Submitted to: American Society for Horticultural Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/27/1994
Publication Date: N/A
Citation: Interpretive Summary: Brassica vegetables like broccoli, cabbage, Chinese cabbage, and leaf mustard are an increasingly important part of the human diet worldwide. They are highly nutritious and have many health benefits, including anti-cancer activity. Research on Brassica germplasm could enhance the production and nutritional benefits of these crops. A first step is to acquire and characterize new germplasm. This study describes the use of molecular markers to establish DNA profiles for an array of new germplasm accessions recently acquired from China, where brassicas comprise 25% of annual vegetable consumption. We used these DNA "fingerprints" to unambiguously identify all 52 different accessions of Brassica rapa (Chinese cabbage, pakchoi, turnip, and broccoletto) and Brassica juncea (leaf, stem, and root mustards) and determine their interrelationships. All accessions of Brassica rapa were shown to be more closely related to other accessions of Brassica rapa than they were to accessions of Brassica juncea, and vice versa. DNA profiles also showed that Chinese cabbage probably originated by hybridization of pakchoi and turnip, rather than as a selection from either pakchoi or turnip. These results could have important consequences for breeders who are attempting to create improved varieties of Chinese cabbage and other vegetable brassicas. Such varieties would promote improved health not only in China but throughout the world.
Technical Abstract: Fifty-two germplasm accessions of Chinese vegetable Brassicas were analyzed using 112 random amplified polymorphic DNA (RAPD) markers. The array of material examined spanned a wide range of morphological, geographical, and genetic diversity, and included 30 accessions of Brassica rapa (Chinese cabbage, pakchoi, turnip, broccoletto), 18 accessions of B. juncea (leaf, stem, and root mustards), and 4 accessions of B. oleracea ssp. alboglabra (Chinese kale). The RAPD markers unambiguously identified all 52 accessions. Nei and Li similarities were computed and used in unweighted pair group method using arithmetic means (UPGMA) cluster analyses. Accessions and subspecies clustered into groups corresponding to the three species, but some accessions of some subspecies were most closely related to accessions belonging to other subspecies. Values for Nei-Li similarities suggest that Chinese cabbage is more likely to have been produced by hybridization of turnip and pakchoi, than as a selection from either turnip or pakchoi alone. RAPD markers provide a fast, efficient method for diversity assessment in Chinese vegetable brassicas that complements techniques currently in use in genetic resources collections.