| The fungus of Fusarium wilts of cabbage can infect all the vegetables of Brassica, the disease became more and more severe in northern areas in China and it affected the cabbage productivity in a great degree. The traditional control methods such as seed treatment, rotated planting and fungicide using have little function on the disease prevention because the fungus could live several years in soil without planting cabbages. Breeding resistant cultivars would be the most effective method to eliminate this destructive disease. The use of MAS might increase the breeding efficiency, and developing stable PCR molecular markers linked to resistant genes has very important significance on molecular breeding of cabbage Fusarium wilt.The analysis of resistance character was based on two different inbred lines that were selfed for several generations, the line 8024 was resistant and 6A was susceptible to Fusarium wilt. The F2 generation from the cross of 8024×6A was used to develop markers linked to the resistant gene and the genotype of each F2 line was confirmed according to separated resistant characteristic of the corresponding F3 line. The F2 plant DNA from 10 stochastic homozygous resistant plants and 10 homozygous susceptible plants were used to establish two homozygous resistant pools: R1, R2 and two susceptible pools: S1, S2. With the method of BSA, the AFLP marker technology was combined to develop molecular markers linked to the resistant gene of Fusarium wilt in cabbage and the AFLP marker was transferred to a SCAR marker which would be more stable and valuable for MAS. The map distances between the resistant loci and the markers was analyzed according to the mapping population which was comprised of 142 F2 lines and the commonality of the SCAR marker was checked in two different F2 populations which contained 50 lines in each.The main conclusions are as follows:1) In this study 10 F1 plants and 142 F2 plants were investigated after two weeks inoculation with the pathogen, and all 10 F1 plants were no host reaction. 32 plants in F2 population displayed host necrosis and dead in 45 day after inoculation and the other 110 plants were no host reaction. The F2 population segregated for 110 resistant versus 32 susceptible lines, which is in accordance with a 3:1 segregation rate (χ2 = 0.460<χ20.05,1=3.841), indicating that the Fusarium wilt resistance is controlled by a single dominant gene (FOC-1).2) The BSA method and AFLP technology were used to screen out AFLP markers linked to the resistant gene of Fusarium wilt in cabbage. And the map distances between the resistant loci and the AFLP markers was analyzed according to the mapping population which was comprised of 142 F2 lines. Two AFLP marker linked to the gene were obtained, E-ATT/M-CAC211 and E-AGA/M-AGT186.3) The AFLP fragments of E-ATT/M-CAC211 and E-AGA/M-AGT186 were cloned and sequenced, according to the character of the sequences two SCAR primer pairs were designed, and they were checked in resistant and susceptible plants, DNA from resistant/susceptible bulks, parents. The results showed stable after three parallel experiments and it revealed that the two AFLP markers were transferred into SCAR markers successfully. The marker E-ATT/M-CAC211 was an dominant marker, which can amplify the excise fragments in the maternal plant, the susceptible pool. According to the analysis in F2 generation the recombination frequency was 3.3%, the map distance between this marker and the resistant gene was concluded with JoinMap 3.0 and showed 2.78cM, and the marker was named S46M48199. And the fragment E-AGA/M-AGT186 was transferred to a codominant marker, named S39M42214, it can amplify 209bp fragments in resistant parental line and resistant pool, whereas 214bp fragments in susceptible parental lines and susceptible DNA pool, and the recombination frequency between the marker and the resistant loci was 6.8% according to the analysis in F2 segregation population. The map distance between them was 3.55cM with the calculation by JoinMap 3.0.4) Analysis of F66 and C1 populations which were detected by phenotypic assay, was performed in order to test the capacity of the developed marker to predict the resistance or susceptibility to Fusarium wilt in different varieties. And F66 from a cross of 97057×73A, C1 from a cross of 98023×406, contained 50 F2 inbred lines in each population. 97057 and 98023 were two inbred lines highly resistant to the disease, while 73A and 406 were two inbred lines highly susceptible. The result was shown that the consistency between marker identification of S46M48199 and phenotypic assay in F66 and C1 was about 81% and 83% respectively, and the consistency of marker S39M42214 showed 86% and 90% respectively. |
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