Isolation and Morphological Characterization of Sclerotium rolfsii-Inciting Stem rot Disease in Groundnut (Arachis hypogaea L .)

Sclerotium rolfsii is a highly threatening pathogen,affecting more than 500 hosts worldwide. In the present study, ten different isolates of Sclerotium rolfsii were isolated from groundnut growing regions of Tamil Nadu, and their morphological characteristics were observed on potato dextrose agar (PDA) medium. The virulent isolate SR-8 produced pure white with thin mycelia growth, very fast growing mycelium, dark brown colored sclerotia, and the highest number of sclerotia /plate (538). The pathogenicity test was conducted on pot-cultured, grown groundnut plants. The virulent isolate SR-8, S. rolfsii, is infected at various stages of its growth and development in groundnut plants. Lipid peroxidation and pathogenicity are crucial to identify the virulent nature of the pathogen. The pathogenicity of the virulent isolate SR-8 that produced the highest disease incidence was 89.29 % and had a high amount of lipid peroxidation of 0.9589 μmol/g. The least virulent isolates produced the minimum amount of lipid peroxidation and disease incidence. All the ten isolates exhibited different cultural and morphological characteristics, lipid peroxidation rates, and various levels of disease incidence on groundnut.