烟草赤星病抗性主效QTL人工选择响应研究

分析赤星病抗性主效QTL的人工选择响应,可为烟草赤星病抗性分子标记辅助选择提供一定的理论基础。本研究利用与主效QTL紧密连锁的分子标记J9和J4,分析随机群体、人工选择群体和自然群体中响应分子标记的等位基因频率,研究相关标记位点在不同群体中的等位基因变化规律。结果发现:(1)赤星病抗性主效QTL等位基因在不同选择强度(5%、10%和20%)的正向选择条件下均发生了显著性偏分离,其中在10%的正向选择强度下偏分离显著性最高。(2)在不同世代(F3、F4、F5和F6)的赤星病抗性育种选择群体中,J9位点抗病亲本等位基因型频率显著高于感病亲本基因型频率,表明来源于抗源净叶黄的主效抗性QTL与赤星病抗性显著关联。(3)在198份自然群体中,包括烟草赤星病抗性品种中烟86、单育二号在内的50份烟草种质携带与抗源净叶黄相同的基因型,表明该主效QTL被广泛应用于烟草赤星病抗性改良中。本研究验证了之前定位到的主效抗病QTL的准确性;分析了该主效QTL的人工选择响应,相关结果为烟草赤星病抗性改良提供了一定的理论基础。

Response of Major Effect QTL to Artificial Selection for Resistance to Brown Spot Disease in Tobacco

The objectives of this study were 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. 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, 0.002and 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.