Screening,identification and antagonistic mechanism of antagonistic yeasts against the spoilage mould of apple

In order to control postharvest disease of apples,Penicillium expansum,Alternaria alternata and Aspergillus niger were used as indicator strains to screen antagonistic yeasts isolated from apple peel. The antagonistic mechanism of yeast was also preliminarily studied. Based on its morphological characteristics,physiological and biochemical characteristics and ITS sequences,the antagonistic yeast strains Y4 and Y9 were identified as Candida railenensis and Aureobasidium pullulans,in which A. pullulans was a fungus like yeast. Optimal concentration of C. railenensis was 10⁹ CFU/mL,and it could significantly inhibit the mycelia growth,spore germination and germ tube growth of P. expansum,A. alternata and A. niger. Scanning electron microscopy showed that C. railenensis was able to surround and adsorb the spore of spoilage fungi,compete with them for nutrition and space,and also adsorb P. expansum mycelia and thus interact directly with them. Competition nutrition and competition space were the main mechanisms of C. railenensis,and its biocontrol effect was a combined result of many ways.