EFFECT OF AZIDE RESISTANT MUTANTS OF AZOTOBACTER CHROOCOCCUM ON YIELD AND NITROGEN CONTENT IN TWO COTTON GENOTYPES.

Seventeen azide resistant mutants were isolated from six strains (103, HT-54, HT-54 (2), 10P, E-12 and MSX 9) of Azotobacter chroococcum. All the parent strains were tested for their minimal inhibitory concentration (MIC) by growing cells in liquid medium containing different concentrations of sodium azide (5 μ gml1 to 200 μ gml1). The strains showed different MIC values indicating that the resistance pattern varied with each individual strain. These azide resistant mutants were assessed for their performance on two cotton cultivars- Gossypium hirsutum, var. H- 117 and Gossypiun herbaceum var. HD-123 under pothouse conditions for various plant parameters. Inoculation of cotton seed with Azotobacter mutants showed better results than inoculation with their respective parental strains. Azide resistant mutants showed increased plant height, early flowering, more yield, high biomass and high total nitrogen content. Better performance by these mutants might be due to high indole acetic acid, ammonia excretion and high nitrogenase activity. [ABSTRACT FROM AUTHOR]