Molecular characterisation of Sicilian Prunus persica cultivars using microsatellites

In Sicily, a large indigenous population of cultivated peaches, nectarines, and platicarpa (flat peaches) shows a wide range of fruit quality and ripening periods. This diverse assortment of local cultivars is a resource, not yet exploited, for breeding programmes. The main purpose of this study was to fingerprint these indigenous accessions and to evaluate the molecular diversity between them. Forty indigenous and nine international accessions were analysed using 15 microsatellite, simple sequence repeat (SSR), markers. Some of the main morphological characteristics, such as flower type, petiole gland shape, flesh colour, and fruit ripening time, of these cultivars were also recorded. The number of alleles per primer pair in the 49 cultivars ranged from 3 to 10 (mean = 5.1), and 36 cultivars showed a unique finger-print. Eleven of 79 alleles were found only in the Sicilian cultivars. For the 40 indigenous accessions analysed, the mean observed heterozygosity was 0.44, and the mean F-index was 0.3, indicating a high level of inbreeding. The level of genetic similarity was estimated using the Nei and Li coefficient and two dendrograms were constructed using the UPGMA method. In the dendrograms, peaches, nectarines and platicarpa from Sicily and elsewhere essentially formed six distinct groups. The 15 SSR markers were useful for detecting homonyms and synonyms, but in some cases did not distinguish indigenous accessions that were phenotypically different. Inbreeding, co-ancestry and mutation are discussed as possible explanations for the co-identity of these microsatellite genotypes.