SUPPRESSION OF BOTRYTIS BLIGHT IN CUT ROSE FLOWERS WITH GIBBERELLIC-ACID - EFFECT OF CONCENTRATION AND MODE OF APPLICATION

Symptoms of Botrytis blight in petals of harvested rose flowers inocul ated after harvest with suspensions of Botrytis cinerea conidia become visible after five-seven days. The development of Botrytis blight was significantly suppressed in detached petals of cvs. Mercedes and Sona ta treated for 24 h with a 20 mg l(-1) solution of GA(3). Botrytis was suppressed to a lesser extent in petals of cvs. Celica and Ilseta, wi th no effect recorded in cvs. Golden Times and Madelon. To obtain a si milar level of suppression in intact flower buds to that obtained in d etached petals, a postharvest spray of GA(3), with a concentration of 346 mg l(-1) (1 mM) was required. Soon after harvest, the inner petals of cv. Mercedes were more sensitive to B. cinerea than the outer peta ls, whereas the converse was observed when petals were removed from bu ds maintained for five days in a vase. Neither spore germination, germ -tube elongation nor the linear growth of the fungus mycelium were aff ected by gibberellin. Use of GA(3) for control of Botrytis blight in r ose flowers as an alternative to environmentally-hostile fungicides is proposed.