Papaya (Carica papaya L.), Caricaceae of tropical fruit trees, as one major fruit crops in Taiwan The phenotype of papaya cultivars/lines are very similar, and not easy to detect between cultivars/lines often causing difficulties in breeding. The genetic relationships among 27 papaya cultivars and lines were examined using 26 simple sequence repeat (SSR) markers. The number of alleles per locus of the SSR markers ranged from 2 to 4 (average 3.12), for a total of 81 alleles. The levels of observed and expected heterozygosity for 81 polymorphic loci varied from 0.07 to 1.00 and from 0.33 to 0.72, averaging 0.20 and 0.55, respectively. The average polymorphism information content values were 0.470. A dendrogram was created according to the 26 SSR markers by the unweighted pair-group method with arithmetic mean. The banding patterns obtained from the SSR primers allowed most of the cultivars and lines to be distinguished, with the exception of vegetative clones. According to the dendrogram, the 27 papaya cultivars and lines were clustered into two main clusters and three individual clusters. As expected, the dendrogram showed that derived cultivars and lines are closely related to their parental cultivars; the genetic relationships between papaya cultivars agree with the genealogy of their breeding history. In conclusion, SSR analysis is an efficient method for papaya cultivar identification and can offer valuable informative characters to identify papaya cultivars.
