Comparative Effectiveness of Symptomatology and ELISA For Detecting Two Isolates of Grapevine Leafroll on Graft-inoculated Cabernet franc

Abstract

An enzyme-linked immunosorbent assay (ELISA) was compared to the standard woody indexing procedure for effectiveness in detecting grapevine leafroll associated virus (GLRaV) 3 and 4 in infected grapevines of cvs. Pinot noir (PN) and Thompson Seedless (TS). Four plants per plot of individual Cabernet franc (CF) indicator plants were each graft-inoculated with buds from 24 vines of PN and TS infected with the GLRaV 3 and 4, respectively. Inoculated indicators were established in the field, observed periodically for symptoms, and assayed by ELISA. All plots showed GLRaV symptoms and positive ELISA reactions by the end of the first full growing season for GLRaV 3 and by the end of the second full growing season for GLRaV 4. Results on an individual plant basis were similar, whereby 92% to 95% of CF inoculated with GLRaV 3 or GLRaV 4 were positive for symptoms and ELISA. ELISA reactions for GLRaV 3 were consistently higher than those for GLRaV 4. Virus transmission was not dependent on growth of inoculated buds. We conclude that ELISA is useful for rapid detection of GLRaV 3 and 4 in dormant wood of source grapevines and in inoculated CF indicators.