Abstract
ABSTRACTSimple sequence repeat (SSRs) markers derived from Malus were used to assess their transferability in the analysis of the genetic diversity and relationship of some Pyrus species. All studied microsatellite loci produced fragments and were polymorphic among the studied samples. Fifty-one allelic variants were detected at eight SSR loci, ranging from five (MS14h03, CH02b10 and CH03g06) to nine (CH02h11a), with a mean of 6.37 alleles per locus. A relatively high level of diversity was recorded among the studied accessions. The average of Shannon's index (I) was 1.04. The Dice genetic similarity coefficient ranged greatly and ‘Khoj 1’ (a member of P. communis) and ‘Shinko’ (a cultivar belonging to P. pyrifolia) had the lowest (0.21) values, while ‘Chojuro’ and ‘Nijisseiki’, two cultivars belonging to P. pyrifolia, had the highest genetic similarity (0.97) among the studied samples. Bayesian cluster analysis and principal coordinates analysis plot separated the P. pyrifolia samples from other species, and formed three distinct groups, indicating high genetic differences between P. pyrifolia and other studied pear species. Several private alleles were observed in some of the studied species that would be of great importance for species identification. Furthermore, in 23 samples, more than two alleles were observed in the CH04e03 locus, indicating presence of locus duplication in these samples. Our observations suggest that, for this locus, at least two homologous chromosomes or genomic regions may be presented in the genome of some pear samples.
Highlights
Pear (Pyrus spp.), apple (Malus domestica Borkh.) and quince (Cydonia oblonga M.) are three main commercial species in the Rosaceae family, subfamily Pomoideae
Yamamoto et al [6] observed that Simple sequence repeats (SSRs) from apple produced discrete amplified fragments in pear accessions and reported that these loci can be utilized for the evaluation of genetic diversity in Pyrus spp
Our observations suggest that at least two homologous chromosomes or genomic regions exist for this locus in some of the studied pear genomes
Summary
Pear (Pyrus spp.), apple (Malus domestica Borkh.) and quince (Cydonia oblonga M.) are three main commercial species in the Rosaceae family, subfamily Pomoideae. In comparison with other fruit species of Rosaceae, pear has been less subjected to molecular investigations and its genetic resources are neither completely recognized nor exploited This is somewhat due to the wide crossing has occurred among different species of this genus, which resulted in the high heterozygosity and low phenotypic diversity among various Pyrus species and subsequently made the estimation of genetic diversity in this genus difficult [6]. Simple sequence repeats (SSRs), a popular type of molecular markers, are versatile tools and have potential to be used in genetic diversity studies, germplasm characterization, cultivar discrimination, identification of progenies from different crosses, detection of duplications and genetic fingerprinting among different plants. Eight SSR primer pairs developed from apple were used to assess their transferability and to evaluate the genetic diversity and relationship of 47 accessions of five Pyrus species
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