An Azotobacter with partially deleted nifL and constitutive nifA can save a good amount of urea fertilizer without affecting wheat yield

15^th Asia-Pacific Biotechnology Congress

July 20-22, 2017 Melbourne, Australia

Hirendra K Das, Umesh K Bageshwar, Madhulika Srivastava, Peddisetty Pardha-Saradhi, Sangeeta Paul, Sellamuthu Gothandapani and Ranjeet S Jaat

Jawaharlal Nehru University, India
Delhi University, India
Indian Agricultural Research Institute, India
National Research Centre for Plant Biotechnology, India

Posters & Accepted Abstracts: J Bioprocess Biotech

Abstract :

Soil bacteria belonging to the genus Azotobacter can reduce atmospheric nitrogen into ammonia, which can be assimilated by plants. About 20 genes are involved in the process of nitrogen reduction. Expression of all these genes is dependent on a positive regulator NifA. In the presence of ammonia, the negative regulator NifL, gets activated and interacts with NifA to neutralize it. As a result no nitrogen is reduced by wild type Azotobacter when ammonia is formed or produced by nitrogenous fertilizers. In two species of Azotobacter studied by us, the nifL and nifA genes were present in the same operon, nifL being proximal and nifA distal to the promoter. The nifLA promoter was also regulated by ammonia. We partially deleted the nifL gene and inserted a constitutive promoter there, thus bringing the nifA gene under its control. Ammonium only marginally affected acetylene reduction (a measure of nitrogen reduction) by the engineered Azotobacter strain. When wheat seeds were inoculated with the engineered strain and sown, the crop yield was enhanced by 60%, without any application of urea or other chemical nitrogenous fertilizer. The crop yield, however, was enhanced only by 10% when the wheat seeds were inoculated with the wild type strain. When we applied urea, the wheat plants arising from the seeds inoculated by the engineered strain, could yield the same amount of crop using ~85 kg less urea (~40 kg less nitrogen) than the usual ~257 kg urea (~120 kg nitrogen) per hectare. Wheat plants from the seeds inoculated with the engineered strain had much higher dry weight and nitrogen content and assimilated molecular 15 N much better than plants from seeds inoculated with the wild type strain. Inoculation of the wheat seeds with the engineered strain did not adversely affect the microbial population in the rhizosphere soil.

Biography :

Email: hirendas@hotmail.com