Multiple disease resistance in cauliflower

Abstract

Five temperate cauliflower ( Brassica oleracea var. botrytis) varieties, KT-9, KT-16, PSB-1, PSBK-1 (from Katrain, H.P., India) and KPS-1 (Kalimpong, West Bengal, India) were evaluated in the field over a period of 2 years for their multiple resistance to alternaria blight ( Alternaria brassicae , A. brassicicola ), black rot (Xanthomonas campestris pv. campestris ) and downy mildew (Peronospora parasitica) diseases and for their performance for some economic characters. Varietal response to individual disease varied with the year. Whereas KT-9 performed better against alternaria blight and black rot, KPS-1 did so against downy mildew. The former had more deposition of epicuticular wax on its foliage. The test varieties did not reflect significant differences in their biochemical traits. The relationship among diseases and that between diseases and economic characters differed in different years. Downy mildew had the potential markedly to reduce curd yield (r = 0.8604). Black rot could effectively predispose plants towards increased attack of alternaria blight (r = 0.9073). The latter produced bigger lesions (r = 0.8821) on black rot affected plants. The mean multiple disease score for 1987-88 and 1988-89 was the least in the case pf KPS-1 and PSB-1. Whereas these varieties hold promise in their disease reaction, the latter seemed better as far as horticultural traits are concerned.