The linkage maps of Dendrobium species based on RAPD and SRAP markers.

Dendrobium plants are used commonly as tonic herbs and health food in many Asian countries, especially in China. Here we report the genetic map construction of two Dendrobium species with a double pseudo-testcross strategy using random amplified polymorphic DNA (RAPD) and sequence-related amplified polymorphism (SRAP) markers. A F(1) mapping population of 90 individuals was developed from a cross between D. officinale and D. hercoglossum. A total of 307 markers, including 209 RAPD and 98 SRAP, were identified and used for genetic linkage group (LG) analysis. The D. officinale linkage map consisted of 11 major linkage groups and 3 doublets, which covered 629.4 cM by a total of 62 markers with an average locus distance of 11.2 cM between two adjacent markers. The D. hercoglossum linkage map contained 112 markers mapped on 15 major and 4 minor linkage groups, spanning a total length of 1,304.6 cM with an average distance of 11.6 cM between two adjacent markers. The maps constructed in this study covered 92.7% and 82.7% of the D. hercoglossum and D. officinale genomes respectively, providing an important basis for the mapping of horticultural and medicinal traits and for the application of marker-assisted selection in Dendrobium breeding program.