Characterization of Athelia rolfsii associated with southern blight of pointed gourd (Trichosanthes dioica) in India

Pointed gourd (Trichosanthes dioica Roxb) is a perennial cucurbitaceous vegetable popular in the eastern and northern parts of India. In July 2018, an occurrence of southern blight disease was observed in a pointed gourd crop grown in Odisha state located in the eastern part of India. The typical symptoms included angular necrotic patches and disintegration of leaf tissues with the vein and veinlet intact, exhibiting a diagnostic netted pattern of veins. Silky white, fan-shaped mycelial growth with sclerotial bodies was observed on the lower surface of infected leaves. Eventually, the infected leaves dried up, leaving several bare patches in the field. Associated fungi were isolated, which resembled the reference strain Athelia rolfsii based on colony characteristics. Phylogenetic analysis of the internal transcribed spacer of rRNA gene region confirmed that the isolates were A. rolfsii. Pathogenicity was successfully proved on detached leaves as well as on potted pointed gourd plants. On the basis of symptoms associated with the disease, fungal morphology, molecular identification, and pathogenicity tests on host plants, the causal fungus was identified as A. rolfsii. This is the first report of southern blight disease caused by A. rolfsii on pointed gourd in India.