ASHS 2024 Conference

Assessing Apple Cultivar Responses to Low Oxygen Limit Determination Using Chlorophyll Fluorescence and Respiratory Quotient - Hnin Phyu Lwin
Understanding how physiological maturity and storage regime affect skin greasiness on WA 38 apples - Carolina Torres
Chlorophyll to Carotenoid Ratio Measured Nondestructively Correlates with Peel Pigment Content and Canopy Attachment Position of ‘Granny Smith’ Apples - Manoella Mendoza
Early Spectral Differences on Scald Disorders in ‘Granny Smith’ Apples - Rene Mongollon
Apple Ripening After DCA Storage: Assessing The Risk Of Flavor Loss - Randolph Beaudry
The Impact Of Hot Water Treatment On Organic Apple Quality With Different Storage Systems - Sadat Amankona
Fungicides and Scald Inhibitor Diphenylamine Shift Microbiomes of ‘Fuji’ Apples Through Short Term Cold and Room Temperature Storage - Connor Lane
Pyrus communis: A Model for Studying Climacteric Ripening and Senescence - Amit Dhingra
Characterization of Postharvest Rots and the Susceptibility to Decay of 38 European Pear Genotypes during Cold Storage. - Tamara Collum

Dynamic controlled atmosphere (DCA) is a prominent technology used worldwide for long-term apple storage. In Washington, the adoption of DCA technologies to manage low oxygen levels is limited, partly because the benefits are not clearly demonstrated for some major cultivars, such as ‘Honeycrisp’ and new varieties like ‘WA 38’. The response of ‘Honeycrisp’, ‘Gala’, and ‘WA 38’ apples to lower oxygen levels was monitored monthly until 8 months of storage (1oC or 3oC) through chlorophyll fluorescence (CF) and respiratory quotient (RQ) by a stepwise decrease in O2 levels at each time point during 2023/2024 season. Ethanol and acetaldehyde concentrations were obtained from fruit juice before and after the lower oxygen limit (LOL) determinations. ‘Honeycrisp’ and ‘Gala’ apple cultivars showed differences in LOLs determined through CF or RQ. CF LOL for ‘Honeycrisp’ was approximately 0.3-0.2 kPa O2 compared to 0.1 kPa O2 for ‘Gala’ while RQ response occurred at 0.1 kPa O2 level in both cultivars. ‘WA 38’ apples displayed inconsistent CF responses at 0.3 and 0.4 kPa oxygen levels. Ethanol concentration increased after low oxygen stress irrespective of the cultivar. During the first month of storage and after the low oxygen stress, ‘Honeycrisp’ apples accumulated (in average) 120 ppm of ethanol, ‘Gala’ 2.92 ppm, and ‘WA 38’ 4.24 ppm. Towards the end of storage, the ethanol concentration showed an increase for ‘Gala’ (25 ppm), which was not observed for the other two cultivars. Small amounts of acetaldehyde were accumulated only in ‘Honeycrisp’ apples. This study highlights the different responses of apple cultivars to low oxygen stress during the lower oxygen limit (LOL) determination, with ‘Honeycrisp’ being the most sensitive one among the cultivars tested. Further seasons are needed to confirm these results and include the seasonal-dependent responses in each cultivar.

‘WA 38’ (Cosmic Crisp®) is the newest cultivar released by the Washington State University apple breeding program, and today in its sixth year of commercial production in WA. This cultivar has a high pack-out, i.e. highly colored fruit and few external and internal defects. Nevertheless, skin greasiness has been one of the main defects at harvest and postharvest, making waxing during packaging challenging, and affecting the cosmetic appearance. Since the starch degradation index is the only maturity index used to commercially harvest WA 38, the correlation between maturation and the onset of greasiness was studied during two seasons. Different maturity indices pre-and postharvest (firmness, soluble solid content, internal ethylene concentration (IEC), starch index (1-6), IAD values) along with skin greasiness were evaluated from 3-4 weeks before harvest (WBH) until 6 months in air (1oC) or controlled atmosphere (2.5 kPa O2, 1.5 kPa CO2) storage in fruit from four commercial orchards (#1 to #4; 2nd-4th-leaf). In 2022 and 2023 the rate of change of all maturity indices were block-dependent. In both years, IEC was detected in up to 80% of the fruit sampled four WBH in orchard #1 (average 0.3 ppm). At this same time point, only 16% of the fruit had started the starch degradation process (SI=1.5/6.0). The climacteric peak occurred 3-5 months into cold storage, and it was block-dependent. Greasiness on fruit skin was detected 2 WBH in two of the four orchards in 2022; in 2023 this occurred at commercial harvest. Overall, there was a higher incidence (and severity) of greasiness in fruit from air storage compared to CA, and in both cases, it increased during the shelf-life period (7 d at 20oC). The results indicate that fruit greasiness appears to be more related to fruit maturity and perhaps seasonal weather than tree age, nevertheless, additional seasons are needed to confirm these results.

‘Granny Smith’ is an important apple variety for Washington State, where it has consistently been ranked as the third most-produced conventional cultivar since 2017. This apple variety is highly susceptible to sunscald, a sun-stress-related postharvest disorder that typically appears after three months of cold storage and makes apples unmarketable. Previous research has shown that a decrease in chlorophyll (chl) and an increase in carotenoids (car) in fruit peel have been associated with increased sunlight exposure and the development of sunscald. In order to assess the use of the chl/car ratio measured non-destructively with a Vis/NIR hyperspectral imager as a predictive index for sun exposure and sunscald development postharvest, ‘Granny Smith’ apples were picked from the periphery and inner canopy sections of the tree in 2021 and 2023 seasons. Fruit position in the canopy was documented during sampling and later correlated with hyperspectral images, chlorophyll, and carotenoid content in the peel. Subsequently, the collected peel sample was immediately frozen with liquid nitrogen and stored at -80°C. The chl/car ratio obtained from the reflectance values from the hyperspectral images was well correlated (r2 = 0.82) with the destructive determination of the ratio. Based on k-means clustering analysis, samples were grouped in accordance with the chl/car ratio and associated with fruit position on the tree. Apples with the highest chl/car ratios (1.4 to 1.7) were those located on the shaded portion of the trees. Apples with sunburn had the lowest chl/car ratios (0.1 to 1.2) and were located on the periphery of the tree. The results indicate that the chlorophyll to carotenoid ratio measured non-destructively at harvest can potentially be used for pre-storage sorting of ‘Granny Smith’ apples based on relative sun exposure and sunscald susceptibility, reducing postharvest losses. However, the establishment of the index reliability can benefit from additional years of data collection.

‘Granny Smith’ apples are highly susceptible to skin browning (=scald). These disorders can significantly reduce fruit’s marketability due to their unattractive appearance. Superficial scald and sunscald have different etiologies but their symptoms are similar and easily mistaken. The oxidation of α-farnesene causes superficial scald (SS); on the other hand, sunscald (SC) is a non-oxidative process that affects only the sunlit sides of the fruit. To correlate the spectral fingerprint with fruit susceptibility to these disorders, hyperspectral images (400-1000 nm, 640x865 px; Headwall Photonics, Bolton, MA) were taken at harvest from sun-exposed and unexposed sides of the fruit (n=216; ~26,000 px) and later, after six months in air storage (33 oF), correlated with scald incidence. The dataset grouped 145 asymptomatic, 117 with SS and 170 with SC fruit. After pre-processing spectral information (Savitzky-Golay dev, standard normal variate), iPLS wavelength selection showed that bands from 400 to 650 and 900 to 950 nm were the most accurate for at-harvest spectral differentiation between superficial and sunscald symptoms. A neural network classification model was trained (18,226 px) and validated on an independent dataset (7,808 px), achieving overall accuracies of 78 % and 73 %, respectively. After prediction, SC px obtained the highest classification metrics (accuracy 87 %, precision 86 %); meanwhile, the asymptomatic class showed the lowest metrics (accuracy 74 %, precision 60 %). These preliminary results showed that in the same way, sunscald could be identified close to harvest using hyperspectral fingerprints, superficial scald could also be predicted at harvest on susceptible fruit and differentiated from sunscald susceptible fruit.

Dynamic controlled atmosphere (DCA) storage suppresses the ripening of apple fruit during storage to a greater extent than standard CA storage. DCA is a relatively new technology, and it has the potential to markedly alter the volatile profile of apple fruit. It has been found that DCA storage can suppress the most important aroma volatiles of stored apple fruit. What we don't know is the length of time and the conditions needed to recover that loss in aroma, especially when DCA is applied in combination with the ethylene action inhibitor 1-methylcyclopropene (1-MCP). A critical concern about 1-MCP is that apple flavor is compromised in treated fruit because aroma volatiles are so closely linked with ethylene response. Apple fruit from high-value cultivars were stored under a DCA regimen (approximately 0.4% O2), with and without 1-MCP treatment, for 3, 6, and 9 months. Following removal of fruit from DCA, the volatile profile and fruit quality traits were measured for up to 5 weeks while being held at room temperature. The recovery of aroma formation following storage for 6 months was essentially immediate for ‘Red Delicious’ fruit if 1-MCP was not used. The recovery was a little slower for one of the replicate studies if DCA was used. If the fruit were treated with 1-MCP, there was a 2-week delay in the recovery of aroma formation. ‘Evercrisp’ aroma formation was much lower than ‘Red Delicious’ and the responses to DCA and 1-MCP differed from that of Red Delicious. Aroma formation remained very low for 3 to 4 weeks at room temperature following CA and DCA storage and never recovered following 1-MCP treatment for the 5-week duration of the study. The data for aroma formation after 9 months was similar to that at the 6-month time point for ‘Red Delicious’ in terms of 1-MCP responses. However, the effect of DCA seemed to be more pronounced, suppressing aroma recovery for an additional week at room temperature. For ‘Evercrisp’, the 9-month data were quite similar to those from 6 months storage.

There has been a surge in demand for organic apples in the U.S. in the last decade. Washington State supplies more than 90% of them because of the ideal climate and soil conditions that favor production. Thermotherapy methods are widely used in Europe to reduce postharvest rots, but they have not been adopted in the U.S. because of their potential detrimental effects on fruit quality. The objective of this research was to evaluate the impact of hot water treatments at harvest on fruit quality during long-term storage. ‘Royal Gala’ and ‘Honeycrisp’ apples were immersed at 49 °C or 52 °C for 2 minutes in a controlled hot water bath immediately after harvest. After fruits were dried at 20 °C, they were placed in controlled atmosphere (CA; 2 kPa O2, 0.5 kPa CO2, 1°C-‘Royal Gala’, 3oC-‘Honeycrisp’) and air (RA; 1°C-‘Royal Gala’, 3oC-‘Honeycrisp’) storage for up to 9 months. Fruit quality (firmness and titratable acidity), defects, and physiological disorders were evaluated 1 and 7 days at 20 °C. In general, ‘Royal Gala’ apples immersed at 49 °C and stored in CA had no decay after 3 and 6 months of storage, but it was the highest (around 9%) in ‘Honeycrisp’ in both CA and RA. Peel damage was less at 49 °C for both ‘Royal Gala’ (RA-1.3%; CA-5%) and ‘Honeycrisp’ (RA-7.4%; CA-2.8%) compared to 52 °C after 3 months. Fruit firmness and titratable acidity were statistically different (p≤0.05) at 49 °C compared to 52 °C after 3 months. Although the hot water treatment in ‘Royal Gala’ apples was effective in reducing decay incidence without compromising fruit quality, the opposite was found in ‘Honeycrisp’; therefore, further research is needed to confirm these results and understand the variety-dependent effect.

Speakers: Dr. Daniel Neuwald and Mr. Felix Büchele
The first presentation in the webinar will be "Redefining the cooling load in apple fruit storage" given by Mr. Felix Büchele. Cooling systems in fruit storage are typically designed based on simplified estimations of the heat load during initial cool-down and an arbitrarily chosen optimal duration for heat removal. However, this approach overlooks heat transfer and cool down characteristics of the horticultural product, resulting in overdimensioned cooling systems in commercial storage facilities. The DyNatCool project aims to simulate the transient heat loads during long-term storage of fruit and validate it in large scale storage experiments, for an optimized dimensioning of cooling systems and improved energy efficiency.
The second presentation will be given by Dr. Daniel Alexandre Neuwald: "Practical & Cost-Effective Strategies for Enhancing Economic and Ecological Sustainability in Fruit Storage". Long-term storage is an essential tool for farmers to optimize their marketing strategy and provide customers throughout the year with fresh and locally produced fruit. However, as energy prices soar in Germany, the postharvest sector faces substantial economic challenges. Rising costs for storage are not compensated by a similar development in market prices, as farmers are competing with imported and freshly harvested fruit, often produced under cheaper conditions. Traditional recommendations for improved energy efficiency during storage usually involve costly renovations of room structures or installations of new equipment. In his talk, Dr. Neuwald shares practical insights on how even small adjustments in storage management can yield substantial energy savings without breaking the bank.

Recent studies have shown that the native microbiome plays an important role in biocontrol efficacy, but in comparison less is known about how the microbiome responds to conventional and natural product fungicides. This study investigated the effects of conventional fungicide fludioxonil, natural product fungicide natamycin, and scald inhibitor diphenylamine (DPA) on the microbiomes of ‘Fuji’ apples (Malus x domestica) from 1-28 days of cold storage and 7 days of room temperature after the cold storage. We hypothesized that fludioxonil would have a smaller effect on the microbiome than natamycin due to being more limited in targeting specific pathogens, and that antioxidant activity from DPA would shift the microbiome. DPA showed a strong effect on the fungal microbiome that increased with storage time, while natamycin resulted in modest fungal shifts and fludioxonil resulted in no observed shifts. While chemical treatment was not a predictor of bacterial microbiome variation, bacterial communities shifted throughout storage with many of the trends reversing when samples were removed and left at room temperature. Time in cold storage decreased the relative abundance of Pseudomonas and DPA application reduced the relative abundance of Aureobasidium, both notable biocontrol genera. These results highlight how chemical applications like DPA may have unintended effects on beneficial microbes that protect crops from pathogen infection.

Fruits constitute a critical part of a healthy diet. However, they often perish prior to consumption due to unpredictable ripening. Especially in climacteric fruit, blockage in the perception or synthesis of ethylene has been used to prolong shelf life. European pear (Pyrus communis) are classified as climacteric fruit. However, System 2 ethylene production requires a genetically pre-determined period of cold conditioning, which triggers ripening—in addition, applying 1-MCP, an ethylene perception inhibitor, indefinitely blocks ripening. Using a physiological and developmental transcriptomics approach, we have shown that in 1-MCP fruit stored in a controlled atmosphere, activating alternative respiration via glyoxylic acid stimulation of AOX expression can reverse the effect of 1-MCP. Interestingly, 1-MCP fruit without CA storage responds differently to glyoxylic acid. It shows classic signs of senescence. The underlying processes of ripening and senescence can be discerned by utilizing the fruit that has been treated differently post-1-MCP application. This knowledge is expected to aid in identifying strategies to prolong fruit shelf life.

Phytopathogenic fungi can cause rots during cold storage leading to the loss of pear fruit and significant economic costs. Currently, all commercially available pear varieties are susceptible to postharvest rots. Genetic resistance to fruit rot pathogens including Penicillium expansum and Colletotrichum spp. has been identified in wild apple germplasm. The objective of this study was to evaluate diverse genotypes of European pears (Pyrus communis L.) for disease incidence during cold storage and evaluate susceptibility to prevalent phytopathogenic fungi by directly challenging fruit using a wound inoculation method. Fruit from 38 pear genotypes were harvested at maturity, then evaluated weekly for the presence of postharvest rots during cold storage. If rot was observed, the diseased fruits were removed from cold storage and fungal isolates were collected from fruit with disease symptoms. The identity of fungal isolates was determined based on morphology and genetic sequencing of marker genes including ITS and TEF1. After 12 weeks in cold storage, the incidence of rot ranged from 8.3% to 100%. Colletotrichum was the most prevalent genus isolated from the rotting pears. Twenty pear genotypes were directly challenged with P. expansum or C. fioriniae using a wound inoculation method on fruit that was harvested at commercial maturity. Five genotypes had significantly reduced disease development when challenged with P. expansum compared to susceptible varieties Gem and Bartlett. Four of these five genotypes also had significantly reduced disease development when challenged with C. fioriniae. One additional genotype was found to have significantly reduced disease development when challenged with C. fioriniae but was highly susceptible to P. expansum. These results will be a valuable resource for pear breeders and aid efforts to develop European pear varieties that have genetic resistance to fruit rot pathogens.

Non-invasive Assessment of Haskap Growth (Lonicera caerulea) Utilizing X-ray Computed Tomography and Image Processing - Arturo Duarte Sierra
Vase Life Prediction for Cut Roses Using Deep Learning and Hyperspectral Imagining Techniques - Yongtae Kim
Extending the Postharvest Storage of Caladium Tubers to Unlock Late-Season Pot Plant Production Potential in Florida - Gasselle Cordova
Analysis of Oxidative Decreases in Hop (Humulus lupulus L.) Bitter Acids Produced Postharvest - Katie Stenmark
Transcriptome Analysis Revealed that Metabolites and Hormone Signaling Pathway Differently Respond to Non-chilling and Chilling Temperatures in Cucumber (Cucumis sativus L.) Fruit During Storage - Yujin Sim
Fresh Weight of Indoor-Grown Lettuce under Different Postharvest Storage Practices -Caroline Blanchard
Modified Hydrocooling and Optimized Postharvest Handling Practices Can Improve the Shelf Life of Water Spinach During Summer in Humid Subtropical Regions - Wei Shiang Liao
Discovery of Biomarkers for Postharvest Pecan Color Stability Using Metabolomics and Machine Learning Algorithms - Min Jeong Kang
Evaluating the Effects of Controlled Atmosphere Storage on Two Georgia-grown Pecan Cultivars - Ramsey Corn

The latest advances in technology have made it easier to accurately assess the quality of fresh produce, reducing the amount of physical handling required. Computed tomography (CT) is a non-intrusive method that can effectively monitor and categorize fresh produce at different stages of development and maturity. Implementing novel CT scanning techniques can provide innovative means for classifying fresh produce in the early stages of development. The present work provides information for the calculation of the volume and the porosity of the haskap during its ontology. Samples of haskap were taken at four stages of growth prior to harvest and at the time of harvest. Image data were acquired using X-ray microcomputed tomography (SkyScan 1272, Bruker, Billerica, MA, USA) at a resolution of 19.69 μm per pixel, operating at 60 kV and 166 μA, using a 0.25 mm aluminum filter. The resultant data was exported to the BMP file format. BMP files were then processed using Avizo 3.0 (Thermo Fisher Scientific, Waltham, Massachusetts, USA). Automated thresholding using factorization in criteria was applied to the 8-bit images. Subsequently, the images were labeled and an axis connectivity of 26 neighborhoods was established. Finally, a measurement was derived using the volume fraction tool. The results showed that the porosity at stage 3 was 26.56%. It then decreased to 7.52% in the 4th stage and reached a peak of 13.45% during the harvesting stage. These results may have implications for commercial cultivation strategies and optimization of pre- and post-harvest practices and add to the existing understanding of Haskap growth and development.

Japan is a major export market for the Korean cut rose flower industry. The longevity of cut roses significantly influences consumer purchasing decisions, prompting Japan to establish a quality guarantee system to ensure cut flower longevity. However, existing longevity guarantee methods rely heavily on subjective evaluations, overlooking critical factors such as senescence characteristics and disease infections. Hyperspectral imaging (HSI) technique is used for quality control of many fruits and can be performed at video rates, and could thus provide accurate data on aspects of cut flower quality. The You Only Look Once version 8 (YOLOv8) and Random Forest models for object detection and classification enable consistent quality assessment and swift longevity prediction. In this study, we developed a non-contact and rapid detection technique for the potential longevity of cut roses using deep learning techniques based on HSI data. Cut ‘Unforgettable’, ‘Egg Tart’, and ‘Catalina’ rose flowers were held in wet conditions during the exportation to Japan. HSI data within the visible near-infrared range 450-900 nm wavelengths were obtained for analysis of the disease infection and quality of cut roses. Image data of diseased cut roses were collected and corresponding data processing was carried out to build diseased cut roses and quality detection dataset. We developed the longevity prediction model based on scoring a grading standard on the flower quality and this model was then used to predict the longevity and evaluate quality changes of cut roses after exporting to Japan. The results showed that the longevity of exported cut roses was 8 d (‘Egg Tart’), 5.9 d (‘Catalina’), and 4.9 d (‘Unforgettable’). The longevity of cut roses was primarily terminated by gray mold disease (‘Unforgettable’ and ‘Catalina’), petal wilting and discoloration (‘Egg Tart’ and ‘Catalina’), and petal abscission (‘Catalina’). The predictive accuracy of the three rose flowers longevity prediction model was three rose flowers ‘Egg Tart’ (r2=0.80), ‘Unforgettable’ (r2=0.78), and ‘Catalina’ (r2=0.65). These results demonstrate that the combination of HSI and deep learning is a reliable method for evaluating the longevity of exported cut roses.

Florida is home to the largest caladium production in the world, supplying essentially all the global caladium tuber demand. These plants are famous for their vibrant leaf colors and patterns and are asexually propagated through tubers. Following plant development, tubers are harvested and stored for a few months before being forced from March to September for potted plant production and direct landscape planting. During extended postharvest storage, caladium tubers face the risk of severe weight loss, tissue decay, and Fusarium tuber rot. The current practice of storage under ambient conditions with high temperatures and high relative humidity exacerbates weight loss and tuber rot. The challenges of long-term tuber storage make it difficult to produce pot caladium plants for winter holidays, including Thanksgiving, Christmas, and New Year. These challenges also affect the commercialization of tubers in the Southern Hemisphere during the summer. Opening these marketing opportunities can allow growers to extend and increase their production. Additionally, the identification of caladium tubers suitable for late-season production will give Florida growers a competitive advantage. To identify caladium varieties with long-term tuber storage potential and late-season production, 12 varieties were evaluated to target Thanksgiving and Valentine’s Day. No.1-sized tubers were potted in 5-inch containers and grown in a greenhouse. For each variety, 10 tubers were monitored for sprouting and leaf expansion and later evaluated for plant quality using a rating scale from 1 to 5. Eight cultivars were identified as suitable to grow for Thanksgiving, whereas 3 were identified for Valentine’s Day based on long-term storage potential and plant performance. Identification of cultivars will allow growers to expand their commercialization window not only for major holidays but also to supply tuber demand to the Southern Hemisphere.

Nearing maturity, female hop plants develop inflorescences called hop cones. Inside of a mature hop cone is the lupulin gland where glandular trichomes are present. Within the lupulin gland, the glandular trichomes secrete alpha acids (α), and beta acids (β). Hop bitter acids are extremely sensitive to photolysis and oxidation reactions causing the degradation of α-acids and β-acids which negatively affect their use in beer, and the beer brewing industry accounts for 98% of world use of hops (Fandino et al., 2015). Determining hop storage index (HSI) is a way to measure the amount of α and β-acids lost during postharvest handling. HSI is a ratio determined by measuring the spectrophotometric UV absorption of hop extract at 275nm for oxidative compounds, and 325nm for bitter acids. Bitter acids and any oxidative decreases were determined in eight cultivars of hops (‘Cascade’, ‘Chinook’, ‘Comet’, ‘Mount Rainier’, ‘Newport’, ‘Tahoma’, ‘Willamette’, ‘Zeus’) produced at the Cimarron Valley Research Station in Perkins, Oklahoma. Mature hop cones were hand harvested at 80% moisture and dried at ambient temperature to 8-10% moisture using a centrifugal fan. Hops were stored no longer than six months frozen under nitrogen in vacuum sealed bags until analysis. Hop bitter acids were extracted using toluene and UV absorbance was measured at 355, 325, and 275nm using a spectrophotometer. Based on the HSI, hops were assigned a quality score of good (0.4). Seven of the eight cultivars of hops were of good quality (‘Cascade’, 0.20; ‘Chinook’, 0.19; ‘Comet’, 0.17; ‘Mount Rainier’, 0.12; ‘Newport’, 0.23; ‘Tahoma’, 0.18; ‘Willamette’, 0.22). ‘Zeus’ hops were of questionable quality (0.31) but contained a slightly higher moisture content at storage (11%) than the other cultivars (7-10%), which could have negatively affected hop storage quality. Understanding sources of oxidative stresses to hop bitter acids during postharvest handling is valuable information for determining and maintaining hop quality.

Cucumber (Cucumis sativus L.) fruit is sensitive to chilling temperatures during storage, and the physiological mechanism of chilling injury (CI) is not well known. Understanding the chilling response in cucumber fruit is necessary to delay CI and extend the storage duration during postharvest. In this study, our goal was to identify CI symptoms and investigate key factors influencing on the chilling response in cucumber fruit (C. sativus var. ‘Hangang’). To assess the severity of CI symptoms, cucumber fruits were stored at low temperatures of both 13 °C (non-chilling response) and 2 °C (chilling response) for 9 d and exposed to 20 °C. As a result, various CI symptoms of discoloration, shirankage, water-soaking and necrosis area appeared on a cucumber fruit peel stored at 2 °C, resulting in loss of its marketability from 6 d. To clear the cellular mechanism of CI symptoms, transcriptome analysis was conducted in cucumber fruit stored for 1 d (early response) and 6 d (late response). The results suggested that phytohormone synthesis and signalling played major roles in chilling responses. To reveal the main phytohormone involved in the chilling response, eight phytohormones were quantified in cucumber fruit peel using LC-MS/MS. Among them, ABA was not sufficiently accumulated at 2 °C compared to 13 °C during the early response, and SA levels gradually increased by persisting chilling stress. Through these results, major phytohormone synthesis and signalling genes were selected by RT-qPCR. For further understanding of CI, targeted metabolite analysis was conducted, and amino acids such as isoleucine, serine, valine, threonine, and sucrose were identified as significant metabolites for acclimating to chilling temperatures. These findings help to elucidate the hormonal mechanisms involved in chilling response as well as the complex interplay of various molecular components involved in chilling response of cucumber fruit during storage.

Two-thirds of food waste occurs once the product has reached the consumer. In an effort to extend the shelf-life of produce, a common practice of hydroponic lettuce growers, particularly those who use controlled environment production systems such as greenhouses or indoor growing facilities, is to harvest the lettuce without removing the root tissue. However, the postharvest quality of this “living lettuce” has not been a focus of academic research, and its effect on the shelf-life of the produce is unknown. In this study, lettuce harvested from an indoor production facility that utilizes a vertical hydroponic setup was subjected to four postharvest treatments. Treatments included harvesting the complete lettuce plant or removing the roots after harvesting and storing the harvested produce either inside or outside of a plastic clamshell. Lettuce was stored for 28 days at 4 °C and 85% relative humidity. Fresh weight of the lettuce heads was assessed for 18 days post-harvest. As days in storage increased, the fresh weight of lettuce decreased by 0.37 grams per day. The rate of lettuce fresh weight decrease was the same across postharvest treatments, but the lettuce with roots intact stored inside a plastic clamshell had a higher fresh weight across all measured time points. A better understanding of the relationship between fresh lettuce weight and storage time under different postharvest conditions can help to increase the shelf life of the stored produce and reduce food waste.

In an effort to improve the shelf life of water spinach (Ipomoea aquatica Forsk.) and amaranth (Amaranthus tricolor L.) during summer in humid subtropical regions like northern Taiwan, the study investigated the effectiveness of modified hydrocooling and optimized postharvest handling practices. Most farmers in Taiwan often compromised postharvest vegetable quality due to uneven cooling. The first trial implemented a modified hydrocooling system using a 10-minute 5°C shower with a multi-hole perforated pipe and smaller baskets for precooling to substitute the conventional method. The results showed that the modified hydrocooling improved cooling uniformity and reduced vegetable loss rates. Meanwhile, for some farmers needed to meet the specialized market requirement which extend vegetable shelf life, the second trial conducted optimized postharvest handling practices including storage vegetables at 11°C, consistently clean 10°C water for washing/hydrocooling, and wrapping vegetables in plastic film. These practices revealed significantly decreased the water spinach quality loss for longer duration but less effective for amaranth. Even with the addition of hypochlorous acid in washing/hydrocooling water, the shelf life of amaranth was difficult to extend due to severe pre-harvest leaf disease. In conclusion, the study showed that modified hydrocooling offers benefits for most conventional farmers by reducing vegetable loss rates. On the other hands, for farmers needed to meet the specialized market requirement, optimized postharvest handling practices significantly improves the quality of water spinach in longer shelf life. Also, the research emphasized the importance of disease management in amaranth cultivation for postharvest quality.

Nut kernel color is a crucial quality indicator affecting consumers' first impression of the product. In the postharvest stage, nut kernels (e.g., pecans) gradually darken with increasing blue/red colors, which have a negative impact on consumers' preference. While growing evidence suggests that plant phenolics and their derivatives are linked to pecan kernel color, the compounds (biomarkers) responsible for kernel color stability during storage remain elusive. We hypothesized that: (1) the phenotype of pecan color exhibits notable variation among different cultivars during storage; and (2) this variation is attributed to changes in metabolites and their combination effects in the stage of phenolic biosynthetic pathways related to color formation. Here, pathway-based metabolomics with machine learning (ML) algorithms were employed to identify key metabolites of postharvest pecan color stability. Nine pecan cultivars with different color stabilities were selected, and the color of each cultivar was measured over a 6-month storage period (0, 1, 2, 3, and 6 months). Metabolites in phenylpropanoid, flavonoid, and anthocyanin biosynthetic pathways were analyzed in the outer layer of the kernel (testa) using liquid chromatography–mass spectrometry. Different ML models were compared to find relevant biomarkers of pecan color phenotypes. Lasso regression and support vector machine (linear kernel) in conjunction with recursive feature elimination were chosen as the most effective models to select biomarkers that predict the kernel color of pecans. Results revealed twenty marker compounds (flavonoid precursors, flavonoids, anthocyanidins, and anthocyanins) within phenylpropanoid, flavonoid, and anthocyanin biosynthetic pathways, and their roles in pecan color phenotypes during storage. Our findings provide a foundation for future research in the area and will help select genes/proteins for the breeding of pecans with stable and desirable kernel color. The collected information on biomarkers and their effects will also help set up strategies for the quality control of pecans after harvest.

Pecans are an important commodity in Georgia with 180,000 planted acres in 2022. The crop undergoes quality deterioration through lipid oxidation, off-flavor development, and kernel browning in storage. Many new varieties have been introduced to the State with little known about their storage viability. Knowing the varieties performance after harvest can help growers plan for an uncertain market by reducing storage costs. The standard industry technique for storage is low temperature (0°C) cold rooms, which can quickly become expensive over long periods of time due to rising electricity costs. The addition of controlled atmosphere (CA) may possibly aid in reducing oxidation rate and kernel browning during storage. The controlled atmosphere would reduce the amount of oxygen (O2) substituted by carbon dioxide (CO2). Previous studies reported shelf-life increases after oxygen levels were reduced to 2-3% using nitrogen (N2), however carbon dioxide is less commonly seen. Half pecan kernels were hand shelled and sorted before being stored under varied conditions for up to five months. Three treatments were applied to two GA pecan varieties (‘Desirable’ and ‘Sumner’). Conditions included elevated storage temperature at 10 °C, low temperature storage (5 °C) plus CA (10% CO2 4% O2), high temperature storage plus CA, and a control of cold storage at (0 °C). Quality assessments were conducted every month for change of weight, firmness, and color values. Firmness values were conducted using MecMesin texture analyzer to penetrate the half kernel until the breakpoint was achieved. A significant difference was seen in ‘Desirable’ when comparing the days of storage against the atmospheric conditions in the chroma values with the CA treatments exhibiting higher chroma. The Sumner variety saw significant differences in the chroma after two months of storage and varied differences in lightness values throughout storage. A significant difference was seen between the two varieties in firmness values with Sumner exhibiting higher firmness.

Speaker: Dr. Al Kovaleski
Studies in species spanning the seed plant phylogeny, including ornamental plants, urban trees, and woody perennial fruit crops have shown that dormancy progresses at a similar pace for all when using a cold hardiness-related phenotype. However, clear differences exist in “chill requirement” and adaptation across environments even for cultivars within the same species. While these concepts appear to be in conflict, they are not. Here we will explore ongoing work, and a combination of data and modeling approaches to understand how this comes to be based on new dormancy theory.