Diversity and Molecular Characterization of Endophytic Actinomycetes Associated with Banana (Musa spp.) Cultivars in Tamil Nadu, India

Abstract

Banana (Musa spp.) is one of the most important fruit crops in Tamil Nadu; however, its productivity is critically threatened by Fusarium wilt incited by Fusarium oxysporum f.sp. cubense (Foc). Endophytic actinomycetes, particularly members of the genus Streptomyces, have emerged as promising eco-friendly alternatives to chemical fungicides due to their dual roles in biocontrol and plant growth promotion. To investigate their diversity and functional potential, systematic surveys were conducted between July 2023 and January 2024 across five major banana-growing districts representing different genome groups (AB and AAA) and diverse soil types.  Endophytic actinomycetes were isolated from surface-sterilized pseudo stem and root tissues and subjected to phenotypic and biochemical characterization, including colony morphology, Gram reaction, cell morphology, spore formation, and assays for catalase, oxidase, gelatin hydrolysis, starch hydrolysis, casein hydrolysis, and H₂S production. Molecular identification was performed by amplifying the 16S rRNA gene using universal primers (27F/1492R), followed by sequencing, BLAST analysis, and phylogenetic reconstruction with MEGA X. Nine unique isolates were resolved, identified as Streptomyces mutabilis, S. tendae, S. calvus, S. griseoviridis, S. colonosanans, S. rochei, S. turius, and S. levis, with amplicon sizes ranging from 1,365 to 1,490 bp. Concordance of biochemical traits with molecular data confirmed their species-level identities. These findings highlight the substantial diversity of banana-associated actinomycetes in Tamil Nadu and underscore their potential applications in sustainable management of Fusarium wilt through biocontrol and growth-promoting mechanisms.