Use of Methyl Jasmonate for Suppression of Botrytis Rot in Various Cultivars of Cut Rose Flowers

Gray mold, caused by Botrytis cinerea on flower petals, is a common disease of greenhouse roses (Rosa hybrida L.). The disease develops rapidly after harvest and causes a significant reduction of cut flowers value. Methyl jasmonate (MJ), known to induce plant defense responses, was examined for postharvest control of this disease in various cultivars of cut roses. We have previously demonstrated (Meir et al., 1998, Postharvest Biol. Technol. 13: 235) that under laboratory conditions, application of MJ to cut roses by either pulsing (24 h at 20 o C) or spraying, provided six rose cultivars with a systemic or local protection against B. cinerea, respectively. Based on these results, a practical application of MJ consisting of simultaneous pulsing and spraying, was developed for growers handling conditions. The treatment included MJ pulsing for 4 h at 20 o C and MJ spraying, followed by continuation of the pulsing for additional 20 h at 6 o C. The flowers were then packed and incubated for two days at 6 o C for air transport simulation, transferred subsequently to water cylinders placed at 20 o C, and artificially inoculated with B. cinerea spore suspension. Experiments performed under these conditions with four rose cultivars (‘Frisco’, ‘Jazz’, ‘Mercedes’ and ‘Red Charm’) showed that the optimal treatment was pulsing with 350 µM MJ and spraying with 500 µM MJ. This combined MJ treatment neither increased ethylene production in petals, nor it was phytotoxic. The MJ treatment effectively suppressed gray mold development following both natural and artificial infection in seven additional rose cultivars (‘Eskimo’, ‘Profita’, ‘Tamara’, ‘Sun Beam’, ‘Pink Tango’, ‘Carmen’, ‘Golden Gate’). In yellow, orange and pink cultivars, the MJ treatment improved petal color by inhibiting color fading during vase life, as assayed visually and by color measurements. Collectively, our findings suggest a possible commercial application of MJ as a useful and environmentally friendly means for suppressing Botrytis rot in cut roses.