Studies On Biocontrol Mechanism And Application Of Antagonistic Yeast Fungus

Bio-control has been paid attention gradually as a new way to control postharvest diseases of fruits and vegetables.It has been studied that many micro-organisms can be used as antagonists of Post-harvest Diseases of the fruits and vegetables,such as bacteria, fungi and yeast,etc.,and the best one is yeast which becomes a research hotspot now because of its good antagonism,non-toxins and being used with chemical fungicides.In this study,by means of UV-mutagenesis we succeeded to obtain a new type of yeast named XY-331from Debaryomyces hansenii on 4min,and through genetic stability test it confirmed that the new yeast named XY-331 have stably antagonism.According to L16(4~5) orthogonal test,It is determined that the optimal culture conditions is the YEPD medium,culture temperature 32℃,culture time 40h,the concentration of salt 6g / L,pH value 5.0.The culture conditions have further been optimized,and the optimal nitrogen source is peptone,the optimal carbon source is glucose, and the optimum for cultivating is darkness.This experiment studied antagonistic effect of XY-331 yeast by the concentration,the processing mode and the vaccination time.The result is that the soft rot of nectarine can be deferred by yeast XY-331 and the incidence initially reduce 57.4%;yeast cell suspension has the best inhibitory effect on pathogenic bacteria,and under the concentration of 1×10~9CFU/mL and before the pathogen inoculation 24h,the yeast cell suspension can effectively reduce the incidence of nectarine,with a significant level(P≤0.05).The experiment also studied the antagonistic mechanism of XY-331 yeast.The yeast in the wound of the fruits can quickly increase,and when inoculating with pathogen at the same time,the quantity of yeast is 1.043 times of quantity of single inoculation,and it confirmed that the mechanism of antagonistic is fighting nutrition and space for living; during storage of nectarine which was immersed in cell suspension of yeast XY-331,the PPO of nectarine showed decreased activity,the POD of nectarine showed higher trend and the PAL of nectarine has increased,and the change of the three defensive ferment has indicated that the mechanism of antagonistic is to strengthen host resistance by inducing substances.