Yanxia Song (Biochemistry And Molecular Biology) Directed By Professor Zhenglong Ren And Professor Jizeng Jia

Genetic studies in wheat have revealed that most agronomic traits are quantitatively inherited and, therefore, it is difficult to detect the genes for these traits in the genome. Chinese wheat genetic resources consist of the important components of wheat genetic resources in the world for their unique characteristics such as early maturity, large grain numbers, wide adaptability and high crossability. Therefore, the urgent research work for Chinese wheat scientists is to discover more valuable genes to breed great and stable yielding, good quality and environmental-friendship varieties from the abundant wheat genetic resources in China. In recent years, with the development of high-density linkage maps, the discovery of such quantitative trait loci (QTLs) has become possible in many species. In this study, genetic linkage map of the recombinant inbred lines (RIL) from YanzhanlxNeixiang188 was constructed using fluorescence and silver-staining detection systems of microsatellite markers. In addition, QTL mapping on important agronomical traits such as early maturity, plant height, crossability etc. were carried out using populations derived from the crosses of YanzhanlxNeixiang188, Hanxuanl0xLumai14, Wenmai6xShanhongmai and Chinese Spring x LovrinlO. The major results and conclusions are described as follows.1. Yanzhanl is a good variety with characteristics of early maturity, high yield and high resistance to several diseases, and Neixiang188 is a widely cultivated variety for its comprehensive traits. These tow varieties were selected to make cross. The RILs with 199 lines used for QTL mapping in this study were established at F₇ generation by single-seed descent method from above cross.2. Two hundred and forty-one polymorphic loci from 1267 SSR makers amplified in theparents were detected in RILs of YanzhanlxNeixiangl88 by fluorescence and silver-staining detection systems of microsatellite markers. The average percentage of polymorphic loci was 19.02% and varied in different kinds of SSR sources. Within the genetic linkage map, 215 markers were distributed in 21 the linkage groups with an average distance of 19.54 cM and a total length of 4202 cM. There were as many as 21 markers in 2 A and as few as 5 markers in 6D and 7D, with an average of 10.27 markers in each linkage group.3. Through mixed-model composite interval mapping, a total of 16 putative QTLs with a LOD threshold of ^3.0 for heading date were detected in three populations derived from YanzhanlxNeixiangl88, Hanxuanl0xLumail4, Wenmai6xShanhongmai respectively, under different environmental conditions. They were located on chromosome IB, 2D, 3A, 3D, 4A, 4D, 5B, 5D, 6B, 6D, 7B and 7D respectively. The numbers of detected putative QTLs in the three populations were seven, seven and two. Compared with reported QTLs of heading date in wheat, the same QTLs were detected on 5B and 5D chromosomes. In different environmental conditions, two major loci were repeatedly detected from YanzhanlxNeixiangl88, while no repeated locus was found from the other two populations. The genetic controlling model of early maturity in Yanzhanl was also revealed by the QTLs from YanzhanlxNeixiang 188. It was indicated that at least 5 QTLs contributed to the early maturity and heading in Yanzhanl. They were located between wmc215 and wms292 on 5D (Vrn-DJ), wmc75 and wms408 on 5B (Vrn-BJ), barcl81 and wms24 on IB, wms539 and wmcl70 on 2D, and between wmc311 and wmc276 on 7B. The results also showed that there existed late maturity related QTLs even in the early maturity varieties, and vice versa. For example, two QTLs which were detected between wmc343 and barcl040 on 3A(Eps-Al) and between wmc331 and cfd71a on 4D made Yanzhanl heading and maturity later. Therefore, analysis on genotypes is very important for discovering new genes from genetic resources.4. A set of 199 RILs of Yanzhanl/Neixiangl88 mapping population was evaluated for 11 agronomical traits such as plant height, maturity period, yield and cold tolerance etc. in three different environments. The results indicated that a total of 56 QTLs were detected with the LOD^3.0, among which 21 QTLs on 8 traits were repeatedly detected in three different environments. Thirteen QTLs related to plant height, ear length, heading date, flowering time, maturity period and cold tolerance were either already reported or had the same locations withreported QTL loci. Though another 43 QTLs were not reported, thirteen of which were detected repeatedly in two different environments. They were spike length QTLs on 6 A, IB, 5D, 4A and 5A, spikelet number QTLs on IB and 5D, grain number QTLs on 5B and 5D, thousand grain weight QTLs on 4D, 2B and 3B, and maturity QTLs on 4B.5. An intervarietal molecular-marker map was used for the detection of genomic regions affecting crossability between wheat (Triticum aestivum L.) and rye (Secale cereale L.). The method of Composite Interval Mapping was conducted on the data from the RIL of the cross between "LovrinlO" and "Chinese Spring (Cs)". Totally, 8 QTLs were detected and explained 75.62% of the variance in crossability variance in the mapping population. The QTLs also revealed the genetic basis of high crossability possessed by Cs. Five QTLs, located between the Xgwm60 and wmc283.1 on 7 A, between Gwm617.1 and wmc206.1 on 5 A, between wmc497.1 and Xgwm66 on 7B, and between wmc363 and Xgwm247.2, between wmc28 and Xgwm497.1 on 5B, totally explained 55.22% of the phenotypic variance of Cs crossability. On the other hand, another 3 QTLs, located between Xgdm38 and gwmll4, between Xgwm341 and Xgdm8 on 3D, between wmc517 and wmc311 on 7B, reduced the crossability ofCs.