Determining the Utility of Simple Sequence Repeat Markers for Examining Genetic Relationships in Pawpaw Varieties

The North American pawpaw [Asimina triloba (L.) Dunal] is a tree fruit native to areas in the eastern United States and is in the early stages of commercial production. Since 1994, Kentucky State University (KSU) has served as the USDA National Clonal Germplasm Repository, or gene bank, for pawpaw. Cultivar loss over the last 100 years may have contributed to an erosion of the genetic base of pawpaw varieties. The assessment of genetic diversity in pawpaw cultivars is therefore an important research priority for the KSU program. In an effort to further examine genetic relationships in pawpaw, simple sequence repeat (SSR) primers were developed by partially sequencing SSR regions in pawpaw. The objective of this study was to determine if recently developed SSR primers for pawpaw could be utilized to examine genetic relationships in pawpaw varieties. Leaf samples were collected from the pawpaw selections Taytwo, Sweet Alice, NC-1, 11-13, 1-23, and three progeny of 11-13 x 1-23. Leaf samples were also collected from a cherimoya (Annona cherimola) tree in the KSU greenhouse; cherimoya is in the same family as pawpaw. DNA was extracted from the leaves using the DNAMITE Plant Kit. Primers B103 and B129 were labeled with FAM and used to amplify SSR products. These products were then separated using a 3130 Applied Biosystems capillary electrophoresis system. Genetic relationships among the pawpaw and cherimoya genotypes were determined