Survey and Isolation of Colletotrichum gossypii Causing Cotton Anthracnose Disease from Different Regions of Rajasthan, India

Cotton (Gossypium spp.) is a major cash crop in India, with Rajasthan being one of the key producing states, though it is heavily affected by fungal diseases such as anthracnose that can severely reduce yield. Accurate identification of Colletotrichum species causing anthracnose is essential, requiring integrated morphological and molecular approaches due to their taxonomic complexity. In the present study, a roving survey was conducted during Kharif 2021–22 in different cotton-growing regions of Rajasthan to assess the occurrence of anthracnose incidence on cotton (Gossypium hirsutum L.) caused by Colletotrichum gossypii. A total of five diseased samples showing typical symptoms such as leaf lesions and boll spots were collected for isolation and detailed examination. The results revealed that the disease was endemic in all surveyed regions. The maximum mean disease severity was recorded in Hanumangarh district (42.25%), followed by Sri Ganganagar district (38.00%). Among the five isolates, isolate RJCG-3 was found to be the most virulent. The pathogen produced hyaline, smooth-walled, falcate to curved conidia with brownish to yellowish acervuli. The length and width of conidia varied from 20.25–28.92 µm and 3.35–3.91 µm respectively in different isolates. The fungal colony exhibited dull white to greyish-white mycelial growth on PDA medium and recorded maximum radial growth (90.00 mm) with profuse sporulation on the seventh day after inoculation.