Flora of North America species comparison

Triticum aestivum is the most widely cultivated wheat. Both winter and spring types are grown in the Flora region. In addition to being grown for bread flour, T. aestivum cultivars are used for pastry-grade flour, Oriental-style soft noodles, and cereals.

Club wheats, sometimes called Triticum compactum Host, are cultivated in the Pacific Northwest for export to Asian markets. They have short (3.5-6 cm), compressed spikes, with up to 25 spikelets having 2-6 florets. Their spike shape varies from oblong or oval with uniformly distributed spikelets to club-shaped with spikelets crowded towards the apex.

No wild hexaploid progenitors of Triticum aestivum are known, but the two distinguishing characteristics of wild Tritcum species, fragile rachises breaking into wedge-shaped units and closely appressed glumes, are found in plants cultivated in Tibet and named T. aestivum subsp. tibetanum J.Z. Shao.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Triticum is a genus of approximately 25 wild and domesticated species. It was first cultivated in western Asia at least 9000 years ago and is now the world's most important crop, being planted more widely than any other genus.

Triticum is native to western and central Asia. It includes diploids (A haplome), tetraploids (AB or AG haplomes), and hexaploids (ABD or AAG haplomes). The world's only reserve designed to protect native populations of wild cereals, the Erebuni Reserve, is located just outside Yerevan, Armenia. It is home to three wild species of Triticum: T. araraticum Jakubz., T. boeoticum, and T. urartu.

Only Triticum aestivum, T. durum, and T. spelta are grown commercially in North America, T. aestivum being by far the most important. The remaining species in this treatment are those most frequently grown by North American plant breeders and wheat researchers. None of the species has become an established part of the North American flora, but they may be encountered as escapes near agricultural fields and research stations, or along transportation routes.

Triticum is sometimes treated as including Aegilops, but the taxa in these genera differ morphologically and ecologically. In addition, species of Triticum sensu stricto are unique in possessing the A haplome, of which there are two forms, Au and Ab. Of the other three haplomes present in Triticum, the D haplome is derived from Aegilops tauschii (Dvorak et al. 1998), and the B and G haplomes are derived from A. speltoides Tausch (Giorgi et al. 2003).

The treatment presented here is based on Dorofeev and Migushova's (1979) monograph of Triticum sensu stricto, with some modification. The assignment of species status to domesticated forms is controversial. It is done here for convenience, and to aid in distinguishing between taxa with distinct morphological, ecological, and evolutionary traits. For a genomically based treatment, see Kimber and Sears (1987).

"Spring wheat" and "winter wheat" refer to the growing season. Spring wheat is planted in the spring and harvested in the summer of the same year; winter wheat is planted in the fall and harvested the following summer. "Hard wheat" and "soft wheat" are terms used to describe wheats with flinty or mealy endosperm, respectively. Flinty endosperm has a higher protein content and is harder than mealy endosperm. At the species level, soft wheat refers to Triticum aestivum; hard wheat refers to T. durum. Within T. aestivum, endosperm type also is graded as either soft or hard; it is never as hard (flinty) as in T. durum.

The width of a spike is the distance from one spikelet edge to the other across the two-rowed side of the spike; its thickness is the distance across the frontal face of spikelet, from one edge to the other. The spike and spikelet measurements do not include the awns. The glumes are measured from the base to the shoulder, and do not include any toothed tip.

(Discussion copyrighted by Flora of North America; reprinted with permission.)