Studies On Genetic Polymorphisms With AFLP And Taxonomy In Brassica Campestris(2n=20)

Variation in amplified fragment length polymorphism (AFLP) markers has been used to establish the extent of genetic diversity and relation in fifty-six landraces and cultivars of Brassica rapa L. (syn. B. campestris L.), one cultivar of Brassica. juncea Czern.et Coss and one cultivar of B. oleracea L. The results indicated there was abundant genetic diversity in Chinese cabbage and their close group (2n=20). Seven EcoR I / Mse I primer pairs produced abundant and clear AFLP bands. A total of 460 AFLP fragments were detected, including 426 polymorphic fragments of them (92.6%). The genetics diversity analysis with seven AFLP primer pairs indicated that different primers exhibited different detective efficiency, and the most efficient amplified primer is E-AAC/M-CAA, which produced 131 polymorphic fragments. While E-AGC / M-CAG only produced 35 polymorphic fragments. AFLP fingerprints revealed that the number of amplified bands was different among cultivars, for examples, B. juncea produced 201 bands, but B. campestris ssp. nipposinica (Bailey) Olsson produced 118 bands.The genetic distance coefficients analysis among cultivars showed that there was the smallest (0.1728) between Shanxibaicaixingyoucai and Aidagan, while the largest (0.9289) between cv. Chixin-29 and B. olerarea L.Tree dendrograms were constructed based on the AFLP marker data by system cluster analysis of WPGMA^ Similar average distance and the longest distance, respectively. The result were:(1) The differences of AFLP fingerprints among B. rapa, B. juncea and B. oleracea were obvious. Thus, molecular analysis based on AFLP markers confirmed the expectations that the B. rapa is a species of Brassica(2) B. rapa can be separated into four groups: B. campestris ssp. rapifera (Matzg.) Sinsk., B. campestris var. chinensis, B.C.ssp. nipposinica (Bailey) Olsson and B. campestris ssp. chinensis (L.) Makino.(3) The AFLP data supported the view of Jiashu Cao that assigned the B. rapa L. ssp. chinensis var. pekinensis (Rupr.) J. Cao et Sh. Cao into B. rapa ssp. chinensis (L.) Makino.(4) The phylogeny of cv. Nantongjiguancai and the cultivar groups of Taicai indicated the relationships of them are close. The cultivar groups of Baicaixingyoucai, cv. Caixin, the cultivar groups of Caitai and the cultivar groups of Tacai were clustered tightly, illustratingthe relatively poor genetic diversity present among them.