreover, the contents of glucose, fructose, malic acid and shikimic acids were higher in PSC treated fruit than the other treatments especially in mature fruit. The branched-chain amino acids, including isoleucine and leucine, glutamic acid and phenylalanine, in all treatments were lower in immature fruit, meanwhile, methionine was higher in mature fruit. Additionally, in immature fruit, the contents of asparagine, serine, threonine and proline in the combination treatment of 1-MCP and PSC were higher than the other treatments. In addition, the phenolic contents of all treated fruit were higher in immature than mature fruit especially in chlorogenic acid, arbutin, caffeic, p-coumaric acid, and gallic acid after long term cold storage. Overall, these results suggested that the higher accumulation of phenolic compounds and specific amino acid contents in immature fruit play as a defense mechanism and enhances cold stress tolerance during long-term cold storage. Furthermore, PSC treatments effectively maintain the postharvest fruit quality by reducing the physiological disorders in cold stored ‘Greensis’ pear.

Blackberry berries are highly perishable fruits, requiring effective postharvest management to maintain quality during storage. This study investigates the shelf-life and postharvest physiology of three blackberry cultivars ‘Ponca’, ‘Freedom’, and ‘Osage’—stored at 0°C for 0 to 7 days and 5°C for 8 to 16 days. Key parameters measured include red drupelet reversion, leakiness, weight loss, acidity (citric, malic, tartaric acid), pH, Brix content, anthocyanin, and antioxidant content. Fresh blackberry fruits of three different cultivars were collected from a commercial garden and stored in 6 oz clamshell boxes under controlled conditions. Physiological parameters such as weight loss, red drupelet reversion, and leakiness were evaluated at 0, 7, 12, and 16 days of storage. For chemical analysis, an additional 6 oz clamshell box for every sample was stored at -40°C at 0, 7, 12, and 16 days to assess acidity, Brix content, anthocyanin, and antioxidant. Results indicate significant varietal differences in postharvest stability. ‘Freedom’ exhibited the highest red drupelet reversion and leakiness, with a steady decline in acidity over time, suggesting rapid deterioration. ‘Osage’ maintained the most stable postharvest quality, showing the lowest red drupelet reversion and highest acidity, which may contribute to improved storage potential. ‘Ponca’ demonstrated moderate stability but exhibited a sharp increase in leakiness and red drupelet reversion at later stages, indicating postharvest instability. Weight loss data revealed that ‘Freedom’ experienced the highest weight reduction, while ‘Ponca’ and ‘Osage’ exhibited greater stability over the storage period. Acidity levels varied significantly among cultivars, with ‘Osage’ retaining the greatest citric, malic, and tartaric acid concentrations, potentially enhancing shelf stability. ‘Freedom’ exhibited the lowest acidity, affecting taste and preservation. pH trends revealed that ‘Freedom’ lost acidity fastest, while ‘Ponca’ maintained stable acidity, making it more suitable for extended storage. These findings highlight the need for cultivar-specific postharvest strategies. While ‘Osage’ appears to have better natural postharvest qualities, ‘Ponca’ and ‘Freedom’ may require optimized storage conditions to minimize quality loss. This study provides valuable insights for improving blackberry storage, reducing postharvest losses, and extending marketability.

Reduced fruit quality throughout cold storage is a major stakeholder-identified factor limiting production and marketability of the profitable apple ‘Honeycrisp’ in the Mid-Atlantic. ‘Honeycrisp’ is known to be a chilling sensitive cultivar when cooled immediately after harvest, therefore fruits are submitted to a postharvest conditioning treatment (10ºC for 7 days) prior to cold storage (3ºC). However, conditioning exacerbates the expression of bitter pit, rendering the fruit unmarketable. Moreover, maturity at harvest is a critical factor affecting apple fruit quality as well as susceptibility to chilling stress. Ethylene, the primary hormone related to hastening fruit maturity, can be regulated via the use of preharvest ethylene regulators. We aimed to characterize and compare the effects of different preharvest ethylene regulators on ‘Honeycrisp’ fruit maturity, quality and chilling sensitivity during postharvest. Three preharvest ethylene regulators with different modes of action were applied based on manufacturer’s recommendations, including 1- methylcyclopropene (1-MCP, Harvista), aminoethoxyvinylglycine (AVG, Retain), Ethephon (Ethrel) and a control. Fruits were harvested at two maturity stages: at the anticipated commercial harvest (CH) and one week after CH (CH 1). After harvest, in each case, fruit were submitted to conditioning (10ºC for 7 days) and then stored at 3ºC. Fruit from all 8 treatments were evaluated at harvest, and after 8, 16 and 24 weeks of storage at 3ºC, followed by a shelf-life period (7 days at 20ºC). Our results show that preharvest ethylene regulator treatments impacted fruit maturity and quality of ‘Honeycrisp’ apples during storage. Ethylene production was reduced in 1-MCP and AVG treated fruit, with the latter showing the lowest values throughout storage during both harvest dates. Concurrently, 1-MCP and AVG treated fruits displayed a higher flesh firmness as well as a greener background color (as indicated by higher IAD values) compared to Ethephon- treated and control fruit. Skin blush was negatively affected by 1-MCP and AVG applications, which were maintained throughout postharvest, with AVG-treated fruit exhibiting the significantly lower values. Effects on starch pattern indices and soluble solids contents were inconsistent. Chilling sensitivity, through the presence of soft scald, was not observed, but 1-MCP treated fruit presented the highest bitter pit incidence, followed by AVG-treated fruit, while Ethephon and control fruit displayed the lowest. This study contributes to understand how preharvest ethylene modulation influences ‘Honeycrisp’ apple maturity and quality throughout storage.

Blackberry (Rubus spp.) production in Georgia is valued at $19.9 million annually with approximately 1,900 planted acres, mostly concentrated in the southern part of the state. Blackberries have been increasingly planted in Georgia as a dynamic alternative crop that can diversify and support blueberry growers’ income. The harvest season is short, starting in mid-May and ending mid-July. The planted genotypes are mainly from other Southeastern breeding programs often with little to no testing on their suitability for the local growing conditions. Four University of Arkansas-bred cultivars – ‘Caddo,’ ‘Osage,’ ‘Ouachita,’ and ‘Ponca,’ were selected with a goal to identify the most appropriate cultivar for production in Georgia climatic conditions. Blackberries were hand-harvested, field-packed, placed in cold storage for up to 21 days, and evaluated over a two-year harvest period from a commercial field in Holt, GA (31.5957˚N, 83.1507˚W). Red Drupelet Reversion (RDR) is a major postharvest disorder where fully ripe, black drupelets revert to red color after harvest. Assessments for RDR incidence were conducted immediately after harvest and every seven days, along with measurements of berry physicochemical traits. Consumers' taste panels were conducted a day after harvest. A high incidence of RDR was quantified at harvest and after storage for ‘Ouachita,’ followed by ‘Ponca,’ ‘Caddo’ and ‘Osage.’ In addition, the panelists favored ‘Caddo’ blackberries, while ‘Ouachita’ was the least preferred cultivar. Appropriate preharvest and postharvest practices, in combination with timely, gentle harvests should be employed to decrease RDR incidence and maintain fruit quality.

Edible nanoparticle coating materials were developed from sweetpotato peel tissue combined with sodium alginate and tested for their efficacy in reducing sweetpotato and potato postharvest deterioration. The bio-based nanoparticle coatings applied as thin films to the surface of sweetpotato roots and potato tubers reduced postharvest weight loss and respiration rate. The sweetpotato peel-based nanoparticle coating formulations included 1% and 2% sodium alginate. To enhance the structural integrity of the coatings, they were cross-linked by immersion in a 1% calcium chloride solution. The crosslinked formulations significantly outperformed non-crosslinked coatings and uncoated samples by minimizing weight loss (to below 2.0%–4.0% versus 3.5%–6.5% in controls) and decreasing respiration rates (to 5-13 mL CO₂/kg·h versus 7-20 mL CO₂/kg·h in controls) over extended storage periods. The enhanced performance is attributed to the formation of a dense, mechanically robust coating matrix. Sweetpotato peel tissue nanoparticles combined with sodium alginate and crosslinked with calcium chloride offer promise as sustainable coating materials for reducing fresh produce postharvest deterioration

Fresh grapefruit consumers are trained to expect vivid yellow-orange peel color, depending on the variety, even though peel color has little to do with internal maturity or quality. The greasy spot rind blotch disease has been in Florida for many years, ascribed to a fungal pathogen called Zasmidium citri-griseum (previously named Mycosphaerella citri). Besides causing defoliation, it also mars the peel with tiny black specks that cause the rind to remain green, even after degreening. The spots can coalesce into black patches in extreme cases, sometimes called “pink pitting” or greasy spot rind blotch. Growers had this disease under good management, but within the past five years, fruit with similar symptoms started appearing as early as November, when nighttime temperatures are low, and peel color should improve instead of regreening. The symptoms are like greasy spot rind blotch, but there are few to no symptoms on the leaves of the same trees. Thus, the industry generally refers to the disorder as “greasy green” until a more definitive identification of the causal agent and disease development is determined. In a 2021 grower survey, 89% of respondents experienced the disorder to some extent, with packers reporting losses ranging between $20,000 and $1.7 million. There was no consensus among growers and packers regarding the cause of greasy green or the factors contributing to the problem. While studies are underway to determine if the disorder is indeed related to greasy spot rind blotch, studies were initiated to determine if affected fruit could be degreened effectively, as many packers often ended up abandoning degreening attempts on affected fruit and not using them for the fresh market. Our tests found that even after degreening (5 ppm ethylene at 27oC) red and white grapefruit for up to 5 days, their peel color still was not acceptable (