Characterization and Identification of Pawpaw Cultivars and Advanced Selections by Simple Sequence Repeat Markers

Pawpaw [Asimina triloba (L.) Dunal.], a tree fruit native to eastern North America, is in the beginning stages of commercialization. Cultivars available in the early 20th century have been lost, and significant genetic erosion may have occurred. Polymorphic microsatellite marker loci were developed from enriched genomic libraries. Five marker loci were used to fingerprint 28 cultivars and 13 selections. For the 41 genotypes, 102 alleles were amplified and major allele frequency (0.16-0.94), number of genotypes (2-27), and allele size (144-343 bp) varied greatly by locus. Four loci were highly polymorphic, as indicated by values for expected heterozygosity (H(e)), observed heterozygosity (H(o)), and polymorphism information content, but only two alleles were detected at locus Pp-C104. A high level of genetic diversity was observed in the studied genotypes. The H(o) (0.68) and H(e) (0.70) were similar and indicated few null alleles. In the 41 genotypes, 39 unique fingerprints were observed. These new microsatellite marker loci will be useful for cultivar fingerprinting, management of collections, and investigation of genetic diversity in collections and wild populations. Grouping of genotypes in an unweighted pair group method with arithmetic mean dendrogram was generally consistent with their origins.