Interaction of new diazotrophic endophytic bacteria and nitrogen fertilization on wheat crop under field conditions

Diazotrophic bacteria belonging to different species may be associated with grasses, such as wheat, promoting increases in plant growth and grain yield. Afield experiment was carried out to evaluate the benefits and economic viability of inoculation of new homologous isolates of endophytic diazotrophic bacteria on wheat genotypes, under varying nitrogen doses. Three strains of endophytic diazotrophic bacteria (IAC-AT-8- Azospirillum brasiliense, IAC-HT-11- Achromobacter insolitus, IAC-HT-12- Zoogloea ramigera) were tested on two wheat genotypes (ITD- 19-Triticum durum L. and IAC-370-Triticum aestivum hard L.) under three doses of nitrogen fertilizer (0, 60 and 120 kg ha(-1)). Shoot dry matter, shoot N accumulation and N efficiency index were evaluated at tillering and at physiological maturity. Grain yield, yield components and the harvest index for biomass and N were evaluated at harvest. At the tillering stage, only the biomass production of genotype IAC-370 was increased by Azospirillum brasiliense and Achromobacter insolitus inoculation and N addition. However, the effect of these new diazotrophic endophytic bacteria strains was not genotype-specific for other parameters. Azospirillum brasiliense inoculation increased spike N content. At the highest nitrogen level (120 kg ha(-1)), Achromobacter insolitus increased the grain yield. Although inoculation did not substitute N fertilizers, it had a positive effect on the farmers' profit.