Allele Mining for Genome Designing of Pear

Pear is among the most important fruit crops in the world, especially in temperate zones. Elite pear cultivars are adjusted to cold climate and can be grown in temperate zones. Pear juvenile period can last more than 7 years, and therefore, the fruit quality can be tested after a long period. To accelerate the breeding process and improve the understanding of the genetic regulation of important agricultural traits, it is critical to detect the genomic regions that are associated with those traits and can lead to the identification of the casual gene. The main targets of pear-breeding programs are resistance to biotic stress and fruit quality traits. However, due to recent rise in temperatures worldwide and the predictions of future global warming, we expect a reduction in the chilling hours. Sufficient chilling during the dormancy period in the winter is required for deciduous trees, such as pear and apple, to be able to produce sufficient amount of a high-quality fruits. Therefore, pear cultivars that can thrive in warm conditions are in a high demand. Over the last 20 years, pear genomic resources have been remarkably improved, and as a result, the identification of major genes and quantitative trait loci (QTLs) linked to important agronomic traits is more feasible. This allows to develop molecular markers to enable marker-assisted selection in the breeding process and to identify the candidate genes. Although methods to characterize genes such as RNA-seq are common in pear genetic research, functional gene studies are relatively rare in pear due to the long period that required before it is feasible to test reproductive traits. However, recent advances in transient transformation have been reported in pear. This chapter includes most relevant results of QTLs, identified and putative genes associated with resistance to biotic stress, fruit quality, and traits related to vegetative growth and climate adaption. The presented studies can provide tools for genomic selection that can contribute to accelerate pear-breeding programs and provide the knowledge for future functional genomics studies.