Evaluation of new IRAP markers of pear and their potential application in differentiating bud sports and other Rosaceae species

Abstract

Inter-retrotransposon amplified polymorphisms (IRAP) are one of the main components of the retrotransposon-based molecular marker system, but currently have no applications in pear. In this context, new IRAP markers were developed and used to study the genetic polymorphism of pear cultivars and bud mutants. In total, eight polymorphic IRAP markers were selected in ten genotypes of pear with a wide variation in genetic backgrounds and for further genotypic identification of cultivars and bud sports. A total of 76 alleles with an average of 9.5 per locus were amplified and 96.05 % showed polymorphism. Through genetic structure analysis, 62 pear cultivars were divided into two groups, i.e., Oriental and Occidental pears, with a few samples showing a distinct admixed genetic background. When polymorphic IRAP markers were tested on a total of 33 bud sports and their corresponding parent cultivars, the genetic similarity coefficient ranged from 0.54 to 0.96. Each bud mutation was separated from its original variety, and 92.3 % of bud sports clustered perfectly with their original varieties. Furthermore, the transferability of pear IRAP to apples and other Rosaceae species was very high, ranging from 87.5 to 100 %. Our results demonstrate that IRAP markers are an excellent tool for the study of genetic relationships and comparative genomics analysis in pear and Rosaceae species.