Identification of a walnut (Juglans regia L.) germplasm collection and evaluation of their genetic variability by microsatellite markers

摘要

The characterization and evaluation of walnut ( Juglans regia ) germplasm constitute important aspects of taxonomic analysis and are valuable tools for breeding programs. In this work, a collection of 57 common walnut cultivars, mainly coming from Spain and the USA, has been studied with microsatellite markers. To carry out this work, 32 primer pairs flanking simple sequence repeats previously developed in Juglans nigra were screened to select the loci that presented high polymorphism and that were easier to score. The 19 selected microsatellite markers allowed the discrimination of the studied cultivars, with a total of 97 alleles detected and an average of 5 alleles per locus, confirming that these markers are more suitable tools for walnut identification than other molecular markers studied previously. The genetic similarity estimated from the molecular data clearly separated the Spanish walnuts from the Californian genotypes. Allelic data are presented for use as size standards to assist in correcting laboratory-tolaboratory variation of allele size calling. Some of them are compared with previous results published and the discrepancies found are discussed.