First report on incidence of inflorescence blight and pod rot (Choanephora infundibulifera) on dolichos bean (Dolichos lablab, L.) and yard long beanin (Vignaunguiculata sub sp. sesquipedalis) India

Abstract

Inflorescence blight and pod rot caused by Choanephorasp. were recorded in two major vegetable crops viz.dolichos bean and yard long bean at a very high degree of severity. Usually, the disease occurs in mild proportions without causing economic loss during rainy season in Kerala (June to September) affecting vegetable crops like cowpea and bhendi. However, during the year 2016, the disease was noticed with a very high severity of more than 90 per cent on two crops grown at two different locations in Thrissur district of Kerala during October to January. None of the commonly used fungicides could control the disease. The pathogen was found to be luxuriantly growing on the inflorescences of dolichos bean and on the fruits of yard long bean. The first incidence of the disease was recorded during the last week of October, 2016. The disease spread was almost cent per cent on susceptible genotypes of dolichos bean and more than 90 per cent in variety ‘Vaijayanthi’ of yard long bean. A study was conducted exploring the pre disposing factors leading to the occurrence of the disease in epidemic proportions.Meteorological factors affecting the disease were studied and it was found that there is positive correlation of the disease severity with increasing atmospheric temperature and rainfall.Atmospheric temperature more than 30oC along with high humidity and rain fall during the preceding week are found to be the major pre disposing factors lead to the epidemic in both the crops. The pathogen was isolated and based on morphological characters, identified as Choanephora sp. Pathogenicity was proved by inoculation on healthy inflorescence stalks.Molecular characterization of the pathogen confirmed the identity as Choanephora infundibulifera. This is the first report of the pathogen on dolichos bean and yard long bean in India.