Wheat breeding for end-product use

Abstract

High grain yield is the primary objective of most wheat breeding programs around the world. In some countries, for example Australia and Canada, a new wheat cultivar must meet a prescribed level of quality before it can be registered for commercial production. For most traditional uses, wheat quality derives mainly from two interrelated characteristics: grain hardness and protein content. Grain hardness is a heritable trait but it can be strongly affected by abnormal weather conditions such as excessive rainfall during the harvest period. Protein content is weakly heritable and strongly dependent on environmental factors such as available soil nitrogen and moisture during the growing season. In addition, each end-use requires a specific 'quality' in the protein. Quality is determined by the molecular structure of the major proteins of flour which, in turn, controls the interactions of the proteins during the breadmaking process. Durum wheats have the hardest grain texture and are usually high in protein content. They are especially suited to the production of pasta because of their highly vitreous grain (high milling yield of semolina), unique combination of storage proteins for good cooking quality of pasta, and high yellow pigment content required for attractive appearance of cooked product. All three characteristics are highly heritable and can be readily improved by conventional breeding. Recent research has shown that the presence of γ-gliadin 45 is a reliable marker of good cooking quality. This marker is now used for screening early generation material in many durum wheat breeding programs. Common (hexaploid) wheats cover a wide range of grain hardness and protein content. The hardest wheats of this class, generally highest in protein, are used for pan bread. Considerable progress has been achieved in research of the molecular properties of flour proteins that are required for highest bread quality. The key protein component in this regard is glutenin. Segregating breeding populations can be screened by electrophoresis or high performance liquid chromatography for the presence of desirable glutenin subunits. Common wheats of medium hardness and lower protein content are used for other types of bread and noodles. Wheats with softest texture and lowest protein are used for cakes and cookies. In some end-uses, e.g., Chinese-type noodles, starch quality is important together with protein quality; this feature should be taken into consideration in developing a screening strategy for wheats for this application. Screening tests that reflect end-use requirements for most of the known products are available, and should be applied in testing wheats according to intended use.