CHARACTERIZATION OF ETHYLENE DIAMINE RESISTANT MUTANTS OF Azospirillum Spp. DERIVED FROM WHEAT
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Date
2001-08-08
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UNIVERSITY OF AGRICULTURAL SCIENCES GKVK BANGALORE
Abstract
Experiments 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.
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