Tetraploid wheat (Triticum turgidum L.) is an important species within the genus Triticum and harbors many desirable agronomic traits. The classification, origin, and evolution of tetraploid wheat remain confused and controversial, resulting in useless germplasm resources. Two classification systems for tetraploid wheat are widely used: 1) tetraploid wheat comprises two species; 2) all forms of tetraploid wheat are classified as one species. The present study aimed to reassess the classification of tetraploid wheat using phylogenetic analysis of nuclear rDNA internal transcribed spacer region (ITS) sequence data, fluorescence in situ hybridization (FISH) karyotyping, and observation of meiotic pairing behavior in F1 hybrids. Network analysis of ITS sequences indicates that tetraploid wheat was not closely related to other Triticeae species with the exception of Aegilops speltoides and Ae. sharonensis. Phylogenetic analysis of ITS sequences and FISH show that Triticum turgidum and T. timopheevii clustered on distinct branches, and meiotic pairing in F1 hybrids of these species showed a high frequency of univalents. Meiotic behavior of F1 hybrids among forms of T. turgidum revealed a low number of univalents (means < 2) except for T. turgidum ssp. dicoccoides. The significant variation on chromosomes 1A, 2A, 5A, 1B, 2B, 3B, and 6B in the FISH hybridization patterns were observed between T. turgidum ssp. dicoccoides and other T. turgidum accessions. Furthermore, the results of ITS phylogenetic analyses correspond closely with observations of meiotic behavior and FISH karyotyping. The present results indicate that T. turgidum and T. timopheevii are two distantly related species of different origins. Triticum turgidum ssp. dicoccoides should be maintained as a subspecies of T. turgidum whereas other forms of T. turgidum should be reclassified as varieties.

Tropical and subtropical Caulerpa species are epidemic to northern and southern Taiwan seashore. We here describe the molecular characteristics of rRNA gene, including the internal transcribed spacers (ITS) in this genus and a comparison was made with associated species sequences registered in the GenBank. A total of nine specimens (C. racemosa var. microphysa, macrophysa, peltata, laetevirens, C. serrulata and C. elongata) were investigated. Samples were collected and distinguished first from morphological characteristics. The genomic DNA was individually extracted using CTAB protocol. To amplify the 18S rRNA, ITS1, 5.8S rRNA, ITS2 and 28S rRNA sequences, a primer pair NS7 and ITS4, sequences located in nuclear rRNA region, was used. The range of 980–1100 bp DNA fragment from genomic DNA of individual plant was generated from polymerase chain reaction (PCR). Amplified fragments were sequenced automatically with ABI sequencer. The sequences were aligned with those of other Caulerpa species retrieved from the GenBank. The phylogenetic tree was constructed using Clustal method. The comparison of whole sequence and 18S rRNA and ITS1 region among these specimens shows that the interspecies divergence within C. racemosa var. microphysa, macrophysa, peltata and laetevirens is larger than those of intraspecies of C. taxifolia, C. serrulata and C. elongata. It is supposed that they (C. racemosa var. microphysa, macrophysa, peltata and laetevirens) should be in the position of different species in Caulerpa genus from the present rRNA sequences analysis. The sequences of 5.8S region are shown more conserve than that of 18S region. The identity of ITS1 and ITS2 regions in present species are low, comparing with C. taxifolia, C. maxicana.