| Summary: | 碩士 === 國立臺灣大學 === 園藝暨景觀學系 === 106 === Grafting is widely used in commercial production of vegetables in Cucurbitaceae and Solanaceae so as to, e.g., improve resistance to soil-borne diseases and tolerance to abiotic stresses, promote plant vigor, increase yield, and induce or promote flowering. In Taiwan, the production of cabbage (Brassica oleracea L. var. capitata) ranked the first (399,174.53 tons) among all kinds of vegetables in 2016. Due to the lack of low temperature in tropical or subtropical countries, the flowering of cabbage often faces many difficulties, which is essential for breeding and seed production. In addition, one of the most serious diseases on cultivated and wild crucifers in Taiwan is clubroot disease which caused by a soil-borne plant pathogen, Plasmodiophora brassicae Woronin. In contrast, Japan has a long history in breeding of resistant varieties against clubroot disease, which highly contributes to reduce and control of this disease in Japan. This research aims to identify the best rootstocks for promoting cabbage flowering and clubroot disease resistance, respectively. With ‘K-Y cross’ cabbage used as scion, the identification was conducted among the rootstocks chosen from the genus of Brassica, so that the occurrence of grafting incompatibility may be reduced. For promoting cabbage flowering, the chosen rootstocks were Chinese kale, rape, leaf mustard, Chinese cabbage, broccoli, cauliflower, and cabbage. The flowering rate of each of grafting combinations in the lowland is 0%. In the highland, the flowering rates of some of the grafting combinations were slightly higher than the ungrafted control (50%), but the highest one was only 57.14%. In addition, no significant difference in days to flowering was found between the grafting combinations and the control. The results indicated that only limited plants chosen for rootstock were able to promote the flowering of ‘K-Y cross’ cabbage. For promoting clubroot disease resistance, the result showed that isolate ‘CY’ and ‘MF’ were classified into group 4 while isolate ‘HG-02’ was in group 1 in Hatakeyama method. Three cultivars of Chinese kale were tested for clubroot disease resistance ability because there is no epidemic revealed in Taiwan. However, the result showed severe symptom in Chinese kale. Then, five clubroot resistant cultivars were chosen to test resistance in different pathogen concentration in Taiwan and Japan. The result showed five cultivars were resistant to isolate ‘CY’ and ‘HG-02’ no matter which concentration were used. In grafting experiments, the results showed resistant cultivars being as rootstock were resistant against isolate ‘CY’ while the susceptible cultivar being as rootstock was not. Based on the results, grafting can solve the clubroot disease problem when resistant cultivars were used as rootstocks.
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