Molecular approaches to assist the screening and monitoring of postharvestbiocontrol yeasts

Nineteen yeast isolates obtained from the surface of several fruits and veg etables grown in Southern Italy and Israel were compared by molecular analy sis using arbitrarily primed polymerase chain reaction (AP-PCR) and random amplified polymorphic DNA technique (RAPD-PCR). Genetic analysis made it po ssible to distinguish between closely-related genitically different strains which had the same morphological characteristic, and to discard isolates w hich were genetically identical. Following PCR characterisation, 6 isolates were selected and tested for their biocontrol activity against major posth arvest pathogens (Penicillium digitatum on grapefruit, Botrytis cinerea, Rh izopus stolonifer and Aspergillus niger on table grape and B. cinerea and R . stolonifer on cherry tomato). All the isolates showed a good biocontrol e fficacy on both wounded and non-wounded fruits. Furthermore, the preharvest application of the most effective antagonist (LS15) on table grape resulte d in a significant reduction in grey mold ranging from 28.3% to 38.2% compa red to the untreated control. The RAPD-PCR technique was also useful for id entifying and monitoring the survival of the antagonist after field applica tion.