Taxonomic Relationship Between Chinese Kale And Other Varieties In Brassica Oleracea L.

Chinese kale, a kind of Cruciferae Brassica species which originated in China, with its juicy delicate flower stalks and leaves for food, is one of the famous China characteristic vegetables in the world. For many years, there are two absolutely opposite views on taxonomic relationships between Chinese kale originated from China and Brassica oleracea L from Mediterranean coasts:One view is that Chinese kale is a variety of Brassica oleracea L, and it is named as B. oleracea var. alboglabra; another view is that Chinese kale is a independent species of Brassica oleracea L which should be called B. alboglabra. Moreover, it is still unknown about how Chinese kale evolved. This paper used different varieties of Chinese kale and representative varieties of Brassica oleracea (including broccoli, reproductive organs as product; ohlrabi, bulbs as products and cabbage, leaves or leaf balls as product). The study focus on the botanical characteristics in various growth periods, cross compatibility indexes of Chinese kale and Brassica oleracea, growth and development of F2 generation, as well as electron microscopy scanning of the pollens, POD isozymes, etc.. to discuss taxonomic status and genetic relationships of Chinese kale and Brassica oleracea. It is designed to provide theoretical basis for classification of Brassica oleracea.Botanical characteristics in different periods of Chinese kale and Brassica oleracea exhibited that there are few differences between seedling stages, but great differences in harvest time and full flowering stages. Cluster analysis results showed that there are great differences between different growth and development periods. And in harvest period and full flowering stages, the efficacy of classification based on botanical characters is the best, and it is consistent with results of traditional taxonomy.Chinese kale and the three representative varieties of Brassica oleracea can cross successfully with an average compatibility index of 13.4. All hybrids could develop into normal and fertile plants, and they had a compatibility index of 14.1 when self-crossed. The hybrids showed combined morphologies of their parents, with different degrees of biases toward broccoli, kohlrab, cabbage, respectively. It was also found that the F2 seeds germinated normally. Cluster analysis with coefficient of similarity of 2.78 implied that two Chinese kale cultivars could be classified into one group, two cabbage cultivars and eight Fj hybrids crossed with two cabbage cultivars and two Chinese kale cultivars could be classified into one group, two broccoli cultivars and eight F1 hybrids crossed with two broccoli cultivars and two Chinese kale cultivars could be classified into one group, and two kohlrab cultivars and eight F1 hybrids crossed with two kohlrab cultivars and two Chinese kale cultivars could be classified into one group. The relationship between Chinese kale and cabbage was closer than that between Chinese kale and broccoli or kohlrabi. Therefore, we conclude that Chinese kale and Brassica oleracea L. most likely belong to the same species, and hypothesize that Chinese kale as another variety of Brassica oleracea may be evolved from cabbage.Electron microscope scanning of pollens and isoenzymes of Chinese kale, Brassica oleracea and their hybrids further certified the conclusions above. The shapes of pollens of Chinese kale, Brassica oleracea and their hybrids are similar. The shapes are all longer spherical from equatorial observation and nearly circular or three-split round from polar observation, with three channels and ringing in equal space distribution; three common peroxidase isozymes bands are detected in all varieties. Chinese kale and some other varieties in Brassica oleracea L. possess four enzymes bands in common, and Chinese kale have no distinct band. However, it also indicated that there is close genetic relationship between Chinese kale and Brassica oleracea. Cluster analysis analysis based on pollen morphology and isozymes were consistent with that based on botanical characteristics. Therefore, we conclude that it is acceptable to consider Chinese kale as another variety of Brassica oleracea.