English

Abstract

This study aimed to screen myxobacteria strains with strong activity against Phytophthora infestans and to study its secondary metabolites. Myxobacteria were isolatedfrom a soil sample using the rabbit feces as bait. A strain inhibitive to P. infestanswas identified by morphological observation and 16S rRNA sequence analysis. The fermentation parameters were optimized through a combination of univariate analysis and orthogonal optimization. The stability and antimicrobialactivities of the secondary metabolites were determined using the filter paper method, and the effects on the development of the potato late blight and its pathogen were determined using the in vitroleaf method. The myxobacteria B25-I-1 isolated from a soil sample showed strong activity against P. infestansand was identified as Myxococcus xanthus. The optimal fermentation conditions of M. xanthusB25-I-1 were as follows: inoculum size of 10%, shaking at 180 rmin-1, incubation temperature of 32°C, and incubation time of 8 days. The secondary metabolites were highly tolerant to high temperature, treatment with protease K, andultraviolet and natural lights. Besides P. infestans, the secondary metabolites also showed variant antagonistic effects againstEscherichia coli,Staphylococcus aureus,Bacillus subtilis,Saccharomyces cerevisiae,Fusarium oxysporum, Rhizoctonia solani, and Sclerotinia sclerotiorum. The results of the potato late blight control on potato leaves indicated that the secondary metabolites could significantly inhibit the infection of detached potato leaves caused by P. infestansand caused no damage to the leaves of different varieties of potatoes by themselves. This study provides basic data for the the development of a biopesticide against potato late blight.© 2021 Friends Science Publishers