Efficacy of botanical extracts on imparting systemic acquired resistance against rice sheath blight incited by Rhizoctonia solani

The present study unravels the antifungal ability and physio-biochemical basis of resistance induced by botanical extracts against the sheath blight disease of rice incited by Rhizoctonia solani. In vitro screening of botanical extracts against R. solani revealed that an increase in the concentration of botanical extracts increased the inhibition of mycelial growth, though maximum inhibition occurred at 50% concentration. A. indica exhibited the highest mycocidal ability, followed by M. azedarach and T. ciliata. In field experiments, spraying of promising doses of botanical extracts led to a significant reduction in the severity index, AUDPC, and r-value when applied 2 days before inoculation. An increase in the endogenous SA content of treated plants gave an indication of the activation of SAR. The induction of resistance was accompanied by the accumulation of various host-related antioxidants and defence enzymes in susceptible cultivar. The results indicate that botanical extracts induce the early activation of disease resistance and that this is mediated through the expression of defence mechanisms. A. indica provided excellent control and reduced the disease severity, followed by extracts of M. azedarach. The results of the study are significant for developing an environmentally friendly biocide that could be considered an effective tool in integrated management programmes for a sustainable system of sheath blight control.

Automated summary

The study reveals the antifungal ability of botanical extracts against sheath blight disease in rice. In vitro screening showed that an increase in concentration of botanical extracts led to increased inhibition of mycelial growth of Rhizoctonia solani. Field experiments demonstrated a significant reduction in disease severity when botanical extracts were applied before inoculation. The results suggest that botanical extracts induce early activation of disease resistance and could be an effective tool in sheath blight control.