ABSTRACT
Spontaneous mutants resistant to methionine sulfoximine (Msx), methyl alanine (Mal) and methyl ammonium chloride (Mac) were derived from A. chroococcum strain A103. Msx and Mal-resistant mutants expressed 1.73 to 10.98% of the fully derepressed nitrogenase activity when grown in Burk's medium containing ammonium acetate. Mac-resistant mutants did not express nitrogenase activity in ammonium acetate supplemented medium. The mutants excreted ammonia even after 2 days of growth and some mutants excreted more ammonia as compared to the parent. Selected mutants were inoculated on wheat (Triticum aestivum) and barley (Hordeum vulgare) under field conditions. Majority of the derepressed mutants increased grain yield of wheat and barley varying from 1.2 to 33.3%. However, host-dependent effects on grain yield were observed with different mutants. Two mutants, Mal 27 and Mac 19 showed significant increase in grain yields of both the crops. The results suggest that metabolic analogue-resistant mutants of Azotobacter have potential for use as a biofertilizer for cereal crops.
Subject(s)
Alanine/analogs & derivatives , Ammonia/metabolism , Azotobacter/drug effects , Edible Grain/microbiology , Drug Resistance, Microbial/genetics , Methionine Sulfoximine/pharmacology , Methylamines/pharmacology , Mutation , Nitrogen Fixation , Nitrogenase/geneticsABSTRACT
Effects of methionine sulphoximine (MSX) on glutamine synthetase activity and ammonia accumulation in the leaves of barley, sorghum and Moricandia arvensis were studied. Glutamine synthetase activity of sorghum leaves was relatively resistant to MSX treatment during initial stages. All the three plant species exhibited considerable accumulation of ammonia arising from non-photorespiratory sources, in response to MSX treatment. Minimal estimates of the rate of glycine decarboxylation were made employing MSX and isonicotinyl hydrazide together in the treatment solution. Changes in the pool sizes of amino acids involved in photorespiratory nitrogen metabolism as affected by MSX have also been investigated.