Discovery of species-wide EST-derived markers in Rhododendron by intron-flanking primer design

From two cDNA libraries made of flowers of the evergreen Rhododendron simsii hybrid ‘Flamenco’ and the deciduous species Rhododendron luteum, 323 cDNA fragments were randomly sequenced and functions were assigned. Reliable homologies were found for 31% of the fragments. For mapping applications, EST-derived markers were developed on 127 sequences. Since polymorphisms are more prone to come about in introns, primers were selected to have an elevated probability to be intron-spanning. The utilised approach resulted in an overall polymorphism-generating efficiency of 35% (45 polymorphic markers). The transferability of these cDNA-based EST markers among plant species was confirmed within the Rhododendron genus. The markers developed here are currently screened for the construction of genetic linkage maps of four crossing populations of R. simsii hybrids.