Transgenic Manipulation of Wheat Quality

Bread wheat has no wild hexaploid progenitor in nature but has been domesticated by humans over the last 10,000 years from natural hybrids of diploid and tetraploid species (Salamini et al 2002). Diploid einkorn and tetraploid emmer wheat were cultivated by Neolithic humans and, together with wild species such as Triticum urartu, Aegilops tauschii, and A. speltoides, formed part of the complex evolutionary path that led to the bread and durum wheats farmed today (Feldmann 2001). Over the last 50 years, developments in breeding methods, together with improvements in chemical inputs and farming practices, have permitted major advances in wheat breeding, exemplified by the many thousands of highly adapted wheat varieties now available with significant yield and quality benefits. Particularly significant was the exploitation of Rht-Bl and Rht-Dl dwarfing genes and the shuttle breeding methods used by the International Maize and Wheat Improvement Center (CIMMYT), Mexico, in the 1950s (Borlaug 1983, Reynolds and Borlaug 2006). The use of wide hybridizations to generate substitution, addition, and translocation lines, together with information on how quantitative trait loci, specific genes, or induced mutations influence end-use quality traits, is now well established in wheat breeding. Complementary progress has been made in research laboratories, where DNA transformation has had a significant impact on our understanding of the roles played by the specific genes controlling quality traits. Genetic modification using recombinant DNA, either originating from within the species gene pool (intra- or cisgenic) or from different species (transgenic), has the potential to drive major improvements in wheat quality.This chapter describes the latest developments in wheat genetic manipulation and how this is providing an understanding of the specific genes regulating quality traits. We also discuss the application of these methods to wheat gluten protein composition and other quality target