Anti-biofilm and anti-virulence potential of 3,7-dimethyloct-6-enal derived from Citrus hystrix against bacterial blight of rice caused by Xanthomonas oryzae pv. oryzae.

The present investigation for the first time explains the anti biofilm and anti virulence potential of Kaffir lime oil (KLO) and its major constituent, Citronellal (3,7-dimethyloct-6-enal) against Xanthomonas oryzae pv. oryzae, causal organism of bacterial blight disease of rice. KLO at 500 ppm showed potential activity against X. oryzae pv. oryzae. Among the major components identified, citronellal (CIT) at 75 μM concentration was found to significantly inhibit biofilm along with the swimming and swarming potential of X. oryzae pv. oryzae. In contrary, CIT did not affect the metabolic status and growth kinetics of the bacterial cells. Gene expression analysis showed down regulation in motA, cheD, cheY, flgF, gumC, xylanase, endogluconase, cellulose, cellobiosidase, virulence and rpfF transcript levels by citronellal treatment. However, an insignificant effect of 75 μM CIT treatment was observed on motB, flgE, pilA, estY, pglA, protease and lytic genes expression. Finally, the observations recorded were in confirmity with the virulence leaf clip test as lesion length was significantly decreased (39%) in CIT treatment as compared to the control leaves inoculated with only X. oryzae pv. oryzae. Overall, the findings obtained advocate the use of CIT for promising anti biofilm and anti virulence activity which in turn can be used for managing the blight disease in rice.