Diversity and functional characterization of bacterial endophytes dwelling in various rice (Oryza sativa L.) tissues, and their seed-borne dissemination into rhizosphere under gnotobiotic P-stress

Abstract

Aim Endophytic bacterial diversity in four rice cultivars grown in two soil-types, their plant-probiotic features and rhizospheric deployment under P-stress were investigated. Methods Oryza sativa cvs. TCN1, TCS10, TK8, and TN71 were cultivated in greenhouse using non-sterile acidic and near-neutral paddy soils for 60 days. Root, stem and leaf tissues were screened for culturable bacterial endophytes using nutrient agar. Endophytes were identified and profiled for plant-probiotic features. The richness, Shannon-Weiner diversity, evenness and Venn's distribution in terms of endophytic strains were evaluated. Seed-borne endophytes were characterized through DGGE. The deployment of endophytes into the rhizosphere in TCN1 and TK8 under gnotobiotic P-stress was assessed.Results A total of 52 distinct endophytic bacterial strains affiliated to 5 classes and 20 discrete genera exhibiting differential plant-probiotic features were isolated from various tissues of four different rice cultivars. The diversity and distribution of endophytes fluctuated with soil-type, tissue-type and rice genotype. Gnotobiotic insoluble P treatment revealed significantly enhanced deployment of P-solubilizing rhizobacteria in TCN1 as compared to soluble P and P-lacking control. Conclusions Rice endophytic bacteria are diverse, and their distribution within the plant and deployment as rhizobacteria were found to be influenced by host genotype, edaphic factors and nutrient stress.

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