Preliminary genetic linkage maps of Chinese herb Dendrobium nobile and D-moniliforme

Dendrobium is an endangered genus in the orchid family with medicinal and horticultural value. Two preliminary genetic linkage maps were constructed using 90 F-1 progeny individuals derived from an interspecific cross between D. nobile and D. moniliforme (both, 2n = 38), using random amplified polymorphic DNA (RAPD) and intersimple sequence repeat (ISSR). A total of 286 RAPD loci and 68 ISSR loci were identified and used for genetic linkage analysis. Maps were constructed by double pseudo-testcross mapping strategy using the software Mapmaker/EXP ver. 3.0, and Kosambi map distances were constructed using a LOD score a parts per thousand yen 4 and a recombination threshold of 0.4. The resulting frame map of D. nobile was 1474 cM in total length with 116 loci distributed in 15 linkage groups; and the D. moniliforme linkage map had 117 loci placed in 16 linkage groups spanning 1326.5 cM. Both maps showed 76.91% and 73.59% genome coverage for D. nobile and D. moniliforme, respectively. These primary maps provide an important basis for genetic studies and further medicinal and horticultural traits mapping and marker-assisted selection in Dendrobium breeding programmes.