烤烟几种化学成分的QTL初步分析

Preliminary QTL Analysis of Several Chemical Components in Flue-Cured Tobacco (Nicotiana tabacum L.)

以含137个株系的烤烟DH群体(G-28×NC2326)及其亲本为材料,在以前作图数据的基础上,新增23个标记。将这些标记数据合并起来构建了包括11个ISSR标记和158个RAPD标记、由27个连锁群组成的烤烟分子标记遗传连锁图,覆盖长度2094.6cM,相邻标记间的平均图距为15.95cM。利用4个环境下的试验数据进行了总糖、烟碱、氧化钾3种烟叶化学成分的QTL初步分析,共检测到7个加性效应QTL和9对加加上位性效应QTL,其中3个加性QTL和3对上位性QTL存在QTL与环境互作效应(QE)。表明在烤烟总糖、烟碱、氧化钾的遗传控制中除加性效应外,上位性效应也具有重要作用。对于烟碱、氧化钾检测到加性QTL与环境互作效应,对于总糖、氧化钾检测到上位性QTL与环境互作效应,利用这些与环境具有互作效应的QTL进行标记辅助选择时宜考虑特定的环境条件。

The chemical components are the important traits influencing the leaf quality of tobacco. QTLs linked to the chemical components can be used for marker-assisted selection in leaf quality improvement in tobacco. The objective of this study was to identify QTLs linked to several chemical components in the flue-cured tobacco. A population of 137 doubled haploid （DH） lines derived from a cross between two flue-cured tobacco cultivars G-28 and NC2326 was employed to construct the genetic linkage map. Twenty-three new markers were obtained by ISSR and RAPD analysis, and were combined with the previous marker data for the construction of linkage map. A genetic linkage map consisting of 11 ISSR markers and 158 RAPD markers was developed. The map consisted of 27 linkage groups and spanned 2 094.60 cM with an average distance of 15.95 cM between adjacent markers. The data for three chemical components including total sugar （TS）, nicotine （NIC） and potassium oxide （KO） were collected from a field experiment conducted in four different environments, and a full-QTL model and the corresponding mapping software were used for the preliminary QTL analysis. Seven additive effect QTLs and nine pairs of epistatic QTLs were detected. The results indicated that epistasis played important roles in the genetic basis of the chemical components in the flue-cured tobacco. For the epistatic QTLs, in which the individual QTL showed no additive effect, it should be efficient to select the QTL combinations rather than the single QTL. Three additive QTLs and three pairs of epistatic QTLs were found to involve in QTL-by-environment interactions （QE）： The additive QTL-by-environment interactions were detected for NIC and KO, and the epistatic QTL-by-environment interactions were detected for TS and KO. QTL-by-environment interactions presumably arise from the differential gene expression in various environments and their application in marker-assisted breeding programs would require careful consideration with regard to a particular set of environmental conditions. The present study provides a starting point for detecting QTLs for economically important traits and for understanding the genetic basis of the traits.