Evaluation of biocontrol potential of Pichia guilliermondii yeast isolated from Urmia Lake in control of postharvest diseases of grapevine

Postharvest diseases cause a lot of damage to grapes and reduce the quality and marketability of the product. These infections are mainly caused by the fungal species Penicillium expansum and Botrytis cinerea, which are the most important pathogen of postharvest grape rot worldwide. Biological control has become important to control these postharvest diseases due to the recent global awareness of the side effects of chemical agents. In this study, the biocontrol ability of yeasts isolated from Urmia Lake basin against postharvest diseases of grapes has been investigated. We used 11 yeasts belonged to Pichia guilliermondii species isolated from Urmia Lake basin. The results of inhibitory activity of 11 P. guilliermondii isolates against two postharvest pathogens of grape, P. expansum and B. cinerea, showed that three yeast isolates can considerably inhibit both fungi in dual culture method on PDA medium. Three promising isolates were selected to reduce postharvest decays of grape at the storage period.  The results exhibited that three yeast isolates could significantly reduce grape decays. The yeast isolate 8 by reducing 82.3% of grape decays, showed the strongest activity against P. expansum. The yeast isolate 10 was found the most effective isolate to suppress B. cinerea decay on grape by 78.5%.