INFECTION OF PLUM AND NECTARINE FLOWERS BY BOTRYTIS-CINEREA

The ability of Botrytis cinerea to infect plum and nectarine flowers w as studied in moist chambers and in the orchard. Within 36 h of inocul ation, the pathogen penetrated and colonized the stamens, styles and p etals on shoots placed in moist chambers, causing blossom blight. Simi lar lesion development was observed following inoculation with dry and wet conidia. Hyphae were usually distorted in stylar tissue, but grew normally in petals and filaments. Growth of the fungus through filame nts into the sepals or floral tubes, or through the transmitting tissu e of the style into the ovary, was never observed. Symptoms of blossom blight were not observed on inoculated shoots in the orchard. The flo ral tube, bearing the sepals and stamens, dehisced within 14 days of f ruit set and infected floral parts did not remain attached to young de veloping fruit. No relation was found between post-harvest decay and f lower infection. Losses following post-harvest decay might have been c aused by direct penetration of ripening fruit and not by flower infect ion. The importance of infected floral parts as a source of secondary inoculum on ripening fruit is discussed.