Studies on the breeding of clubroot-resistance in cole crops. 1. Screening of cole crops for clubroot-resistancen (1)

Studies on the breeding of clubroot-resistance in cole crops. 1. Screening of cole crops for clubroot-resistancen (1)

1978

A:PS

Screening of the breeding materials for clubroot-resistance was conducted at the naturally infested field for four years (1970-1973). The physiological race of Plasmodiophora brassicae Woronin found in the testing field was estimated to be `race 2` according to Williams`s method. The incidence of clubroot on the directly sowing plot was somewhat earlier than that on the transplanting plot where healthy 18-day old seedlings were transplanted, although the difference was not so great. Under the natural condition the incidence of clubroot was noticed 25-35 days after sowing and a rapid multiplication of the club was observed 10-15 days after the incidence of clubroot. The degree of the plant wilt or the delay in the plant growth reflected fairly well in the degree of clubroot incidence, but some varieties showed light wilt in spite of high incidence of clubroot and some varieties showed severe wilt in spite of light incidence of clubroot. As a result, it was thought that it was very difficult to judge the clubroot-resistance only from the plant growth of the tops. In Chinese cabbage plants affected only lightly by clubroot were selected and their progenies were tested for the disease resistance. However, they did not show any stronger resistance compared with their parental lines or varieties. Clubroot-resistance of cole crops was tested. The results were as follows; Out of the cabbage group (n=9), leaf-cabbage and head-cabbage showed wide difference in resistance, among them were included the varieties with high resistance and the highly susceptible varieties. Out of them, highly resistant varieties were found in leaf-cabbage including `K-269` which had almost no clubs. Resistant varieties were found in head-cabbage: `Bindsachsener 72754, Bohmerwaldkohl 72755, 72756` and `Aichi-Daibansei, Bansei-Nanbu` (latter two are the Japanese varieties). Those varieties seemed promising as the breeding materials. All the test varieties belonging to n=10 group (Chinese cabbage, turnip and mustard green) were highly susceptible to clubroot. It seemed that much more numbers of varieties should be tested in order to find out the promising resistant sources from this group. Because of the fact that any highly resistant varieties are not available at present, some moderate resistant varieties should be used in order to decrease the damage connecting with other controlling measures including environmental improvement and chemical control. For this purpose, such testing methods enabling us to select some moderate resistant varietie sshould be developed. The varieties of n=18 group (mustard) were highly susceptible and attacked severely by clubroot. Out of the n=19 group (swede and oil-rape groups), swede showed wide range of resistance like cabbage group. Varieties of oil-rape in Japan were susceptible and attacked severely by the Plasmodiophora brassicae Woronin. This is presumably due to the relatively simple differentiation of this crop in Japan. [AS]

no.4:1-25, VEGETABLE AND ORNAMENTAL CROPS RESEARCH STATION, BULLETIN (SERIES A)

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