Savalgi, V.P.Rao, Hema C.2022-08-082022-08-082017-05https://krishikosh.egranth.ac.in/handle/1/5810186135A total of 113 isolates of Gluconacetobacter diazotrophicus isolated from sugarcane, maize, pineapple and carrot roots through survey from Dharwad, Belagavi, Uttara Kannada, Haveri and Shivamogga districts of Karnataka during 2014, were characterized morphologically, physiologically and biochemically and subjected for in vitro nitrogen fixation which ranged between 14.01 to 147.1 µg mg-1. The highest N2 was fixed by the native isolate NFGS25 (147.1 µg mg-1). Twenty best isolates were screened for further functional characterization viz., P and Zn solubilization, phytohormone production, antagonistic activity and endoglucanase activity. The zone of solubilization of P and Zn (3.1 and 2.5 cm), IAA and GA production (11.54 and 10.1 µg ml-1) and endoglucanase activity (86 µg ml-1) were maximum in NFGS25. The highest per cent inhibition was exhibited by NFGS25 against Rhizoctonia bataticola (83.33%) and Exserohilium maydis (88.86%). Five best isolates (NFGS25, NFGS26, NFGM5, NFGM6 and NFGP7) were selected for screening of growth parameters and N uptake of maize in the pot trial. The results revealed that plant height, stem girth, root length, chlorophyll content, dry weight, per cent N and N uptake were significantly highest in the treatment inoculated with NFGM5 at 75 % RDN followed by NFGS25 at 75% RDN. The population of G. diazotrophicus was maximum in the treatment NFGM5 at 75 % RDN (7 x 104 cfu ml-1). Based on their performance in pot trial, two efficient isolates (NFGM5 and NFGS25) were selected for field trial and confirmed as G. diazotrophicus isolates by molecular characterization. The results of the field experiment conducted during kharif 2016 at MARS, Dharwad, revealed that all the growth and yield parameters (number of cobs, cob weight, grain yield per plant and test weight) were significantly highest in the treatment NFGM5 at 75% RDN followed by NFGS25 at 75% RDN. The maximum grain yield of 183.33 q ha-1 (15% higher than control) was observed in the treatment NFGM5 at 75 % RDN which was better than the reference strain Azospirillum ACD15 with 75% RDN. Thus it is evident that the inoculation of native isolates of G. diazotrophicus (NFGM5 and NFGS25) at 75% RDN promotes better growth, grain yield and saves nitrogenous fertilizer up to 25% of recommended dose in field condition.EnglishThesis