VEGETABLE AND ORNAMENTAL RESEARCH IN THE GULF SOUTH
Location: Southern Horticultural Research
Title: Development and Characterization of Simple Sequence Repeats for Flowering Dogwood (Cornus florida L.)
Submitted to: Tree Genetics & Genomics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 8, 2007
Publication Date: December 18, 2007
Citation: Wang, X., Trigiano, R.N., Windham, M.T., Scheffler, B.E., Rinehart, T.A., Spiers, J.M. 2007. Development and Characterization of Simple Sequence Repeats for Flowering Dogwood (Cornus florida L.). Tree Genetics & Genomics Vol 4, no.3 pp.461-468.
Interpretive Summary: Flowering dogwood (Cornus florida L.) is one of most popular woody ornamental species in North America and is also grown in Asia and Europe. Over 200 cultivars of dogwood have been developed for the nursery industry in the United States. Flowering dogwood is an obligate outbreeding with self-incompatibility system, which necessitates that all cultivars are produced vegetatively either by budding onto native rootstock or via rooted cuttings. Molecular markers proposed in the last decade offer a promising tool for dogwood breeding. We used a modified enrichement method to construct four microsatellite-enriched libraries and a simple PCR method to detect SSR motifs from these microsatellite-enriched libraries. The SSR markers developed in this study will be used to construct a linkage map for an F2 mapping population of C. florida L. and to analyze the genetic diversity of flowering dogwood cultivars and breeding lines, along with other related Cornus species.
Abundant, co-dominant simple sequence repeats (SSRs) markers can be used for constructing genetic linkage maps in marker-assisted breeding programs. Enrichment methods for SSR motifs were optimized with the ultimate aim of developing numerous loci for disease resistance mapping and cultivar identification for flowering dogwood (C. florida L.). Small insert libraries using four motifs (GT, CT, TTG and AAC) were constructed. Colony PCR of 2208 selected clones with two vector universal primers and one synthetic complementary repeat oligo indicated that about 47% or 1034 of the clones harbored one of the four SSR motifs. Sequencing the putative positive clones confirmed that nearly 99% (1021/1034) of them contained the desired motifs. Of the 871 unique SSR loci, 617 were di-nucleotide repeats (70.8%), and 254 were tri-nucleotide or more repeats (29.2%). In total, 379 SSR loci had perfect structure, 237 have interrupted and 255 have compound structure. Primer pairs were designed for all loci and 351 pairs, or 64.7%, were from (GT)n/(CA)n motif. Most of tri-nucleotide repeats were not used for primer design because of very short length of the repeated units. The 351 SSR primers were used to evaluate 38 flowering dogwood cultivars and lines. Most of the loci (332 out of 351) produced the predicted PCR product. Nineteen did not amplify any products. Additionally, of the 332, 218 revealed polymorphisms between two parents of an F1 cross. These SSR loci constitute a valuable resource of ideal markers for both genetic linkage mapping and gene tagging of flowering dogwood.