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20213
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Subject: Microbiology × End date: 2021 × Start date: 2021 × Thesis Type: Ph.D ×
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    ThesisItemOpen Access
    Exploration of zinc solubilizing bacteria and their prolific contribution in zinc biofortification of rice grains
    (G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand), 2021-12) Upadhayay, Viabhav Kumar; Singh, Ajay Veer
    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.
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    ThesisItemOpen Access
    Functional and molecular characterization of rhizobacterial antagonists against foliar blight pathogens of wheat, Bipolaris sorokiniana and Alternaria triticina
    (G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand), 2021-02) Jaggi, Vandana; Sahgal, Manvika
    Foliar blight pathogens affect the wheat production and growth worldwide. The application of chemical fertilizers to control the disease has harmful effects to human health and environment. Fortunately, rhizobacteria can be used as an alternative strategy for the sustainable disease management. In present study, a total of forty five rhizobacteria isolated from rhizosphere soil of wheat cultivated in five agroclimatic regions across four India states were tested for in vitro antagonistic activity against two foliar blight pathogens; Bipolaris sorokiniana and Alternaria triticina causing wheat spot blotch and leaf blight respectively. In addition, all 45 rhizobacteria were tested for production of hydrolytic enzymes (chitinase, protease, cellulase, amylase, and lipase) and PGP traits (solubilization of phosphate & zinc, production of ammonia and siderophore). Six isolates scoring (Ʃ=>12) on bonitur scale were selected for further studies. The isolates P10, UP11, MH13, MP17, MH12, and MP14 were subsequently identified as Bacillus methylotrophicus (MN099430.1), Bacillus subtilis (MN099431.1), Bacillus sp. (MN099432.1), Streptomyces sp. (MN099435.1), Lysinibacillus sp. (MN099433.1), and Staphylococcus epidermidis (MN099434.1) respectively. In vivo pot trial revealed that seed bacterization plus booster dose of bacterial treatments resulted in lowest disease incidence (DI %) than foliar spray 24 hrs after pathogen infection against both the foliar blight pathogens. Reduction in spot blotch incidence in wheat plants treated with the isolates P10 (T2) UP11 (T3) was significant with48.66% and 50.33 % DI respectively. Likewise, percrent reduction in the incidence of leaf blight by P10 and UP11 was 49.26% and 50.33% respectively. The pot experiments also revealed that P10 and UP11 considerably increased plant biometric parameters. Therefore, B. methylotrophicus strain P10 and B. subtilis strain UP11 were equally effective to control both the foliar blight pathogens individually as well as in a complex. Antifungal metabolites produced by P10 and UP11 were analyzed in ethyl acetate extract by GC-MS and 29 and 30 compounds were identified respectively. A compound, isobutylhexahydropyrrolo [1, 2-a] pyrazine-1, 4-dione was dominant and abundant in both the strains. In silico studies revealed a strong interaction (ΔG-6.76) between the dominant compound and, ceratoplatinin, a phytotoxic protein of fungus B. sorokiniana. Hence, we suggest that strain P10 and UP11 has the potential to be used in sustainable agriculture.
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    ThesisItemOpen Access
    Bioconversion of photooxidatively delignified woody biomass of Salix alba into bioethanol using C6/C5 co- sugar fermenting yeast Pichia kudriavzevii BGY1
    (G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand), 2021-03) Bisht, Neha; Tewari, Lakshmi
    Presently bioethanol is considered as the most sustainable and eco- friendly fuel in contrast to non- renewable fuels. The present study was carried out for identification and characterization of potential ethanogenic yeast. Native yeast cultures were isolated from diverse fruit sources. Based on qualitative and quantitative screening for ethanol production two ethanogenic yeast were selected and subjected to UV and gamma mutagenesis with aim to enhance stress tolerance limit and sugar fermenting ability. Based on phenotypic and 5.8 S ITS rRNA gene sequencing, the isolate BGY1 and its mutant BGY1- γ m were identified as Pichia kudriavzevii BGY1 and Pichia kudriavzevii BGY1- γ m. The woody biomass of Salix alba was first subjected to chemical, biological, chemi- biological and photonanocatalyst mediated pretreatments for removing lignin and improving saccharification efficiency. Combined photonanocatalyst induced and cellulase enzyme aided alkaline oxidative pretreatment decreased the lignin content from 18.7 to 4.0 %. The pretreated substrate was then saccharified into fermentable sugars using cellulase enzyme from the fungal isolate (Aspergillus terrus PPCF). Optimization of saccharification resulted in 57.2 % of saccharification efficiency in 24 h. Then, the potential microbial strains in mono/co-cultures were screened for their alcohol producing efficacies using saccharified Salix alba wood biomass. Bio-conversion of saccharified wood employing potential strains into bio-ethanol was carried out in batch cultures through SHF and SSF process. Finally the co- culture of P. Kudriavzevii BGY1 and P. Kudriavzevii BGY1-γ m were selected for alcoholic fermentation. Alcoholic fermentation of saccharified Salix alba wood powder using co- culture of yeast P. kudriavzevii BGY1 and P. kudriavzevii BGY1- γ m at 32º C under SSF batch fermentation process was found superior over batch fermentation under SHF process. Under optimized conditions maximum ethanol yield 13.0 % was achieved with saccharified Salix alba wood.