Genetic Diversity Of Hybrid Parents In Brassica Napus And Purity Identification Of Hybrids By Molecular Markers

Male sterility is an important way of utilizing rapeseed heterosis. In the breeding of hybrids, how to choose parents is a key step to gain strong heterosis and efficiently use heterosis. It is helpful for selecting parents and forcasting prospect of breeding to clearly know relationship, pedigree derivation, genetic diversity and genetic distances of the used parents.Seed, as a source of agricultural production, is an important component of world trade. To be commercial seed, hybrid plays an important role in seed trade. In seed market, a few people sell adulterated or inferior seeds and even illegally gain hybrid parents to produce hybrids. All these actions severely damage the lawful rights and benefits of the breeders or legal companies. In hybrid production, a trace of pollens of sterile lines for its incomplete male sterility or the effect of temperature or photoperiod will produce sterile plants in FI population. High proportion of male sterile plants will affect hybrid yield. Therefore, how to protect hybrid parents and identify hybrid purity becomes more and more important in hybrid production and commercialization.Genetic diversity of hybrid parents in Brassic napus was evaluated with molecular markers so as to make clear their relationship, pedigree and genetic distances and offer theoretic reference for breeding. Meanwhile, DNA fingerprint of hybrid parents was constructed so as to provide molecular testimony and means for protecting hybrid parents. It was hopeful to select one kind of useful molecular markers from RAPD and SSR for hybrid purity test.The main results as follows:1.16 SSR and 3 ISSR primers selected out from 106 SSR and 19 ISSR primers were used to analyse the genetic diversity of 50 Brassica napus including 21 male sterile lines, 18 restorer lines and 11 check cultivars. 101 polymorphic bands including 82 SSR and 19 ISSR bands were used for clustering analysis with UPGMA. 50 Brassica napus were classified into 6 groups. All sterile lines were clustered into Group VI and restorer lines into Group I - V when threshold value was 0.2727. These results indicated that restorer lines had more genetic diversity than sterile lines and that genetic distance between the sterile lines and the restorerlines was larger than that among the sterile lines or among the restorer lines.2. DNA fingerprints of 39 hybrid parents were created with 16 SSR primers. By DNA fingerprints analysis, Na10G08 and P037 were selected out to identify hybrid purity of H9901 (8086A×8759R), NalOG08 to identify hybrid purity of H9905 (8110A × 8759R). Both of them, to be codominant markers, can identify false hybrids not only from selfed seeds of male and female but also from foreign pollen and mechnical contamination.3. Two RAPD primers (S2087 and S88) amplfying the specific band of the parent 8759 were selected out from 220 random primers to identify hybrid purity of H9901 and H9905. After comparsion among RAPD and SSR, SSR was chosen as the most suitable marker to identify hybrid purity. It was due to that SSR needed low identification cost and can use unpurified DNA. Moreover, SSR was more reliable and polymorphic than others.