New disease and first report of marasmioid fungus, Marasmius palmivorus (Sharples), causing white root rot in Arachis hypogaea L.

Groundnut (Arachis hypogaea L.) plants showing distinct symptoms of necrosis of leaves and severe rotting of roots were observed in an agricultural field at Arakkonam, Tamil Nadu, India. The rhizomorphs of the phytopathogenic fungus were obtained from the rotted roots of the diseased plants and were cultured in the laboratory, and based on the morphological characteristics and nucleotide sequencing analysis of ITS and nLSU region, the phytopathogen was identified as Marasmius palmivorus. The isolated fungus produced distinct fruiting bodies (basidiocarps) when grown under the laboratory conditions. The fungus grew as cottony white colonies on the potato dextrose agar medium and were found to contain septate and clamp connections when examined under light microscope. The pathogenicity of the isolated fungus was assessed by inoculating it on healthy groundnut plant under glasshouse conditions; this resulted in the establishment of typical disease symptoms, which confirmed the pathogenicity of the fungus. The fungal pathogen re-isolated from the artificially inoculated plants was used for molecular characterization and confirmed that the organism was M. palmivorus. To the best of our knowledge, this is the first report on the occurrence of M. palmivorus, causing white root rot disease in A. hypogaea L.