Evaluation of Plant Growth Parameters by In vitro and Ex vitro Inoculation of Micropropagated Banana Plantlets with Rhizospheric and Endophytic Bacterial Inoculum

Abstract

Banana propagation is dependent on propagation by tissue culture for industrial purposes. Due to lack of native endophytes in tissue culture plantlets, reintroduction of beneficial microorganisms to tissue culture plantlets become popular as a useful foundation for improving the level of establishment, increasing plant growth parameters, protecting the plantlets against pest and diseases and overall performance for field plantation. In the present study, rhizospheric and endophytic four bacterial species (Pseudomonas fluorescens, Bacillus putida, Bacillus pumilus, Bacillus amyloliquefaciens were isolated from different parts of healthy banana plants such as root, leaf and pseudostem. Banana tissue culture plantlets were cultured for root formation stage on MS medium and used as host for artificial inoculation. Then, bacterial inoculation was carried out with tissue culture plantlets both in vitro and ex vitro conditions. All banana plantlets used for this experiment were successfully acclimatized and survived in the greenhouse. The experiment consisted of three treatments: (1) bacterial inoculum with in vitro rooted plantlets for 2 weeks (2) bacterial inoculum with ex vitro (hardening) plantlets (3) control with sterilized distilled water. Among these treatments, in vitro inoculation affected significantly increased plant height, number of leaves and plant girth for all data collection times with the highest increment indices: (24.0, 7.0, and 7.3). Ex vitro inoculation showed the second highest increment indices: (22.0, 6.9 and 6.3) for plant height, number of leaves and plant girth, respectively. The lowest number of plant growth parameters were observed in control treatment for all four data collection time (19.0, 6.2, and 6.0). According to the results, application of mixtures of bacterial inoculum was effective for enhanced plant growth parameters of tissue culture banana plantlets under greenhouse condition. In addition, two weeks artificial inoculation during in vitro plantlets stage was found the most suitable method for application of microbes with tissue culture banana plantlets which can promote the microbial rhizosphere of banana prior to field plantation.