Chapter 1 - Botanical features of wheat

Abstract

Wheat plants are grasses belonging to the monocot family Poaceae. Cultivated wheat consists of five species: diploid einkorn (genome AA), tetraploid emmer and durum wheat (AABB), and hexaploid common wheat and spelt (AABBDD). Triticale (AABBRR) is a man-made cross of durum wheat and rye. Wheat grains are produced as dry one-seeded fruits, botanically defined as caryopsis. They consist of five main compartments: Fruit coat (pericarp) (4–5% of grain weight) and seed coat (testa) (1%) are the outer layers and surround the whole grain. The inner compartments (endosperm) comprise the aleurone layer (6–9%) and the starchy endosperm (80–85%). The germ (3%) is located on the dorsal side of the caryopsis. Common wheat and durum wheat have been the target of intense breeding with a specific focus on high grain yield, resistance against diseases and pests, and high quality of end products. Most breeding programs include hybridization of two promising parents, but artificial genetic mutation by irradiation and chemicals or adding and knocking down specific genes or gene segments (genetic engineering) are also possible.