Molecular Analysis of the Genetic Relationship and the Attribution of Some Unsubstantiated Resources of Hawthorn (Crataegus)

Abstract

The genus Crataegus (hawthorn), belonging to the subfamily Maloideae in the Rosaceae family, has a long history of cultivation in China because of its important medicinal values. we carried out a phylogenetic reconstruction with nuclear (ITS) and three intergenic chloroplast DNA sequences (trnH-trnK, trnG-trnS, and psbAtrnH) data using ML and MP to estimate the genetic relationships, chloroplast haplotypes, and the origin of 17 species and 108 accessions of Crataegus and the attribution of some unsubstantiated resources in China. Malus baccata L. and Malus pumila L. were used as outgroups taxa. We further analyzed the basic phylogenetic framework of the genus. Our analyses produced multiple outcomes: (1) Crataegus in northern and southern China were divided into two branches, which had their respective origin relations and different speciation events. Crataegus might have originated in Europe and North America; (2) the classification of most samples based on the molecular data was in good agreement with the morphological classification. However, incongruence between the chloroplast and nuclear data supported the hypothesis of a hybrid origin for Crataegus brettschneideri Schneid, with Crataegus maximowiczii Schneid or its ancestor as the maternal parent and Crataegus pinnatifida Bunge as the male parent; (3) Chloroplast haplotypes and haplotype network graph analyses revealed 15 haplotypes among the specimens. H12 (Crataegus cuneata Sieb.) was a chloroplast ancestral haplotype of Crataegus in southern China, and H14 might be the direct origin haploid of the Pinnatifidae group.