Submitted to: Genetic Resources and Crop Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 13, 2010
Publication Date: January 1, 2011
Repository URL: http://www.springerlink.com/content/c404m461448gp6r3
Citation: Njuguna, W., Hummer, K.E., Richards, C.M., Davis, T.M., Bassil, N.V. 2011. Genetic diversity of diploid Japanese strawberry species based on microsatellite markers. Genetic Resources and Crop Evolution. http://www.springerlink.com/content/c404m461448gp6r3. 58:1187-1198. Interpretive Summary: The strawberry collection at the United States Department of Agriculture (USDA) - Agricultural Research Service (ARS) - National Clonal Germplasm Repository (NCGR) in Corvallis, Oregon, consists of 1769 accessions from 17 species and 37 countries. Molecular techniques which include DNA-based methods are now routinely used to evaluate genetic diversity in plant collections. The objective of this study was to use molecular markers called “microsatellites” to assess the genetic diversity of two asian wild diploid strawberry species collected in Hokkaido, Japan. Genotypes of the outcrossing species were more diverse than those belonging to the self fertile Asian species. Seedlings from each species grouped except for three genotypes that appear to be hybrids of these two species. Morphological features that were intermediate between the two species further support their hybrid nature. Long term preservation of the two species in our gene bank should include seeds generated from each of the 10 groups generated in this study.
Technical Abstract: The United States Department of Agriculture (USDA) - Agricultural Research Service (ARS) - National Clonal Germplasm Repository (NCGR) in Corvallis, Oregon, is a genebank that preserves strawberry genetic resources. In 2004, representatives of two Japanese diploid species, F. iinumae Makino and F. nipponica Makino were collected during an expedition in Hokkaido, Japan. F. iinumae, or its ancestor, may be a progenitor of the ‘B’ genome for the cultivated octoploid strawberry, F. ×ananassa Duschesne. The objective of this study was to evaluate the genetic diversity of these two species using simple sequence repeat (SSR) markers. Twenty of 82 Fragaria derived SSRs, polymorphic among and within the two species were selected for the genetic analysis of 137 accessions. A significant difference in the genetic diversity between the two species was observed: F. nipponica (0.4542) and F. iinumae (0.1808). Three possible interspecific hybrids were identified from intermediate memberships in the two diploid species groups using the clustering program STRUCTURE. Morphological characterization was done to verify their possible hybrid nature. Principal coordinate analysis followed by non-parametric modal clustering (PCO-MC) grouped accessions into two clusters representing the two diploid species. Further clustering within the species groups using STRUCTURAMA resulted in seven subclusters within F. iinumae and three in F. nipponica, which may represent lineages useful for long term preservation. An octoploid accession was identified from SSR analysis and its ploidy confirmed by flow cytometry. Long term preservation of the species populations and the finding of a limited number of hybrids on the island are discussed.