Plant Growth Promoting Rhizospheric Bacillus spp. Isolated from Black Pepper (Piper nigrum L.)

Background: The rhizosphere contains many beneficial microorganisms which have a positive action on plant growth and development. In both natural and controlled ecosystems, beneficial plant-associated bacteria play a key role in supporting and increasing plant health and growth.
Methods: In this study, plant growth promoting Bacillus isolates associated with the rhizosphere of black pepper (Piper nigrum) were selected and used for bioassay experiments for the host plant as well as for two test plants viz. French bean (Phaseolus vulgaris) and Pea plant (Pisum sativum).
Result: This investigation revealed that the isolates chosen for the study exert a positive effect on the growth of inoculated black pepper plants and the test plants as compared to uninoculated control. Molecular identification of the selected isolates was done based on 16S rRNA gene analysis. All the four isolates exerted a considerable influence on the growth of black pepper cuttings and there is a significant increase in the shoot height and root length compared to untreated cuttings. Seed bacterization of the two test plants resulted in the increment of plant height and a heavier fresh weight and dry weight when compared to control plants. Based on these findings, it is evident that the isolates can be employed to enhance the growth not only of black pepper but of the test plants as well. Hence, according to this study, the selected isolates could be used as plant growth-promoting inoculants to attain the desired results of stem cuttings and seed bacterization.
