ASHS 2025 Conference

Aspergillus flavus is an airborne fungus that can contaminate agricultural commodities very rapidly, including grains and nuts. This pathogen causes aflatoxin contamination in peanuts, which leads to significant crop losses and their quality, particularly in storage conditions. Accurately identifying toxin and non-toxin producing A. flavus isolates is important in terms of effective management because traditional approaches have limitations such as being less effective and time-consuming. To address this problem, we developed molecular tools to differentiate toxigenic and non-toxigenic A. flavus isolates. We identified A. flavus isolates through morphological and species-specific primer (FLA1/FLA2). Also, to characterize toxigenic and non-toxigenic A. flavus isolates, we employed a combination of approaches such as RT-PCR, RT-qPCR, and aflatoxin measurement, focusing on four genes (AflD, AflQ, AflP, AflR) from the aflatoxin biosynthesis gene cluster with primer optimization. In addition, research on the co-infection pattern of aflatoxin contamination on peanut seeds during storage conditions is limited. To address this, we collected peanut isolates from different seed lots and performed ITS sequencing to understand the pattern of microbial communities on peanut seeds during aflatoxin contamination. Regarding aflatoxigenic and non-toxigenic A. flavus detection, different gene expression patterns were observed among four AFs biosynthesis genes. However, by combining gene expression patterns, quantification and AFs production, we differentiated toxin and non-toxin producing A. flavus isolates. These results indicated the efficacy and specificity of these molecular tools, which could be helpful for developing good molecular markers for distinguishing toxigenic and atoxigenic isolates and to manage A. flavus contamination in peanut seed lots. Our co-infection results from peanut seed lots during multiple years observed the infection of diverse microbiota along with A. flavus, which indicates other microbes co-infect with A. flavus infection. This co-infection could trigger aflatoxin production in peanut seeds. Therefore, this approach offers novel insights into peanut seed-associated microbiomes, co-infection and aflatoxin production, shedding light on the correlation between the role of microbial communities and aflatoxin contamination.

Blueberry firmness is a crucial factor affecting shelf-life, fruit quality and consumer acceptance. Rabbiteye (RE; Vaccinium virgatum) blueberries are noted for their tough skin and lower pulp firmness compared to southern highbush (SHB; Vaccinium corymbosum L.). Yet limited firmness data is available on newly released RE genotypes bred for high yield, large berry size and increased firmness. The research objective was to evaluate weight loss, fruit firmness, and berry diameter on 14 RE and 3 SHB genotypes through storage. Blueberries were harvested from E.V. Smith Research station (Tallassee, AL) in 2024, then stored at 4 °C and 85% relative humidity. Four postharvest timepoints were followed: days 0, 14, 28, and 42 in storage. Firmness and fruit size were measured using a FruitFirm1000 texture analyzer, and weight loss was recorded using a digital scale. Significant changes in weight loss (%), firmness (g/mm), and fruit size (mm) during storage were found for the interaction between genotype and days in storage. On day 42, RE genotypes of ‘T-3081’, ‘Vernon’, and ‘T-3075’ exhibited the lowest weight loss at 7.2%, 7.8%, and 7.9%, respectively. Conversely, ‘MS1228R’ (18.3%), ‘MS1110R’ (13.6%), and ‘Titan’ (13.2%) (RE genotypes) and ‘Newhanover’ (14.9%) (SHB genotype) had the highest weight loss. During storage, most cultivars decreased in berry diameter. RE genotypes ‘Titan’, ‘T-3081’, and ‘T-3075’ had the largest diameter (24.9, 24.1, and 26.1 mm, respectively) at harvest and retained fruit diameter through storage (23.7, 23.4, and 26.1 mm, respectively). At harvest (day 0), ‘Titan’ (RE) had the highest firmness (287 g/mm), while ‘MS1110R’ (RE) had the lowest (152 g/mm). After 6 weeks of storage (day 42), RE genotypes of ‘Titan’, ‘Vernon’, ‘T-3075’, and SHB ‘Legacy’ maintained high firmness (˃200 g/mm), while ‘Alapaha’ (RE), ‘NewHanover’(SHB), and ‘MS1110R’ (RE) were lowest (˂150 g/mm). Hierarchical Cluster Analysis (HCA) identified three distinct firmness clusters, categorizing cultivars into enhanced (‘Titan’, ‘T-3075’), moderate (‘Legacy’, ‘Overtime’, and ‘T-3081’), and suppressed firmness (‘Alapaha’, ‘Krewer’, ‘Brightwell’, and ‘MS1110R’). HCA was crucial in selecting 10 genotypes (7 RE and 3 SHB) for future cell wall and texture analysis. This study provided valuable data for growers to select RE genotypes with maintained firmness and shelf-life. This data will aid blueberry breeders in selecting high-quality and competitive RE genotypes.

Enhancing vitamin C concentration in crops like lettuce (Lactuca sativa L.) through biofortification can increase dietary intake for consumers, yet its rapid degradation post-harvest remains a challenge. This limitation necessitates practical strategies to optimize post-harvest retention of ascorbic acid and extend the shelf-life of lettuce. This study aims to assess the effect of ascorbic acid foliar sprays on post-harvest stability of vitamin C content during post-harvest storage. A shelf-life study was conducted under refrigerated (4°C) and ambient (22°C) storage conditions over a 72-hour period. Potential results suggest that higher vitamin C concentrations may enhance leaf chlorophyll content and antioxidant capacity, potentially improving overall plant health and stress resistance. However, increased vitamin C levels could also lead to greater oxidation over time, impacting nutrient retention post-harvest stability. This study is expected to demonstrate the feasibility of vitamin C biofortification as a functional food strategy, enhancing the nutritional profile of lettuce while maintaining acceptable post-harvest quality. The findings from this study could provide valuable insights into improving fresh produce shelf-life and micronutrient retention. This research hopes to address dietary deficiencies while minimizing food waste.

As consumer preferences and needs for strawberries have become increasingly diverse, various strawberry cultivars have been developed in Korea. Although the ‘Seolhyang’ (SH) cultivar still occupies the highest proportion in the strawberry industry, the proportion of strawberry cultivars has unique characteristics, including bigger size, higher ascorbic acid content, or unique color. One of the distinctive cultivars recently gaining attention is a white-pink colored strawberry known as ‘Cinderella’ (CD). Thus, the objective of this study aimed to evaluate the metabolic variations in secondary metabolites between SH and CD cultivars, based on the pigmentation of the fruit peel, which could be 0%, 50%, 75%, or 100%, following a 3-day cold storage period. The fully developed strawberry had a higher fresh weight and fruit diameter in CD than in SH cultivar. The peel color variables, including lightness, yellowness, and hue angle, were gradually decreased with fruit pigmentation. The redness of the peel increased rapidly along with fruit pigmentation in SH, while that of CD showed only a slight increase. The ethylene production rate indicated higher values in SH than in CD during fruit pigmentation. Fruit firmness gradually decreased while soluble solids content (SSC) increased along with fruit pigmentation, regardless of strawberry cultivars. The anthocyanin analysis revealed that the SH cultivar had notable levels of pelargonidin-3-O-glucoside, pelargonidin-3-(6”-malonylglucoside), and cyanidin-3-O-glucoside, which contributed to fruit pigmentation. In contrast, pelargonidin-3-O-glucoside was only detected in the CD cultivar. Based on the volatile organic compounds (VOCs) profiling, a total of 74 VOCs were detected, including 26 esters, 14 alcohols, 12 aldehydes, 9 ketones, 5 terpenes, and 3 acids. In SH cultivar, (E)-2-hexenal, (E)-nerolidol, methyl hexanoate, hexanoic acid, and linalool were major VOCs. On the other hand, methyl hexanoate, ethyl hexanoate, (E)-2-hexenal, mesifurane, and (E)-nerolidol were the main VOCs in the CD cultivar. Therefore, the results indicate that the profiles and levels of anthocyanins and VOCs were differently regulated during the pigmentation of strawberry fruit between SH and CD cultivars.

Production of mandarin, sweet orange, and grapefruit has increased in most tropical and subtropical areas of the world in recent years due to growing market demand for high-quality, blemish-free fruit. Citrus fruit grown in the coastal region of the southeastern U.S. are more susceptible to blemishes and poor peel color than those grown in cooler climates. Early season, Florida mandarins are commonly degreened by treating with ≤ 5 ppm of ethylene for 12 h to 72 h at 29 °C /96% relative humidity (RH). However, optimal citrus degreening conditions vary with citrus cultivar, growing area, stage of maturity and season. Additionally, degreening can negatively affect mandarin quality (flavor, nutrition, acidity, sensory acceptability) and promote postharvest decays. The objective of this study was to evaluate the postharvest quality of two seedless mandarin cultivars degreened at temperatures lower than the commercial standard of 29 °C. These cultivars were released by the University of Florida breeding program: ‘UFGlow’, grown on ‘Rich’ trifoliate, ‘Carrizo’ citrange or ‘Sun Chu Sha’ mandarin rootstocks, and ‘UFSunrise’, grown on ‘Rich trifoliate’, ‘Carrizo citrange’ or HRS 812 rootstocks and were compared to the commercial cultivar ‘Owari-satsuma’, grown on ‘Carrizo citrange’ rootstock. On the day of harvest, fruit of each cultivar were pooled, treated with 5.0 μL·L-1 ethylene in a humidified, flow-through system for 72 hr at 20, 25 or 29 °C and 95% RH, then transferred to 8 °C/87% RH and evaluated weekly for 21 days. The three cultivars had better peel color and higher peel total carotenoid content when degreened at 25 or 29 °C than at 20 °C. Soluble solids content and total titratable acidity changed slightly during storage, independent of degreening treatment. Degreening did not affect ascorbic acid content; fruit total antioxidant capacity (oxygen radical absorbance capacity, ORAC) declined less with the ethylene treatment but remained constant in ‘UFGlow’. The best degreening treatment for these seedless mandarin cultivars was 5 ppm ethylene at 25 °C/96% RH for 72 hr, resulting in the best peel color, highest total peel carotenoids content, less weight loss and firmer fruit. Although ‘Owari’-satsuma developed better color at 29 °C, weight loss was significantly higher than when degreened at 20 or 25 °C.

We had earlier showed that spectrometric scanning of dehusked, fresh sweetcorn-on-the-cob (SOTC) in the visual (Vis) blue wavelength range (Vis-blue) offered an alternative nondestructive brix quantitation. In this report, we demonstrate that scanning in the Vis-blue is effective in a wide range of sample temperatures including freezing temperatures where the in-market infrared (IR) scanners fail. This is an important development for instore consumer decision-making experience. Eight packs of frozen (~-340C) SOTC in thin, translucent polyethylene packing bags were evaluated. Each pack contained at least12 pieces of SOTC, representing three different commercial brands bought directly from two different groceries stores on St. Croix. The samples were transported in ice and kept frozen (at temperature conditions as in the stores) until the time of measurements. At least six random SOTC were marked for IR and Vis-blue data every 5 minutes from freezing to room temperatures (~22degC) until the samples were completely thawed. The thawing temperatures at which each instrument was able to start recording were noted. The IR was insensitive at temperatures below ~160C, while the Vis-blue scanner recoded brix on frozen samples all the way to room temperatures and at complete sample thaw. The Vis-blue scanner also measured all frozen samples through the plastic packaging and directly on samples taken out of the packing. The Vis-blue scanner was also able to obtain spectral signals on the SOTC while the samples were in the freezer, but the signals were weak and, in some cases, when the sample packaging was completely covered in ice. With further developments and refinements, the Vis-blue scanning method can be integrated into scanning devices for quality assessments of frozen corn.

Avocado (Persea americana Mill.) is a subtropical fruit prized for its nutritional properties, versatility, and health benefits. Florida growers have shown interest in expanding avocado production into South-Central Florida due to the decline in citrus production resulting from greening and canker diseases. However, the worldwide market is mostly dominated by the ‘Hass’ cultivar, a Guatemalan (G) x Mexican (M) avocado hybrid with excellent eating quality and the ability to withstand long-distance shipping and postharvest handling. Florida focuses on larger green West-Indian (WI) or WI x G avocado hybrids, suited to subtropical climates. There is a need to identify WI genotypes that are well-adapted to South Central Florida conditions and evaluate their production and quality potential in this region. But the relationship between genotype and maturity is not yet fully understood. This study focuses on determining when these should be harvested to reach full ripeness and achieve the best eating quality, through correlation between dry matter (DM), firmness, and taste preference. A taste panel consisting of 25 panelists evaluated the sensory attributes of avocados that reached firmness equal to 15 N or lower. The results show that WI varieties and their hybrids, despite both low and high DM content (16.4% to 28.4%), are well-accepted by the panelists with taste ratings ranging from 5 (neither like nor dislike) to 6.6 (like moderately). The characteristics that contributed to the panelists' preference include buttery, creamy, nutty, and sweet. Additionally, fruits harvested later tended to show an increase in DM and a decrease in ripening time. Fruits, when harvested at their full physiological maturity, require 10 days to reach full ripeness at room temperature (20°C - 22°C). This study contributes to understanding factors that can help optimize fruit quality and provide valuable insights for the Florida avocado industry.

Blueberries are valued for their flavor and nutritional content, yet postharvest data on rabbiteye (RE; V. virgatum A.) genotypes remain limited. In this study fruit quality of 16 RE and 3 southern highbush (SHB; V. corymbosum L.) genotypes were evaluated through cold storage. Fruit harvested in 2024 from E.V. Smith Research Center (Tallassee, AL) were stored at 4°C and 85% relative humidity in a randomized complete block design. Measurements were taken on days (d) 0, 14, 28, and 42 including color attributes (L*, a*, b*, C*, h* CIELAB units), soluble solids content (SSC, °Brix), titratable acidity (Tacid) and pH. Total anthocyanins (mg/g), phenolics (mg/100g), and DPPH antioxidant capacity (mM/100g) were quantitated via UV-VIS spectrophotometry. Significant interaction for days in storage*genotype were observed in Tacid and SSC:Tacid ratio. Tacid was highest in ‘MS1228R’ and ‘MS1234R’ (42d; 0.73 and 14d; 0.77) and lowest in ‘Legacy’ and ‘NC5303’ (42d; 0.30 and 0d; 0.31). The SSC:Tacid ratio was highest in ‘Brightwell’ (0d; 47.47) and lowest in ‘Vernon’ (0d; 19.76). SSC decreased with increased storage time (0d to 28d) by 0.69 °Brix while pH increased from 0d (3.31) to 42d (3.54). Genotype differences indicated ‘Brightwell’ and ‘Ochlocknee’ had the highest SSC (16.5 and 15.9 °Brix) compared to ‘T-3075’ and ‘New Hanover’ (12.4 and 12.1 °Brix). pH was highest in ‘Legacy’ and ‘New Hanover’ (3.67 and 3.63) and lowest in ‘T-3075’ and ‘MS1234R’ (3.25 and 3.19). Across all storage timepoints, RE genotypes were higher in total anthocyanins, phenolics and antioxidant activity at 16.54 mg/g, 298.40 mg/100g and 21.41 mM/100g, respectively compared to SHB genotypes at 11.35 mg/g, 213.90 mg/100g and 17.19 mM/100g. Hierarchical cluster analysis (HCA) indicated 3 clusters of interest. In cluster I, ‘Vernon’, ‘Overtime’ and ‘MS1595R’ had enhanced C* and h*. In cluster II, ‘Brightwell’ and ‘Ochlocknee’ indicated enhanced anthocyanin, phenolic and antioxidant activity, while ‘T-3075’ and ‘T-3072’ had suppressed phytonutrient content in cluster III. The industry accepted range for blueberry SSC is 11.2-14.3 °Brix and all genotypes in this study met industry standards. Some RE selections, e.g., MS selections, were above the U.S. accepted range (0.2 to 0.5) for Tacid relating to sour/tart flavors. HCA was useful in sub-selecting RE and SHB genotypes for sensory and electronic analysis to assess flavor patterns. Identifying fruit quality and flavor traits postharvest will aid in selecting superior RE germplasm to enhance consumer acceptance and inform breeding efforts.

Romaine lettuce (Lactuca sativa L. var. longifolia) is a highly nutritious, leafy green vegetable that can be easily grown hydroponically, offering a sustainable and efficient alternative to conventional agricultural practices. Although hydroponically grown lettuce is less susceptible to microbial infection compared to its soil-grown counterparts, contamination with human pathogens is still possible. Sterilization methods, such as ultraviolet (UV) light treatment, may be employed to control contamination in the hydroponic system, but its effect on lettuce postharvest quality remain unclear. The aim of this study was to investigate the impact of nutrient solutions treated with two doses of UV-C on the harvest and storage quality of the romaine lettuce cultivar 'Sparx' grown in a deep-water culture (DWC) hydroponic system. Nutrient solutions were either left untreated (control) or treated three times over a six-week growing period with UV-C (254 nm) at two different flow rates, delivering estimated UV-C doses of 18.93 mJ/cm² (low) or 37.85 mJ/cm² (high) per treatment. Postharvest quality was evaluated by measuring leaf length, fresh weight, dry root weight, water loss, soil plant analysis development (SPAD), color, texture, visual quality, respiration rate, micronutrient content, and nutritional content at time of harvest and over a seven-day storage period. We utilized a randomized complete block design, and the experiment was repeated three times. Lettuce grown in the low dose UV-C-treated nutrient solution had significantly longer lettuce leaf length, higher fresh weight, and higher vitamin C content compared to the high dose UV-C treatment. Additionally, fresh shoot weight was significantly higher in the low dose UV-C-treated lettuce compared to the high dose treatment. In terms of visual quality, the high dose UV-C treatment showed significantly better visual quality at the end of storage compared to lettuce grown in the control nutrient solution. No significant differences were observed for dry root weight, water loss, SPAD, texture, color, or micronutrient content between the three treatment groups. Overall, this study demonstrates that UV-C-treated nutrient solution had no negative impact on quality parameters of hydroponic lettuce at harvest or during storage, indicating that UV-C treatment, particularly at lower doses, may be a viable option for effectively sterilizing hydroponic systems without compromising lettuce postharvest quality.