Exploiting endophytic bacteria towards managing squash powdery mildew disease

Natural substances like phenolic and flavonoid compounds from extracts of wild plants are used for the control of many plant diseases. Endophytic bacteria were isolated from 7 wild plants growing at Maarafai and Kancesorup Wadies on Jebel Elba, Egypt, and the effect of these endophytic bacterial were studied as an alternative tool against Podosphaera xanthii infecting squash plants. This study showed the efficacy of endophytic bacteria strains (Bacillus amyloliquefaciens strain BMAT1, B. firmus strain BMAT2, B. pumilus strain PMOE1 and B. subtilis strain BKEC1) for controlling powdery mildew of squash plants. The effects of fresh cultures of the four bacteria on disease severity in vivo were evaluated. Mixed treatment of the tested bacteria showed the greatest reduction in disease severity, increasing peroxidase, polyphenol oxidase, and total phenols in the squash leaves as well as crop yield. The highest concentrations of phenolic compounds were found in quinic and ellagic acids, while the highest concentrations of flavonoid components were found in apeginin. Treatment with a combination of four bacterial cultures increased the maximal activity of total phenols, peroxidase, and polyphenol oxidase. These findings suggested that endophytic bacterial strains could be used as environmentally friendly substitutes for synthetic fungicides to control powdery mildew of squash plants. •Wild plants were the sources of 23 bacterial isolates used in this study.•Bacterial isolates were tested for their antagonistic effect against Podosphaera xanthii, the causal agent of powdery mildew on squash.•High reduction in disease severity was observed by a mixed treatment of endophytic bacteria.•High levels of defense-related enzyme activities were observed in the plants with mixed treatment of endophytic bacteria.•Increased phenolics were observed in the squash leaves treated by a mix of endophytic bacteria.