Effect Of Morphology Change Of Antagostic Yeast On Stress Tolerance And Biocontrol Efficacy

In recent years,the use of biocontrol agents to control plant disease has been proved to be one of the safe and effective measures to replace chemical pesticides.Utilization of the yeast naturally-occurring in the surface of fruits and vegetables as antagonists is one of new methods for control of postharvest diseases.To understand the basic aspect of yeast biology is essential for uncovering the biocontrol mechanism.It has been found that when certain yeast strains grew to some density level,their morphology could change from single cell-type to biofilm-type(embedded within a self-produced matrix of extracellular polymeric substance)on certain media surfaces.In this project,two kinds of yeast antagonistic strains P.kudriavzevii and P.cecembensis were employed to study the effects of morphological changes on the stress resistance,intracellular antioxidant enzyme activity,and cell damage degree.The results showed that:(1)P.kudriavzevii and P.cecembensis had higher stress resistance in adverse environment after being transformed from yeast-like form to biofilm form.(2)The activities of Catalase ?Super Oxide Dismutase and Glutathione peroxidase in the biofilm form yeast were higher,and the contents of Malondialdehyde and carbonyl accumulation were significantly lower than those of yeast-like form.(3)Biofilm form yeast P.kudriavzevii have faster growth and reproduction rate compared with its own yeast-like form.P.cecembensis biofilm form cells have faster growth and reproduction rate in apple fruit too.(4)Biofilm form of P.kudriavzevii exhibited better control efficacy against gray mold and anthracnose on pear fruit.And biofilm form of P.cercembensis exhibited better control efficacy against penicillium on apple fruit.Taken together,P.kudriavzevii and P.cecembensis had greater biocontrol efficacy after morphological transformation.This may be due to the fact that the biofilm form yeast had higher activity of antioxidant enzymes,higher survival rate,better adaptable ability in the wound adverse microenvironment which is the first step to competition for the living space and nutrients,resulting in a better control effect.