DNA Markers and Molecular Breeding in Pear and Other Rosaceae Fruit Trees

Pear (Pyrus spp.) is one of the most important edible fruits belonging to the family Rosaceae. DNA markers, molecular genetics and genomics, and molecular breeding of pear have greatly progressed over the last few decades. The development of reliable DNA markers, such as simple sequence repeats and single nucleotide polymorphisms, has allowed DNA profiling of pear accessions, assessment of the genetic diversity within pear species, and analyses of phylogenetic relationships among pear species. Reference genetic linkage maps and genome-wide molecular markers have enabled practical marker-assisted selection for resistance to black spot and/or pear scab diseases, self-compatibility, harvest time, and fruit skin color in Japanese pear breeding programs. Molecular breeding has been shown to more than triple the selection efficiency of practical breeding compared with conventional breeding. Furthermore, breeding programs using two novel genomics-based approaches—genome-wide association studies and genomic selection—focusing on fruit quality and texture, and quantitative traits for breeding, are in progress. Co-linearity and functional synteny have been identified between pear and apple (Malus × domestica Borkh), and have been used to efficiently predict the function of a gene of interest and develop selection markers in related species.