COMPARATIVE EFFECTIVENESS OF SYMPTOMATOLOGY AND ELISA FOR DETECTING 2ISOLATES OF GRAPEVINE LEAFROLL ON GRAFT-INOCULATED CABERNET FRANC

An enzyme-linked immunosorbent assay (ELISA) was compared to the stand ard woody indexing procedure for effectiveness in detecting grapevine leafroll associated virus (GLRaV) 3 and 4 in infected grapevines of cv s. Pinot noir (PN) and Thompson Seedless (TS). Four plants per plot of individual Cabernet franc (CF) indicator plants were each graft-inocu lated with buds from 24 vines of PN and TS infected with the GLRaV 3 a nd 4, respectively. Inoculated indicators were established in the fiel d, 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 ful l growing season for GLRaV 4. Results on an individual plant basis wer e 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 wer e consistently higher than those for GLRaV 4. Virus transmission was n ot dependent on growth of inoculated buds. We conclude that ELISA is u seful for rapid detection of GLRaV 3 and 4 in dormant wood of source g rapevines and in inoculated CF indicators.