Construction Of A Molecular Genetic Map And Analysis Of Quantitative Trait Locus In Betula Platyphylla Suk

The Betula platyphylla Suk.is pioneer and excellent broad-leaved pulp tree in northeast and inner-Mongolia region.To accelerate the gentic inprovement of B.platyphylla complex character,such as grouth,material,quality,it is necessary to construction of a molecular genetic map and locate the charcter,so as to provide a basis for marker assisted selection breeding.Therefor,the study was done in this paper:(1) After measurement fiber length trait(FLT) of 32 individuals from B.platyphylla population in intensive seed orchard,the individual whose fiber length was larger than the mean value plus one standard deviation was selected as paternal,and the individual whose fiber length is smaller than the mean value minus one standard deviation was selected as maternal.Hybridization was carried out under control,and then a molecular genetic linkage map was constructed with 80 F1.(2) Polymorphism of amplified parents was analysized,223 high polymorphic RAPD primers were screened out from 1,200 primers,and 27 pairs of high polymorphic SSR primers were screened out from 330 pairs of primers.Parents and 80 Fl generation were amplified with screened RAPD primers and SSR primers,415 RAPD polymorphic markers and 70 SSR polymorphic markers were obtained.Afterχ~2 text,410 belonged to 1:1 segregating site,and 45 belonged to 3:1 segregating site,others were found distorted from the normal 1:1 ratio.(3) Altogether 410 sites segregating 1:1 were used to construct parent-specific linkage maps with pseudotestcross strategy,including 203 for paternal and 207 for maternal.Linkage maps was estimated and drawn with MapMaker3.0 and Mapdraw Ver.2.0 software, respectively.The linkage maps consisted of 203 marker sites inl6 groups(four or more sites per group),6 triples and 8 pairs for paternal,which covered the map distance about 1,402.4cM (Kosambi units).The average map distance between adjacent markers was 13.1cM,and 207 linked marker site for maternal were mapped onto 17 groups(four or more sites per group),5 triples and 9 pairs,which covered the map distance about l,440.7cM,and the average map distance between adjacent markers was 12.5 cM.(4) Composite interval mapping method of Windows QTL Cartographer V2.5 was used in QTL analysis of B.platyphylla important traits,such as seedling height,girth and so on. With LOD≥2.0,two QTLs affecting plant height were detected,six QTLs affecting plant girth were deteced.One QTL affecting seedling height was detected in paternal linkage populations. Its additive effect was -5.57 and contribution rate was 9.76%to phenotypic variance. Meanwhile one QTL affecting girth was detected with additive effect 0.04 and contribution rate 17.54%to phenotypic variance.One QTL affecting seedling hight was detected in maternal linkage populations with additive effect -6.14 and contribution rate 12.54%to phenotypic variance.Five QTL affecting girth were detected,and their additive effects were 0.03,0.16,0.15,0.05,-0.25 and contribution rates were 9.12%,16.01%,16.72%,18.94%,19.84%to phenotypic variance,respectively.