Assessing Genetic Diversity of American Wildrice (Zizania palustris L.) with a Set of Highly Polymorphic SSR Markers.

American wildrice is a crop still undergoing domestication. Within its proposed center of diversity (the Great Lakes region of the North American continent), there are still many naturally occurring, populations of wildrice in lakes and rivers.  These populations are considered to be highly heterogeneous because wildrice is a cross-pollinated species. To date, only a few studies have attempted to quantify and compare the genetic diversity of wildrice. SSR markers were developed from genomic DNA sequences of a related species, Zizania texana, which were known to contain SSR (simple sequence repeat) sequences. Eleven sets of marker primers that were able to amplify Z. palustris DNA were used to estimate the genetic diversity among  several populations, including wild accessions, cultivars, and breeding populations. Results for the first seven populations tested (N=45 to 52 per population) revealed 384 alleles among the eleven markers, ranging from 24 to 53 alleles per locus. Each population tested had a number of alleles (range: 9 to 29) that were unique to it and no other. A total of 126 unique alleles were distributed across all seven populations. Polymorphic information content (PIC) values were estimated from allele frequencies for each marker. They averaged 0.70 (range: 0.45 to 0.93). Allele frequencies were also used to calculate Nei72 genetic distance coefficients. One breeding population that was subjected to more rigorous selection had the fewest unique alleles, and also had greater distance from the wild populations. Results show that a great deal of genetic diversity is contained within wild populations, and considerable genetic diversity remains within breeding populations.