Studies On Genetic Diversity Of Flowering Chinese Cabbage (Brassica Campestris L.ssp.chinensis Var.utilis Tsen Et Lee) By RAPD Analysis

Flowering Chinese cabbage is the most area under cultivation vegetable in Guangdong Province. Moreover, it is one of the most important vegetables which are exported to HongKong and Macao and Southeast Asia. RAPD analysis was employed to detect the genetic diversity of 28 flowering Chinese cabbage cultivars and 3 green Chinese cabbage cultivars. The cultivars that are close on genetic relationship could be gathered together. The main conclusions were drawn as followings:1. Genomic DNA extractionIntegrated and sufficient genomic DNA is precondition of RAPD reaction. The modified CTAB method has been employed to extract the genomic DNA from flowering Chinese cabbage which contains abundant polysaccharides .The DNA samples were suitable for RAPD analysis. The ratios of OD₂₆₀ and OD₂₈₀ determined by UV spectrometers were about 1.8 and the ratios of OD₂₆₀ and OD₂₃₀ were about 2.0. The genomic DNA output of per gram flowering Chinese cabbage exceeded 160 μg. Moreover, the results of electrophoresis were all single and bright bands.2. Establishment of RAPD reaction systemRAPD reaction is susceptive to experimental procedure and condition, so it's very important to make the experimental conditions standardization. Through the optimization of every factor that would affect the results of RAPD, The optimal RAPD reaction system was established: A 25uL reaction solution with 0.8U Taq DNA polymerase, 0.28umol/L primer, 30ng template DNA, 2.0mmol/L Mg2+, 0.20mmol/L dNTPs. The reaction program was devised at 94°C for 5 minutes and followed by 37 cycles, each with 1 minute at 94°C, 1 minute at 36 °C, 2 minutes at 72°C, and a final extension at 72 °C for 10 minutes.3. Screening polymorphic primers80 primers were applied to screen those primers that could produce polymorphic bands in 6 typical flowering Chinese cabbage cultivars. 9 primers which produced 22 polymorphic bands were screened out. The ratio of polymorphic bands was 44.9%.4. The analysis of genetic diversity of flowering Chinese cabbageThe 9 screened polymorphic primers were performed to the RAPD reaction of genomic DNA. The cultivars that are close on genetic relationship could be gathered from the RAPD fingerprints. The results of cluster analysis could avoid the influence of environment and offer new theory bases for the study of flowering Chinese cabbage.