Molecular Identification Of Self-incompatible Genes In Chinese Cabbage(Brassica Rapa L.ssp.pekinensis)

Chinese cabbage (Brassica rapa L. ssp. pekinensis) originated fromChina, and it is one of the most important vegetable crops in Asia, especiallyin China, Japan and Korea. Chinese cabbage have the characteristic ofself-incompatibility(SI). Self-incompatibility in Brassica plants issporophytically controlled by a single multi-allelic locus (S-locus). The Sgenotype information of inbred lines not only could make the parents of F1hybrids compatible when crossing, but also can use to identify the purity ofhybrid.The traditional method of identifying S alleles of Brassica istest-crossing.Regardless counting the number of seeds or observing thenumber of growing pollen-tubes, this method only can be used during theperiod of flowering, and the expression of SI is influenced by environmentalfactors and the physiological condition of plants, so this method not onlywastes time and labor power, but also its accuracy is very poor. Theapplication of molecular biology to analyzing S alleles of inbred lines canimprove the efficiency of breeding. This study is divided in two parts: 1.In this study, ten early mature inbred lines and ten late mature inbredlines whose horticultural trait and SI are stable were used to detect their SIgenes. By complete diallel crossing in early mature group and in late maturegroup respectively, and then counting their compatibility index, the mainresults were as following: 1.1 There were seven S genotypes at least in early mature group.B30003 and B30044 had the same S genotype; B30015 and B30095 possiblyhad the same S genotype; B30059 and B30069 possibly had the same Sgenotype. We also found the S gene of B30003 and B30044 was heterozygous, 3大白菜自交不亲和基因的分子鉴别and the alleles of the S heterozygous gene showed different relationships instigma and pollen respectively. In pollen, the alleles exhibited dominant andrecessive relationship, but they were independent in stigma. 1.2 These S genotypes were different each other in late mature group.The S gene of B30083 was heterozygous too. The relationship of its S alleleswas the same as that of B30003 and B30044. 2.By PCR-RFLP analysis, the main results were as following : 2.1 Class II SLG fragment were amplified by using DNA templets of allof twenty inbred lines. However, there were not the Class I SLG specificfragment in B30003, B30021, B30044, B30071, B30124, B30130 and B30162.And there were not the SRK specific fragment in B30003, B30021, B30044,B30130, and B30162. 2.2 The number restriction endonucleases for SRK fragments were morethan those for SLG fragments. These two types of SLG fragments could becleaved by same restriction endonucleases, but they couldn't be cleaved bysome restriction endonucleases which can cleave SRK fragments. Thepolymorphism of restriction fragment length of Class II SLG fragment was thepoorest, and the polymorphism of SRK was the best. 2.3 By cleaving Class I SLG fragment, we found B30059 and B30069had specific restriction fragments and B30009 had specific restrictionfragments in early mature group. In late mature group, we observed specificrestriction fragments of B30190 and that of B30206. 2.4 By cleaving Class II SLG fragment, we only found B30083 hadspecific restriction fragments in late mature group. 2.5 By cleaving SRK fragment, we found three kinds of S genotypes,that was S genotype of B30009, that of B30071, and that of B30059 andB30069, had specific fragments, in early mature group. In late mature group,we also found three kinds of S genotypes, that was S genotype of B30124, thatof B30190, and that of B30206, had specific fragments.