Unlocking Spanish pear genetic diversity: strategies for construction of a national core collection.

Spanish pear germplasm collections are crucial for preservation, research, and breeding efforts. However, genetic diversity and structure is unknown at national level. A coordinated national project analyzed 1251 accessions from 7 Spanish pear collections using an internationally recognized set of 14 SSRs to enhance the utilization of these collections. Key findings included the identification of 760 unique genotypes (490 diploids and 270 triploids). Notably, genotypes represented by a single accession accounted for 49% of the total, indicating high vulnerability of this material. Using a Bayesian clustering method revealed two main genetic groups, G1 containing most foreign cultivars and G2 retaining local Spanish cultivars, which were further divided into two other subgroups using a nested approach, revealing moderate but significant differentiation among them. The populations were renamed according to the origin of the reference samples assigned to each group as 'South' (G1.1), 'Western Europe-1' (G1.2), 'Western Europe-2' (G2.1) and 'No-Pyrus communis' (G2.2). The results led to the creation of a 'generalist' collection, aiming to maximize genetic diversity representativeness, starting with 68 genotypes but expanding to 111 to achieve better allele recovery. This core collection is a valuable resource for genetic studies and conservation, enhancing efforts to preserve pear biodiversity.