Journal of Biotechnology & Biomaterials
Open Access

Abstract

Applicability of two Bacillus strains isolated from standard compost was assessed as a reliable alternative in the management of the anthracnose in chilli pepper. Out of twenty promising antagonistic bacterial isolates, two were genotypically characterized as Bacillus spp. based on 16S rRNA analysis. Selected two antagonistic Bacillus strains significantly suppressed the mycelial growth and the spore germination of chilli pepper anthracnose causal agent Colletotrichum truncatum (p<0.05). Malformation of the fungal hyphae was dominant in the area subjected to antagonism. One of the major antagonistic mechanisms extended towards the anthracnose pathogen C. truncatum by these two Bacillus strains was detected as antibiosis in the cellophane overlay technique. They produced antifungal peptides, lipopeptides and also minute amount of organic solvent soluble molecules as antifungal compounds against C. truncatum. These antifungal compounds showed minimum inhibitory concentrations of 3200 ppm and 2460 ppm on C. truncatum and also these metabolites are thermally stable up to 120ºC while they could retain the antifungal properties more than 10 weeks under cold conditions and up to eight weeks at room temperature. One of the Bacillus strains produces a bacteriocin like small peptide inhibitory against C. truncatum. Induction of latent host defense mechanisms is another antagonistic mechanism employed by this Bacillus sp. upon C. truncatum infection in chilli pepper. The tested Bacillus sp. could enhance the expression of defense related PAL and PO enzymes in chilli pepper plants upon C. truncatum infection. Also these antagonistic Bacillus strains promote chilli pepper plants’ growth through the production of significant amounts of Indole Acetic Acid (IAA) which is a growth hormone as an indirect mechanism against C. truncatum. They also showed a prominent swimming and swarming ability indicating their high potentiality in colonizing plant tissues paving the way for successful green house and field applications. These two strains effectively managed the seed borne infection of C. truncatum resulting healthy chilli pepper seedlings with good vigor. Also they effectively managed the fruit decay caused by C. truncatum at color breaking stage and green stage suggesting the suitability of Bacillus spp. as a potential candidate to be used in the development of a biocontrol agent against chilli pepper anthracnose causal agent C. truncatum.

Biography

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