SUPPRESSION OF BOTRYTIS ROT IN CUT ROSE FLOWERS BY POSTHARVEST APPLICATION OF METHYL JASMONATE

Grey mould, caused by Botrytis cinerea infection on rose (Rosa hybrida L.) petals, is a common disease of greenhouse roses, that significant ly reduces the ornamental value of the cut flowers. Methyl jasmonate ( MJ), a natural growth regulator postulated to induce plant defense res ponses, was tested for postharvest control of the grey mould disease i n various cut rose cultivars (Mercedes, Europa, Lambada, Frisco, Sacha and Eskimo). Systemic protection against B. cinerea was evident for a ll cultivars examined, in flowers pulsed with 200 mu M MJ following ei ther natural or artificial infection. At this concentration, MJ also s ignificantly reduced lesion size and appearance, as evaluated by a det ached petal bioassay. However, local protection, following simultaneou s application of B. cinerea spores and MJ directly to flower petals, w as not provided by less than 300 mu M MJ. These MJ concentrations neit her caused any phytotoxicity on leaves and petals, nor impaired flower quality and longevity. A direct antifungal effect of 100-400 mu M MJ on spore germination and germ-tube elongation of B. cinerea was obtain ed in vitro, with complete inhibition at 400 mu M MJ. These results su ggest that MJ pulsing provides systemic protection against Botrytis ro t by inducing resistance mechanisms in the treated cut roses without i mpairing flower quality. (C) 1998 Elsevier Science B.V. All rights res erved.