The Host Range of Downy Mildew, Peronospora parasitica, from Brassica oleracea, Cabbage and Broccoli Crops.

Abstract

Three cabbage plants, 2 broccoli plants and 1 broccoli plant infected by P. parasitica from Kagawa, Mie and Tottori, in Honshu, Japan, respectively, were collected. Five single spore isolates from each sample were prepared, and the host range of 30 single spore isolates was investigated. Cotyledons of Brassica oleracea (18 cultivars of cauliflower, cabbage and broccoli), B. campestris (8 cultivars of Pak-choi, mizuna, rape, Chinese cabbage and turnip), 1 Indian mustard cultivar, 1 sarson cultivar and 2 radish cultivars, were used in the host range tests. All the B. oleracea plants (except 2 cabbage cultivars) were highly susceptible to all the isolates tested, and it is suggested that these are host species of P. parasitica. Sarson was moderately susceptible, and was considered to be a possible host species. B. campestris, Indian mustard and radishes were resistant, and were considered to be non-host species. All the isolates were considered to belong to the same strain and the strain was considered specific to B. oleracea and possibly to sarson. Among B. oleracea plants, 2 cabbage cultivars (Golden Best and YR-Sawamidori) were resistant. There were no differences in pathogenicity between the single spore isolates tested.