Cucumis sativam (L.) is a creeping vine grown as an off-season vegetable crop. During a survey of major cucumber growing districts of Rajasthan, a new disease "Choanephora fruit rot of cucumber" was first time observed and recorded in 2019-2020. The survey provided baseline information on the distribution, occurrence, and incidence of Choanephora fruit rot in the major cucumber growing area of the Rajasthan state.
During the survey, discussions were held with the farmers concerned, regarding occurrence, incidence, and yield losses due to this disease. Choanephora cucurbitarum is the new emerging pathogen as well as a serious threat to cucumber and other vegetables in India. The disease incidence was recorded ranged from 45.61 % to 64.22 %. During the rainy season (July-November), the temperature was 28-30°C with high humidity (70-90%) that favored disease development. During the survey typical symptoms of Choanephora fruit rot were observed under polyhouse condition as water-soaked lesions on immature & young fruits, leaf and flowers that progressed to rapidly soft rotting of the infected tissues, the fruit surface was covered by a dense whitish cottony mycelial growth of fungal hyphae born black to brown fructifications and on the surface of diseased fruit, a cushiony mat resembling developing sporangiola emerged.
Cotton-like white mycelium and black spore masses were formed by the fungus isolated from diseased tissues on PDA. Pathogenicity tests were performed by the spore suspension method and single mycelial disc inoculation technique. Re-isolation of pathogenic fungus from diseased inoculated fruit completed Koch's postulates. The causative fungus was identified as Choanephora cucurbitarum (Berk & Ravenel). According to the available literature, the current studies confirm the first occurrence of cucumber fruit rot caused by Choanephora cucurbitarum in India.
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Kumar, Sunil & Ahir, R & Singh, Mahabeer & Rathore, G & Maurya, Shivam & Kumari, Poonam. (2022). First Report of Choanephora Fruit Rot (Choanephora cucurbitarum) on cucumber and their Incidence and Occurrence under Protected Cultivation in India.