The Rubus genus consists of more than 600 species that are distributed globally. Only a few Rubus species, including raspberries and blueberries, have been domesticated. Genetic diversity within and between Rubus species is an important resource for breeding programs. We developed genomic microsatellite markers using an SSR-enriched R. coreanus library to study the diversity of the Rubus species. Microsatellite motifs were discovered in 546 of 646 unique clones, and a dinucleotide repeat was the most frequent (75.3%) type of repeat. From 97 microsatellite loci with reproducible amplicons, we acquired 29 polymorphic microsatellite markers in the Rubus coreanus collection. The transferability values ranged from 59.8% to 84% across six Rubus species, and Rubus parvifolius had the highest transferability value (84%). The average number of alleles and the polymorphism information content were 5.7 and 0.541, respectively, in the R. coreanus collection. The diversity index of R. coreanus was similar to the values reported for other Rubus species. A phylogenetic dendrogram based on SSR profiles revealed that seven Rubus species could be allocated to three groups, and that R. coreanus was genetically close to Rubus crataegifolius (mountain berry). These new microsatellite markers might prove useful in studies of the genetic diversity, population structure, and evolutionary relationships among Rubus species.

Jae Young Song, Xiang-min Piao, Yu-Mi Choi, Gi-An Lee, Jong-Wook Chung, Jung-Ro Lee, Yeonju Jung, Hong-Jae Park, Myung Chul Lee. PBB 2013;1:374-84. http://dx.doi.org/

Proso millet (Panicum miliaceum L.) or broomcorn millet is among the most important food crops to be domesticated by humans; it is widely distributed in America, Europe, and Asia. In this study, we genotyped 578 accessions of P. miliaceum using 37 single-sequence repeat (SSR) markers, to study the genetic diversity and population structure of each accession. We also investigated total phenolic content (TPC) and superoxide dismutase (SOD) activity and performed association analysis using SSR markers. The results showed that genetic diversity and genetic distance were related to geographic location and the fixation index (Fst). Population structure analysis divided the population into three subpopulations. Based on 3 subpopulations, the population is divided into six clusters in consideration of geographical distribution characteristics and agronomic traits. Based on the genetic diversity, population structure, pairwise Fst, and gene flow analyses, we described the topological structure of the six proso millet subpopulations, and the geographic distribution and migration of each cluster. Comparison of the published cluster (cluster 1) with unique germplasms in Japan and South Korea suggested Turkey as a possible secondary center of origin and domestication (cluster 3) for the cluster. We also discovered a cluster domesticated in Nepal (cluster 6) that is adapted to high-latitude and high-altitude cultivation conditions. Differences in phenotypic characteristics, such as TPC, were observed between the clusters. The association analysis showed that TPC was associated with SSR-31, which explained 7.1% of the total variance, respectively. The development of markers associated with TPC and SOD will provide breeders with new tools to improve the quality of proso millet through marker-assisted selection.