RESUMO
Aim: The aim of the present study was to understand the basic pathogen dynamics of Colletotrichum species infecting chilli crop in the Andaman and Nicobar Islands for disease management practices. Methodology: Twenty fungal isolates associated with chilli (Capsicum annuum) anthracnose disease from diverse locations of tropical Andaman, India were characterized using polyphasic approaches. Results: Upon morphological studies, out of twenty isolates, fourteen isolates were found chromogenic and eleven showed concentric ring pattern of mycelial growth. Based on conidial morphology, the isolates were grouped into two species (C. capsici and C. gloesporioides). The pathogenicity tests on three chilli varieties revealed difference in the pathogenic potential among the collected isolates. The sequence analysis using internal transcriber spacer (ITS) region revealed the presence of two other species C. siamense and C. plurivorum, in addition to C. gloesporioides and C. capsici. Interpretation: The present study revealed the presence of high level of genetic and pathogenic variability among the Colletotrichum isolates infecting chilli in Andaman Islands.
RESUMO
Bacillus spp. isolated from different soils of Andaman Islands was characterized for antimicrobial potential by different methods. Among 65 strains tested, six Bacillus strains showed best in vitro antagonistic potential against solanaceous bacterial wilt pathogen Ralstonia solanacearum. The identity of the Bacillus strains were confirmed using 16S rRNA gene sequencing and biolog based phenotypic fingerprinting. The functional analysis revealed that most of the strains were positive for the production of IAA, siderophore and phosphate solubilization. In glass house and field studies, Bacillus amyloliquifaceans strain (Bs_Abi) showed significant biocontrol efficacy (92.1 and 73.7%, respectively) against brinjal bacterial wilt disease. The antimicrobial potential of Bs_Abi were further ascertained by presence of nine antimicrobial peptide (AMP) gene biosynthesis in PCR amplifications which confirmed the presence of peptide genes for six antibiotics (iturin, bacillomycin D, mycosubtilin, surfactin, bacilysin and subtilin). Our study revealed that the utilization of such antagonistic Bacillus spp. with multi antimicrobial peptide genes and more functional traits from tropical/ extreme soils would play a vital role in management of eggplant bacterial wilt disease and in formulation of new bioinoculants for improving the cropping system in Andaman and Nicobar Islands