Association analysis of heat-resistance traits in Clematis

The genus Clematis is an important ornamental vine flower popular worldwide. High temperature reduces the visual quality of Clematis in summer, and identification of molecular markers associated with heat resistance in Clematis will contribute to efficient selection of elite varieties. In our research, 127 accessions of the genus Clematis from nine countries were used for association analysis. These accessions were screened with 44 pairs of expressed sequence tags-simple sequence repeat (EST-SSR) primers and 22 pairs of sequence-related amplified polymorphism (SRAP) primers. A total of 133 EST-SSR and 81 SRAP polymorphic loci were detected. There were six and seven markers associated with the heat-resistance index using a General Linear Model and a Mixed Linear Model, respectively. Among these markers, SSR38160, SSR80-230 and SRAP31-105 were significantly associated with heat resistance in both models, with effect values of 4.8-6.73%. This is the first report on association analysis of the genus Clematis and these markers could assist in the selection of materials for heat-resistance breeding programs and further genetic investigations.