WHEAT BREEDING FOR END-PRODUCT USE (REPRINTED FROM WHEAT - PROSPECTS FOR GLOBAL IMPROVEMENT, 1998)

High grain yield is the primary objective of most wheat breeding progr ams around the world. In some countries, for example Australia and Can ada, a new wheat cultivar must meet a prescribed level of quality befo re it can be registered for commercial production. For most traditiona l uses, wheat quality derives mainly from two interrelated characteris tics: grain hardness and protein content. Grain hardness is a heritabl e 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 s uch as available soil nitrogen and moisture during the growing season. In addition, each end-use requires a specific 'quality' in the protei n. Quality is determined by the molecular structure of the major prote ins of flour which, in turn, controls the interactions of the proteins during the breadmaking process. Durum wheats have the hardest grain t exture and are usually high in protein content. They are especially su ited to the production of pasta because of their highly vitreous grain (high milling yield of semolina), unique combination of storage prote ins for good cooking quality of pasta, and high yellow pigment content required for attractive appearance of cooked product. All three chara cteristics are highly heritable and can be readily improved by convent ional breeding. Recent research has shown that the presence of gamma-g liadin 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 gra in hardness and protein content. The hardest wheats of this class, gen erally highest in protein, are used for pan bread. Considerable progre ss 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 chromat ography 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 n oodles, starch quality is important together with protein quality; thi s feature should be taken into consideration in developing a screening strategy for wheats for this application. Screening tests that reflec t end-use requirements for most of the known products are available, a nd should be applied in testing wheats according to intended use.