Seasonal dynamics and optimal diagnostics of<i>Grapevine red blotch virus</i>in a British Columbian vineyard
Dieter Kahl, D. Thomas Lowery, Miranda M. Hart, José Ramón Úrbez-Torres
Abstract
Tracking the occurrence and spread of Grapevine red blotch virus (GRBV) depends on robust and reliable diagnostics. Tissue sampling strategy and optimal choice of molecular test are critical for diagnostic success. This study investigated GRBV titres from several grapevine tissues, including roots, buds, cortical scrapings, and leaves, at varying distances from the cordons, and at different times during the growing season and winter dormancy. Two common nucleic acid extraction techniques were compared, a low-cost high-throughput nucleic acid extraction method (GES) and a DNA column purification method. Optimal combinations of sampling parameters were determined for summer and winter diagnostics. In dormant samples, cortical scrapings yielded the highest GRBV titres and produced no false-negatives. In summer samples, basal leaves yielded high GRBV titres throughout the summer months, with only one false negative on the earliest sample date. These two tissues provide the best samples for reliable and reproducible GRBV diagnostics. The crude GES and DNA column purification methods performed comparably well for binary diagnostics, however, the GES method performed poorly in quantitative analysis.