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Biofertilizers
Main thrust of activities
For a sustainable agriculture system, it is imperative to utilize renewable inputs which can maximize the ecological benefits and minimize the environmental hazards. One possible way of achieving this is to decrease dependence on use of chemical nitrogen fertilizers by harvesting the atmospheric nitrogen through biological processes. With these considerations, the Department is supporting a programme on R&D and application of biofertilisers. A programme ws supported on the integrated use of biofertilizers with chemical fertilizers and other manures in cropping systems prevalent in various agro-climatic zones of the country. In addition efficient strains have to be isolated and improved further through transgenosis.
A network project on Development of Transgenic Biofertilizers which are efficient Nitrogen fixers and Phosphate solublisers, was launched in the 10th plan period. Under this programme development of transgenic biofertilizers, has been undertaken by increasing copy number of nif genes; incorporation of hup genes wherever hydrogenase enzyme is not produced and knocking off negative regulatory gene from the regulatory operon.
Achievements
Under Integrated Nutrient Management (INM) studies, biofertilizer component has not received adequate attention in the past. Keeping this in view, a National Network Project was launched in 1999 for 3 years on the ‘Role of biofertilizers in INM’ embracing 17 centres throughout the country. The objective was to establish useful biofertilizer packages for yield optimisation of some major crops in various cropping systems in different regions. In addition to generating field data on biofertilizers used in integration with reduced levels of chemical fertilizers, advanced molecular tools were employed for genotypic characterization of microbial strains for their identification and performance evaluation in the field. A number of INM packages have been developed for Poplar-Eucalyptus, Mungbean-Wheat-Bajra, Rice-wheat, Rice-Rice, Sugarcane, Rice-Wheat-Pulse and saline area based cropping systems. The packages developed were demonstrated to about 5000 farmers. In addition molecular methods were used to study nodule occupancy in legumes.
Leads obtained
Phosphoenol pyruvate carboxylase (pqq) synthase gene has been transferred to Azospirillum. It was found that the transconjugant Azospirillum now possess mineral phosphate solubilizing (MPS) ability. No change was observed in the nitrogen fixation of these transconjugants. The pqq synthase gene was isolated from Burkholderia cepacia via PCR amplification of primers designed using the conserved sequence across the gene reported in different species and cloned into E coli. The E coli containing the pqq synthase gene now showed MPS activity. These results indicate the possibility of developing transgenic bacteria by cloning pqq synthase genes into certain gram-negative rhizobacteria. The gene has also been electroporated into Rhizobium and Azotobacter and there it has shown MPS activity.
Glucose dehydrogenase gene (gdh) of Bacillus licheniformis has been successfully amplified using gene-specific primers. The amplicon (802bp) was then cloned into pTZ57. The clone was confirmed as gdh gene by sequencing. Primers have been designed for the gdh sequences of Serratia marcescens and Pseodomonas aeruginosa and the genes would be amplified using specific primers. Pure Genomic DNA has been isolated and attempts are being made to construct a library in pUC18. The library would be screened for the gdh gene clone based on the zone of solubilization. Selected recombinants would be probed for the presence of the gene using heterologous gdh probes.
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