作 者 ：WANG Chao, WANG Jian-Bo, SHI Su-Hua, ZHONG Yang
期 刊 ：植物分类学报 2000年 3期
Keywords:Aegilops, Allopolyploid, ITS sequence, Evolution,
Abstract:
Hybridization with subsequent polyploidy is a prominent process in evolution of higher
plants, but few data address the evolution of homeologous sequences after polyploidy. The internal
transcribed spacer (ITS) of nuclear ribosomal DNA (nrDNA) from eleven allopolyploid species in
Aegilops was investigated by PCR amplification and direct sequencing. The sequences obtained were
used to study the evolution of ITS region in allopolyploid species. The length of ITS region varied
from 599 to 606 bp and the number of variable sites was 93, i.e. 51 and 42 for ITS1 and ITS2 re-
spectively. Some polymorphic sites were observed in polyploid species, and this indicated that the
ancestral sequences had not been homogenized completely by concerted evolution. Distance matrix
analysis of diploid and polyploid species by neighbor-joining method, using Triticum monococcum as
outgroup, resulted in well-resolved neighbor-joining tree indicating that the ITS regions of UUMM
and UUSS genome ( sect. Vertebrata) were homogenizing toward those of UU ancestal genome. This
result is in agreement with the results of ctyogenetics of Aegilops. On the other hand, the neighbor-
joining tree including the D-genome group species (sect. Cylindropyrum and sect. Polyeides ) com-
prised three clades (CC-DDCC, UU-DDMM-DDMMSS-DDMMUU and MM-DDMvMv), which sug-
gested that concerted evolution was homogenizing the ITS region of the polyploid derivatives to either
of their ancestors.