Study On Bacteriostatic Mechanism Of Antagonistic Yeast And Effects On The Quality Of Postharvest Strawberries

Strawberry is one of the fruits which had been cultivated for many years and distributed widely. Strawberry is full of nutrients such as sugar, organic acids and vitamins. Since fruit flesh is soft and succulent, it is susceptible to be invaded by epiphyte microorganisms. During storage, strawberry fruits are easily of decay, threshing and stem shrinking which results in a lot of economic losses during storage, transportation and selling stage. Microbial biocontrol agents have shown grena potential as an alternative to synthetic fungi for the control of postharvest decay of vegetables. Thus, there is an increasing need for isolation of yeasts from new source, selection, testing of the yeast on surfaces of fruits and studying the biocontrol mechanism of the yeast.By in vitro, study the inhibitory effects on Botrytis cinerea of Pichia guilliermondii. In PDA plate confrontation culture, the inhibition effects of Pichia guilliermondii on the Botrytis cinerea of postharvest diseases are distinguished and the gray mold could not grow at the side of P. guilliermondii. Different concentrations of yeast suspension were used to observation the effect of B. cinerea spore germination rate, found that the higher the concentration of yeast suspension, the more significant inhibitory effects. In the zone of inhibition experiments. P. guilliermondii grew faster than B. cinerea, no inhibition zone was produced.By in vivo, the inhibitory effect of washed cell suspension in controlling the natural disease of Toyonoga strawberries was notable and the bio-control efficacy was significantly increased when applied concentration was higher. So the main mode of action of P. guilliermondii must be competitive for nutrients and space. P. guilliermondii introduced the production of resistance activity of fruits to pathogens may be another mechanism of control postharvest disease of fruits.Effects on the storage quality of strawberries of P. guilliermondii was investigated, the result showed that, P. guilliermondii suspension has little effect on fruit respiration, however, the luster can keep fruit and soluble solids content, and significantly reduced weight loss and maintained firmness, extend the storage life of strawberries, which indicates the great potential of P. guilliermondii to control the postharvest decay of fruits and vegetables.