Molecular phylogeny of Chinese vegetable mustard (<Emphasis Type="Italic">Brassica juncea</Emphasis>) based on the internal transcribed spacers (ITS) of nuclear ribosomal DNA |
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Authors: | Xiao-Hua Qi Ming-Fang Zhang Jing-Hua Yang |
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Institution: | (1) Laboratory of Genetic Resources and Functional Improvement for Horticultural Plant, Department of Horticultural Science, Zhejiang University, Hangzhou, 310029, P.R. China;(2) Laboratory of Horticultural Plant Growth, Development and Biotechnology, Ministry of Agriculture, Hangzhou, 310029, P.R. China |
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Abstract: | Sequence variation of nuclear internal transcribed spacer regions of ribosomal DNA (ITS1, 5.8S rRNA and ITS2) from Chinese
vegetable mustards (AB-genome) and its putative parents Brassica rapa (the A-genome) and Brassica nigra (the B-genome) were used to investigate the molecular phylogeny and the probable evolutional pattern of this amphidiploid
species that uniquely formed in China. Totally, 16 accessions of Chinese vegetable mustard those covering nearly all the diverse
variations were included in this study, and together with three accessions of B. rapa and one accession of B. nigra. The results disclosed two strongly supported clades, one containing four accessions of vegetable mustard which have closer
relationship with B-genome species “B.nigra” lineage and the other containing 12 accessions of B. juncea and three A-genome accessions. This classification was in disagreement with the evidence from chloroplast DNA, mitochondrial
DNA, nuclear DNA restriction fragment length polymorphism (RFLP), which suggested that B. juncea was closely related to the A-genome type. For the incongruence, we speculated that the B. juncea crops derived from Chinese have evolved through different recombined events of the diploid morphutypes and evolved unidirectional
concerted evolution. The traditional phenotypic classification of B. juncea was not wholly supported by ITS results, and hence the phylogenetic relationships among these subspecies need to be reconsidered
on molecular level. |
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Keywords: | Brassica juncea Evolution ITS Infraspecific differentiation Phylogenetics |
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