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 significantly reduces the ornamental value of the cut flowers. Methyl jasmonate (MJ), a natural growth regulator postulated to induce plant defense responses, was tested for postharvest control of the grey mould disease in various cut rose cultivars (Mercedes, Europa, Lambada, Frisco, Sacha and Eskimo). Systemic protection against B. cinerea was evident for all cultivars examined, in flowers pulsed with 200 μM MJ following either natural or artificial infection. At this concentration, MJ also significantly reduced lesion size and appearance, as evaluated by a detached petal bioassay. However, local protection, following simultaneous application of B. cinerea spores and MJ directly to flower petals, was not provided by less than 300 μM MJ. These MJ concentrations neither caused any phytotoxicity on leaves and petals, nor impaired flower quality and longevity. A direct antifungal effect of 100–400 μM MJ on spore germination and germ-tube elongation of B. cinerea was obtained in vitro, with complete inhibition at 400 μM MJ. These results suggest that MJ pulsing provides systemic protection against Botrytis rot by inducing resistance mechanisms in the treated cut roses without impairing flower quality.