Keywords: Alternaria brassicae, A. brassicicola, radish cultivars, susceptible, resistance

Leaf spot and blight caused by Alternaria spp. on six radish cultivars (40-days, Pusa Chetki, Mino Early, Chinese Pink, Tokinashi and Pyuthane Red) were studied in natural infection conditions during October 2001 to May 2002 at Rampur, Chitwan. The study was focused on screening of resistant radish cultivars and identification of common species of Alternaria attacking radish. On testing the cultivars of radish, none of them were found completely resistant to the disease, but there were significant differences in the level of infection as well as root and seed yields. Pyuthane Red was found highly susceptible, which had the the highest plant infection at 52 days and nearly 100% at 66 days after sowing with the the lowest root (22.63 ton ha^-1) and seed (34.19 kg ha^-1) yields. On the contrary, Mino Early appeared moderately resistant, which had the the lowest plant infection, 21% at 52 days and 45% at 66 days. Pusa Chetki and Tokinashi were at par in infection level, and had root yield very close to Pyuthane Red. Root yield of 40-days was not considerably affected. Morphological studies of conidia from susceptible cultivars, like Pyuthane Red, Pusa Chetki and Chinese Pink resulted in presence of Alternaria brassicae, Alternaria brassicicola and Alternaria sp. (unidentified) as the pathogens, whereas only two species A. brassicae and A. brassicicola were found in Mino Early, 40 Days and Tokinashi. Out of 240 conidial spores studied, occurrence of A. brassicae, A. brassicicola and Alternaria sp. was 205 (85.41%), 25 (10.41%) and 10 (4.16%), respectively, which indicated that A. brassicae was the predominant pathogen to cause alternaria leaf spot on radish.