ACTIVITY OF THE YEASTS CRYPTOCOCCUS-LAURENTII AND RHODOTORULA-GLUTINIS AGAINST POSTHARVEST ROTS ON DIFFERENT FRUITS

More than 200 yeasts were selectively isolated from microbial populati ons on the surface of different fruits. Fifty of these isolates were t ested against blue mould (Penicillium expansum) on wounded apples. iso lates LS-11 of Rhodotorula glutinis and LS-28 of Cryptococcus laurenti i were rite most effective antagonists. They were further evaluated at 20 degrees C on different fruits (apples, pears, strawberries, kiwi f ruits find table grapes) against several of the main post-harvest path ogens (Botrytis cinerea, Penicillium expansum, Rhizopus stolonifer and Aspergillus niger) and at 4 degrees C on apples inoculated with P. ex pansum. At 20 degrees C the antagonists significantly reduced rot inci dence and showed a wide range of activity on different host-pathogen c ombinations, isolate LS-28 exhibited a higher and more stable activity than LS-11. Both yeasts were also effective against P. expansum in co ld storage conditions. Populations of the two yeasts were assessed on wounded and unwounded surfaces of apples kept at both 20 and 4 degrees C. At either temperature, isolate LS-28 reached greater densities in wounded tissues than LS-11, but had a lower ability to colonize unwoun ded apple skin. The two yeasts were able to grow in culture at tempera tures ranging from 0 to 35 degrees C. In assays performed in vitro at 24 degrees C, the antagonists showed low sensitivity towards several f ungicides commonly applied on fruits and vegetables.