Application of simple sequence repeats in determining the genetic relationships of cultivars used in sweet potato polycross breeding in Taiwan

Simple sequence repeats (SSRs) were used to analyze the genetic diversity and genetic relationships among sweet potato [lpomoea batatas (L.) Lam.] cultivars. These cultivars consisted of Chinese and Japanese materials, landraces as well as cultivars derived either from hybrid or polycross breeding in Taiwan. SSR analysis from eight primer pairs revealed a total of 20 alleles of which 17 were polymorphic (85.0% polymorphism). An average of 2.5 alleles were obtained per SSR primer pair. On average 2.1 alleles per polymorphic SSR locus were amplified. The construction of genetic relationships using unweighted pair group method with arithmetic mean (UPGMA) and principal coordinate analysis (PCA) demonstrated the capability of simple sequence repeats in sweet potato genotype identification and classification of genetic relationships. The UPGMA clustering and PCA revealed that polycross-derived cultivars possessed high levels of genetic diversity and originated from various genetic resources, and suggested the usefulness of polycross breeding strategy in spite of frequent cross-incompatibility. Moreover, high level of genetic variation in polycross breeding lines would assist in obtaining elite sweet potato materials in the future. In addition, most landraces were distantly related to the Chinese and Japanese materials and probably originated from Java and Brahman.