Alternaria macrospora (Zimm.) is most critical phytopathogen causing Alternaria leaf spot disease of transgenic cotton having regional, national, and international significance. In the present research work, Bacillus amyloliquefaciens subsp. amyloliquefaciens strain RLS19 previously isolated from rhizospheric niches of healthy of Bt cotton plant was screened against A. macrospora by dual culture technique. Bacillus sp. significantly killed the radial mycelial growth of A. macrospora, that is, 98.08%. On finding the mechanism, it was revealed that B. amyloliquefaciens subsp. amyloliquefaciens strain RLS19 produced diffusible non-volatile secondary metabolites, siderophore, and chitinase enzyme which make contributions to inhibit the mycelial growth of A. macrospora during dual culture screening. In addition, the gas chromatography–mass spectrometry evaluation of crude extract discovered the presence of three bioactive compounds specifically acetamide, N-methyl-N-[4-(3-hydroxypyrrolidinyl)-2-butynyl]-; pyrrolo[1,2-a] pyrazine-1,4-dione, hexahydro-, and 2,5-Piperazinedione, 3,6-bis(2-methylpropyl)- with the outstanding antimicrobial antibacterial and antifungal activity which contributed in the inhibition of A. macrospora.
Key words: Alternaria macrospora, Bt cotton, Bacillus amyloliquefaciens subsp. amyloliquefaciens strain RLS19, Non volatile diffusible metabolites, Siderophore and Chitinase
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