使用一个新的分子标记PHYB来解决基于使用叶绿体基因和ITS片段鉴定眼子菜属杂种之间的不一致

Potamogeton is one of the most difficult groups to clarify in aquatic plants, which have an extensive range of interspecific morphological and ecological diversity. Internal transcribed spacer (ITS) of nuclear ribosomal DNA is prevalent for phylogenetic analysis in plants. However, most researches have demonstrated that ITS regions show a high percentage of homoplasy in phylogenetic data sets. In this study, eighteen materials were collected in the genus Potamogeton from China and an incongruence was shown between the rbcL and ITS phylogenies. To solve this discrepancy, we sequenced a novel barcode PHYB gene to improve resolution and accuracy of the phylogenetic relationships. The PHYB phylogenetic analysis successfully resolved the incongruence between the rbcL and ITS phylogenies. In addition, six hybrids were confirmed using the PHYB marker, including P. compressus × P. pusillus, P. octandrus × P. oxyphyllus, P. gramineus × P. lucens, P. distinctus × P. natans, P. distinctus × P. wrightii, and S. pectinata × S. amblyophylla. Whereas, only one hybrid was identified (P. compressus × P. pusillus) for the ITS phylogeny, indicating that ITS homoplasy is present in Potamogeton and ITS regions completely homogenized towards to one parental type. Thus, ITS regions maybe have limited utility in phylogenetic relationships for Potamogeton. It is recommended that a three-locus combination of chloroplast DNA, ITS and PHYB is potential to effectively reveal more robust phylogenetic relationships and species identification.