Genetic characterization of pear varieties revealed by chloroplast DNA sequences

Nucleotide sequences at six noncoding regions of cpDNA (chloroplast DNA), atpB-rbcL spacer, trnL-trnF spacer, accD-psaI spacer, ndhA intron, rp116 intron and rpoC1 intron, were identified for eight pear varieties from five species. A total of 38 mutations such as nucleotide substitution, deletion and insertion were found in more than 5.7 kbp of nucleotide sequences. A cladogram based on the mutations showed four types including one European pear group and three Asian pear groups. Nucleotide sequences at the trnL-trnF were revealed for 33 pear varieties and eight mutations were identified. A cladogram obtained from the data showed that Asian pear varieties were divided into six groups and that intraspecific as well as interspecific diversities existed in Asian pears, whereas European pear varieties were identical with respect to the trnL-trnF region. Maternity analysis of eight pear varieties derived from interspecific crosses was conducted using the trnL-trnF sequences. Four varieties showed different nucleotide sequences from their described female parents, suggesting the possibility of reverse combinations of female and male parents. There was no contradiction between two hybrid varieties and their female parent.