Biocontrol Potentials of Antimicrobial Peptide Producing Bacillus Species: Multifaceted Antagonists for the Management of Stem Rot of Carnation Caused by Sclerotinia sclerotiorum

Abstract

<i>Bacillus</i> species are widely exploited as biocontrol agents because of their efficiency in impeding various plant pathogens with multifaceted approach. In this study, <i>Bacillus</i> species were isolated from rhizosphere of various plants viz., carnations, cotton, turmeric, and bananas in Tamil Nadu state of India. Their potential to control the mycelial growth of <i>Sclerotinia sclerotiorum</i> was assessed <i>in vitro</i> by dual plate and partition plate techniques. <i>B. amyloliquefaciens</i> strain VB7 was much effective in inhibiting mycelial growth (45% inhibition of over control) and sclerotial production (100%). PCR detection of AMP genes revealed that <i>B. amyloliquefaciens</i> (VB7) had a maximum of 10 diverse antibiotic biosynthesis genes, namely, <i>ituD, ipa14, bacA, bacD, bamC, sfP, spaC, spaS, alba</i>, and <i>albF</i>, that resulted in production of the antibiotics iturin, bacilysin, bacillomycin, surfactin, subtilin, and subtilosin. Further, metabolites from <i>B. amyloliquefaciens</i> strains VB2 and VB7, associated with inhibition of <i>S. sclerotiorum</i>, were identified as phenols and fatty acids by gas chromatography mass spectrometry (GC-MS). Delivery of bacterial suspension of the effective strains of <i>Bacillus</i> spp. as root dip was found promising for the management of stem rot of cultivated carnations. Minimal percent disease incidence (4.6%) and maximum plant growth promotion was observed in the plants treated with <i>B. amyloliquefaciens</i> (VB7).