Wheat

Triticum spp.

1. Identification and origin

Wheat (Triticum spp.) is a genus of grasses of the Poaceae family, which includes species cultivated since the Neolithic. The agronomically most relevant species are Triticum aestivum L. (common or bread wheat), Triticum durum Desf. (durum wheat) and, on a smaller scale, Triticum monococcum L. and Triticum dicoccum Schrank. Wheat originated in the Fertile Crescent and spread globally as one of the principal food crops.

2. Economic importance

Wheat is one of the most important crops in the world, the dietary staple of a large part of the population. T. aestivum is used above all for breadmaking, pastry and feed, while T. durum is essential for pasta products and semolinas. In Portugal, durum wheat is most prominent in the Alentejo, while common wheat is grown in several dryland and irrigated regions. Its economic value results from high demand, industrial versatility and strategic importance in food security.

3. Botanical characterisation

Triticum spp. plants are annual, with hollow stems and alternate linear leaves. The inflorescence is a spike composed of spikelets arranged along the rachis. The grains are caryopses rich in starch and proteins (particularly glutenins and gliadins). The root system is fasciculate, deep and efficient in the exploitation of water in dryland soils. The morphology and the cycle vary between species and cultivars, influencing climatic adaptation.

4. Soil and climate requirements

Wheat adapts to temperate and Mediterranean climates, with good tolerance of winter cold. It prefers well-drained soils of medium texture, with a pH between 6.0 and 7.5. It is sensitive to waterlogging and to high acidity. Productivity is favoured by adequate autumn–winter rainfall, moderate temperatures during grain filling and good nitrogen availability. Durum wheat requires hotter and drier conditions in the final phase of the cycle.

5. Main pests

• Cereal aphid (Sitobion avenae, Rhopalosiphum padi) — sap sucking and transmission of viruses
• Grain weevil (Sitophilus granarius) — damage to stored grain
• Caterpillars (Helicoverpa armigera, Mythimna unipuncta) — reduction of leaf area
• Frit fly (Oscinella frit) — damage to seedlings and tillers
• Nematodes (Heterodera avenae) — root cysts and reduction of vigour

6. Main diseases

• Brown rust (Puccinia triticina) — leaf pustules and loss of productivity
• Yellow rust (Puccinia striiformis) — yellow stripes and necroses
• Septoria leaf blotch (Zymoseptoria tritici) — leaf spots and reduction of photosynthesis
• Fusarium head blight (Fusarium graminearum, F. culmorum) — bleaching of the spike and mycotoxins
• Powdery mildew (Blumeria graminis f. sp. tritici) — white coating and reduction of vigour

7. General crop management

Wheat management is based on selecting cultivars suited to the climate and the production system (dryland or irrigated). Crop rotation is essential to reduce the pressure of foliar and soilborne diseases. Nitrogen fertilisation should be balanced and adjusted to the productive potential. Certified and treated seed reduces the risks of early diseases. Monitoring of rusts, septoria and aphids is critical at sensitive stages. Harvesting should occur when the grain reaches a moisture level adequate for safe storage.

Bibliographic references

• EPPO Global Database – Triticum spp.
• CABI – Crop Protection Compendium – Triticum spp.
• Curtis, B. C. et al. (2002). Bread Wheat: Improvement and Production. FAO Plant Production and Protection Series.
• Shewry, P. R. (2009). Wheat. Journal of Experimental Botany, 60, 1537–1553.
• Reynolds, M. P. et al. (2012). Improving wheat yield potential. Journal of Experimental Botany, 63, 433–449.