[Construction of genetic linkage maps of silver birch based on AFLP markers]

Based on the inheritance and segregation of amplified fragment length polymorphism (AFLP) markers, the first middensity linkage map for silver birch was constructed using a pseudotestcross mapping strategy. A segregating population including 80 progenies from the cross between Betula platyphylla Suk and B. pendula Roth was obtained. A set of 64 primer combinations were screened, and 34 pair primer combinations were selected to generate AFLP markers within a sample of 80 F1 progenies. A total of 451 segregating sites were identified. Among them, 362 belonged to 1:1 segregating site, and 41 belonged to 3:1 segregating site, 20 belonged to 1:3 segregating site, and others were found distorted from the Mondelian ratio. Altogether 362 sites segregating 1:1 (testcross configuration) were used to construct parent-specific linkage maps, 201 for B. platyphylla and 161 for B. pendula. One linkage maps resulted consisted of 201 marker sites in 14 groups with four or more sites per group, 10 triples and 14 pairs for B. platyphylla, which covered a map distance about 1 296.1 cM (Kosambi units), and the average map distance between adjacent markers was 15.5 cM. Another linkage maps resulted consisted of 161 marker site for B. pendula were mapped onto 17 groups with four or more sites per group, 8 triples and 4 pairs, which covered a map distance about 1 035.8 cM, and the average map distance between adjacent markers was 12 cM. Those maps can be used in QTL analysis and molecular assistant selection in birch breeding.