Effect of burkholderia contaminans on postharvest diseases and induced resistance of strawberry fruits

Abstract

This study takes strawberry-fruits as the test material and discusses the effect of Burkholderia contaminans B-1 on preventing postharvest diseases and inducing resistance-related substances in strawberry-fruits. Soaking and wound inoculating is performed to analyze the inhibitory effects of different treatment solutions on the gray mold of postharvest strawberry-fruits. The count of antagonistic bacteria colonies in the wound is found, and the dynamic growth of antagonistic bacteria and the pathogenic fungus is observed by electron microscopy. The results indicated that, either by soaking/ wound-inoculating, the fermentation and suspension of antagonistic bacteria significantly reduced the incidence of postharvest diseases of strawberry-fruits. With wound inoculation, the inhibition rate of antagonist fermentation and suspension (1 × 1010 cfu/ml) respectively reached 77.4% and 66.7%. It also led to a significant increase in the activity of resistance-related enzymes, i.e., phenylalanine ammonia lyase (PAL), 4-coumarate coenzyme A ligase (4CL), cinnamate-4-hydroxylase (C4H) and chalcone isomerase (CHI). On 1 d and 2 d post-treatment, the activity of 4CL was respectively 3.78 and 6.1 times of the control, and on 5 d, the activity of PAL was increased by 4.47 times the control. The treatment of antagonistic bacteria delayed the peaking of cinnamyl-alcohol dehydrogenase (CAD) activity and promoted the accumulation of lignin and total phenols. The antagonistic bacteria could be well colonized in the wounds. On 4-5 d post-inoculation, the count of colonies was 108 times of that upon inoculation. Electron-microscopy indicated that the antagonistic bacteria delayed the germination of pathogenic spores in the wounds, and inhibited further elongations of the mycelia.