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Wheat Information Service
Number 90:37-41 (2000)
Research article
Phylogenetic study of five morphological groups of
hexaploid wheat (Triticum aestivum, L. em Thell.) based on
cytological analysis
Wenguang Cao1, G. Scoles and P. Hucl
Department of Plant Sciences, Crop Development Centre, University
of Saskatchewan, 51 Campus Drive, Saskatoon, Sask., Canada S7N
5A8.
Summary
The genetic relationships among the five groups of hexaploid
wheat: common, spelta, macha, vavilovii and semi-wild
wheat (SWW) are not clear although wheat taxonomic and phylogenetic
studies have been conducted for several decades based on
morphological and cytogenetic analyses. A cytological study of a
half-diallel cross involving common, spelta, macha, vavilovii
and semi-wild wheat was conducted to assess phylogenetic
relationships among these five morphological groups of hexaploid
wheat. C-value coefficients of genetic similarity in this study were
calculated based on the number of chiasmata in hybrids. The
dendrogram based on the C-value coefficients suggests that common
wheat is most closely related to vavilovii followed by spelta
and SWW, and least related to macha.
Key words: Macha, Spelta, Vavilovii, Semi-wild wheat,
Phylogenetic relationships.
Introduction
T. aestivum was divided into six subspecies based on
morphological characters: vulgare, sphaerococcum,
compactum, spelta, macha and vavilovii (MacKey 1966).
However these subspecies have more recently been recognized as groups
within T. aestivum with distinct morphological characteristics
(Barnes and Beard 1992). Among these groups, spelta, vavilovii
and macha have a fragile rachis and are not free-threshing
(Singh et al. 1957).
Recently, another hexaploid wheat, semi-wild wheat (SWW), was found
in Tibet (Shao et al. 1983). This wheat has a spring habit and grows
as a weed in barley and wheat fields. Cytogenetic analysis suggested
that the genomic constitution of SWW was AABBDD because it exhibited
full chromosome pairing and high fertility when crossed with common
wheat (Shao et al. 1983; Chen et al. 1988). Based on meiotic analysis
of F1 hybrids with euploid or double ditelosomics of T.
aestivum cv. Chinese Spring, and also N-banding, Chen et al.
(1988) concluded that the chromosome constitution of SWW was similar
to that of the cultivar Chinese Spring. Morphologically, SWW has a
rachis fragility and a non-free threshing characters which
distinguish it from common wheat. When SWW matures, its spikelets
separate naturally and fall to the ground. Although wheat taxonomic
and phylogenetic studies have been conducted for several decades
based on morphological and cytogenetic analyses, the relationships
among the five groups of hexaploid wheat: common wheat, spelta,
macha, vavilovii and semi-wild wheat (SWW) are not clear. The
objective of this study was to determine the phylogenetic
relationships among these five morphological groups of hexaploid
wheat based on cytological analysis.
1: Corresponding author: Eastern Cereal and Oilseed Research Center,
Agriculture and Agri-Food Canada, BIgd. 50, 960 Carling Ave. Ottawa,
ON K1A 0C6 Canada. (e-mail: caowen@em.agr.ca)
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