The Discovery And Artificial Selection Response Of Resistance Gene To Fungal Disease In Tobacco

Black shank disease and brown spot disease are two main fungal diseases of tobacco,and brought great distress and economic loss to tobacco production every year, while the cultivation of resistant varieties is the most effective way to solve the problem of the fundamental. The experiment consists of two parts:(1) Using black shank resistant varieties Beinhart1000-1 as female, susceptible varieties xiaohuangjin 1025 as male to make cross, using xiaohuangjin 1025 as recurrent parent to make backcross, get group BC2F2, BC2F3. And then by molecular marker-assisted selection(MAS) to mapping black shank disease resistance QTL of Beinhart1000-1.(2) To assess the response of major effect QTL to artificial selection for brown spot disease and to provide some useful information for molecular marker assisted selection(MAS) for tobacco breeding. The results are as fllows:1.Using black shank resistant varieties Beinhart1000-1 as female, susceptible varieties xiaohuangjin 1025 as male to make cross, using xiaohuangjin 1025 as recurrent parent to make backcross, get group BC2F2, BC2F3. In different years, we grow BC2F2 and BC2F3 under different environment, then inoculating phytophthora 0 races to the two groups, five times in total. In laboratory, we used the screened 119 pairs of polymorphic primers to amplify 120 BC2F2 individuals. And then we used MapQTL 6.0’s MQM model method and MapChart 2.2 to obtained two linkage groups: one is the 1th linkage group, containing six markers covering 15.36 cM, the other is the 2th linkage group, containing 18 markers covering 135.97 cM in total. And we detected three black shank resistance QTLs, two are located in the 1th linkage group, the left one is in the 2th linkage group.2. To analyze response of major effect QTL to different artificial selection in different populations, the distribution of the all alleles at the two marker loci in the extreme populations selected from JYH/NC82 cross in different generations and a panel of 198 tobacco accessions were detected based on the major effect QTL with flanking molecular markers of J9 and J4. And there were three results:(1) the deviation of the JYH alleles at J9 loci exhibited the significance in the positive extreme populations under 5%, 10% and 20% selection intensities. The P value from X2-test for allelic frequency under different intensities(5%, 10% and 20%) were 0.015, 0.002 and 0.050, respectively.(2) There was a significant increasing of the JYH allelic frequency in different generations(F3, F4, F5 and F6) derived from the cross JYH and NC82, indicating that the allele from JYH at J9 loci increase resistance to brown spot disease significantly.(3) In the panel of 198 tobacco accessions, 50 tested accessions, including highly resistant cultivars for brown spot disease such as zhongyan86, danyu2 and so on, have the same genotype with JYH cultivar. The result showed that the resistant alleles from JYH had been used widely in tobacco breeding. The major QTL associated with resistance to brown spot had been identified repeatedly and the response of major effect QTL to artificial selection for resistance to brown spot disease was evaluated. These results could provide information on MAS for improvement of resistance to brown spot disease in tobacco.