Evaluation of New Simple Sequence Repeat Markers for Assessing Pawpaw Genetic Diversity

The North American Pawpaw [Asimina triloba (L.) Dunal] is a tree-fruit native to Kentucky and the southeastern region of the United States. The tree can grow up to 12 meters in height, and bear nutritious fruits which are rich in amino acids. Kentucky State University serves as the USDA National Clonal Germplasm Repository for pawpaw. Research concerning pawpaw genetic diversity and DNA fingerprinting are priorities, and an efficient DNA marker system is essential for conducting the research. The objective of this study was to test if newly developed Simple Sequence Repeat (SSR) DNA markers are polymorphic or monomorphic. The SSR markers were developed based on pawpaw genomic libraries for the di-nucleotide repeat GA, and for tri-nucleotide repeats ATG and AAT. After primary selection with agarose gel electrophoresis system, thirty-three pairs of SSR markers were selected for further Polymerase Chain Reaction (PCR) with DNA extracted from different pawpaw cultivars. Twenty SSR primers were labeled with FAM or HEX for further study and used to amplify 10 pawpaw varieties. The SSR-PCR products were separated using a 3130 Applied Biosystems capillary electrophoresis system. The observed number of alleles at each locus, sizes of the alleles, number of genotypes, and allele scoring quality of the markers will be reported.