A Culture-dependent Study of Bacteria Associated with the Roots of Organically and Inorganically Cultivated Rice Accessions

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Rice is one of the most important staple foods consumed by the maximum human population in the world. India possesses a large number of traditionally maintained rice landraces which are cultivated using traditional practices or minimal fertilizer input. Such landraces may be associated with unique microbial flora adapted to various biotic and abiotic stresses. This work aimed to study the diversity of bacteria associated with roots of 18 randomly selected landraces from Jawhar, Maharashtra, grown under organic cultivation practices, and the cv. Indrayani from Mulshi, Maharashtra, grown using conventional cultivation practices. The cultivation-based approach yielded a total of 40 bacterial isolates. Isolates were purified and identified by sequencing the 16S rDNA region. Isolates were tested for plant growth-promoting characteristics such as nitrogen fixation, phosphate solubilization, IAA production, etc. 22 isolates tested positive for nitrogen fixation either by acetylene reduction or the presence of nifH gene, 27 had phosphate solubilization and 39 had IAA production ability. Bacterial diversity demonstrated the dominance of phylum Proteobacteria and isolates belonging to 11 genera and 23 species e.g., Stenotrophomonas sp., Bradyrhizobium sp. etc. PCA showed a clear difference between bacterial diversity associated with landraces and cv. Indrayani. Our findings provide a basis for further investigations into the role and impact of microbial communities in plant growth promotion. Rice is one of the most important staple foods consumed by the maximum human population in the world. India possesses a large number of traditionally maintained rice landraces which are cultivated using traditional practices or minimal fertilizer input. Such landraces may be associated with unique microbial flora adapted to various biotic and abiotic stresses. This work aimed to study the diversity of bacteria associated with roots of 18 randomly selected landraces from Jawhar, Maharashtra, grown under organic cultivation practices, and the cv. Indrayani from Mulshi, Maharashtra, grown using conventional cultivation practices. The cultivation-based approach yielded a total of 40 bacterial isolates. Isolates were purified and identified by sequencing the 16S rDNA region. Isolates were tested for plant growth-promoting characteristics such as nitrogen fixation, phosphate solubilization, IAA production, etc. 22 isolates tested positive for nitrogen fixation either by acetylene reduction or the presence of nifH gene, 27 had phosphate solubilization and 39 had IAA production ability. Bacterial diversity demonstrated the dominance of phylum Proteobacteria and isolates belonging to 11 genera and 23 species e.g., Stenotrophomonas sp., Bradyrhizobium sp. etc. PCA showed a clear difference between bacterial diversity associated with landraces and cv. Indrayani. Our findings provide a basis for further investigations into the role and impact of microbial communities in plant growth promotion.