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Wheat Information
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Number 85: 52-55 (1997)
Proposal
Nomenclature
in Triticeae with emphasis on D genome diploid species
P.K. Gupta
Department of Agricultural Botany, CCS University, Meerut,
India
Yen et al.(1997), in the latest issue of WIS (No. 84: 56-59),
discussed the issue of nomenclature of D genome diploid species of
the tribe Triticeae. This was necessitated to clarify the confusion
due to the common usage of two different names, namely Aegilops
squarrosa L. and Triticum tauschii (Cosson) Schmal for the
same species (D genome diploid species). The issue is also partly
relevant to a bigger question asking whether Aegilops L. be
retained as a separate genus or merged in an enlarged genus
Triticum L. emend Bowden. We earlier discussed this issue in
some detail (Gupta and Baum 1986), which escaped the attention of Yen
et al. (1997), while dealing with the problem. Therefore, we like to
add to the present discussion, the genesis of the recent usage of the
name T. tauschii for D genome species in preference to Ae.
squarrosa by a group of cytogeneticists during the last more than
35 years. Yen et al. (1997), while outlining the history of the
nomenclature of D genome species, emphasized that Ae. tauschii
and T. tauschii are both valid scientific names for the D
genome diploid species. However, the usage of T. tauschii for
the D genome diploid species in recent years is neither due to the
validity and/or priority of this name, nor due to rejection of Ae.
squarrosa as an illegitimate name. Instead, the known
evolutionary history of bread wheat, and the nomenclature of hybrids,
were used to suggest that the complete genus Aegilops be
merged in an enlarged genus Triticum. Consequently, T.
tauschii was suggested as the new name for the erstwhile popular,
though illegitimate name, Ae. squarrosa.
As discussed by us earlier (Gupta and Baum. 1986), Bowden (1959)
regarded hexaploid wheat, T. aestivum L. as a hybrid for
nomenclatural purposes. Since at that time the three diploid
progenitors of hexaploid bread wheat were known to be T.
monococcum, Ae. speltoides and Ae. squarrosa with
some certainty, Bowden (1959) argued as follows: "the parents of
hybrids or the parents of species of hybrid origin and the hybrids or
the species of hybrid origin must be included in separate taxa at the
same rank". Therefore, he had two options, either to place tetraploid
wheat, hexaploid wheat and the three diploid progenitors in separate
genera (same rank at the generic level), or in separate species of
the same genus (same level at the species level). He accepted the
latter alternative to allow minimum disturbance to the existing
species of the genus Triticum. Consequently, he proposed
that Ae. speltoides and Ae. squarrosa be treated as
species within the genus Triticum. This was done by merging
the whole genus Aegilops into an enlarged genus
Triticum L. emend Bowden. Consequently, new names were proposed
for all diploid and polypIoid Aegilops species. We realized
that the above argument used by Bowden (1959) was applicable only to
nothogenera, and not to the established botanical genera
like Triticum L. and Aegilops L. (Gupta and Baum
1986). We, therefore, believed that it was neither necessary nor
appropriate to merge Aegilops with Triticum, by
treating Triticum aestivum as a hybrid that originated from
three diploid species. Our contention found support
from a note in the Article H.3.4. of the code, which reads as
follows: "taxa, which are believed to be of hybrid origin need not be
designated as nothotaxa".
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