SUPPRESSION OF BOTRYTIS BLIGHT IN CUT ROSE FLOWERS WITH GIBBERELLIC-ACID - EFFECTS OF POSTHARVEST TIMING OF THE GIBBERELLIN TREATMENT, CONIDIAL INOCULATION AND COLD-STORAGE PERIOD

The susceptibility of rose flowers (Rosa x hybrida cv. Mercedes) to Bo trytis cinerea was affected by the age of the flowers after harvest at which they were inoculated. The development of Botrytis blight was su ppressed by spraying flower buds with a 1-mM solution of GA(3), althou gh the effect of GA(3) was limited by flower petal senescence. Applica tion of GA(3) either prior to or after conidial inoculation suppressed development of Botrytis blight. GA(3) application suppressed Botrytis blight development even after the flowers were kept in cold-storage c onditions. A hypothesis of a dual effect of GA(3) in the suppression o f Botrytis blight in cut rose flowers is proposed. Firstly, it may inh ibit senescence-related malfunction of cell membranes. Secondly, GA(3) may stimulate formation of endogenous compounds inhibiting Botrytis b light development in the petals. The possible use of gibberellins for control of Botrytis blight is discussed.