| Populus plants widely grow in the temperate and frigid zone of northern hemisphere. In China, it naturally distributes in the subtopic and temperate area. Populus is playing an important role on the production of industry construction wood, veneer, paper pulp and firewood and on ecological and environmental construction. Based on the techniques of amplified fragment length polymorphism (AFLP) and microsatellite (SSR) marker, a hybrid molecular linkage map of Populus deltoides ×R cathayana was constructed in this research and QTLs of several important wood property were ordered in the constructed map. The major results are described as follows:1. Forty-one AFLP primer pairs and 39 SSR primer pairs were selected and used for the genetic linkage map construct of the P. deltoidesXR cathayana hybrid. Forty-one AFLP primer pairs generated 873 polymorphism fragments and each AFLP primer pair produced 21.3 polymorphism fragments in average. Among 873 polymorphism fragments, 784 fragments segregated in a ratio of 3:1, which accorded with the role of Mendel. In 39 SSR markers, 26 markers segregated in a ratio of 1:2:1.2. A genetic linkage map of P. deltoides×R cathayana was constructed based on 784 AFLP markers and 26 SSR markers and by using 87 F2 individuals. 19 major groups, 16 doublets, 7 triplets and 5 small groups were identified in this map. 356 AFLP makers and 12 SSR markers, total 368 makers, were ordered on the 19 major groups. This map covers 3382.4 centiMorgan (cM) of genome length, and the average distance between two markers is 9.69 cM.3. The genome length of P. deltoides×R cathayana hybrid was estimated. It is between 2607cM and 3319 cM and is 3042 cM in average and one centi-Morgan represents 3.8× 105bp real physical distance in average. The expected genome coverage was calculated and it was 96.7% with the equation of LANGE & BOEHNKE (1982), and it was 98.4% with method of BISHOP et al. (1983).4. Fiber length (FL) traits showed heterosis in the F2 population of R deltoidesXRcathayana. Wood specific gravity (WSG) trait showed declining in close-hybridization. A significant negative correlation between fiber width (FW) and WSG (r = -0.479) and a significant positive correlation between FL and FW (r = 0.330) were detected. However, microfibre angle had no significant correlations with other traits. The genetic variations coefficient of those traits is between 9% and 12%.5. Total 20 quantitative trait loci (QTLs) for 4 traits of WSG, MFA, FL and FW were detected by using interval mapping based on existing linkage map. Of those QTLs, 6 loci were related to WSG and their total phenotypic variation contribution was 27.1%; 3 loci were related to MSA and their phenotypic variation contribution was 38.6%. 5 loci were related to FL and their phenotypic variation contribution was 65.3%; 6 loci were related to MSA and their phenotypic variation contribution was 69.0%. The work of QTLs mapping and QTLs effectiveness analysis on P. deltoides X R cathayana sets a solid base for its practices of genetic manipulation of some important quantitative traits, molecular marker assistant breeding and screening, genome mapping and aimed gene isolation.
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