Exploration of zinc solubilizing bacteria and their prolific contribution in zinc biofortification of rice grains
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Date
2021-12
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
The current study was an endeavor to characterize zinc-solubilizing bacteria, bearing massive plant growth-promoting traits, from the rhizosphere of millets (barnyard millet and finger millet). In addition, the study was conducted to evaluate the effect of potential bacterial strains and their consortia on growth and the biofortification benefits by assessing improved level of zinc assimilation in rice under pot and field conditions. A total of 130 bacteria were isolated and tested for zinc solubility characteristics, of which only 10 bacterial isolates were selected based on their zinc solubilization potential. Finally, 3 bacterial isolates (BMAR64, FMAR105 and BMRR126) were selected based on the quantitative pattern of zinc solubility potential and their compatibility with one another, and were used for the development of bacterial consortia. These bacteria solubilized Zn profoundly determined quantitatively in liquid broth by AAS and SEM-EDX. These zinc-solubilizing bacterial strains were characterized on the basis of morphological, biochemical tests and 16S rDNA sequencing. These isolates BMAR64, FMAR105 and BMRR126 were recognized as Pantoea rodasii, Serratia marcescens and Burkholderia cepacia, respectively, and they were also found to have genes for organic acid production (gcd and gdh). All three bacterial isolates and their consortia were evaluated for their effect on rice plants (variety- Pusa Basmati -1) in a pot trial in which the treatment with bacteria and their consortia with ZnO supplementation established narrative of Zn-biofortification and improvement in the growth of rice plant. The zinc solubilizing bacterial consortia (Consortium 1 and Consortium 2) with ZnO supplementation exhibited the maximum Zn content in grains of rice (variety- Pusa Basmati-1) in both the Terai and Katchar region of Northern part of India. The treatments containing single bacterial inoculants (BMRR126) with 60% RDF and Consortium (BMAR64+FMAR105+BMRR126) with 100% RDF with ZnO amendment exhibited promising level of Zn content in grain of rice plant (variety- Pant Dhan 18) grown in Terai region. All treatments containing zinc-solubilizing bacterial strains increased rice crop productivity in terms of several aspects such as plant height, dry matter accumulation, number of tillers and effective tiller, grain yield, straw yield, biological yield, panicle length, number of grains per ear, and thousand grain weight. The soil parameters (pH, EC, organic carbon, NPK, available Zn, and soil dehydrogenase activity) also positively influenced under all bacterial treatments compared to uninoculated control. The present study gives an impression of the use of zinc solubilizing bacteria and their consortia as effective bioinoculants (supplementation with economic feasible source of zinc, i.e. ZnO) to harness zinc biofortification of rice crops in more ecofriendly way for sustainable agriculture. Our study clearly highlights the need for zinc-solubilizing bacteria to achieve the benefits of zinc biofortification in different regions.