Morpho-Molecular Characterization of Bacterial Endophytes from Different Banana (Musa sp.) Cultivars across Tamil Nadu, India

Abstract

Banana (Musa spp.) is a major fruit crop in Tamil Nadu, but its productivity is severely affected by Fusarium wilt, caused by Fusarium oxysporum f. sp. cubense (Foc). Chemical management provides only limited, unsustainable control, emphasizing the need for eco-friendly approaches. Beneficial bacterial endophytes, which colonize plant tissues without causing harm, offer promise for plant growth promotion and biocontrol of pathogens. The present study aimed to isolate and identify bacterial endophytes from diverse banana cultivars across major growing regions of Tamil Nadu, with the long-term goal of developing sustainable disease management strategies. A survey-based experimental study was conducted at the Department of Plant Pathology, Faculty of Agriculture, Annamalai University, in collaboration with banana fields between July 2023 and May 2024. Field surveys were carried out in five districts representing AAA and AB genome groups cultivated on different soil types. Healthy pseudo stem and root tissues were collected, surface sterilized, and cultured on nutrient agar. Pure isolates were characterized through colony morphology, Gram staining, and biochemical assays (starch hydrolysis, citrate utilization, indole production, catalase, oxidase, methyl red). Genomic DNA was extracted by the CTAB method, and 16S rRNA gene fragments were amplified using universal primers. Ten morphologically distinct bacterial endophytes were identified. Gram-positive isolates included Bacillus thuringiensis and B. velezensis, while Gram-negative isolates comprised Pseudomonas aeruginosa, Alcaligenes faecalis, Alcaligenes sp., Myroides odoratimimus, Stenotrophomonas maltophilia, and Providencia stuartii. The isolates exhibited diverse colony and biochemical traits. Notably, Bacillus and Pseudomonas spp. are known for biocontrol and growth promotion, underscoring their potential for integration into eco-friendly management strategies against Fusarium wilt in banana cultivation.