Daniel J. Anco

Transformation of Phomopsis viticola with the green fluorescent protein.

Phomopsis viticola is the causal agent of Phomopsis cane and leaf spot on Vitis spp., a persistent and economically important disease in temperate regions. Here we describe the transformation of this fungus with two different constructs (pBHt2_sGFP and pIGPAPA) containing the green fluorescent protein (GFP) and the hygromycin B resistance gene (hph). Protoplast-mediated transformation yielded mitotically stable transformants with no change in virulence on grape internodes and leaves in comparison to the wild type. These transformants will be critical tools for elucidating fungal penetration of host plants, invasive growth and the nature of its host association.

Effects of Temperature and Wetness Duration on the Sporulation Rate of Phomopsis viticola on Infected Grape Canes

Controlled-environment studies were conducted to examine effects of temperature (T) and wetness duration (W) on the sporulation rate of Phomopsis viticola on infected grape canes and to determine effects of interrupted wetness duration (IWD) on sporulation. A split-plot design was used to determine T and W effects, with T (5, 12, 15, 18, 20, 22, 25, 28, and 35°C) as the whole-plot and W (11, 23, 35, 47, and 71 h) as the subplot. Linear and nonlinear mixed models were fitted to the data. Lower and upper limits of sporulation were estimated to be 4 and 36°C, respectively, based on the modeling results, optimum sporulation was near 21°C, and sporulation increased monotonically with increasing wetness duration. Of the examined models, a generalization of the Analytis Beta model fit the data best, based on a collection of goodness-of-fit statistical criteria. To determine effects of IWD, a split-plot was used, with T (12, 15, and 20°C) as the whole-plot and IWD (0, 2, 4, 8, 12, and 24 h) as the subplot. Generally, sporulation declined with increasing IWD. An IWD of 8 h or more resulted in significantly and substantially less sporulation compared to the control (0 h IWD) (P < 0.01). Temporal patterns of spore density in the field were determined using a repeated-measures design, in which spore density and environmental data were measured in the vineyard during and following individual rain events over 3 years. The developed model from the controlled-environment study, coupled with a time-of-season weight function and a dispersal index (based on total rain per rain episode), predicted the trend in spore density over time reasonably well, although the total magnitude of spore density could not be predicted because the density of lesions was not known. Results can be used for improving the accuracy of a disease warning system that currently only considers infection of grapes by P. viticola.

Postharvest Quarantine Treatments for Diaphorina citri on Infested Curry Leaves

Studies were conducted to evaluate treatments that reduce survival and attachment of Diaphorina citri nymphs on infested curry leaves (Bergera koenigii). Decontamination of curry leaves infested with D. citri in relation to disinfectant (none or Pro-San), temperature (0, 40, and 50°C), and treatment duration (0, 5, 10, and 20 min) was examined using a split-split plot design. Experiments were performed three times. Treatment duration did not significantly affect D. citri nymph survival or removal (P > 0.2). Temperature and disinfectant each significantly affected D. citri nymph survival and removal (P < 0.031). The interaction of temperature and disinfectant was significant with respect to nymph survival (P < 0.0001) but did not significantly affect removal (P = 0.4589). Tissue damage was significantly affected by temperature (P = 0.0056), duration (P = 0.0023), the interaction of temperature and duration (P = 0.0320), and the interaction of disinfectant, temperature, and duration (P = 0.0410). Of the treatments resulting in 100% D. citri nymph mortality on infested curry leaves, 40°C for 5 min with Pro-San was accompanied with the least proportion of curry leaf tissue damage (0.14 greater than untreated control, P = 0.25). Results from these studies may be useful in formulation of future regulatory policies regarding trade of citrus foliage, especially those used as condiments.

First Report of Rust caused by Puccinia arachidis on Peanut in South Carolina

Puccinia arachidis Speg. (phylum Basidiomycota, class Pucciniomycetes) causes rust on peanut (Arachis hypogaea L.) and is a biotroph. In September 2016, several plants exhibiting numerous rust-colored pustules characteristic to peanut rust (Subrahmanyam 1997) on abaxial leaf sides were observed in two plots (12.19 × 12.67 m) at approximately 5% incidence of total leaflets (≈3% severity) in a localized area of approximately 2 × 2 m in a peanut field in Blackville, SC (Barnwell County) on the commercial variety ‘Georgia 12Y’. Also in September, identical symptoms were observed in a localized area of approximately 3 × 3 m (80% leaflet incidence, 40% severity) in a commercial field (≈40 hectares) of ‘Georgia 06G’ (industry-standard runner variety) in Orangeburg County, SC. Both locations were managed under reduced fungicide programs. The Barnwell County location received four applications of chlorothalonil alone as part of a separate disease study, whereas the Orangeburg County field received five chlorothalo...