Comparative assessment of multi-trait plant growth-promoting endophytes associated with cultivated and wild Oryza germplasm of Assam, India

This paper presents a comparative study of endophytic bacteria from cultivated (Oryza sativa) and wild rice (Oryza rufipogon) plants and their functional traits related to plant growth promotion. A total of 70 bacterial isolates were characterized by both biochemical and molecular identification methods. Taxonomic classification showed dominance of three major phyla, viz, Firmicutes (57.1%), Actinobacteria (20.0%) and Proteobacteria (22.8%). Screening for in vitro plant growth-promoting activities revealed a hitherto unreported endophytic bacterium from wild rice germplasm, Microbacterium laevaniformans RS0111 with highest indole acetic acid (28.39 +/- 1.39 mu g/ml) and gibberellic acid (67.23 +/- 1.83 mu g/ml) producing efficiency. Few other endophytic isolates from cultivated rice germplasm such as Bacillus tequilensis RHS01 showed highest phosphate solubilizing activity (81.70 +/- 1.98 mu g/ml), while Microbacterium testaceum MKLS01 and Microbacterium enclense MI03 L05 showed highest potassium (53.42 +/- 0.75 mu g/ml) and zinc solubilizing activity (157.50%). Fictibacillus aquaticus LP20 05 produced highest siderophore (64.8%). In vivo evaluation of plant growth-promoting efficiencies of the isolates showed that Microbacterium laevaniformans RS0111, Microbacterium testaceum MKLS01 and Bacillus tequilensis RHS 01 could increase rice grain yield by 3.4-fold when compared to the control group. This study indicates the potentiality of rice endophytes isolates as an effective bioinoculants.

Automated summary

This paper compared endophytic bacteria from cultivated and wild rice plants, identifying several strains with high plant growth-promoting activities. The study revealed the potential of rice endophytes as effective bioinoculants with the ability to significantly increase rice grain yield.