Construction Genetic Linkage Map Of Dendrobium Based On Molecular Markers

Dendrobium species were epiphytic plants of Orchidaceae and the traditional precious Chinese medical herbals. To date, the genetic maps of Dendrobium were rarely reported at home and abroad. In this study, we first constructed F1 hybird population derived from the cross of two Dendrobium species:D.officinale (from Jinhua, Zhejiang) and D.moniliforme (from Simao, Yunnan) based on the pseudo-testcross strategy. Then the genetic linkage map of Dendrobium were successfully constructed by using the molecular markers of EST-SSR, SRAP, ISSR and RAPD. The aim of the paper was to provide the detailed and informative genetic mapping of medical traits and breeding programs in Dendrobium by the marker-assisted selection. The main results were as follows:1. In this paper, EST-SSR marker was firstly been utilized to construct genetic map. As an anchor tag, the EST-SSR marker would be necessary to merge and integrate the different chromosome map or linkage groups of Dendrobium. Meanwhile, it provided an effective method for developing the high-density genetic linkage map of Dendrobium.2. On the basis of the clear, stable and polymorphic bands detected from EST-SSR, SRAP, ISSR and RAPD primers,563 polymorphic bands were generated by the PCR amplification between the both parents and the F1 hybird colony. Among these markers,259 loci were from the male parent (D.officinale) with accounting for 46%, and 269 loci from the female parent (D.moniliforme) with accounting for 47.78%. The rate of parents loci in the offspring was close to 50%, in line with the normal distribution of hybrid combinations of sites.3. Three separated patterns of the makers were obtained in this paper. The first pattern was Mendelian segregation. The total of makers was 481 with accounting for 85.44%. The second pattern was partial segregation. The total of markers was 78 with accounting for 13.85%. The third pattern was abnormal segregation. The total of markers was 4 with accounting for 0.71%.4. Mapmaker 3.0/Exp and Mapdraw V2.1 software were used to construct their genetic maps based on the polymorphic loci data tested from the segregating population. For the paternal map,220 loci were arranged into 22 major linkage groups (LGs), each containing a minimum of four markers, and a further 46 markers were distributed 10 triplets and 8 doublets, leaving 37 markers unlinked. The map covered a total distance of 1425.9cM. For the maternal map,226 markers were assignable to 20 LGs, with 14 triplets and 8 doublets, the map covered a total distance of 1332.6 cM. The average distance of the parents map was 10.41 cM between adjacent markers, meeting the requirements of constructing the framework linkage map.