Metabolite profiling of PGPR Bacillus subtilis BGKMR1: A potential strategy for managing Fusarium equiseti causing wilt in bitter gourd (Momordica charantia L.)

Wilt caused by Fusarium equiseti is one of the most destructive diseases that leads to substantial yield loss in bitter gourd. The F. equiseti strain CBEFE1((PQ111513.1) which was identified morphologically with falcate shaped three septate macroconidia and oval shaped microconidia and molecularly confirmed through amplification of the ITS region at 560bp was used for this study. Plant growth promoting rhizobacteria (PGPR) act as a sustainable biocontrol agent against major plant pathogens through multiple mode of actions. PGPR were isolated from native rhizopshere region in bitter gourd. The isolated PGPR Bacillus subtilis BGKMR 1 shows maximum mycelial inhibition of 68.73 % against F. equiseti in dual plate assay. The presence of metabolites produced by B. subtilis and F. equiseti along with its interaction were identified through the GCMS profiling. Primarily, pathogenic compound squalene (8.88 %) was identified in F. equiseti and antifungal compound 1,4-benzenedicarboxylic acid (6.1 %) was identified in B. subtilis. Further, B. subtilis BGKMR 1 during its interaction shows propanoic acid (14.69 %) which was found to have effectiveness against F. equiseti. KEGG analysis revealed pyrimidine metabolism in F. equiseti and nitrogen, alanine, aspartate and glutamate metabolism in B. subtilis and propanoate metabolism pathways were detected during its interaction. B. subtilis BGKMR 1 promote the seed germination rate upto 96 % and vigor index to 1919.04 when compared to control. The seed treatment with soil application of B. subtilis BGKMR1 reduced disease incidence upto 25.95 % under glass house condition. Moreover, B. subtilis BGKMR1 treated plants shows enhanced defense enzymes activity such as peroxidase, polyphenol oxidase and phenylalanine ammonia-lyase indicating induction of systemic resistance. Therefore, B. subtilis BGKMR 1 contains novel antifungal metabolites which were identified via GC-MS and induced defense enzyme activity highlights its practical application as a sustainable and eco-friendly solution for managing wilt disease in bitter gourd.