Construction Of A Genetic Map And Mapping Of Juvenile Growth-related QTLs In Torreya Grandis "Merrilli"

A semi-sib mapping population has been established in Torreya grandis'Merrilli'and such molecular marker analysis systems as AFLP, ISSR and RAPD (including primers screened) that are suitable to Torreya grandis'Merrilli'are also established. With RAPD marker, endosperm DNA is analyzed and genomic DNA is analyzed with ISSR and AFLP. Based on the marker analysis, a genetic linkage map of Torreya grandis'Merrilli'is constructed. With consecutive 3-year data of basal diameter and height of seedlings, QTLs are analyzed. What has been done has laid a foundation for marker-assisted selection and breeding in Torreya grandis'Merrilli'. The main results are as follows:1.Totally 440 polymorphic markers have been obtained, out of which 91 are RAPD markers, 149 are ISSR markers, and 155 are AFLP markers.2. With P=0.05, a X2 test is performed. As a result, a total of 262 molecular markers, viz. 75 RAPD markers, 119 ISSR markers and 68 AFLP markers, accounting for 59.5% of the total, follow Mendelian segregation ratio and are grouped into 10 linkage groups with MapMaker version 3.0. The genetic map constructed covers 7137.9 cM of the genome, with an average marker interval of 28.2 cM. Each linkage group has markers ranging from 8 to 71 and a length of 138– 1898.5 cM. Linkage Group 1, the largest group, has 71 markers, covering 1898.5 cM with an average of 27.1 cM and Linkage Group 7, the smallest one, has 8 markers, covering 138 cM with an average of 20.1 cM.3. Four base diameter-related QTLs are detected from Linkage Groups 1, 5 and 9, out of which 2 QTLs are located in Linkage Group 9. Four height-related QTLs are detected from Linkage Groups 1, 2, 5 and 8.4. Phenotypic effects of basal diameter and height-related QTLs on seedling growth are yearly increasing, but the effect of two basal diameter-related QTLs in Linkage Group 9 on basal diameter is decreasing in terms of genetic effects, so is the height-related QTL in Linkage Group 5. This may be due to positive environmental effects.5. Based on our study, it is confirmed that functional mapping is powerful in detecting dynamic QTLs that affect developmental changes during ontogenetic growth in a ling-lived forest tree.