PHYLOGENETIC RELATIONSHIPS OF TWO REPRESENTATIVE LEPIDIUM SPECIES (BRASSICACEAE) IN QINGHAI PROVINCE

Lepidium belongs to Tribe Lepidieae of the family Brassicaceae. There are about 15 species and one variety in China, which are distributed throughout the country. So far, the systematic studies of this genus at the species level still depends on morphological characters, and there is little data on their molecular phylogeny. A total of 162 specimens of Lepidium latifolium and Lepidium obtusum were collected from Qinghai Province. Combined with sequences from GenBank, the phylogenetic relationships of Lepidium were analyzed based on nrITS gene. The results showed that Lepidium clustered into a large Glade (Clade A), in which L. hirtum together with L. campestre as a sister group of L. pmfoliatum formed a sister Glade (98/1) and was located at the bottom. In the middle part, L. densiflorum clustered with L. virginicum (100/1). At the top L. sativum, L. obtusum and L. latifolium L. apetalum L. ruderale formed parallel clades (61/0.83). These results were inconsistent with morphological data. Meanwhile, the haplotype network based on the sequenced nrITS sequences indicated that 6 haplotypes (Hap4-Hap9) of L. obtusum were obtained through a 22-step mutation from haplotype Hapl from L. latifolium, and the initial haplotype (Hap9) was collected in Xining City, followed by one-step mutation into Hap4 which was widely spread in Qinghai Province. Hap4 transformed into other haplotypes by undergoing one-step mutation (Hap6, Hap7 and Hap8) or two-step mutation (Hap5), respectively. These results will provide the basis for future experiments and further accumulate data for molecular systematic studies of the Chinese Lepidium at species level.