Microbial consortia as a biocontrol strategy for bacterial blight in basmati rice

Basmati rice is in high demand in the world market because of its fine, soft, long and distinctive aromatic grains. Bacterial leaf blight (BLB), caused by Xanthomonas oryzae pv. oryzae, is a destructive disease, resulting in enormous yield loss in basmati rice. Chemical management against BLB is effective but not the preferred approach because of its detrimental effects on humans, environment and ecological disruption. In the present study, seed treatment, seedling treatment and foliar application with microbial antagonists, such as Trichoderma harzianum and Pseudomonas fluorescens, and a consortium encompassing both microorganisms plus Trichoderma asperellum, were assessed against BLB in basmati rice. Among all the bio-formulation treatments, seed treatment with the microbial consortium revealed significant (p<0.05) results, achieving maximum inhibition of BLB incidence, intensity and lesion length of 48.56, 52.42 and 45.41 percent respectively, compared to the untreated control. Simultaneously, the same treatment also resulted in significant (p<0.05) enhancement of growth attributes, such as panicle length (55.83%), plant fresh weight (15.55%), grains per panicle (38.23%), test weight (55.49%) and yield (47.68%). A maximum increase in superoxide dismutase and hydrogen peroxide activities by 81.58 and 84.29 percent respectively over the control was also recorded. The results of the study suggest that the effectiveness of BLB management under field conditions applying the microbial consortium (T. harzianum+T. asperellum+P. fluorescens) was similar to that of the chemical control. Further, efforts are being made to evaluate the biocontrol activity of the microbial consortium in large-scale field experiments and its commercial potential.