Plant Growth Promoting Potential of Rhizobacteria Isolated from Cannabis Sativa L.

Abstract

In current study, PGPRs (Plant Growth-Promoting Rhizobacteria) were isolated from the rhizospheric soil of Cannabis sativa and assessed for their potential of auxin biosynthesis and enhancement of growth of Vigna mungo. Strains identified on account of morphological characteristics and Gram’s staining were confirmed by 16S rRNA gene analysis for final taxonomic status. Nine bacterial strains showed similarity with genus Bacillus while B16 and B17 showed similarity with Serratia marcescens and Stenotrophomonas maltophilia, respectively. Colorimetric analysis of bacterial culture supernatants revealed the auxin synthesis and production ability of the isolated strains at 0 and 500 µg ml-1 concentrations of L-tryptophan. At 500 µg ml-1 L-tryptophan concentration, B. subtilis (B15), S. maltophilia (B17) and B. subtilis (B11) produced significant levels of 217.1, 197.3 and 116.4 µg ml-1 auxin, respectively (P<0.05). In vitro rooting assay manifested a significant increase of 60% and 84% in root length with B. subtilis (B15) and B. subtilis (B11) over control, respectively (P<0.05). For pot trials seeds of Vigna mungo treated with bacterial strains single cultures were evaluated for their ability to enhance plant growth. For shoot length, P. aryabhattai (B9) and B. licheniformis (B3) recorded 75% and 74% increases, respectively, over control (P<0.05). For fresh weight, B. subtilis (B5) and P. aryabhattai (B9) showed 33% significant improvements, over control (P<0.05). While B. subtilis (B5) exhibited 31% increase in dry weight, in comparison with control (P<0.05). The results demonstrate that bacterial strains isolated from C. sativa can synthesize auxin and thus promote the growth of V. mungo.