Biohardening with Plant Growth Promoting Rhizosphere and Endophytic bacteria induces systemic resistance against Banana bunchy top virus

Tissue culture banana has emerged as one of the leading global agro based industrial technologies. However, the banana plants are found to be more susceptible to pests and diseases due to their pliable nature and lack of withstanding in the natural environment. Banana bunchy top disease (BBTD) caused by Banana bunchy top virus (BBTV) is the most serious virus disease of banana and plantain world wide. Biopriming (or) biohardening refers to treatment of tissue culture banana plantlets with microbial inoculants to strengthen the plantlets against biotic and abiotic stresses. Forty plant growth promoting endophytic bacteria (PGPE) were isolated from the corm and roots of banana and tested for the ability to induce systemic resistance against BBTV. Phenotypic and molecular characterization of the endophytic bacteria revealed the presence of Pseudomonas and Bacillus species. Micropropagated banana plantlets were tested for the presence of BBTV by ELISA, DIBA and PCR and the uninfected plants were biohardened with two rhizobacterial (Pseudomonas fluorescens, Pf1, CHA0) and endophytic bacterial (EPB5, EPB22) strains. Plants treated with mixtures of rhizobacterial and endophytic bacterial formulations viz., EPB5 + EPB22 + Pf1 + CHA0 was significantly effective in reducing BBTV under field conditions recording 33.33% infection with 60% reduction over control. The expression of defense-related enzymes and pathogenesis related proteins were more in the plants treated with rhizosphere and endophytic bacterial formulations than the control plants. The morphological and physiological characters were also well pronounced in the treated plants indicating its plant growth promoting nature. Thus, the present study clearly demonstrated that PGPR and PGPE mediated induction of systemic resistance in banana plants against BBTV have the potential role in the management of BBTD.