کنترل زیستی Penicillium digitatum و Penicillium italicum برروی پرتقال با استفاده از جدایه‌های مخمری مقاوم به سرمای گونه Aureobasidium pullulans

Worldwide, citrus rots caused by Penicillium digitatum and Penicillium italicum are one of the most aggressive postharvest diseases of citrus fruits. Considering the environmental issues with the excessive use of chemical fungicides for humans and the environment, the use of products based on biological agents has received special attention. Among biological agents, some yeast has been shown to possess antagonistic activity against fungi and are considered as safe and sound alternatives for chemical pesticides. Searching for sustainable alternatives to chemical fungicides, cold-adopted yeasts as potential biocontrol agents were used. Antagonistic potential of yeast isolates were screened, in vitro and in vivo. At first, antagonistic activities of 8 yeast strains of Aureobasidium pullulans against the pathogens were screened by dual culture method in vitro. In vivo antagonistic activity of isolates was tested on citrus fruits. Fronts wounded in equatorial position (a single wound/fruit, approximately 3 mm in depth × 3 mm in width) using a sterile needle. Each wound was inoculated with 30 µL of cell suspension of antagonist microorganism adjusted to a concentration of 108 CFU/mL. After 24 h, each wound was inoculated with 20 µL of an aqueous suspension of P. digitatum or P. italicum (105 conidia/mL). The results of inhibitory activity of 8 isolates of A. pullulans against P. digitatum and P. italicum, showed that three yeast isolates (G11, G15 and G36) can considerably inhibit growing of both fungi based on dual culture method on PDA medium and this three promising isolate were evaluated for their ability to suppress postharvest decays of citrus in vivo. Yeast isolates could significantly reduce citrus decays. The yeast isolate G15 by reducing 80.13% of citrus fruits decays, showed the strongest activity against P. digitatum and the yeast isolate G11 was found the most effective isolate to suppress P. italicum decay on citrus by 76.49%. Based on results isolates G11 and G15 were highly effective and can be used as potential biocontrol agents in controlling the post-harvest decay of citrus caused by P. digitatum and P. italicum. The direct screening methods applied in this study favored the recovery of efficient candidates for application as biological control agents to combat fungal infestations of citrus fruits.