Complete chloroplast genome sequences of Wonwhang (Pyrus pyrifolia) and its phylogenetic analysis.

The complete chloroplast genome of Wonwhang (BioSample SAMN05196235), Pyrus pyrifolia, was assembled and analyzed by de novo assembly using whole-genome sequencing data. The accession NC_015996 was used as a reference sequence in this study. The total chloroplast genome size of the Wonwhang was 159,922 bp in length, including a pair of inverted repeat regions (IRs) of 26,392 bp that are separated by a large single-copy region of 72,023 bp and a small single-copy region of 19,235 bp. A total of 132 genes, including 93 protein-coding genes, 31 tRNA genes and eight rRNA genes, were predicted from the chloroplast genomes. Among them, 18 genes occur in IRs, containing nine protein-coding genes, five tRNA genes and four rRNA genes. The GC content of Wonwhang chloroplast genome is 36.6%. The phylogenetic analysis with nine Rosids species and three other species revealed that Wonwhang was clustered with Malus genus.

Identification of Pyrus single nucleotide polymorphisms (SNPs) and evaluation for genetic mapping in European pear and interspecific Pyrus hybrids.

We have used new generation sequencing (NGS) technologies to identify single nucleotide polymorphism (SNP) markers from three European pear (Pyrus communis L.) cultivars and subsequently developed a subset of 1096 pear SNPs into high throughput markers by combining them with the set of 7692 apple SNPs on the IRSC apple Infinium® II 8K array. We then evaluated this apple and pear Infinium® II 9K SNP array for large-scale genotyping in pear across several species, using both pear and apple SNPs. The segregating populations employed for array validation included a segregating population of European pear ('Old Home'×'Louise Bon Jersey') and four interspecific breeding families derived from Asian (P. pyrifolia Nakai and P. bretschneideri Rehd.) and European pear pedigrees. In total, we mapped 857 polymorphic pear markers to construct the first SNP-based genetic maps for pear, comprising 78% of the total pear SNPs included in the array. In addition, 1031 SNP markers derived from apple (13% of the total apple SNPs included in the array) were polymorphic and were mapped in one or more of the pear populations. These results are the first to demonstrate SNP transferability across the genera Malus and Pyrus. Our construction of high density SNP-based and gene-based genetic maps in pear represents an important step towards the identification of chromosomal regions associated with a range of horticultural characters, such as pest and disease resistance, orchard yield and fruit quality.