Abstract: 【Objective】As an important agronomic trait, the dwarf character of tree is significant to fruit intensive culture. The dwarf traits of pear originated from variety ‘Le Nain Vert’, a chance seedling of Pyrus communis, is determined by a dominant gene PcDw, which sequence information is still unknown. Development of DNA molecular markers tightly linked to the PcDw locus could provide important information for identifying of this gene.【Method】Using 2 different F₁ populations obtained from ‘Aishengli’בChili’ and ‘2-3’בLvbaoshi’, respectively, as plant materials, 2 pairs of bulks for dwarf type/standard type were sequenced through IIB restriction association site DNA (2b-RAD) technology, and then single nucleotide polymorphism (SNP) markers were detected between the dwarf and standard bulks based on the principle of bulked segregant analysis. After that, those SNPs located on the PcDw mapped chromosome were selected and tested on the whole population to confirm their linkage relationship to the PcDw gene by high-resolution melting (HRM) analysis.【Result】A total of 67 186 260 reads were produced from the 2b-RAD sequencing of the 4 samples (2 pairs of bulks). That means the average reads per sample was 16 796 565. Statistical analysis of the filtered raw reads showed that the average unique tags per sample were 86 810, and the average sequencing depth was 77× which was enough for accurate genotyping. For the 4 libraries, mapping through SOAP software indicated that the high quality reads containing the restriction site accounted for more than 70% of the raw reads, which means the high quality of sequencing. Totally 1 317 polymorphic SNP markers were screened between the dwarf bulks and standard bulks derived from the 2 different populations, and 8 of them were mapped on the PcDw-localized chromosome scaffold00074. Further detection of the 8 SNPs through HRM analysis showed that 2 and 4 SNP markers co-segregated with the PcDw locus were identified from population ‘Aishengli’בChili’ and population ‘2-3’בLvbaoshi’, respectively. According to the different shapes of the melting curves of amplicons, the dwarf/normal phenotype could be distinguished effectively. The recombinants for each marker and the target trait were not found in both of the two populations, which contained 215 and 168 progenies, respectively. 【Conclusion】The combination of 2b-RAD sequencing and HRM analysis technology is an efficient method for exploiting molecular markers of important agronomic traits in fruit trees. In this study, a total of 4 SNP markers co-segregated with the PcDw locus were identified based on this strategy.

Key words: pear, dwarf traits; PcDw, SNP marker, 2b-RAD, HRM