Bioprospecting native endophytic and epiphytic diazotrophs of Oryza sativa (L) for plant growth promotion and biocontrol

Global food security and sustainable agriculture are two major concerns for escalating human population and the rise in food demands piles up the usage of chemical fertilizers and pesticides. This drastically affects microbial diversity, deteriorates soil fertility, and causes ecological imbalance. A significant and substantial amount of functional N fixing bacterial community inside and in close vicinity of roots supply N efficiently in irrigated ecosystems and their diversity can be altered by organic and inorganic inputs in wetland rice cultivation system. The study explored the existence of culturable diazotrophs bacterial diversity in rice-grown soils those were non fertilized and differently fertilized at Rajendranagar farm fields of ICAR-Indian Institute of Rice Research (IIRR), Hyderabad, India. The bacterial isolates were identified by 16S rRNA , and the isolated species of bacterial genera Microbacterium , Mesobacillus and Brevundimonas were not reported earlier in the rice cultivation system. Each of these bacterial isolates is capable of synthesising indole-3-acetic acid (IAA), ammonia and aminocyclopropane-1carboxylate deaminases, 90 percent of the bacterial isolates can produce amylase, 80 per cent have antifungal activity, 70% were diazotrophs and varied percentages of bacterial isolates reported other essential PGP traits. Significant improvement in seedling growth with the application of bacterial isolates was observed. Five of the ten bacterial isolates improved root length, shoot length, total biomass, and seed vigour index by 11–63%, 18–38%, 4–68%, and 20–56% respectively, compared with the control (sterile water) in sterile 0.7% water agar.