ASHS 2024 Conference

The Effect of Fruit Tree Virus and Viroid Infections on Tree Growth and Fruit Quality - Sang Yun Cho
Bacteriophage as an Alternative Method to Control Salmonella enterica in Water-Recirculated Systems for Lettuce Production - Camila Rodrigues
Transfer of Escherichia coli from Plastic Mulch to Tomato and Pepper Fruit by Ground Contact in a Field Environment - Autumn Burnett
Assessing the Impact of Biological Soil Amendments of Animal Origin on Bell Pepper Microbial Safety, Soil Properties, and Quality - Daniel Leiva
Inhibiting Foodborne Pathogens and Biofilms on Fresh Produce by Nano-emulsions Developed from Lactobacillus-Derived Exopolysaccharide and Eugenol - Sangeeta Balyan
Evaluating Nutritional Quality and Consumer Acceptability of Lettuce (Lactuca sativa L.) Grown with a Movable High Tunnel - Cary Rivard

This study aimed to investigate the impact of virus and viroid infections on tree growth and fruit quality attributes in apple, pear, peach, and grape. Trials were conducted in 2019 at the National Institute of Horticultural and Herbal Science in Korea, utilizing virus-infected, viroid-infected, combined virus/viroid-infected, and uninfected trees in an experimental fruit-tree orchard. Additionally, the experimental orchard served as an exhibition package for farmers and agricultural workers. Annual measurements of tree growth were compared between virus-free and virus/viroid-infected trees. Fruit quality attributes, including yield, weight, firmness, titratable acidity, and anthocyanin content, were assessed during 2021-2023. The results revealed significant differences between virus-free trees and those infected with virus, viroid, or both. Viral and viroid infections led to reduced tree height, trunk area, fruit yield, fruit weight, and anthocyanin content, while increasing fruit firmness and titratable acidity, respectively. These findings are expected to contribute to fruit tree virus and viroid disease control and fruit cultivation management. Furthermore, we anticipate that this research will enhance the understanding of agricultural stakeholders through scientific and comprehensive evidence on the damages caused by fruit tree viruses and viroid infections, thereby stimulating the adoption of virus-free stocks and promoting their widespread distribution.

In recent years, controlled environment agriculture (CEA) has gained popularity as a sustainable and efficient method of cultivation, offering solutions to challenges posed by traditional farming practices and meeting the growing demand for high-quality produce. However, advancements in CEA have raised concerns about food safety, requiring new approaches to minimize the risk of produce contamination. This research explores the effectiveness of a bacteriophage cocktail as a biocontrol agent against Salmonella contamination in lettuce grown in water-recirculating systems. Salmonella Newport and Salmonella Typhimurium (103 CFU/mL) were inoculated into aquaponic and hydroponic nutrient solutions into a water-recirculating system to mimic sporadic contamination, followed by treatment with a bacteriophage cocktail (S7, S10, and S13) at different multiplicities of infection (MOI 0.01 and MOI 1). The results demonstrated a significant reduction in Salmonella Newport and Salmonella Typhimurium populations at both MOI 0.01 and MOI 1 in aquaponic and hydroponic nutrient solutions, with levels reaching below the limit of detection (LOD) after 3 to 4 days of bacteriophage cocktail inoculation. From the plant parts, there was a significant reduction in the microbial population of Salmonella serovars in media plugs and roots from the hydroponic nutrient solution, reaching levels below the LOD in both phage cocktail treatments after a 2-day inoculation period. Contrarily, significant reductions were not observed in Salmonella serovar levels in plant roots and media plugs from the aquaponic nutrient solution treatment. These findings highlight the potential of utilizing bacteriophages to improve food safety in indoor-grown lettuce by controlling Salmonella populations while also indicating the necessity for further research to understand the microbial dynamics within each type of system.

In the southeast US, tomatoes (Solanum lycopersicum) and bell pepper (Capsicum annuum) are typically staked and trellised and grown using plastic mulch for weed control. The Produce Safety Rule that is part of the Food Safety Modernization Act requires that fruit from tomato and pepper be declared non-harvestable if they fall to the ground or contact the ground through drooping while attached to the plant before harvest. The objective of this study was to quantify percent transfer from plastic mulch inoculated with Escherichia coli with green fluorescent protein (GFP) to pepper and tomato fruit making ground contact in spring and fall growing seasons. E. coli GFP was spot inoculated on plastic mulch in the field using ten - 10 µL drops (100 uL total) at approximately 7 log CFU/mL and allowed to dry for at least 1 h before fruit contact. In the spring season, white and black colored plastic mulch were compared and in the fall season, reused (second crop) plastic mulch and new white plastic mulch were compared. Fruit contacted the ground by drooping (remained attached to the plant) with a contact time of 1 h or 24 h as well as contact through dropping fruit at heights of 30 cm, 60 cm, and 120 cm (n=9 per treatment). After inoculum was allowed to dry on the plastic mulch, the E. coli population was reduced an average of 2.8 and 4.8 log CFU/mL, in the spring and fall seasons, respectively. In both seasons all dropped peppers had significantly different percent transfer than dropped tomatoes, while drooping fruit were not significantly different between the two commodities. In the fall, dropped fruit on new plastic had significantly greater bacterial transfer than fruit which was dropped on reused plastic for both tomato and pepper. No significant differences were obtained between drooping duration treatments or between the different height of dropping in either season. There was relatively low transfer overall from both drooping and dropping of fruit on inoculated plastic mulch, regardless of crop or season. Further, in this inoculated study, results suggest that there was a significant reduction in E. coli populations in a field setting after a short period of exposure to the natural environment.

The shift towards sustainable food production has forced farmers to explore alternative practices, such as the use of Biological Soil Amendments of Animal Origin (BSAAOs). However, concerns due to food safety regulations restrict the use of BSAAOs on crops consumed raw. This study assessed the microbial safety of bell peppers, the impact of BSAAOs on soil properties, and on quality. The field experiment was established with 36 plots (88 ft2) planted with bell pepper seedlings on 12-inch centers for a total of 20 plants/plot. BSAAO treatments consisted of either raw CM, PL, or non-BSAAO (NB) application, with each treatment being either tilled or top dressed. E. coli/Total Coliforms were determined from soil samples collected during weeks 1, 3, 6, and 12 and from harvested bell peppers during weeks 13 and 14. Nalidixic acid resistant E. coli was inoculated on bell peppers for a 5-day die-off determination (40 inoculated on the upper portion and 40 on the side). Ammonium and nitrate content in soil was determined before and after the establishment of the experiment, while SOM content was determined from soil samples collected after the experiment. Higher levels of E. coli (1.1–2.6 log CFU/g) and total coliforms (4.1–4.7 log CFU/g) were reported in plots with BSAAO application as compared to NB plots (1.00–1.17 log CFU/g; 3.89–4.14 respectively), although levels decreased significantly after one week. E. coli levels on bell peppers previously inoculated declined by over 2 logs within four days, with a die-off rate of 0.57 and 0.51 log CFU/cm2/day for bell peppers inoculated on top and on the side, respectively. CM tilled plots had slightly higher E. coli levels (0.02 log CFU/ cm2). The quality of bell peppers was unaffected by BSAAOs. NB top dressed and CM tilled plots had higher soil organic matter (SOM) content (2.18 and 2.08%, respectively) while both CM and PL increased soil nitrate and ammonium content significantly by the end of the experiment. CM and PL can enrich soil with inorganic nitrogen without compromising produce quality. However, the use of untreated BSAAOs poses a risk of cross-contamination, which highlights the importance of minimizing potential contamination events. Overall, this study highlighted the potential of CM and PL as BSAAOs to enhance soil fertility while maintaining food safety. It emphasized the need for appropriate management practices to mitigate risks associated with microbial contamination, ensuring the safety and sustainability of food production systems.

The proliferation of foodborne pathogens and the formation of biofilms poses a major threat to the food industry, particularly in fresh produce. Raw and minimally processed fruits and vegetables are often sold to consumers in ready-to-use or ready-to-eat forms and are at the forefront of this risk. These products lack preservatives and rarely undergo any heat processing prior to consumption, making them more susceptible to contamination. To address this, we synthesized an oil/water emulsion encapsulating eugenol, using exopolysaccharide extracted from Lactobacillus as a natural emulsifier, and investigated its effectiveness against pathogenic cell populations within biofilm matrices. Different strains of Listeria monocytogenes, Salmonella, and E. coli were studied; results reveal substantial variations in biofilm-forming abilities among different E. coli, Salmonella, and L. monocytogenes strains. Specifically, L. monocytogenes V7 and Scott A strains displayed resistance to the emulsion, resulting in a minimal reduction of 2.8 log CFU/cm2 on the stainless-steel surface within the biofilm. Conversely, other strains exhibited reductions ranging from 3 to 4.5 log CFU/cm2. Most strains’ biofilm inhibition was 85% on plastic surfaces, whereas L. monocytogenes V7, Scott A, and Salmonella enterica ATCC 35664 showed less inhibition. The emulsion was applied to fresh produce (tomatoes, blueberries, and lettuce), where the reduction in E. coli and Salmonella biofilms, along with planktonic cells, varied from 0.53 to 5.1 log CFU/cm2, indicating that the emulsion significantly inhibited the growth of the tested pathogens. In conclusion, the results indicate that biofilm inhibition depends on the microbial species due to the observed individual variation in strains. However, combining eugenol and exopolysaccharide as emulsions is a promising natural alternative and sustainable technology for removing pathogenic biofilms. This research has the potential to advance food safety and hygiene standards, with practical applications in preserving fresh produce and disinfecting surfaces. This work was supported by USDA-NIFA- SCRI- 2017-51181-26834 through the National Center of Excellence for Melon at the Vegetable and Fruit Improvement Center of Texas A

Light quality is known to affect the growth and phytochemical content of numerous crops, including lettuce (Lactuca sativa L.). High tunnel production of lettuce provides many benefits to growers including increased yield due to higher soil temperatures and protection from abiotic stressors, such as strong wind and heavy rains. However, the use of UV-blocking polyethylene films can also result in lower antioxidant capacity and phenolic content, leading to a decrease in nutritional quality compared to lettuce grown in the open-field. Movable tunnels provide the ability to expose the crop to full-spectrum light once the crop has grown to full size. Our objective was to identify management strategies to optimize yield, phytochemical production, color, safety, and consumer acceptability of red-leaf cultivar (‘New Red Fire’). Lettuce was planted in a movable high tunnel April 2022 and exposed to 0, 2, 7, or 14 days of full sun prior to harvest. Total marketable yield, leaf color (L*a*b* color space), total phenolic content (TPC) and anthocyanin content were measured at harvest. Lettuce consumers (N=100) were asked to rate overall liking and various sensory attributes using continuous intensity scales, CATA, and open-ended comments. Total marketable yield and TPC were not affected. Leaf redness (a*) and anthocyanin content were significantly higher after 14, 7, and 2 days of full-sun exposure compared to 0 days. Significant differences were found in consumer liking for overall liking, color intensity, and ruffleness. The crop that was exposed to 14 days of full-spectrum light had a higher liking and more red color intensity. Using a movable tunnel system provides lettuce growers the ability to affect the color, phytochemical content, and consumer liking of their crop to varying degrees. This level of flexibility provides local, small-scale growers a crucial advantage in marketing their produce.

Evaluation of Pierce's Disease-resistant Grapevine Cultivars in South Carolina - Annie Bruno
Diversity and Abundance of Bees Visiting Grape Flowers in Wisconsin Vineyards - Christelle Guedot
The Grape Health Index: Validation of a New Methodology for Quantifying Wine Grape Spoilage by Means of FT-MIR Spectroscopy - Sonet Van Zyl
World Grape Rootstocks Pedigree Review - Alireza Rahemi
Genome Database for Vaccinium: Genomics Data and Tools to Facilitate Research - Jodi Humann
Use of Glycine Betaine and Kelp Extract Mitigates Heat Stress in Red Raspberry (Rubus idaeus) - Givemore Munashe Makonya

Recently, there has been an increased interest in wine grape (Vitis vinifera) production in South Carolina (SC). The warm and humid climate in SC creates a conducive environment for a high risk of disease incidence. Despite the typical climate, SC has droughts periodically. Pierce’s Disease (PD), caused by the xylem-limited bacterium Xylella fastidiosa (Xf), is a major limiting factor to grapevine cultivation throughout the United States and, specifically, in the southeastern U.S. However, PD-resistant grapevine cultivars have been released by UC Davis. Xf-infected grapes can be heavily influenced by water deficit. Preliminary data from a drought-stress experiment in the Summer of 2023 indicated two PD-resistant cultivars perform well under a water deficit. The objective of this study was to evaluate the water dynamics and gas exchange of PD-resistant cultivars during periods of drought. In March 2023, five PD- resistant cultivars and one French-American hybrid were planted in a variety trial at Musser Fruit Research Center in Seneca, SC. The drought-stressed PD-resistant ‘Paseante Noir’ and ‘Errante Noir’ had similar carbon dioxide assimilation to well-watered PD-resistant cultivars. PD-resistant cultivar ‘Ambulo Blanc’ showed the worst leaf water status and lowest carbon dioxide assimilation when stressed. In 2024, physiological measurements, such as sap flow, trunk diameter, gas exchange, and water potential, were taken throughout the growing season. Our results supported previous research that some PD- resistant grapevine cultivars perform well in the field under drought conditions.

Bees play an essential role in plant pollination and the ecosystem services they provide to increase the quantity and quality of many agricultural crops. Many food crops are either dependent on, or benefit from, bee pollination, yet bees have experienced population declines due to a combination of factors including pesticide exposure, susceptibility to pathogens and parasites, habitat loss through land use intensification, and lack of suitable resources. Most studies on pollinator conservation and pollination services focus on pollinator-dependent crops and fail to address the role self- and wind-pollinated plants, such as grapes, play in maintaining or threatening pollinators. In vineyards, bees are often overlooked, as they are not required for the pollination of grape. This study aimed to survey the bees visiting grape flowers of cold climate grapes by recording the abundance and diversity of bees. Observations were conducted at six commercial vineyards in South Central Wisconsin during grape bloom, late May to mid-June in 2022. At each vineyard, vines of mixed cold-climate grape varieties were observed between 10:00 and 17:00 hrs on six separate days. Timed observations (5 min per vine) of bees visiting grape inflorescences were conducted at ten randomly selected grape plants per plot per day. In addition, each day, one 10 min wandering transect was walked along two adjacent rows of grape vines and all bees observed visiting grape inflorescences were recorded. To prevent destructive sampling, bees were identified in the field to species when known or assigned to one of 14 pre-determined morphospecies representing 24 likely genera. Timed plant observations showed a total of 1,059 floral visitations, with an average of 0.31 /- 0.16 bees per minute of sampling. During the wandering transects, a total of 417 floral visitations were observed, with 1.44 /- 0.43 bee visits per minute of sampling. This research underscores the need for reduced pesticide inputs, particularly around bloom time, to protect the diversity and abundance of bees visiting grape inflorescences.

For wineries processing hand harvested grapes, a visual inspection of microbial spoilage is expedient and cost effective. However, due to the increasing adoption of machine harvesters, which frequently rupture berry skins making visual inspection less precise, and the high degree of error of visual inspections between individuals, a quantitative approach to assess spoilage is needed. Fourier Transform Mid-Infrared Spectroscopy (FT-MIR), combined with multivariate analysis, is being investigated as an approach to predict grape health as a sample that can be analyzed in less than one minute. Calibration data was obtained from grape samples of Chardonnay, Riesling, Petite Sirah, and Zinfandel, which were sorted into fractions of 0, 5, 10, 15, and 20% microbially impacted clusters in healthy grape material, and analyzed using the spectrophotometer. The spectral data was analyzed using the Partial Least Squares (PLS) regression. Predicting factors included volatile acidity (VA), gluconic acid, ethanol, lactic acid, glucose-fructose content, Brix, titratable acidity, tartaric acid, malic acid, pH, alpha amino nitrogen, ammonia, and yeast assimilable nitrogen (YAN). A model was selected which optimized for a high coefficient of determination (R2) and a low root mean squared error (RMSE). Additional selection criteria included the extent to which predicting factors have been observed to correlate with microbial spoilage in other studies. The model selected had a R2 of 0.620 and a RMSE of 4.596, making it suitable for identifying grapes marked by spoilage. The output of the model was converted to Grape Health Index (GHI) Scores for better usability by operators at the test stand. The GHI was implemented at the test stands of two large-scale wineries during the 2022 and 2023 seasons. Additional wineries will be added in 2024. The testing of the impact of microbial spoilage on wine aging is currently underway. Wines made in 2018, 2019 and 2020 are evaluated for color degradation and browning, anthocyanins, tannins, pigments, and acetaldehyde. The results will be compared with the original harvest results for comparative analysis concluding the project.

Grapes belong to the Vitis genus, which includes about 80 species and is considered as two sub-genera, including Euvitis and Muscadinia. Muscadine grapes are sometimes considered as a separate genus in different classification systems and include three species: Muscadinia rotundifolia, Muscadinia munsoniana, and Muscadinia popenoei. The Euvitis sub-genus includes the most commercially important grape varieties. Euvitis is divided into three groups. 1) The American group consists of about 30 species that are important for rootstock breeding; 2) The Asian group consists of about 50 species, which, up to this point, have been underutilized for grape cultivation; and 3) The Eurasian group consists of a single species, Vitis vinifera L., which includes two sub-species of V. vinifera: V. vinifera subsp. sylvestris, considered to be the wild form of grape; and V. vinifera subsp. vinifera, refers to cultivated forms. Of all species in the genus Vitis, the V. vinifera, is undoubtedly the most important worldwide for commercializing grapes and represents the most cultivated varieties worldwide. Other grape species contributed to breeding programs beyond the traditional efforts of rootstock hybridization from wild species. An aphid-like pest, phylloxera (Daktulosphaira vitifoliae), causes damage by feeding on the structural roots of V. vinifera, eventually leading to vine death. In an effort, American Vitis species that coevolved with phylloxera were eventually used as rootstocks for the widely planted V. vinifera scion cultivars. Later, crosses between these wild species became common, and historical breeding efforts led to the modern grape rootstock breeding programs currently active worldwide. Two-thirds of American species have already been used for rootstock breeding. However, it has been reported that the most commonly available rootstocks are derived from just three American species (Vitis berlandieri, Vitis rupestris, and Vitis riparia). Therefore, the most common grape rootstocks have a narrow genetic base, and efforts to extend the gene pools for breeding programs by using other species are of ongoing importance to the industry and scientific community. There are around 1500 grape rootstocks developed in the world, of which around 50 are commonly used as commercial rootstock and play a fundamental role in resistance to biotic and abiotic stresses and adaptation of grapevine to different environmental conditions, a factor that has opened commercial grape growing to regions that might otherwise be overlooked.

The Genome Database for Vaccinium (GDV, www.vaccinium.org) is a community database resource for Vaccinium researchers and breeders. The database contains genomics data for blueberry, cranberry, bilberry, and lingonberry that are integrated with other types of data such as genetic maps, markers, and QTL/GWAS. The genomics data is accessible via a plethora of search interfaces and tools. GDV has over 40 genomes and allows users to view the genomes in JBrowse, query sequences against the genomes in BLAST and view genome synteny via the Synteny Viewer tool. Highly utilized genomes in JBrowse contain tracks of aligned markers, GWAS, and QTL. Standard GDV analyses on the genomes include synteny analysis and functional annotation of predicted genes with InterPro protein domains and GO terms as well as homology to known proteins. The genes and mRNAs of each genome, along with the functional annotations and orthologs/paralogs, are searchable on GDV. Representative genomes are available in the PathwayCyc tool which displays metabolic pathways and allows for transcriptomics or metabolomics data overlays. GDV also has the genomes and structural pangenomes from the Vaccinium Pangenome Project, a product of VacCAP. Expression datasets that are mapped to genomes are also available to explore using the Expression Heatmap tool. Also available in GDV is the Breeding Information Management System (BIMS) that allows breeders to manage and analyze the phenotypic and genotypic data and provides public access to GRIN phenotype data. This presentation will showcase how to access these genomics data through various tools.

Heat stress poses a significant threat to global food production and security by disrupting plant physiological and biochemical processes. Global simulation models predict a 4 to 5°C increase in atmospheric temperatures by the year 2100, as well as increases in the frequency of extreme heat events. This has necessitated preemptive measures to enhance the resiliency of horticultural crop production. Biostimulants, a class of agricultural products, show great promise in mitigating heat stress effects by enhancing physiological and biochemical stress tolerance. However, limited research exists on the efficacy of commercial biostimulant products in improving heat stress tolerance in horticultural crops. This study evaluated the impacts of three exogenously applied commercial biostimulants representing a range of active ingredients and included FRUIT ARMORTM, Optysil®, and KelpXpressTM [active ingredients glycine betaine, silicone, and kelp (Ascophyllum nodosum) extract, respectively], plus a water control, on physiological, biochemical, and growth parameters in different raspberry genotypes exposed to continuous heat stress (Tmax ≥ 35°C/day) in a glasshouse. Over a 28-day period, the biostimulants and the water control were applied weekly to three raspberry genotypes (‘Meeker’, WSU 2188, and ORUS 4715-2). The results indicated that ‘Meeker’ consistently maintained high chlorophyll fluorescence (Fv/Fm) and photosynthesis under control and biostimulant treatments. In contrast, WSU 2188 and ORUS 4715-2 exhibited increased Fv/Fm and photosynthesis when treated with FRUIT ARMORTM. Additionally, KelpXpressTM application improved Fv/Fm in WSU 2188. ‘Meeker’ and WSU 2188 treated with FRUIT ARMORTM and KelpXpressTM accumulated more anthocyanins and had greater shoot and total biomass compared to ORUS 4715-2. These findings underscore genotype-specific and biostimulant-dependent responses to heat stress mitigation. The superior physiological performance by ‘Meeker’ under both control conditions and biostimulant treatments indicates heat tolerance in the genotype. Furthermore, higher anthocyanins accumulation, improved Fv/Fm, enhanced gas exchange, and greater total biomass of WSU 2188, as well as improved Fv/Fm of ORUS 4715-2, suggests that application of the biostimulants contributed to enhanced repair and maintenance of photosystem II (PSII) structural integrity, improved photosynthetic performance, and increased antioxidative capabilities, which may have contributed to higher total biomass of raspberry treated with FRUIT ARMORTM relative to the untreated control. In summary, the positive impacts on physiological, biochemical, and growth parameters support the potential role of biostimulants in enhancing thermotolerance in raspberries and other horticultural crops exposed to heat stress.

Haplotype-Phased Genome Assemblies of ‘Sulhyang’ Strawberry (Fragaria ×ananassa) using PacBio Revio Sequencer - Youngjae Oh
Exploring the molecular basis of rootstock-mediated growth vigour in macadamia: Unravelling aquaporin gene dynamics - Pragya Dhakal Poudel
Multivariate Analysis of Fruit Composition Diversity Among the North Carolina Strawberry Germplasm Collection - Gina Fernandez
Improving Blueberry By Dissecting Fruit Texture - juan david jimenez pardo
Assessment of Fruit Composition and its Influence on Flavor and Consumer Preferences in Blackberry - Katelyn Lust-Moore
Sugar Content and Gene Expression Dynamics in Apple Spurs in Response to Fruit Load and Gibberellins - Qiuyi Fu
A Census and The Conservation of Malus coronaria in Michigan - Lily Christian

Cultivated strawberry (Fragaria ×ananassa Duch, 2n = 8× = 56) belongs to the family Rosaceae and is an allo-octoploid species. We report here a high-quality haplotype-phased genome assembly of a representative Korean short-day cultivar, ‘Sulhyang’ using a trio-binning approach. Using PacBio Revio long reads of ‘Sulhyang’ and whole genome paired-end reads (Illumina) of two parents ‘Akihime’, and ‘Yukbo’, we completed telomere-to-telomere phased genome assemblies of both haplotypes. The ‘Sulhyang’ genome was 797 Mb , with a long terminal repeat (LTR) assembly index (LAI) of 17.28. The genome was phased into two haplotypes, phase-1 (784.9 Mb with contig N50 of 12.34) and phase-2 (781 Mb with contig N50 of 16.04 Mb). The BUSCO analysis detected over 99% of conserved genes in the combined phased-1 and phased-2 assembly. Both haploid assemblies were annotated using RNA-Seq data representing various F. ×ananassa tissues from the NCBI sequence read archive, resulting in a total of 104,099 genes in the primary assembly. This haplotype-phased reference genome for ‘Sulhyang’ will broaden our knowledge of strawberry genome evolution and gene functions.

Rootstocks play a crucial role in shaping plant growth and vigour, driven by a complex interplay of physiological, molecular, and genetic factors. Aquaporins (AQPs), as key water transport proteins, are emerging as pivotal component in understanding rootstock-mediated vigour. However, evidence for rootstock effects in macadamia remains limited with no exploration into the mechanisms of rootstock-mediated vigour control, hindering progress in rootstock development for this crop. In this study, we aimed to explore the role of AQPs by conducting a genome-wide investigation on whole genome sequence of Macadamia integrifolia (‘HAES741’). This study identified 37 putative macadamia AQP (miAQP) genes belonging to 5 different sub-families including 11 plasma membrane intrinsic proteins, 10 tonoplast intrinsic proteins, 10 Nod26-like intrinsic proteins, 2 small and basic proteins and 6 X-intrinsic proteins. miAQP genes are unevenly distributed across 11 chromosomes with chromosome 7 possessing the most genes. To investigate the differential expression of plasma membrane intrinsic proteins (PIPs), in high- and low-vigour rootstocks, root, leaf, and stem tissues were collected from trees with a single scion ‘HAES741’ grafted on to 7 different rootstock genotypes . RNA from tissue samples were extracted by a modified CTAB RNA extraction protocol using the Zymo-spin™ IICR Column. RNA quality and quantity was checked via nano spectrophotometer and gel electrophoresis. Primer pairs for 11 PIP genes and 2 housekeeping genes (ACT and EF1b) were designed using Primer BLAST in NCBI. RNA samples were subjected to a real time quantitative RT-PCR. The tissue specific expression data will be analysed to observe differential expressions, if any, between high and low vigour rootstocks and scions. Differential expression patterns reveal the PIP genes associated with vigour control. The correlation between gene expression levels and rootstock vigour provides better understanding on the intrinsic molecular mechanism vigour regulation in macadamia. Moreover, comparative analysis of PIP gene expression between rootstock and scion can provide insights into the rootstock-scion interactions. Overall, results from this study offer a better understanding of the molecular basis of rootstock-mediated vigour control with implications for rootstocks development and orchard optimization in macadamia.

Strawberries are a highly sought-after fruit for their flavor, color, and nutritional benefits. In this study, strawberry fruit from 268 commercial cultivars and advanced selections from the North Carolina breeding program were evaluated to determine and characterize genotype diversity, relationships, and overall trends in fruit composition. Fifteen marketable, fully red, firm fruit were harvested per genotype between April and June of 2022 from a greenhouse core collection and held at -20°C until analysis. Juice from thawed fruit was used to collect total soluble solids (SSC), total titratable acidity (TTA), and pH data. Strawberry juice was also extracted with acidified methanol (0.1ml/1.6 ml total) and supernatants used to determine monomeric anthocyanin content (TA) using the pH differential method. Agglomerative hierarchical clustering (AHC) and multivariate analysis of variance (MANOVA) sorted genotypes into four clusters, highlighting significant differences in fruit composition profiles. The majority of commercial cultivars, and 38 advanced selections, were grouped together in Cluster 1. This cluster was distinguished by lowest SSC (7.0%), TTA (0.72%), and TA (31.22 mg/100g) values. In contrast, Cluster 2 containing 41.4% of germplasm had fruit highest in TA (54.57 mg/100g). Fruit from genotypes in Cluster 3 had high pH and %SSC, and the smallest group (Cluster 4), with 13.1% of the germplasm, had low pH and was significantly greater in %TTA. Regional strawberry breeding programs were found to group together. The Florida germplasm were grouped in Cluster 1, North Carolina commercial genotypes in Cluster 2, and two advanced New Jersey genotypic lines were found in Cluster 3. California day-neutrals were found in Cluster 1, while short-day genotypes were split between the first two clusters. Additionally, the first two principal components in PCA analysis captured 64.88% of the total variance, with both pH and TTA largely contributing to PC1 (91.1%), SSC in PC2 (71.1%), and TA associated with PC3 (77.4%). Variation in pH and %TTA had a more pronounced effect on genotype profiles and were the primary driving force for germplasm separation and differentiation. This work represents the first instance where an entire germplasm collection was assessed together in a single evaluation. The determination of genotype diversity, characterization of relationships among the genotypes and the fruit composition parameters, and visualization of trends within the collection will help guide future breeding decisions for developing new strawberry cultivars with improved quality.

Breeding efforts to improve blackberry (Rubus subgenus Rubus) flavor have previously been a subjective and imprecise process. The flavor perception of blackberries is largely controlled by interactions between sugars, acids, and volatile components. The aim of this study was to determine what combinations of these biochemical compounds result in positive flavor perception by the average consumer to assist in determining breeding targets. In the first year of data collection, consumer panelists assessed pureed frozen blackberries from the University of Arkansas Fruit Breeding Program for overall liking, aroma, flavor, sweetness and sourness across 24 sensory panels. Pearson correlation coefficients were generated to determine the relationship between overall liking and significant effects. Positive correlations to overall liking were significant for flavor intensity (0.99), aroma intensity (0.50), and sweetness intensity (0.89) indicating increases in flavor, aroma, and sweetness resulted in greater liking. Sourness was found to have a negative correlation with overall liking (-0.81). The positive correlation between liking and Brix (0.54) aligns with the perceived sweetness relationship, similarly the negative relationship between liking and titratable acidity (-0.59) aligns with perceived sourness. Panelists’ perceptions of fruity or indulgent flavors such as grape, banana, strawberry, apple, jam and candy produced significant positive correlations with overall liking. While fruit presenting flavors described as citrus, grassy, earthy, musty, pine, or chemical produced significant negative correlations with overall liking. The volatiles associated with these perceived flavors were also assessed using gas chromatography mass spectrometry.

Blueberry texture is a critical trait impacting mechanical harvesting, transportation resilience, shelf life, and consumer preference. Its complexity arises from multiple attributes, requiring a depth understanding for developing breeding tools to generate varieties with superior texture profiles. In this study, a diverse group of southern highbush blueberry (SHB) genotypes, reflecting various textures, were subjected to mechanical phenotyping, consumer perception analysis, and cell wall composition analysis. By conducting instrumental analysis using a texture analyzer, three key parameters crucial for genotype differentiation based on texture were identified. Consumer perception analysis revealed moderate agreement in texture classification between breeders and panelists. Additionally, cell wall composition analysis highlighted galacturonic acid as a potential monosaccharide capable of categorizing texture. The integration of mechanical phenotyping, consumer perception analysis, and cell wall composition analysis offers a comprehensive approach to dissecting blueberry texture. This enables breeders to select and develop blueberry varieties meeting consumer expectations, enhancing market competitiveness, and supporting the growth and sustainability of the global blueberry industry.

Many commercial apple (Malus x domestica Borkh.) cultivars follow a biennial bearing cycle, alternating between an “on” year with a heavy crop load and an "off" year with few if any fruit. It is commonly thought that biennial bearing is conditioned by repression of floral initiation by developing fruit. Although various studies have provided some insights into the regulation of flowering and biennial bearing by fruit load, the associated molecular-genetic pathway involved remains unclear. The objective of this study is to evaluate the influence of fruit load on the expression of specific, presumed flowering genes in the spur leaves and shoot apex, focusing on the potential role of sugars in this process. The hypothesis is that the potential accumulation of photosynthates in the leaf or shoot apex related to the absence of a strong sink (developing fruit) promotes floral initiation by directing the expression of floral-promotive genes. To test this, physiologically similar ‘Royal Red Honeycrisp’ trees were manipulated to influence fruit load. The accumulation of soluble sugars (fructose, sorbitol, glucose, and fructose) in the spur leaf and shoot apex was evaluated using a gas chromatograph. RNAs were extracted and gene expression patterns in the leaf and apex were evaluated using quantitative RT-PCR and direct sequencing; results will be presented. This study should provide new insights into the fundamental mechanisms of biennial bearing in apple. This may lead to approaches to limit the impact of biennial bearing in existing orchards, and genetic information useful for apple cultivar improvement.

Crop wild relatives are important genetic resources for cultivar improvement. Domesticated apple (M. x domestica) cultivars grown in North America are heterogeneous hybrids of Asian and European Malus species, with no known genetic contribution from native apples. M. coronaria (Sweet Crabapple) is the only native apple species found within the major apple-producing Great Lakes region. In spite of its potential importance for apple cultivar improvement, the genetics of this species has not been well studied, and only a few accessions are maintained in the USDA National Plant Germplasm System (NPGS). The objective of this research was to identify and collect new accessions of M. coronaria for the NPGS, focusing on the northernmost extent of its range in Michigan. To locate living trees, we combined analyses of historical records in 12 herbaria and the North America Fruit and Nut Tree Data, along with crowdsourcing using the popular online platform, iNaturalist. We identified a total of 158 M. coronaria records from herbaria and the fruit tree dataset. Records were removed from consideration if they were cataloged earlier than 1950, did not include collection coordinates, were redundant, or were not collected in the state of Michigan. iNaturalist listed 309 sightings of M. coronaria in Michigan; of these, we determined that a majority were likely misidentified based on the phenotypic characteristics in the images provided by the observer. Finally, Google Earth was used to rule out locations where the M. coronaria individuals had likely been lost due to anthropogenic activity. Ultimately, this three-factored approach identified only 64 sites within the state of Michigan where a living tree would likely be found. Our results provide strong evidence that M. coronaria is in decline within its native range in Michigan, underscoring the importance of conservation efforts for this species.

Monitoring High Tunnel Soil Temperature Fluxes to Understand Soil Health Implications - Bret Lang
Performance of Semi-Controlled Protective Net House at Farmers’ Field to Make The Year-Round Availability of Quality Vegetables and Higher Benefit Cost - AKM Quamruzzaman
Evaluating The Effect Of Cultivar On Garlic Growth And Yield - Stephen Mensah
Optimizing Butterhead Lettuce Production in a High Tunnel Environment - Alan Walters
Resource Use Efficiency, Yield, and Quality of Amaranth Grown as a Summer Leafy Green in Alternative Soilless Systems - Pradip Poudel
Differential performance of Radicchio cultivars in New Hampshire - Becky Sideman
Comparative Analysis of Biodegradable Mulch Use in Hill-side Strawberry Production - Amrita Mukherjee

High tunnel soil health is crucial for successful and sustainable crop production within protected environments. Soil microbial activity is highly temperature-dependent, and soils that are slightly warmer will foster increased metabolic rates within soil communities enhancing microbial diversity and enzymatic activity, promoting nutrient availability. However, little is understood about the potential for microbial activity during colder seasons in norther latitudes when high tunnels are taken out of production and soils are left fallow. Temperature variation in high tunnels could also create variation in microbial community activity, creating spatial nutrient variation with impacts on production the following season. To analyze soil temperature fluxes, we buried an array of 27 soil sensors four inches deep within the soil in a newly built, 30-foot-wideby 96-foot-long tunnel located in Brookings, South Dakota. The high tunnel was oriented east to west and soil was bare. Soil temperatures were recorded at 30-minute intervals from December 22 to March 15, (2023 – 2024). Air temperature and light (lux) data was also collected inside of the high tunnel as well as external weather data from a nearby (>1km) Mesonet weather station. We used multiple linear regression to model the relationship between average internal soil temperature and internal light and temperature data. We also compared sensor location (latitude, longitude, and Euclidean distance from the center of the high tunnel) on soil temperature within the high tunnel using an ANOVA and multiple linear regression to examine how sensor location was related to soil temperature. Our top model of internal soil temperature showed light, internal temperature, and the interaction between light and internal temperature explained a large amount of high tunnel soil temperature variation (R2 = 0.87, p < 0.0001). There was also significant variation in soil temperature throughout the high tunnel, with the daily mean difference of 3.12 degrees Celsius (p < 0.0001) observed between our sensor at the center of the high tunnel and our sensor near the northwest corner of the high tunnel. Our top model showed that latitude, the quadratic of longitude, and the Euclidean distance from the center of the high tunnel explained a moderate amount of high tunnel soil temperature variation (R2 = 0.44, p < 0.0001). This analysis demonstrates a need to further investigate how microbial communities react to temperature variation within high tunnels when they are not in production.

Assessing the impact of cultivar on garlic growth and yield ensures satisfactory productivity and better management of genetic resources for growers in North Dakota. A field experiment was conducted at the NDSU Horticulture Research Farm, located near Absaraka, ND to evaluate the effect of cultivar on the growth and yield of garlic. Twenty-nine garlic cultivars were arranged in a randomized complete block design (RCBD) with 4 replications. The leaf number, bulb diameter, bulb weight, scape weight and length were recorded throughout the growing season. The results showed significant differences between cultivars for all the variables evaluated. The highest bulb diameter(60.5 cm) was recorded in ‘German White’, while the lowest diameter (38.9 cm) was recorded in ‘German Red’. The highest bulb weight(73.4 g) was with ‘German White’ while ‘Italian Loiacono’ resulted in the lowest bulb weight(21.2 g).The number of leaves was recorded at 30, 45, 60, and 80 days after sprouting (DAS). The average number of leaves was similar for all cultivars until 60 DAS when ‘Ukrainian Red’ had the highest number of leaves (11) and ‘German Red’ had the fewest leaves (7). ‘Dakota White’ produced the longest scapes while ‘Italian Loiacono’ and ‘White Spring’ did not produce any scapes. ‘German White’ recorded the heaviest scapes (13.8 g). In conclusion garlic cultivar affected the growth and yield when grown under North Dakota environmental conditions. ‘German White’ appeared to be the most adapted to North Dakota environmental conditions while ‘Italian Loiacono’ and ‘German Red’ were the least adapted.

The production of fast-growing vegetable crops (such as specialty type lettuces) in slightly modified environments using high tunnels are widely underutilized. These structures can be used in the Midwest for winter production of a wide variety of leafy greens, including specialty lettuce. These crops have potential to garner a market premium due to high demand when there are not many other local vegetables for sale. Therefore, a study was conducted in 2020 and 2021 to evaluate four butterhead lettuce varieties (‘Nancy’, ‘Rhapsody’, ‘Red Cross’ and ‘Skyphos’) to determine optimal density for maximum revenue generation on a 3 ft wide raised bed. Three rows per bed and at 9 in. between plants worked best for ‘Nancy’, ‘Rhapsody’ and ‘Skyphos’, while for ‘Red Cross’ (a small more erect growing variety), 4 rows per bed at 12-inch spacing between plants maximized productivity. Head diameters were also highest for ‘Nancy’, ‘Rhapsody’ and ‘Skyphos’ using the 3 row, 12 inch between plant spacings. Overall gross revenues obtained per high tunnel, depending on plant density and variety, ranged from $3,600 to $6,000 (sold per piece at $4 each) or $1,753 to $7,279 (sold by weight at $6/ lb) for a typical 26’ (wide) x 48’ (long) high tunnel. Although most revenues increased when sold by weight, some increased by 50% (e.g., Rhapsody when grown at 3 row and 12 in spacings). Additionally, ‘Nancy’ (green-leaf type) and ‘Skyphos’ (red-leaf type) tended to be of higher quality than the other varieties evaluated and would be the better varieties to grow in a lower Midwest high tunnel environment. Both ‘Nancy’ and ‘Skyphos’ had optimal gross revenues when grown at 3 rows per bed with 9 in-row spacings when sold by piece ($4,500) or weight ($6,979 and $6,426, respectively). Thus, it is important for growers to understand the importance of butterhead variety selection and plant density in a high tunnel, as well as the method sold to maximizes revenues.

Soilless growing systems (SGS) integrated into controlled environment agriculture (CEA) offer a viable solution for increasing food production in densely populated areas with limited land, water, and nutritional security. The design, components, inputs, and nutrient management of alternative SGS along with the plant genotype, directly impact crop yield, nutritional value, and resource use efficiency. As the adoption of CEA and SGS continues to expand, there is a growing need to compare and evaluate the performance of alternative SGS in terms of resource use efficiency, crop yield, and impact on crop nutritional quality. To this purpose, a study was undertaken to assess the performance of five alternative SGSs including Deep Water Culture (DWC), Nutrient Film Techniques (NFT), Ebb and Flow, Drip irrigation, and the Kratky system concerning yield, nutritional quality, and resource use efficiency, using green and red stripe amaranth cultivar as test crops. As expected, the Kratky system had the lowest dissolved oxygen levels in the nutrient solution compared to other SGSs. Among the growing systems, DWC and NFT exhibited higher fresh and dry biomass production compared to drip irrigation, ebb and flow, and the Kratky system. There was no distinct difference in leaf fresh and dry weight between cultivars, but green amaranth displayed higher stem fresh and dry weight than red stripe amaranth. Dry matter content remained unaffected by the SGS, while red stripe amaranth exhibited higher dry matter content compared to green amaranth. The Kratky and DWC systems utilized 34.2% and 25.6% less nutrient solution, respectively, compared to the ebb and flow system, which had the highest nutrient solution consumption compared to other methods. DWC had the highest water use efficiency (WUE, dry biomass produced per liter of water used). Nitrate content in amaranth leaves was higher when grown in NFT compared to drip irrigation, DWC, and ebb and flow, but was similar to Kratky. The red stripe cultivar displayed higher nitrate content than the green one. Regarding bioactive compounds, green amaranth exhibited higher total antioxidants and flavonoids, whereas DWC and NFT led to lower total phenols and flavonoids compared to the Kratky, ebb and flow, and drip irrigation systems. In conclusion, the DWC and NFT systems maximized yield, with DWC having higher water use efficiency, while Kratky, ebb and flow, and drip irrigation system resulted in higher nutritional quality of the amaranth grown as a summer leafy vegetable.

Radicchio (Cichorium intybus var. latifolium) is grown widely throughout Europe, especially northern Italy. This crop features several groups that differ in color, shape, and culinary use, and there is considerable phenotypic variation among and within groups and cultivars. The New England growing climate is very different from that of major production regions in Europe and the pacific northwestern U.S. The availability of varieties to commercial growers in the U.S. has expanded greatly, but there remains a need for regionally relevant information about performance of these varieties. In Durham, NH, USA we grew 30 (2022) and 34 (2023) cultivars of radicchio belonging to seven main groups (Chioggia, Castelfranco, Treviso, Sugarloaf, Verona, Rosa del Veneto, and Lusia). In both years, they were seeded on 20-21 June, and transplanted on 14-15 July. Plants were harvested and weighed as they reached market maturity, or considered unmarketable due to bolting, rot, tipburn, or failure to head. We used standard cultural practices for the region: plants were grown in double rows on 30-inch-wide raised beds covered with white-on-black plastic mulch with drip irrigation. The weather in 2022 and 2023 differed greatly, with 2022 experiencing warm and dry conditions, and 2023 much wetter and cooler. The percentage of heads that became marketable ranged from 0-94% in 2022, and from 10-95% in 2023. Several cultivars had very high percentages of unmarketable heads, due to tipburn, rot, bolting, or failure to head. We also observed cultivar differences in susceptibility to powdery mildew. In both years, the cv. Rubro developed powdery mildew early and developed severe symptoms, several others eventually developed symptoms, and some never did. For traditional round red Chioggia types, several cultivars had very high percentages of marketable heads, and appear to be well adapted to production in the northeast. We identified cultivars within both sugarloaf and Treviso types that were well adapted, with high percentages of marketable heads. The cultivars we evaluated within the Lusia and Rosa del Veneto types were especially interesting from a culinary and attractiveness point of view, but had high percentages of rot (Lusia types) and very long days to maturity required (Rosa del Veneto types).

Comparative analysis of biodegradable mulch use in hill-side strawberry production Plastic film (PF) is widely used in crop production, yet global environmental concerns urge for reduced plastic waste. Biodegradable and bio-based mulches emerge as promising alternatives, potentially crucial for sustainable agriculture. This significance is emphasized by the hypothesis that small farms prioritize sustainability and seek to reduce plastic waste in soil and food systems, especially if these alternatives match or exceed the benefits of plastic mulch. However, there is limited data available on the effectiveness of biodegradable paper (BP) and bio-based film (BB) in small-scale crop production, an area frequently affected by heat and drought stress. A field experiment was conducted on a strawberry field in Redlands, San Bernardino County, California during the seasons of 2022 and 2023, respectively. This study was conducted to identify the most appropriate alternative to plastic mulch in hill-side production systems under the Mediterranean climate as it relates to yield and fruit quality at harvest day. We used four common mulches in small farms in California, polyethylene mulch (PE), landscape paper mulch (PA), Coconut liner mulch (CL), Biodegradable plastic mulch (MB), and bare soil (control) with the most popular ever-bearing variety, ‘Albion’. To investigate the suitability and efficacy of his mulches, we recorded the soil properties (temperature, moisture, and pH) daily, fruit yield (fruit weight and fruits/plant) biweekly, and fruit quality (Soluble solid and color) at harvest considering farm stand or U-pick sale service. Our results indicate that the highest total yield in terms of total fruit weight and number of fruits per plant grows under MB, CL, and PF mulch respectively. No notable differences were observed among treatments in fruit quality parameters such as soluble solids and color. The soil under the coconut coir liner had the highest moisture content, compared to PE, BDM, and bare ground treatments. No significant difference was found among the treatments in weed control. By the end of the cropping period, all treatments adequately covered the soil surface. However, in the buried part of the mulches, the PA mulch exhibited considerable degradation before the end of the season, while the MB showed faster signs of biodegradation. Based on crop productivity and the different mulch efficacy observed in our study, this production system with CL and MB is a good alternative to compare to PE and PA mulches for ever-bearing hillside strawberry production in the Mediterranean climate.

This year’s PB session will combine a keynote speaker session, business meeting and PB 2024 award ceremony together.
1. Keynote speaker: Hui Duan, USDA-ARS-REE (45 minutes) Biotechnology of Woody Ornamental Plants
2. PB business meeting (30 minutes) Chair annual report, elect new chair, chair elected and secretory. Plan next year’s work.
3. 2024 Plant Biotechnology Interest Group annual award ceremony (45 minutes)