Management of collar rot of bell pepper (Capsicum annuum L.) by extracts and dry biomass of Coronopus didymus shoot

Abstract

Bioassays were performed to assess the potential of Coronopus didymus for managing collar rot disease of bell pepper, caused by Sclerotium rolfsii. In laboratory bioassays, methanolic shoot extract of C. didymus was partitioned with n-hexane, chloroform, ethyl acetate and n-butanol. Concentrations from 3.125 to 200 mg ml− 1 of each fraction were evaluated against the target fungal species. All concentrations of the ethyl acetate fraction gave complete inhibition of fungal growth. Thin layer chromatography of the ethyl acetate fraction yielded two unidentified compounds 1 and 2 with Rf values of 0.531 and 0.787, respectively. Antifungal activity of these compounds was assessed using the minimum inhibitory concentrations (MICs) technique. Mancozeb was used as a reference compound. Compound 2 was found to be highly effective against S. rolfsii with MIC value 7.81 μg ml− 1 which was at par with the MIC of mancozeb. In a pot trail, dried powdered shoots of C. didymus were mixed at 1%, 2% and 3% (w/w) in soil already inoculated with the target fungal pathogen. A negative control with no fungal inoculation or soil amendment and a positive control with S. rolfsii inoculation but no soil amendment were also included. The treatment with 3% soil amendment significantly suppressed the collar rot disease. There was 50% and 13% disease incidence and mortality, respectively, with 3% treatment compared with 91% and 40%, respectively, in the positive control. This study suggests that collar rot of bell pepper can effectively be managed by exploiting the antifungal potential of C. didymus.