Endophytic bacteria from diseased plant leaves as potential biocontrol agents of cucumber Fusarium wilt

Abstract

Screens for Fusarium wilt antagonistic bacteria have generally focused on screening for antagonistic strains from healthy plants, with few reports of screening for antagonists from leaves of diseased plants. In this study, we used cucumber leaves infected with Fusarium wilt disease for the isolation of antagonists and a total of four endophytes with obvious antagonistic effects were screened. Based on the results of physiological and biochemical experiments and 16S rDNA gene sequencing, four strains were identified as Paenibacillus polymyxa (Y-4, Y-6, Y-14) and Bacillus Zanthoxylum (Y-9), and all antagonistic strains exhibited the ability to produce amylase, pectinase and hydrogen peroxide (H2O2). In pot test, antagonistic bacteria were able to significantly reduce the disease index in cucumber seedlings challenged with the pathogen. Four strains of antagonistic bacteria can alleviate the damage caused by Fusarium oxysporum f. sp. cucumerinum (FOC) invasion by increasing the photosynthetic efficiency, antioxidant capacity and root vigor of cucumber seedlings. In conclusion, the leaves of cucumber diseased strain may also be a potential source for screening novel antagonistic agents against cucumber Fusarium wilt. The screened four strains of antagonists had a certain biocontrol potential against FOC and could play a certain role in environmental-friendly agriculture in the future.