SAVALAGI, V. P.SHUBHA, S.2019-09-172019-09-172001-08-08Th-6041http://krishikosh.egranth.ac.in/handle/1/5810128573Experiments were conducted to isolate native Azospirillum strains from the rhizoplane and endorhizosphere of 27 wheat genotypes and 32 Azospirillum isolates were obtained. Among these six were Azospirillum lipoferum, 13 were Azospirillum brasilense and 13 isolates could not be grouped into either of the two categories. The isolate WAS-lo was found to fix in vitro high amount of nitrogen (24.80 mgN/g of malate) and could reduce acetylene (584ri moles/mg of protein/h). All the Azospirillum isolates were checked for the different salt tolerance levels, metal resistance and resistance ro ethylenediamine. Based on above observations, the Azospirillum isolate WAS-15 with maximum resistance to ethylenediamine (0.02%) and higher acetylene reduction activity was subjected to mutation by gamma irradiation and NTG. All the mutants were characterized for colony morphology on different media and biochemical characterization, to observe any change has occurred as compared to its wild type. The observation revealed that mutant GWAS-15-3 could fix higher amount of nitrogen (50.17 mg of N/g malate) along with higher nitrogenase activity (1200 r| moles/mg protein/ h). This was followed by GWAS-15-6 which could also fix higher level of nitrogen (48.91 mg of N/g malate) along with higher nitrogenase activity (1098 r\ moles/mg protein/h). Paranodules in wheat were obtained at 0.6ppm concentration of 2,4-D and plasmid profile of the wild type were observed. Both mutants GWAS-15-3 and GWAS-15-6 possessed higher ammonia excretion than their wild type. Nitrogenase activity was not repressed in both the, mutants even in presence of 0.1 mM NH4CI.ennullThesis