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Wheat Information Service
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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