Salicylic acid blocks rice leaf blight by inhibiting biofilm formation of Xanthomonas oryzae pv. oryzae in rice

Abstract

Xanthomonas oryzae pv. oryzae is a destructive bacterial disease of rice. Due to the development of resistance by the existing bactericides, an alternative eco-friendly management strategy should be identified to contain the disease. The present study focused on the efficacy of salicylic acid (SA) and their metabolically active biomolecules against X. oryzae pv. oryzae during their interaction. The biofilm inhibition clearly expressed the aggregation, separation and presence of dead cells at various concentrations of SA. The highest biofilm production was observed for untreated control with maximum O.D. value. There is a significant difference in their O.D. values on the concentrations of SA. While studying the inhibition percentages, the chloramphenicol @ 0.2% recorded the highest percentage (76.65%) which shows significant results with SA at 250 ppm (75.56) followed by 100 and 50 ppm which exhibited no significant differences in their inhibition percentages (65.78% and 45.74%, respectively). Under CLSM the Xoo cell aggregation and separation has been observed at 50 ppm and 100 ppm and diminished at 250 ppm respectively. Under in silico analysis, the biomolecules from SA, viz., tetradecanoic acid, methyl oleate, and decyl acrylate, were extracted with a higher area percentage against Xoo target proteins with chloramphenicol as a positive control. Tetradecanoic acid has the highest -C DOCKER energy of 39.46 kcal/mol with the effector proteins of Xoo. The docked metabolites, were subjected to in planta assays, among them tetradecanoic acid recorded minimum lesion size of 0.6 cm at 5000 ppm followed by decyl acrylate (1.5 cm).Our results suggest that overexpression of NPR 1, PAL and LOX has been documented at SA at 250 ppm which can be used to improve BLB resistance in rice. The present study concludes that salicylic acid plays a signalling role inhibition of Xoo biofilm, a source of biomolecules, activation of various plant defence responses against Xoo.