Management of collar rot of bell pepper (Capsicum annuumL.) by extracts and dry biomass of Coronopus didymusshoot

Bioassays were performed to assess the potential of Coronopus didymusfor managing collar rot disease of bell pepper, caused by Sclerotium rolfsii. In laboratory bioassays, methanolic shoot extract of C. didymuswas partitioned with n-hexane, chloroform, ethyl acetate and n-butanol. Concentrations from 3.125 to 200 mg ml− 1of 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 1and 2with Rfvalues 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 2was found to be highly effective against S. rolfsiiwith MIC value 7.81 μg ml− 1which was at par with the MIC of mancozeb. In a pot trail, dried powdered shoots of C. didymuswere 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. rolfsiiinoculation 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.