Agriculture and Agri-Food Canada, Vineland Station, Ontario, L0R2E0 Canada
Gray mould caused by Botrytis cinerea, a necrotrophic pathogen, can result in yield losses in wine grapes. The application of synthetic fungicides is an important strategy for controlling crop diseases. Intensive and exclusive use of some of the fungicides has resulted in fungicide resistance. Methyl jasmonate (MeJA), a resistance elicitor, has signalling role in eliciting induced systemic resistance (ISR) against diseases in plants. In this study, the effect of exogenous MeJA on the suppression of postharvest botrytis in green grape cultivars, 'Thomson', 'Chardonnay' and 'Vida' and in red grape cultivars 'Merlot', 'Flame' and 'Cabernet Sauvignon' was tested. The grape bunches (15 grapes/bunch and three replicate treatments) were spray-treated with 1mM of MeJA, air dried for 3 hours. Three days after the MeJA treatment, each of the grape berry in the bunch was wounded with a needle and inoculated with 1 × 104 spores of B. cinerea B05.10 and incubated in the dark at 20 °C and 85% RH. Control treatment did not receive MeJA. The lesion diameter was recorded at 7 and 14 days after inoculation. The elicitor, MeJA induced defense response by significantly suppressing the Botrytis gray mould in all the grape cultivars. Defense response, expressed as PAL gene, in grapevine berries towards B. cinerea, was studied. Maximum levels of induction of PAL gene was observed at 48 hours post inoculation and a significantly lower level of PAL gene was expressed in MeJA and B. cinerea infected grapevine berries, as compared to B. cinerea only infected berries.