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Subject: Botany × Author: Dinesh Chandra × End date: 2017 × Start date: 2017 × Thesis Type: Ph.D ×
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    ThesisItemOpen Access
    Isolation, characterization and growth promoting attributes of plant growth promoting bacteria (PGPB) on field crops under irrigated and drought conditions
    (G.B. Pant University of Agriculture and Technology, Pantnagar (Uttarakhand), 2017-01) Dinesh Chandra; Sharma, A.K.
    Plant growth promoting bacteria (PGPB) containing 1-aminocyclopropane-1-carboxylate (ACC) deaminase has been reported to play an important role in alleviation of drought stress. In present study, eight ACC deaminase producing tolerant bacteria were isolated from a rainfed agriculture field of Kumaun region of Central Himalaya, Uttarakhand, India and evaluated for their efficiency in improving the growth of finger millet (Eleusine coracana (L.) Gaertn.), rice (Oryza sativa L.) and wheat (Triticum aestivum L.) under irrigated and drought conditions. These bacteria withstand a substrate metric potential of -1.0 MPa (30% PEG 8000) and therefore are considered to be drought-tolerant. The selected bacterial isolates were identified as Ochrobactrum sp., Pseudomonas sp., and Variovorax sp. by fatty acid methyl ester (FAME) analysis and 16S rRNA gene sequencing. The presence of acdS, the structural gene for ACC deaminase in selected bacterial strains was confirmed by the polymerase chain reaction (PCR). Glass house experiment showed that enhanced level of nutrients and antioxidant properties with the consortium of different bacterial strains. The consortium of Ochrobactrum anthropi DPC9 + Pseudomonas palleroniana DPB13 + Pseudomonas fluorescens DPB15 + Pseudomonas palleroniana DPB16 significantly increased the 1000 grain weight (9.3%, 28.9%), number of grains/panicle or spike (31.3%, 32.4%), grain yield (39.6%, 42.7%), and straw yield (21.1%, 26.9%) of rice and wheat, respectively as compared to their respective non-inoculated plants under organic field conditions. Variovorax paradoxus RAA3 treated plants maximally increase the total tillers/plant (40.0%, 31.7%), number of grains/spike (30.3%, 28.2%), spike length (26.4%, 25.8%), 1000 grain weight (17.4%, 22.0%), grain yield (28.2%, 47.4%), straw yield (11.2%, 26.0%) and harvest index (10.6%, 15.3%) under irrigated and rainfed conditions, respectively as compared to non-inoculated plant. Quantitative RT-PCR (qRT-PCR) based expression analysis of drought responsive genes (helicases and aquaporin) was also performed in response to V. paradoxus RAA3 inoculation in two varieties of wheat (HD 2967 and PBW 660) under irrigated and rainfed conditions The relative expression of aquaporin (TaTIP1;1) is significantly higher (7.26-fold) in the wheat variety PBW 660(drought tolerant), as compared to drought sensitive HD 2967 where expression level of aquaporin is down-regulated. The transcript level of WDH45 is down-regulated in both the varieties under irrigated conditions. In rainfed conditions, the relative mRNA level of wheat DNA helicase (WDH45) is significantly higher in HD 2967 (1.39-fold) than the PBW 660, whereas the expression pattern of aquaporin in PBW 660 is higher (2.70-fold) than the variety HD 2967 under rainfed conditions. This finding may imply PGPB having ACC deaminase activity could turn out to be effective inoculants for improving the growth of plants. Such promising strains could possibly be used under field conditions in rainfed environment where agriculture is exclusively dependent on rainfall.