Abstract
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.
Highlights
The pear (Pyrus spp.) is one of the most cultivated fruit crops in temperate zones
Nuclear simple sequence repeat (SSR) markers allowed the identification of nineteen individuals exhibiting three alleles in at least one of the nuclear SSRs (nSSRs)
The nSSRs detected a total of 136 alleles with sizes ranging from 115 to 256 bp with average values of 17 and 0.29 for the number of alleles and the major allele frequency (MAF), respectively (Table 3)
Summary
The pear (Pyrus spp.) is one of the most cultivated fruit crops in temperate zones. Pyrus species are traditionally divided into two groups based on domestication area and geographic distribution. European pears (P. communis) are cultivated mainly in Europe and the U.S, and Asian. Related wild species influence the pear cultivars origin on Mount Etna pears (P. pyrifolia, P. bretschneideri and P. ussuriensis) grow in East Asian countries. The genus Pyrus belongs to the family Rosaceae, subtribe Pyrinae and contains at least 22 widely recognized primary species, all indigenous to Asia, Europe, and the mountainous area of North America. The worldwide production of European pear relies on a few main cultivars released from the late 18th century onward (or derived from those cultivars)
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