Using microsatellite markers to study the pear (Pyrus) germplazm from the VNIISPK collection

Based on the analysis of SSR loci, the genetic similarity of 32 pear cultivars (Pyrus) from the VNIISPK collection was studied. A cluster analysis of the genetic similarity of genotypes was carried out using 19 microsatellite markers. Based on the data obtained, a dendrogram was constructed using the UPGMA method using the Jacquard coefficient and bootstrap (BP) analysis. The coefficients of pairwise genetic similarity between the varieties ranged from 0.4 (between Podgoryanka and the Bere Russkaya, Mramornaya group) to 0.85 (between Osennyaya Zheltaya and Pervomayskaya). This group had a high BP level– 100% and a close genetic distance – 0.85), and the reliability level (BP,%) was indicated on the dendrogram at a value of more than 50%. According to the clustering results, the pear samples did not form large groups with high BP, which indicated the sufficient genetic diversity of the studied cultivars. There are only three small groups with high BP. Two of them combined two cultivars with a common origin. Thus, Bere Russkaya and Mramornaya, which are descendants from the crossing of Bere Zimnya Michurina × Lesnaya Krasavitsa, joined into one cluster with BP 82. Another group with BP 92 united Viliya and Zaveya, which also have the same origin ([Belorusskaya Pozdnya × (Bere Seraya × Dulya Ostzeyskaya)] × Maslyanaya Ro). The third group combined the cultivars Osennyaya Zheltaya (origin is not known) and Pervomayskaya (Doch Zari × Pozdnya MOSVIR) with BP 100 and the cultivar Prosto Maria ([Belorusskaya Pozdnya × (Bere Seraya × Dulya Ostzeyskaya)] × Maslyanaya Ro) with BP 100 adjoins them at a extended genetic distance. There is no obvious similarity in origin in this cluster. The SSR-analysis method opens up broad prospects in studying the genetic similarity of cultivars.

Elucidating the contribution of wild related species on autochthonous pear germplasm: A case study from Mount Etna

The pear (genus Pyrus) is one of the most ancient and widely cultivated tree fruit crops in temperate climates. The Mount Etna area claims a large number of pear varieties differentiated due to a long history of cultivation and environmental variability, making this area particularly suitable for genetic studies. Ninety-five pear individuals were genotyped using the simple sequence repeat (SSR) methodology interrogating both the nuclear (nDNA) and chloroplast DNA (cpDNA) to combine an investigation of maternal inheritance of chloroplast SSRs (cpSSRs) with the high informativity of nuclear SSRs (nSSRs). The germplasm was selected ad hoc to include wild genotypes, local varieties, and national and international cultivated varieties. The objectives of this study were as follows: (i) estimate the level of differentiation within local varieties; (ii) elucidate the phylogenetic relationships between the cultivated genotypes and wild accessions; and (iii) estimate the potential genetic flow and the relationship among the germplasms in our analysis. Eight nSSRs detected a total of 136 alleles with an average minor allelic frequency and observed heterozygosity of 0.29 and 0.65, respectively, whereas cpSSRs allowed identification of eight haplotypes (S4 Table). These results shed light on the genetic relatedness between Italian varieties and wild genotypes. Among the wild species, compared with P. amygdaliformis, few P. pyraster genotypes exhibited higher genetic similarity to local pear varieties. Our analysis revealed the presence of genetic stratification with a 'wild' subpopulation characterizing the genetic makeup of wild species and the international cultivated varieties exhibiting the predominance of the 'cultivated' subpopulation.