Morphological Characterization and Pathogenicity Test of Alternaria Leaf Spot of Chinese Cabbage (Brassica chinensis L.)

Chinese cabbage (Brassica chinensis L.) is an important leafy vegetable crop. It has good nutritional and medicinal value. Among all diseases affecting the plant, Alternaria leaf spot is a serious disease hampering its successful cultivation. Keeping in view this serious implication, an experiment on Alternaria leaf spot of Chinese cabbage caused by Alternaria brassicae, A. brassicicola and A. alternata was carried out at Main Experimental Station, Vegetable of ANDUA&T, Kumarganj Ayodhya for studying a means to effectively manage the disease. The disease was first appeared in the first week of November as small, yellow to brown spots with a light green to yellow halo. As the disease advances, several lesions coalesced, giving a blighted appearance. Stem and pods were also affected by the disease. The pathogen was readily isolated on 2% Potato Dextrose Agar medium and pathogenicity was proved following Koch's postulates. Cultural and morphological characters were observed as colonies of pure black amphigenous, effused, radial growth, conidia light brown to black in colour. The size of the conidia of A. brassicae, A. brassicicola and A. alternata were found 110.16 -162.0 µm, 94.08 – 120.72 µm and 25.44 - 46.32 µm, having septal variation 5-11, 0-8 and 2-6, respectively.