Control of the chickpea blight, Ascochyta rabiei, with the weed plant, Withania somnifera

Abstract

Abstract Background Ascochyta blight caused by a fungal pathogen, Ascochyta rabiei, is a serious disease of chickpea in most chickpea growing areas of the world. The disease can be controlled by fungicides to reduce the environmental pollution. Main body This study reports the control of Ascochyta blight by using extracts and dry biomass of a weed plant, Withania somnifera (Family Solanaceae). In a laboratory bioassay, a 0.2% concentration of methanolic leaf extract of W. somnifera significantly inhibited the pathogenic fungal growth. Methanolic leaf extract was fractionated with 4 organic solvents of different polarities namely n-hexane, chloroform, ethyl acetate, and n-butanol. The effect of different concentrations (3.125, 6.25, 12.5, 25, 50, 100, 200 mg ml−1) of the 4 organic solvent fractions was assessed on in vitro growth of the pathogen. Among these, ethyl acetate and n-butanol fractions completely inhibited the fungal growth. Ethyl acetate fraction was further subjected to thin layer chromatography to separate the potent antifungal compounds A and B. Compound A was found highly effective against the targeted fungal pathogen with MIC 31.25 μg ml−1, followed by B with MIC value of 250 μg ml−1 as compared to 7.81 μg ml−1 MIC of a commercial fungicide mancozeb. In pot trial, the soil was amended by 1, 2, and 3% dry leaf material of the test plant species. Disease incidence was significantly reduced in 3% dose. Conclusions This study concludes that W. somnifera contains potent antifungal compounds that can be effectively exploited for the control of A. rabiei.