Status and characterization of Sclerotinia species causing stem rot in Egyptian clover

Egyptian clover (Trifolium alexandrinum) is a main fodder legume cultivated in Indian Punjab during winter season. Stem rot caused by Sclerotinia species is the most damaging soil borne fungal pathogen of Egyptian clover imposing serious losses in terms of fodder and seed yield. A survey was conducted in clover growing areas of the state and it recorded 27.0 to 62.5% incidences of stem rot. The diseased samples were also collected from different areas to characterize the Sclerotinia based on cultural, morphological and molecular characters. Based on morphological characterization only one isolate showed fast growth habit with high sclerotia production. The pathogenic characterization of 15 isolates has shown that 2 of them were highly virulent, 11 were virulent and 2 were moderately virulent. Phylogenetic analysis including morphological characters and internal transcribed spacer sequencing has shown the presence of genetic diversity among the isolates. Additionally, genetic variability analysis based on variation in internal transcribed spacer regions of all isolates has shown the existence of interspecies variability and revealed that 90% of isolates causing stem rot of Egyptian clover belonged to S. sclerotiorum and only 10% belonged to S. trifoliorum.