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Open access

Laban K. Rutto, Zelalem Mersha, and Mizuho Nita

The French American hybrid grape cultivars Corot noir and Arandell (Vitis sp.), and Vidal blanc and Petit Manseng (Vitis vinifera), along with different spray programs, were evaluated for potential organic production in Virginia from 2013 to 2014. Results obtained in the study demonstrate that organic wine grape production in Virginia can be achieved by using select grape cultivars and spray programs. With the exception of Vidal blanc, disease severity and disease incidence were below the threshold for maintaining healthy vines in all organically managed grape cultivars. ‘Vidal blanc’ was not sufficiently resistant to downy mildew (Plasmopara viticola), precluding it from potential organic management in Virginia. The study also demonstrated significant disease resistance in Virginia of the cultivar Arandell, released by Cornell University (Ithaca, NY) in 2013. The results suggest that the organically registered fungicide Bacillus subtilis is effective in reducing the severity and incidence of black rot (Guignardia bidwellii) and phomopsis cane and leaf spot (Phomopsis viticola). The chemistry of organically managed berries harvested in 2014 met minimum requirements for wine production with soluble solids, titratable acidity, and pH ranging from 18.7% to 20.2%, 7.6 to 8.0 g·L−1, and 3.3 to 3.4, respectively, in ‘Arandell’ and ‘Corot noir’; and 21.0% to 24.4%, 7.8 to 9.6 g·L−1, and 2.7 to 2.9, respectively, in ‘Petit Manseng’ and ‘Vidal blanc’ juice.

Open access

Guo-Liang Jiang, Laban K. Rutto, and Shuxin Ren

Edamame is a vegetable or specialty soybean (Glycine max (L.) Merr.) with high nutrition and market value. The market demand for edamame has significantly increased in the United States since its health and nutritional benefits became recognized. However, there are a limited number of domestically developed or improved edamame cultivars in the United States, and the knowledge of edamame is very limited. In this study, 86 breeding lines and cultivars of maturity group (MG) V and VI developed in the United States were evaluated in replicated field trials for edamame yield and agronomic traits in Virginia in 2015 and 2016. The results indicated that there were significant differences among the genotypes and between years in all the traits investigated (plant height, fresh biomass, pod yield, pod ratio, fresh seed yield, seed ratio, and 100-seed weights), but the yearly differences for dried 100-seed weight and dried-to-fresh ratio of seeds were insignificant. Genotype-by-year interaction effects were not significant in most cases. Estimates of the broad sense heritability varied with traits, from 23% to 88%. Coefficients of phenotypic and genotypic correlation were mostly low, but fresh pod and seed yields were highly correlated. Fresh biomass exhibited a positive phenotypic correlation with pod and seed yields, but the genotypic correlation coefficients were not significant. Twelve breeding lines were preliminarily identified to have greater edamame yield and desired traits. The information generated in this study will be helpful for edamame breeding and commercial production.

Full access

Laban K. Rutto, Myong-Sook Ansari, and Michael Brandt

Stinging nettle (Urtica dioica) is a specialty crop with economic potential. Apart from being harvested and consumed as a leafy vegetable, stinging nettle has well-documented applications in alternative medicine and industry. However, research on stinging nettle mineral nutrition is insufficient and the current study is part of efforts to establish agronomic guidelines for managed cultivation. Greenhouse experiments were conducted over two seasons (summer and fall) to evaluate stinging nettle growth and dry matter partitioning in response to variations in the supply of nitrogen (N), and N in combination with potassium (K). In the first experiment, seedlings were transplanted into potted media amended with N applied at rates equivalent to 0, 15, 30, 45, 60, and 75 g·m−2, while Expt. 2 consisted of N (15, 45, and 75 g·m−2 equivalent) and K (4, 8, and 12 g·m−2 equivalent) applied in factorial combinations. In Expt. 1, stinging nettle growth was positively correlated with N supply up to 60 g·m−2 during the reproductive phase (summer) and 75 g·m−2 during the vegetative phase (fall), while there was a slight decline in growth and dry matter yield at the highest level of K (12 g·m−2) at all N levels in Expt. 2. In both experiments, growth and dry matter accumulation was higher in the fall than in summer, and high N accounted for significantly more vegetative growth with a concomitant increase in aboveground biomass. Our results suggest that K should be applied at a rate below the growth-limiting threshold of 12 g·m−2. In this study, N strongly stimulated aboveground growth suggesting it is the most important element in stinging nettle nutrition.

Open access

Renée L. Eriksen, Laban K. Rutto, James E. Dombrowski, and John A. Henning

The Pacific Northwest grows the majority of hops in the United States; however, the region is experiencing an increase in the number of days with high heat. In addition, there is an increased interest in growing hops in other warmer regions of the United States. To understand how hop plants respond to high temperatures, we measured several physiological traits of six hop cultivars under a range of temperatures from 15 to 45 °C. We found that hop plants achieved maximal carbon assimilation at temperatures of 21 to 39 °C when given sufficient water. At temperatures of 41 °C and higher, all cultivars experienced declines in carbon assimilation. This was likely due to multiple effects on the cell, including damage to photosystem II (PSII), as reflected in declines in FV/FM, damage to membrane integrity as reflected in electrolyte leakage at high temperatures, and declines in Rubisco activity likely due to degradation of Rubisco activase, as reflected in declines in Vc,max. ‘Cascade’, ‘Willamette’, and ‘Southern Brewer’ may be good candidates for growing in warm climates because all experience relatively high rates of carbon assimilation at high temperatures and did not experience significant declines in FV/FM or increases in electrolyte leakage. ‘Chinook’ appeared susceptible to extreme heat stress and exhibited evidence of irreparable damage to PSII and membrane integrity at 45 °C.

Open access

Laban K. Rutto, Yixiang Xu, Shuxin Ren, Holly Scoggins, and Jeanine Davis

‘Hop’ (Humulus lupulus) cultivar trials were conducted at sites in three Virginia counties (Northampton, Chesterfield, and Madison) in response to demand by the craft beer industry for local ingredients. In 2016, a replicated study involving five cultivars (Cascade, Chinook, Newport, Nugget, and Zeus) was established on an 18-ft-tall trellis system at each site. Weather data influencing infectivity of downy mildew (Pseudoperonospora humuli) and powdery mildew (Podosphaera macularis), two economically important hop diseases, was collected, and to the extent possible, similar cultural practices were applied at each site. Climatic conditions favorable to P. humuli and P. macularis were present throughout the experimental period, and P. humuli infection was widespread at all sites starting from 2017. Among common pests, Japanese beetle (Popillia japonica) was the only one observed to cause significant damage. Unseasonably high rainfall in 2018 led to crop failure at all but the Northampton site, and harvesting was done at all sites only in 2017 and 2019. Yields (kilograms per hectare by weight) in 2017 were found to be ≥45% lower than second-year estimates for yards in the north and northwestern United States. Quality attributes (α and β acids; essential oil) for cones harvested from the Chesterfield site were comparable to published ranges for ‘Cascade’ in 2019, but lower for the other cultivars. More work is needed to identify or develop cultivars better suited to conditions in the southeastern United States. The influence of terroir on quality of commercial cultivars produced in the region should also be examined.