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Wheat Information
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Number 86: 49-53 (1998)
Proposal
Taxonomic
Issues in Triticum L. and Aegilops L.
L. A.
Morrison
Herbarium, Department of Botany and Plant pathology, Oregon State
University, Corvallis, OR 97331-2092, USA E-mail: alura@peak. org
In two recent issues of WIS, Yen et al. (No. 84:56-59) and Gupta
(No. 85: 52-55) discussed nomenclatural and classification problems
in the wheat complex. Yen et al. reviewed the nomenclature of the
wild diploid D-genome species, establishing that the name is
Aegilops tauschii Coss. or Triticum tauschii
(Cosson) Schmalh., depending on the classification followed.
Gupta recommended that the illegitimate name Ae. squarrosa L.
be conserved to avoid further confusion given its popular usage among
wheat researchers. Using this nomenclatural issue as a launching
point, Gupta also discussed the problems of wheat taxonomy,
particularly those resulting from Bowden's (1959) lumping of
Aegilops into Triticum. He also recommended that a
taxonomy workshop be held at the 9th International Wheat Genetics
Symposium (IWGS) in Saskatoon, Canada (August 2-7, 1998). 1 have
several comments to offer on the issues raised in each of these
articles.
Nomenclature and Classification
When Bowden revised the classification of the wheats, he argued
that "a correct nomenclature" required him to lump Aegilops
into an enlarged genus Triticum. As I have pointed out
elsewhere (Morrison, 1993, 1994), Bowden's argument is flawed because
the rules of the International Code of Botanical Nomenclature (ICBM
Greuter, 1994) govern only the naming of taxonomic entities, playing
no role in the construction of classifications. In short, Bowden's
decision for an emended Triticum was based on his own
assessment of how to show evolutionary relationships (via
hybridization) within a taxonomic treatment of the wheats. This very
important procedural point is relevant to the debate over the names,
Ae. tauschii versus Ae. squarrosa.
Nomenclature for the D-genome species has a long, complicated history
as discussed by Yen et al. (1997) and also by Slageren (1994). 1 will
review several facts as they relate to Gupta's conservation proposal.
The name Ae. squarrosa L. (Linnaeus, 1753) was originally
associated with a Linnaean specimen of Ae. triuncialis which
Linnaeus had labeled "3 squarrosa". Although in
disagreement with the original Linnaean concept, the name Ae.
squarrosa did become associated with the D-genome species. In
1850, Cosson corrected the nomenclature by introducing the name
Ae. tauschii. Due to mistakes of other botanists, usage of the
name Ae. squarrosa for the D-genome species continued into
this century. In his emendment of Triticum, Bowden (1959)
adopted an early Triticum concept of the species and
accordingly used the name T. aegilops P. Beauv. ex Roem. &
Shult. Upon discovering that the name T. aegilops was based on the
misidentified Linnaean specimen of Ae. triuncialis (= T.
triunciale), Bowden (1966) changed the name to T. tauschii
(Coss.) Schmalh. Revisions to Bowden's treatment by Morris and Sears
(1967), Kimber and Sears (1987), and Kimber and Feldman (1987) have
maintained the name T. tauschii, which a review of the genetic
literature will show is now in common use. The name Ae.
squarrosa persists among researchers who ignore the current
monographs of Aegilops by Hammer (1980a,b) and Slageren
(1994), choosing instead to follow the outdated classifications of
Zhukovsky (1928) and Eig (1929), or other genetic and
germplasin-oriented treatments with nomenclatural errors such as
those of Kihara (1954), Chennaveeraiah (1960), and the IBPGR (now
IPGRI) Wheat Prograrmme identification guide authored by J.R.
Witcombe (1983).
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