title: Biocontrol agent Bacillus amyloliquefaciens LJ02 induces systemic resistance against cucurbits powdery mildew.
abstract: Powdery mildew is a fungal disease found in a wide range of plants and can significantly reduce crop yields. Bacterial strain LJ02 is a biocontrol agent (BCA) isolated from a greenhouse in Tianjin, China. In combination of morphological, physiological, biochemical and phylogenetic analyses, strain LJ02 was classified as a new member of Bacillus amyloliquefaciens. Greenhouse trials showed that LJ02 fermentation broth (LJ02FB) can effectively diminish the occurrence of cucurbits powdery mildew. When treated with LJ02FB, cucumber seedlings produced significantly elevated production of superoxide dismutase, peroxidase, polyphenol oxidase and phenylalanine ammonia lyase as compared to that of the control. We further confirmed that the production of free salicylic acid (SA) and expression of one pathogenesis-related (PR) gene PR-1 in cucumber leaves were markedly elevated after treating with LJ02FB, suggesting that SA-mediated defense response was stimulated. Moreover, LJ02FB-treated cucumber leaves could secrete resistance-related substances into rhizosphere that inhibit the germination of fungi spores and the growth of pathogens. Finally, we separated bacterium and its fermented substances to test their respective effects and found that both components have SA-inducing activity and bacterium plays major roles. Altogether, we identified a BCA against powdery mildew and its mode of action by inducing systemic resistance such as SA signaling pathway.
authors.affiliation: College of Horticulture and Landscape, Tianjin Agricultural University , Tianjin, China.
authors.forename: Yunlong
authors.initials: Y
authors.lastname: Li
authors.affiliation: College of Horticulture and Landscape, Tianjin Agricultural University , Tianjin, China.
authors.forename: Yilin
authors.initials: Y
authors.lastname: Gu
authors.affiliation: College of Horticulture and Landscape, Tianjin Agricultural University , Tianjin, China.
authors.forename: Juan
authors.initials: J
authors.lastname: Li
authors.affiliation: College of Horticulture and Landscape, Tianjin Agricultural University , Tianjin, China.
authors.forename: Mingzhu
authors.initials: M
authors.lastname: Xu
authors.affiliation: State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences , Beijing, China.
authors.forename: Qing
authors.initials: Q
authors.lastname: Wei
authors.affiliation: College of Horticulture and Landscape, Tianjin Agricultural University , Tianjin, China.
authors.forename: Yuanhong
authors.initials: Y
authors.lastname: Wang
keywords: Bacillus amyloliquefaciens; PR genes; biocontrol agent; powdery mildew; salicylic acid; systemic acquired resistance