Study On Biocontrol Efficacy Of Yeast Candida Oleophila Induced By Mild Salt Stress

Biological control of postharvest diseases utilizing naturally-occurring antagonistic yeasts has been actively studied for the past 30 years.Among the antagonistic yeasts,Candida oleophila has been reported as an effective biocontrol agent against postharvest diseases of various fruits,including apple,peach,citrus,and papaya.Comprehensive studies of C.oleophila at the physiological and molecular level has also been conducted.The postharvest biocontrol system of yeast involves complex(plant host-pathogen-yeast antagonist)interactions,all of which are affected by environmental factors.In the present study,RT-QPCR and Spectrophotometer were used to detect the physiological and biochemical changes in biocontrol yeast,the result that a mild salt stress(1 mol/L Na Cl,for 30 min)pretreatment of Candida oleophila increased its subsequent tolerance to lethal levels of salt stress(6 mol/L Na Cl),and low p H(p H 3.4).The sublethal salt stress induced the activation of antioxidant enzymes in the antagonistic yeast,including catalase,thioredoxin reductase,glutathione peroxidase,and glutathione reductase,at both the transcript and enzyme activity level.Sublethal salt stress-adapted(SA)yeast cells exhibited higher survival,compared to non-stress-adapted(NSA)cells,when exposed to 6 mol/L Na Cl.SA cells exhibited increased efficacy in controlling infection of kiwifruit by Penicillium expansum and Botrytis cinerea,and a higher growth rate in fruit wounds,compared to the NSA yeast.A single gene mutant was constructed by deleting Rlm1-1/ Rlm1-2 single gene,and a series of experiments were carried out to identify the main genes related to salt stress in yeast.Collectively,the study further supports the premise that stress adaptation of antagonistic yeasts can improve their biocontrol efficacy.