Scholarly Works, Virginia Agricultural Experiment Station

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VAES faculty are located at 11 Agricultural Research and Extension Centers in Virginia and three colleges at Virginia Tech (CALS, CNRE, and VMRCVM).

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Time-course RNA-seq analysis of upland cotton (Gossypium hirsutum L.) responses to Southern root-knot nematode (Meloidogyne incognita) during compatible and incompatible interactions
Khanal, Sameer; Kumar, Pawan; da Silva, Mychele B.; Singh, Rippy; Suassuna, Nelson; Jones, Don C.; Davis, Richard F.; Chee, Peng W. (2025-02-24)
Background: The Southern root-knot nematode (Meloidogyne incognita) poses a substantial threat to cotton (Gossypium hirsutum L.) by causing significant agricultural losses. Host plant resistance is the most plausible approach for minimizing these losses. QTL mapping and early transcriptomic studies have identified candidate genes within the QTL regions on chromosome 11 (qMi-C11) and chromosome 14 (qMi-C14). Although these QTL regions have been fine-mapped and candidate genes identified, expression profiling of Meloidogyne-Gossypium interactions across different stages of infection could further refine the list of candidate genes. This study advances our understanding of the molecular mechanisms underlying the resistance conferred by qMi-C11 and qMi-C14 against Southern root-knot nematode. Results: Using time-course RNA-seq analyses across nematode developmental phases, we uncovered transcriptomic events—both genome-wide and within QTL intervals—underlying defense responses during compatible interactions (with Cocker 201, a susceptible line) and incompatible interactions (with M-120 RNR, a resistant line). Basal defense responses were observed in both compatible and incompatible interactions, with stronger expression in the incompatible interaction. Nematode-responsive genes associated with defense pathways showed distinct dynamics, characterized by repression during compatible interactions and early induction, greater diversity, and heightened upregulation during incompatible interactions. This study uncovers a broad repertoire of disease resistance and putative resistance genes, as well as pathogenesis-related genes, ligands, and receptors, that are differentially expressed in response to nematode parasitism. Mapping of these genes across the cotton genome identified promising candidates, including Gh_A11G3090 (PUB21) and Gh_A11G2836 (RPPL1) within the chromosome 11 QTL region, andGh_D02G0257 (RLP12) and Gh_D02G0259 (RLP12) within the chromosome 14 QTL region. Conclusions: The findings of this study deepen our understanding of host-nematode interactions, identify candidate genes for downstream applications, and contribute to advancements in resistance breeding and sustainable nematode management strategies.
Effects of Sericea Lespedeza Supplementation on Steers Grazing Wild-Type Endophyte-Infected Tall Fescue
Poudel, Sanjok; Pent, Gabriel J.; Fike, John H.; Zeller, Wayne E.; Davis, Brittany E. (MDPI, 2025-01-28)
Condensed tannins (CTs) in certain leguminous forages can mitigate toxic alkaloid absorption linked to fescue toxicosis due to their high affinity towards various steroidal and protein-like alkaloids. However, their use as feed supplements remains underexplored. This study evaluated the impact of CT-rich sericea lespedeza (Lespedeza cuneata) pellets on the post-ingestive effects of fescue toxicosis. Twelve steers on wild-type endophyte-infected tall fescue pastures received either sericea lespedeza pellets (LES) or LES with polyethylene glycol (LPEG; negative control) for 12 weeks over three consecutive summers. Body weight, hair coat scores, temperatures (rectal and extremity), cortisol levels, and caudal artery lumen area were measured every four weeks. Steers fed LES showed trends toward higher ADG (p = 0.0999) and reduced hair retention (p = 0.0547) compared to those fed LPEG. Steers on LES also showed hotter tail skin temperatures (p = 0.0053) and cooler rectal temperatures (p < 0.0001) compared to those fed LPEG. LES-fed steers had a 21% larger caudal artery lumen area (p < 0.01), suggesting reduced vasoconstriction. Additionally, LES-fed steers tended to have lower hair cortisol (p = 0.0746), indicating reduced chronic stress. These results suggest that supplementation with CTs may alleviate the post-ingestive effects of fescue toxicosis, potentially by improving blood flow and reducing stress. However, further research is needed to determine whether CTs directly reduce alkaloid absorption, as well as to validate the long-term efficacy of CT supplementation.
Researchers see promise in multi-spectral imaging for latent detection of anthracnose disease on strawberry crop
Aljawasim, Baker; Richardson, Patricia; Samtani, Jayesh; Chandel, Abhilash (Virginia Strawberry Association, 2025-02-01)
Decreasing Preweaning Death Loss in Pigs: Key Management Considerations for Small-Scale Farmers
Estienne, Mark J.; Niblett, Richard T. (Virginia Cooperative Extension, 2024-01-10)
A cooperative study assessing the effects of a second iron injection administered before weaning on growth performance, hematological status, and tissue mineral concentrations of nursery pigs
Chevalier, T. B.; Adeola, O.; Carter, S. D.; Dove, C. R.; Estienne, Mark J.; Levesque, C. L.; Maxwell, C. V.; Tsai, T.; Lindemann, M. D. (Elsevier, 2024-04-01)
Objective: A study involving 7 experiment stations evaluated the effects of a second iron injection adminis- tered before weaning on growth and hematological mea- sures of pigs. Materials and Methods: Pigs (n = 514) were given an iron injection (100–200 mg) on the first day of life. Piglets were then allotted to pairs of similar-weight, same- sex siblings 3 to 5 d before weaning (on d 18–24) with one piglet from each pair receiving a second iron injection. All pigs received common station-specific postweaning diets. Data were subjected to ANOVA with the model contain- ing the terms treatment, station, pair within station, and treatment × station interaction. Results and Discussion: Postweaning ADG was greater for the added-injection group during during 0 to 14 d after weaning, but the response (212.5 vs. 202.6 g) was largely influenced by a single station as evidenced by a treatment × station interaction. The tendency for a treatment × station interaction for overall ADG (d −4 to 28) indicated that iron status was not the most limiting factor for growth at all stations. Hemoglobin concentra- tion was greater for the added-injection group at weaning and d 14 after weaning. Implications and Applications: An additional iron injection before weaning may lead to improved early nursery growth; however, the beneficial effects of an additional iron injection are not universal and are likely dependent on unique herd characteristics including timing and total dosage of iron injections as well as nursery diet supple- mentation.
Leaf Endophyte Community Composition and Network Structures Differ Between Tolerant and Susceptible English Boxwood
Kong, Ping; Li, Xiaoping; Sharifi, Melissa; Bordas, Adria; Hong, Chuanxue (American Phytopathological Society, 2023-09)
Differential tolerance of English boxwood to boxwood blight has been linked to the ratio of culturable bacterial and fungal dominance in the leaf tissue of representative samples. To further understand how the whole endophyte communities may involve the tolerance of large samples, we extracted DNA from healthy leaf tissue of previously identified 28 tolerant (T), 41 moderately tolerant (M), and 21 susceptible (S) English boxwood plants, then sequenced associated bacterial and fungal amplicons using the Nanopore MinION platform. The endophyte community did not differ in diversity among the T, M, and S plants but differed in the abundance of bacteria and fungi, particularly between T and S samples. The bacterial genera Brevundimonas and Ammonifex had higher relative abundance in the T and M communities than in the S community, in which the fungal genera Botrytis and Thermothelomyces and family Chaetomiaceae were more dominant. The same results were obtained when mother and daughter samples in the T community were compared with controls in the S community, suggesting bacteria as a work force in the T community. Cooccurrence network analyses revealed that the T network had more fungal hubs but was less complex, with more positive connections than the S network, suggesting that the T community was supported by a healthier network. The resistance of English boxwood to blight is likely attributed to bacteria dominance and a synergic community network. This study is foundational to constructing synthetic communities and using whole communities of tolerant plants through vegetative propagation for microbemodulated immunity.
Colletotrichum Species Causing Apple Bitter Rot in Virginia: Crop Losses, Distribution and Efficacy of Biorational and Synthetic Fungicides in Field and in vitro
Borba, Matheus C.; Sempeles, Emmanuel M.; Cosseboom, Scott D.; Aćimović, Srđan G. (American Phytopathological Society, 2025)
Apple bitter rot losses in Virginia range from 20 to 90% annually. Distribution of Colletotrichum species in Virginia showed that the Colletotrichum gloeosporioides species complex dominated in the north and central regions, with 66% and 88% of isolates respectively. Colletotrichum acutatum species complex was more prevalent in the south with a 58% dominance shift in mountainous regions. To determine the efficacy of fungicides against apple bitter rot, we assessed 18 treatments of natural origin biorational materials and synthetic fungicides on 'Idared' (ID) and 'Golden Delicious' (GD) apple trees. Over two years, we applied 5 to 6 consecutive spray applications of 15 individual active ingredients from May to August. Bitter rot incidence was evaluated twice each summer. In the first, very rainy year, the top four synthetic fungicides, Omega, Aprovia, ferbam and a grower standard (GS) on ID, and Omega, Captan, Cabrio and Ferbam on GD, achieved 81% to 91% bitter rot control. Biorational materials showed low to no efficacy, allowing 37% to 89% BRI on ID and 21% to 48% BRI on GD. In the second, much drier year, synthetic fungicides achieved 86% to 100% BRI control on GD and 77% to 96% on ID. Among the biorational materials, only Regalia mixed with JMS Stylet oil and only in the second year provided 58% BRI control. EC50 and EC25 assay values for synthetic fungicides aligned well with the field observations. Given the potential for significant economic losses due to bitter rot, reliable fungicides such as Omega (FRAC 29), Aprovia (FRAC 7), Ferbam, Ziram (FRAC M3), and Captan (FRAC M4) are essential management tools for growers. These fungicides should be incorporated into the spray programs to reduce the risk of Colletotrichum resistance to quinone outside inhibitor fungicides, from which commercial apple farms highly depend now. Regalia mixed with Stylet oil offers an additional rotation option during drier years with lower disease pressure.
New fungicide options for managing Sclerotinia blight of peanut
da Silva, Mychele Batista; Langston, David B. (Scientific Societies, 2024-12-02)
Late leaf spot (LLS), caused by Nothopassalora personata, and Sclerotinia blight (SB), caused by Sclerotinia minor, are significant diseases affecting peanut production in Virginia. Field trials were conducted in 2020 - 2022 at two locations per year to identify fungicide programs that manage both diseases. In 2020, pydiflumetofen applied independently, as well as in combination with a premix of azoxystrobin + benzovindiflupyr, provided effective protection against both LLS and SB. This combination demonstrated potential as a cost-effective alternative to fluazinam. Years 2021 and 2022 focused on the most effective timing of pydiflumetofen and the premix of azoxystrobin + benzovindiflupyr. Results demonstrated that the combination of pydiflumetofen and the premix of azoxystrobin + benzovindiflupyr applied 60 and 90 days after planting was most consistent in providing the greatest efficacy against both diseases while improving yield. The tank-mix/premix combination of pydiflumetofen and azoxystrobin + benzovindiflupyr offers effective and economical management of both LLS and SB compared to fungicide programs where fluazinam is added for SB management only.
Apple Bitter Rot: Biology, Ecology, Omics, Virulence Factors, and Management of Causal Colletotrichum Species
Boeckman, Nathanial J.; Borba, Matheus Correa; Bernal, Valentina Valencia; Khodadadi, Fatemeh; Jurick, Wayne M.; Aćimović, Srđan G. (2025-01-12)
Apple bitter rot is caused by various Colletotrichum spp. that threaten apple production globally resulting in millions of dollars in damage annually. The fungus causes a decline in fruit quality and yield, eventually rotting the fruit and rendering it inedible. The pathogen is difficult to keep out of orchards because of its broad host range and transmissibility by rain splash and insects. Once the disease manifests, pathogen identification is difficult due to evolving taxonomy and similar morphology between species. Current management strategies are threatened by an increase in fungicide resistance and regulations on many multisite fungicides, leading to a pressing need for new management options for control. This review aims to summarise the most current knowledge regarding the biology, virulence factors, ecology, omics and emerging management strategies for Colletotrichum species that cause apple bitter rot.
A Bitter, Complex Problem: Causal Colletotrichum Species in Virginia Orchards and Apple Fruit Susceptibility
Khodadadi, Fatemeh; Santander, Ricardo D.; McHenry, Diana J.; Jurick, Wayne M., II; Aćimović, Srđan G. (American Phytopathological Society, 2023-10-23)
Bitter rot, caused by Colletotrichum species, is one of the most devastating summer rot diseases affecting apple production in the Eastern United States. Given the differences in virulence and fungicide sensitivity levels between organisms belonging to the acutatum species complex (CASC) and the gloeosporioides species complex (CGSC), monitoring their diversity, geographic distribution, and frequency are essential for successful bitter rot management. In a 662-isolate collection from apple orchards in Virginia, isolates from CGSC were dominant (65.5%) in comparison to the CASC (34.5%). In a subsample of 82 representative isolates, using morphological and multilocus phylogenetic analyses, we identified C. fructicola (26.2%), C. chrysophilum (15.6%), C. siamense (0.8%), and C. theobromicola (0.8%) from CGSC and C. fioriniae (22.1%) and C. nymphaeae (1.6%) from CASC. The dominant species were C. fructicola, followed by C. fioriniae and C. chrysophilum. C. siamense followed by C. theobromicola developed the largest and deepest rot lesions on Honeycrisp fruit in our virulence tests. Detached fruit of nine apple cultivars and one wild accession (Malus sylvestris) were harvested early and late season and tested in controlled conditions for their susceptibility to C. fioriniae and C. chrysophilum. All cultivars were susceptible to both representative bitter rot species, with Honeycrisp fruit being the most susceptible and M. sylvestris, accession PI 369855, being the most resistant. We demonstrate that the frequency and prevalence of species in Colletotrichum complexes are highly variable in the Mid-Atlantic and provide regionspecific data on apple cultivar susceptibility. Our findings are necessary for the successful management of bitter rot as an emerging and persistent problem in apple production both pre- and postharvest.
First report of Pseudomonas marginalis causing tuber soft rot of potato in Iran
Ghasemi, Simin; Khodaygan, Pejman; Aćimović, Srđan G.; Basavand, Esmaeil (2024-07-25)
In 2016, potato tuber soft rot symptoms were observed in major potato production fields in Jiroft county (southern Kerman province, Iran). Bacteria, which appeared as white to creamy colonies, were isolated from diseased tissues and shown to be pathogenic on potato tubers after inoculation and re-isolation of the isolates. Based on the assessment of colony morphology, biochemical characteristics, and analysis of 16S rRNA and gyrB gene sequences, the pathogen was identified as Pseudomonas marginalis. To our knowledge, this is the first report of P. marginalis causing potato tuber soft rot disease in Iran.
Solar Appeal
Stallknecht, Eric; Lunt, Richard; Runkle, Erik (Ball Publishing, 2024-06-01)
Solar Appeal, Part 2
Stallknecht, Eric; Lunt, Richard; Runkle, Erik (Ball Publishing, 2024-07-01)
Shifts in water use in grapevine due to an invasive sap-feeding planthopper persist following insect removal
Harner, Andrew D.; Leach, Heather; Briggs, Lauren; Smith, Donald E.; Zweifel, Roman; Centinari, Michela (Elsevier, 2025-02-01)
Increasing outbreaks of invasive insect pests pose a substantial threat to the functioning and viability of cultivated and wild woody perennial species worldwide. In the eastern U.S., the spotted lanternfly (Lycorma delicatula White; SLF), an invasive phloem-feeding planthopper, was reported to be able to negatively impact late-season plant carbon dynamics in various woody perennial species following repeated or prolonged infestation and feeding events. However, it remains unclear if SLF infestations also impact plant water relations and if SLF-mediated effects persist when populations are controlled and feeding stops. This study investigated how late-season exposure to SLF impacts whole-plant water relations by assessing diurnal sap flow and trunk radius changes in grapevines subjected to varying infestation densities of adult SLF. In two seasons, vines exposed to high infestation densities (an average of 180 SLFs per vine) for up to 31–32 days of cumulative SLF exposure had significantly lower sap flow rate than those with no SLF, resulting in up to 38 % less daily total water use. Trunk diurnal amplitudes increased under SLF infestation, but impacts were less dependent on infestation density, suggesting that grapevines may be utilizing trunk water storage during infestation to meet both grapevine water use and SLF sap ingestion. In both cases, SLF-mediated effects persisted following removal of SLFs, suggesting that exposure to high populations of SLF can alter patterns of late-season grapevine water use, at least when populations are not effectively controlled. These results indicate that SLF can modify both whole-plant water relations and carbon dynamics concurrently, further defining the implications that intensive infestations by high populations of SLF have for woody perennial whole-plant physiology.
Evaluating Soil Solarization and Mustard Seed Meal as Preplant Treatments for Weed Control in Annual Hill Plasticulture Strawberry Production
Aljawasim, Baker D.; Johnson, Charles; Manchester, Mikel; Samtani, Jayesh B. (Cambridge University Press, 2024-11-15)
Alternative strategies to fumigation are needed to manage weeds and improve fruit yield in the annual hill plasticulture strawberry production system. Field experiments were conducted in Blackstone, Virginia, for two consecutive growing seasons, 2013/14 and 2014/15, to assess the efficacy of 4 wk and 8 wk soil solarization (SS) and mustard seed meal (MSM) at 1121 kg ha−1, alone and in combination, for weed control efficacy and crop yield estimation in an annual hill plasticulture strawberry production system. These treatments were compared to 1,3-dichloropropene (1,3-D) + chloropicrin (Pic) fumigation standard at 188 kg ha−1 and the untreated control (UTC). Over both growing seasons, compared to 1,3-D+ Pic, the SS-MSM-8wk and SS-8wk treatments provided equivalent or reduced cumulative weed count, including weed count of several dominant weed species, annual ryegrass, speedwell, common chickweed, and cudweed. The SS-4wk and MSM-4wk treatments did not affect weed density compared to UTC. The MSM-8 wk and 4 wk treatments reduced cumulative weed counts over UTC. In the second growing season, the total yield was significantly higher in the 1,3-D + Pic fumigation treatment compared with other treatments. The SS-4wk, MSM-4wk, and MSM-8wk treatments did not improve the total or marketable yield compared to UTC. The marketable yield in SS-MSM-8wk was similar to that of the 1,3-D + Pic treatment. In conclusion, the SS-8wk and SS-MSM-8wk treatments may be effective weed management strategies for organic growers, small farms, or growers who cannot use chemical fumigants due to new regulations and potential risks to human health.
Characterization of Boxwood Shoot Bacterial Communities and Potential Impact from Fungicide Treatments
Li, Xiaoping; Tseng, Hsien Tzer; Hemmings, Ginger; Omolehin, Olanike; Taylor, Chad; Taylor, Amanda; Kong, Ping; Daughtrey, Margery; Gouker, Fred; Hong, Chuanxue (American Society for Microbiology, 2022-08-08)
Phyllosphere bacterial communities play important roles in plant fitness and growth. The objective of this study was to characterize the epiphytic and endophytic bacterial communities of boxwood shoots and determine how they may respond to commonly used fungicides. In early summer and early fall, shoot samples were collected immediately before and 1, 7, and 14 days after three fungicides containing chlorothalonil and/or propiconazole were applied to the canopy. Total genomic DNA from shoot surface washings and surface-sterilized shoot tissues was used as the template for 16S rRNA metabarcoding, and the amplicons were sequenced on a Nanopore MinION sequencer to characterize the epiphytic and endophytic communities. The bacterial communities were phylogenetically more diverse on the boxwood shoot surface than in the internal tissue, although the two communities shared 12.7% of the total 1,649 identified genera. The most abundant epiphytes were Methylobacterium and Pantoea, while Stenotrophomonas and Brevundimonas were the dominant endophytes. Fungicide treatments had strong impacts on epiphytic bacterial community structure and composition. Analysis of compositions of microbiomes with bias correction (ANCOM-BC) and analysis of variance (ANOVA)-like differential expression (ALDEx2) together identified 312 and 1,362 epiphytes changed in abundance due to fungicide treatments in early summer and early fall, respectively, and over 50% of these epiphytes were negatively impacted by fungicide. The two chlorothalonil-based contact fungicides demonstrated more marked effects than the propiconazole-based systemic fungicide. These results are foundational for exploring and utilizing the full potential of the microbiome and fungicide applications and developing a systems approach to boxwood health and production.
Epidemiology of boxwood blight in western North Carolina and Virginia and evaluation of the boxwood blight infection risk model
Khaliq, Ihsanul; Avenot, Herve F.; Baudoin, Anton; Coop, Leonard; Hong, Chuanxue (Nature Portfolio, 2024-11-05)
Boxwood blight, caused by Calonectria pseudonaviculata, is a highly invasive emerging disease. Since the first US report in North Carolina and Connecticut in 2011, boxwood blight has spread to over 30 US states, risking more than 90% of boxwood production. Our study investigated the disease field epidemiology and evaluated the boxwood blight infection risk model’s prediction by analysing weekly blight monitoring data collected on detector plants exposed to the prevailing environmental conditions at two different locations (western Virginia and North Carolina) from spring through fall of 2014 to 2017. Boxwood blight was recorded in 61 of 86 weeks, with the highest infected leaf counts recorded in late summer or early fall. Rainfall, high relative humidity outside rainy periods and optimal temperatures (13.6–22.7 °C) during prolonged leaf wetness (> 65 h per week) had a significant positive effect on boxwood blight development. Classification analyses showed that disease predictions from the model using leaf wetness estimated by leaf wetness sensor were more closely aligned with observations from the field than predictions based on algorithms. This study improved our understanding of disease field epidemiology, provided leads to improve the existing model, and generated essential knowledge for formulating effective strategies for blight mitigation.
Assessment of Water Quality, Growth of Penaeus vannamei, and Partial Budget in Super-Intensive BFT and RAS: A Comparison Between Sustainable Aquaculture Systems
Ramiro, Bianca de Oliveira; Wasielesky, Wilson; Pimentel, Otávio Augusto Lacerda Ferreira; Sun, Taozhu; McAlhaney, Ethan; Urick, Stephen; Gonçalves, Fernando H.; van Senten, Jonathan; Schwarz, Michael H.; Krummenauer, Dariano (MDPI, 2024-12-15)
This study evaluated water quality, growth, and partial budget analysis (PBA) for Penaeus vannamei, comparing super-intensive Biofloc Technology (BFT) and Recirculating Aquaculture Systems (RAS). The 69-day trial used 100 L units with two treatments (RAS and BFT), each with three replicates. Shrimp were initially reared in a 30-day nursery to a weight of 0.10 ± 0.04 g and then stocked at 500 shrimp m⁻³. Biofloc growth in BFT was promoted by maintaining a C:N ratio of 15:1, adding dextrose when total ammonia nitrogen (TAN) reached 1 mg L⁻¹. Probiotics (3 g m⁻³) were administered daily to both groups. TAN levels in BFT initially spiked but stabilized after 36 days. Vibrio abundance was initially higher in RAS, but by the end of the trial, it was higher in BFT. Final weight, weekly growth ratio, and yield were greater in BFT, whereas feed conversion ratio (FCR) and water use were higher in RAS. Survival rates were 83.33% in BFT and 88% in RAS. BFT achieved a superior net benefit/cost compared to RAS. Although RAS more effectively controlled nitrogenous compounds, BFT exhibited better growth performance, with higher final weights, lower FCR, and better Vibrio management. The partial budget analysis indicated an economic advantage for BFT, with a net positive benefit of $2270.09 when shifting from RAS to BFT due to lower operating costs and higher shrimp yield. Among these two sustainable production systems, BFT was more productive while utilizing less natural resources.
Identifying an Early Leaf Removal Threshold for Grüner Veltliner, a High-Yielding, High-Vigor Cultivar
Harner, Andrew D.; Smith, Maria S.; Keller, Stephanie T.; Hopfer, Helene; Centinari, Michela (American Society for Enology and Viticulture, 2024-03-11)
Background and goals: Early leaf removal (ELR) is a canopy management practice that can reduce bunch rot and improve fruit maturity by modifying cluster architecture and fruit zone microclimate. The goal of this study was to identify an ELR threshold that balances improvements to fruit quality and reductions in yield for a highly vegetative and high-yielding Vitis vinifera cultivar grown in the eastern United States, Grüner Veltliner. Methods and key findings: Over two consecutive years, we applied a wide range of ELR severities (three to 12 leaves per shoot) at trace bloom (Eichhorn-Lorenz [E-L] stage 19) and evaluated relationships between increasing ELR severity and fruit set, yield param-eters, fruit maturity, bunch rot, and juice volatile composition at harvest. In the first year, increasing ELR gradually reduced fruit set, subsequently lowering yield via reducing berry number and cluster weights. Additionally, ELR increased fruit ripeness while reducing rot incidence. However, extreme ELR (10 to 12 leaves per shoot) negatively affected inflorescence floret number and fruitfulness in the following year. In the second year, only high ELR severities (eight to 12 leaves per shoot) reduced yield parameters, and improvements in fruit ripeness or bunch rot were not observed, likely because of poor weather conditions during fruit ripening. The impact of increasing ELR severities on juice volatile composition was largely limited to benzaldehyde (a volatile phenylpropanoid), which was negatively affected by ELR in both years. Conclusions and significance: Removal of six to eight leaves per shoot appeared to be the optimal ELR severities for grapegrowers seeking crop management and rot reduction for high-yielding cultivars like Grüner Veltliner. However, as reported in the second year of this study, the effects of ELR may vary by year and be limited by unfavorable weather conditions.
Modeling the Impacts of Weather and Cultural Factors on Rotundone Concentration in Cool-Climate Noiret Wine Grapes
Harner, Andrew D.; Vanden Heuvel, Justine E.; Marini, Richard P.; Elias, Ryan J.; Centinari, Michela (Frontiers, 2019-10-15)
The sesquiterpenoid rotundone is the compound responsible for the "black pepper" aroma of many plant species, including several economically important wine grape varieties. Since its identification in wine in 2008, there has been an increased interest in understanding how individual climatic or cultural factors affect the accumulation of rotundone in grapes and subsequently the level of wine "pepperiness." However, no study has assessed climatic and viticultural factors together to identify which variables have the strongest influence on rotundone accumulation. Our study aimed to fill this knowledge gap by developing a predictive model that identified factors that explain rotundone concentrations in Noiret (Vitis sp.) grapes at harvest. Over the 2016 and 2017 seasons, we measured 21 viticultural, meso- and microclimatic variables and concentrations of rotundone in Noiret wine grapes at seven vineyards in the northeastern U.S. Vineyard growing degree days (GDD _v ) and the amount of solar radiation (cumulative solar exposure; CSE_v) accumulated from the beginning of fruit ripening to harvest were the variables best correlated (r = 0.70 and r = 0.74, respectively) with rotundone concentrations. Linear correlations between microclimatic parameters and rotundone concentrations were weaker, but overall rotundone was negatively correlated with low (<15°C) and high (>30°C) berry temperatures. Using the 2-year data set we were able to develop a four-variable model which explained more than 80% of the variation in rotundone concentration at harvest. The model included weather [growing degree days during fruit ripening (GDD _v )] and plant-related variables (concentrations of phosphorus and calcium in the leaf petiole, and crop load). The model we developed could be used by wine producers to identify sites or cultural practices that favor rotundone accumulation in Noiret grapes after performing a model validation with an additional, external data set. More broadly, the statistical approach used here could be applied to other studies that also seek to assess the effects of multiple factors on a variable of interest under varying environmental conditions.

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