Study On Cold Tolerance And SSR DNA Fingerprinting Analysis In Winter Rapa (Brassica. Rapa)

In this study, 8 representative winter rapa cultivars were selected as research materials, studied botanic characteristics, growth period and dry matter accumulation of different cold tolerance cultivars; moreover, superoxide disputes (SOD) activity, peroxidase (POD) activity, soluble sugar contents, soluble protein contents, and free proline contents of 8 cultivars were tested before overwintering. 6 primers which have polymorphic fragments were selected from 29 primers; the DNA fingerprinting of 8 varieties was constructed. Results of this study are as followings:1. Cold tolerance of different cultivarsAccording to calculated results in field, the overwintering rates of 8 cultivars were: MXW-1 (100%), DQW-1 (100%), WYW-1 (90%), Yanyou2 (80%), 02Cza (30%), 9852 (41%), 9889 (39%), Tianyou2 (38%), and 8 cultivars were divided into four groups based on winter survival rate. MXW-1 and DQW-1 were ultra winter hardy cultivars, WYW-1 was strong cold tolerance cultivars, Yanyou2 was cold tolerance cultivars, and the others were ordinary cold tolerance cultivars.2. Botanic characteristics and growth period of different cold tolerance cultivarsBefore winter, the ultra winter hardy cultivars (MXW-1, DQW-1) grew horizontally, and their leaves were dark green or purple, their growing point undercut during the growth, their growth was slow and the number of leaf was 10 before winter, this cultivar has strong roots and longer growth period. But 02Cza, 9852, 9889 and Tianyou2 were growing erection in seedling stage; leaves of them were green or light green, their growth was quick and the number of leaf was 16 before winter, growing trend was exuberant, and they all have shorter growth period.3. The physiological and biochemical characteristics of different cold tolerance cultivarsThe tested results of physiological and biochemical index indicated: changes of enzyme activity and contents of soluble substance were similar of 8 cultivars, but the degree of changing was difference among them. The studies showed that the SOD activity, POD activity, soluble sugar contents, soluble protein contents, and free proline contents of strong cold tolerance cultivars were higher than weak ones. Correlation analysis showed that the physiological and biochemical index correlated closely to winter survival rate of cultivars when they underthrew the low temperature forces. POD activity, soluble sugar contents, and soluble protein contents could be regarded as the guides for selecting the cold tolerance cultivars.4. The SSR fingerprinting of different cold tolerance cultivarsThe DNA fingerprinting was analyzed by SSR marker technique in 8 winter rapa (B. rapa). 6 primers which have polymorphic fragments were selected from 29 primers, in which 4 varieties have unique band. MXW-1 has unique band in Ni2-F02 (No.10) and Ra3-C11 (No.19), the length was 280bp and 350bp. Yanyou2 has unique band in two primers, which has two bands (280bp, 350bp) in Ni2-C12 and 350bp band in Ra3-G11 (No.28). 9889 has unique band (150bp) in Ra3-E04a (No.25); WYW-1 has two bands (300bp, 380bp) in Ra3-E05 (No.26). Ni2-F02 (No.10) could distinguish 8 winter rapa varieties. In addition, combining Ra3-C11 (No.19), Ra3-E04a (No.25) with Ra3-E05 (No.26) also could distinguish them. 4 primers were selected for the construction of DNA fingerprinting.