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.
Muscadines (Muscadinia rotundifolia Michx) are native to the southeastern United States and have been cultivated for fresh consumption, juice, wine, and other processed products for over 100 years. Manual harvesting is one of the main challenges for fresh market production due to high labor costs. This study aimed to determine muscadine fruit and pedicel characteristics influencing fruit detachment force and to unravel the genes, hormones, and regulatory networks governing muscadine abscission. We characterized the fruit detachment force of muscadine berries across eighteen genotypes and at four developmental stages. Following this, we performed a transcriptome analysis using the mature pedicel tissue of two genotypes, a genotype with high fruit detachment force at maturity and a genotype with low fruit detachment force at maturity, to identify differentially expressed and uniquely expressed genes contributing to fruit detachment. Our results suggest that the abscission process and abscission zone development likely occur at different rates in a genotype and developmental stage dependent manner. Our findings provide valuable knowledge on the progression of fruit abscission and insights for controlling fruit detachment force. This will aid in the development of machine-harvestable cultivars which will increase the sustainability and efficiency of muscadine production.
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.
