Based on the genetic inheritance and segregation of random amplified polymorphism DNA(RAPDs) markers,the analysis of linkage groups for birch was performed by using a pseudo-testcross strategy.A segregating population comprising of 79 progenies from the cross between Betula pendula and B.platyphylla was obtained.A set of 1 000 random oligonucleotide primers were screened,and 178 primers were selected to generate RAPD markers within a sample of 79 F\-1 progenies.A total of 296 segregating sites was identified.Among them,273 sites belonged to 1∶1 segregating site,and 36 sites were found distorted from the 1∶1 ratio.The 273 sites segregating 1∶1(testcross configuration) were used to construct parent-specific linkage group,among which 137 sites were found for B.pendula and 136 sites for B.platyphylla.The resulting linkage maps consisted of 117 marker sites in 12 groups(four or more sites per group),2 triples and 3 pairs for B.pendula,which covered the map distance about 1 533.3 cM(Kosambi units),and the average map distance between adjacent markers was 16.4 cM.In the B.platyphylla,162 linked marker sites were integrated into 12 groups(four or more sites per group),2 triples and 4 pairs,which covered the map distance about 1 847.8 cM,and the average map distance between adjacent markers was 19.2 cM.The calculated genome coverage rate of B.pendula and B.platyphylla were respectively 68.5% and 68.9%.Further study is required to integrate the two maps to one density map and to locate important genes on the maps.
