Incongruence between RFLPs of chloroplast DNA and morphological classification in east Asian pear (Pyrus spp)

Polymorphism of chloroplast DNA of 106 accessions of Pyrus (mainly east Asian accessions) was examined. Four haplotypes were observed with the combination of three independent restriction site mutations digested by EcoO109 I, Sal I, and Xba I, respectively. In the occidental pear accessions only the most plesiomorphic type was observed, whereas all four types appeared in the oriental pear accessions. This suggests that the oriental species of Pyrus and occidental ones may have evolved independently. The distribution of four haplotypes in the east Asian pear was quite incongruent with the species or infrageneric classification using mainly morphological characters. Considering the high crossability and much occurrence of suspected interspecific hybrids in wild populations, this disaccord is inferred to be the results of the hybridization and introgression between species.