Construction of Longan (Dimocarpus longan Lour.) Simple Sequence Repeat Fingerprints and Application in Distinctness, Uniformity and Stability Testing

Simple sequence repeat (SSR) markers are highly polymorphism, good reproducibility, abundant number and co-dominant inheritance, and were considered to be one of the preferred molecular markers for DNA fingerprints in distinctness, uniformity and stability (DUS) testing. In this study, 10 representative Dimocarpus longan Lour (longan) varieties with significant differences were selected from 63 longan varieties according to the morphological characteristics. Based on PCR amplifications of the 10 selected varieties, 24 SSR primers pairs were screened from total 300 SSR primers pairs, to establish SSR fingerprints for all 63 longan varieties. The results showed that a total of 127 alleles were detected in 63 longan varieties, with an average of 5.29 alleles for each pair of primers. The Shannon’s index of the 24 pairs of SSR markers ranged from 0.64 to 1.58, with an average of 1.20. The polymorphism information content of each locus ranged from 0.32 to 0.72, with an average of 0.58. Clustering analysis indicated that most of the varieties with close genetic relationships tended to fall in the same cluster, and only a few in different clusters or sub-clusters. The 63 longan varieties were completely identified by the optimal combination of 6 pairs of SSR primers (LY161, LY252, LY137, LY130, LY25 and LY34). Overall, DNA fingerprints of the 63 longan varieties were constructed based on these 24 pairs of SSR primers. This study may provide a technical support for variety identification and similar variety screening in DUS detection in longan.