Using SSR Markers to Determine Genetic Diversity In Six Pawpaw [Asimina triloba (L.) Dunal] Populations From Five States

Pawpaw [Asimina triloba (L.) Dunal] is a native understory tree-fruit in the eastern region of the United States that is in the early stages of commercial production. Kentucky State University (KSU) in Frankfort, Kentucky is the site for the USDA National Clonal Germplasm Repository for pawpaw (Asimina) species, containing over 2000 accessions from 17 different states. Assessment of genetic diversity and collection of unique pawpaw genotypes are important research priorities for the repository. The objective of this study is to use microsatellite (SSR) markers to examine the genetic diversity in six pawpaw populations in the KSU-USDA repository orchard (IN-1, IN-2, KY, MD, NY, and WV). These populations consist of 10 trees from Washington Co., IN (IN-1), 8 trees from Decatur Co., IN (IN-2), 23 trees from Tompkins Co., NY, 13 trees from Tyler Co., WV, 14 trees from Talbot Co., MD, and 20 trees from Fayette Co., KY. Leaf samples were collected from trees in each population and DNA was extracted using the DNAmite Plant Kit. Primers B3, B103, B108, B117, B129, C104, C108, C109, G103, G119, G121, and G124 labeled with FAM or HEX were used to amplify SSR products, and products were separated with a 3130 Applied Biosystems capillary electrophoresis system. The software program Power Marker was used to examine genetic relationships among the pawpaw populations. The SSR markers generated showed significant genetic variation among the pawpaw populations. Several unique genotypes in the populations should be further evaluated by KSU as potential cultivars.