Endophytic microorganisms have been reported from various plants. In the current study, somatic embryogenic cultures of banana (Musa accuminata AAA cv. Grand Naine) were found to have association with endophytic bacteria which were present initially in a covert state. The presence of bacteria was detected only in suspension cultures derived from the somatic embryogenic cultures. The bacteria isolated from embryogenic cell suspension culture were identified as Ralstonia sp. and Bacillus sp. The Ralstonia sp. interestingly showed the presence of various plant growth promoting properties including indole acetic acid and siderophore production. Also the strain was found to have the potential to solubilize phosphate and produce ammonia. Growth enhancement effect of Ralstonia sp. on Vigna radiata seedlings showed promising results and the growth parameters were found to be statistically significant when compared to control. Identification and confirmation of the plant growth promoting properties of Ralstonia sp. makes the study significant with promising applications.

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Rhizobacterial production of plant hormones, ACC deaminase, fixation of nitrogen, solubilization of phosphate and antimicrobial metabolites play very important role in the health and growth of plants. Hence exploration of plant probiotic prospectives of promising rhizobacterial isolates from biodiversity rich areas can have enormous applications to engineer both the biomass and active ingredients of plants. In the present study, rhizospheric spp. R6 and R60 isolated from and were analyzed for tuber and diosgenin enhancement effects in under field conditions for 1 year. Among the two spp. selected, both were positive for ACC deaminase, siderophore, nitrogen fixation, IAA and ammonia production. However, the isolate R6 was found to have additional phosphate solubilizing activity. Quantitative analysis of IAA by HPTLC showed its maximum production by sp. R60 (714.47 ± 8.7 µg/mL) followed by sp. R6 (588.06 ± 7.0 µg/mL). The tubers formed from the sp. R6 treated samples were identified to have significant enhancement in size, root number and diosgenin content when compared to control. Interestingly, HPLC analysis has confirmed twofold higher diosgenin content in sp. R6 treated samples than control during 1 year period of its field growth. The obtained results are of great importance as it involved the utilization of rhizospheric bacteria to improve tuber size which suggests its potential use in developing cost-effective, eco-friendly and multifunctional biofertilizer.

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