Author: Sampat Jat, R.N Bunker, Santosh Kumar, Pokhar Rawal, P.B Singh and Gajanand Jat
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Spinach (Spinacia oleracea L.) is one of the most important leafy vegetable belongs to the family Chenopodiaceae. This crop generally affected by many leaf spots but among all the leaf spots, the Alternaria leaf spot caused by Alternaria alternata (Fr.) Keissler is major threat and destructive disease. The present investigation has been carried out on the aspect of symptomatology, isolation and pathogenicity test of Alternaria leaf spot caused by Alternaria alternata (Fr.) Keissler.) The diseased plant produced typical symptoms of Alternaria leaf spot on spinach appeared as small and circular spots with concentric rings at initial stage which later develop in large size irregular lesions. These circular spots were dark black colour along the margins which encircled the necrotic region, with the spread of disease these necrotic spots turn to appear as blighted lesions. Initially the pathogen produced culture was grayish white in colure, which later turn into dark and becomes greenish black or olive brown with light border on PDA. The pathogenicity of fungus was tested on susceptible variety “All Green” by spore suspension spray under cage house. Initially inoculated plant produced symptoms like; small and circular spots with concentric ring which was later turned into dark black colored large size irregular lesions with necrotic regions.
Spinach, Alternaria alternata, Pathogenicity, Leaf spot, Isolation
In present study the fungus was isolated from leaf of spinach plant and characters of the fungus produced on potato dextrose agar and identified as Alternaria alternate (Fr.) Keissler. The culture was raised with grayish white colure, which later turn into dark and becomes greenish black or olive brown with light border. The fungus produced conidia with one to two longitudinal and two to eight transverse septa. On the basis of above morphological and cultural character, the isolate was identified as Alternaria alternate (Fr.) Keissler. Pathogenicity of isolated culture was proved by following the Koch’s postulates on susceptible spinach cultivar “All Green” in the cage house. The leaf spot symptoms including small and circular spots with concentric ring which was later turned into dark black colored large size irregular lesions with necrotic regions. Re-isolation of pathogen was attempted from diseased leaf which produced culture of Alternaria alternata (Fr.) Keissler, which were identical with the original one that was inoculated
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