Mapping of Genetic Factors That Determine Economically Important Traits of Pear (Pyrus) and Marker-Assisted Selection Techniques

DNA marker technology, being an alternative to classical hybrid selection approach, is a rapid method for identifying genes and loci associated with breeding-important traits at the early stages of ontogenesis, and, consequently, represents an approach for intensifying the breeding process. This review presents an overview of the studies on the identification of the economically important traits in the pear genome, as well as the development and use of marker-assisted selection (MAS) techniques. To date, a number of genetic factors have been identified in the pear genome, including the resistance to diseases and pests, namely, the resistance to European pear scab (V. pirina Aderh) and Asian pear scab (V. nashicola), to black spot (Alternaria alternata (Fr.) Keissler) and brown spot (Stemphylium vesicarium) disease, fire blight (Erwinia amylovora), pear psylla (Cacopsylla pyri), pear slug (Caliroa cerasi), pear blister mite (Eriophyes pyri), self-incompatibility locus, and dwarf trait gene. Major genes and quantitative trait loci (QTLs) for the fruit quality characteristics have also been identified, namely those controlling fruit skin color and fruit russeting, fruit size and weight, taste, the level of ethylene production, and harvest time. It should be noted that Russian studies in this field are limited to the validation and use of MAS techniques developed abroad. According to the experience of Japanese researchers, the use of MAS for several key traits had considerably increased the efficiency of breeding process. Despite the currently limited list of MAS techniques for pears, the high pace of genome research guarantees fairly rapid development of new methods in the future. In combination with new breeding technologies (NBT), the use of MAS for pear is a promising trend in breeding.