Exploration of Triticeae seed storage proteins for improvement of wheat end-product quality

The seed storage proteins (SSPs) of cultivated wheat (Triticum aestivum and T. durum), namely, glutenin and gliadin, impart viscoelastic properties to bread dough, making wheat well suited for bread-making. Extensive studies on wheat SSPs have been carried out and revealed genetic diversity among wheat cultivars. Here, we review the studies of SSPs from more exotic species in the Triticeae tribe, primarily based on our own recent studies. SSPs of barley (Hordeum vulgare), homologous to those in wheat, exhibit quite different properties to wheat SSPs and do not produce viscoelastic dough. However, SSPs of a wild barley species (H. chilense) possess similar characteristics to the proteins of wheat. SSPs of rye (Secale cereale) substituted for wheat SSPs result in inferior quality. SSPs of Aegilops searsii and Ae. longissima have positive effects on quality, while Ae. umbellulata and Ae. geniculata (U-g genome) SSPs have a negative effect on bread-making quality. SSPs located on chromosome 1 M-g of Ae. geniculata and a chromosome 1E of Thinopyrum elongatum have positive effects in addition lines but not in substitution lines for chromosome 1D of wheat. In contrast, SSPs of Th. intermedium have positive effects, even in cases of substitution for chromosome 1D of wheat, indicating promising potential for improvement of bread-making quality of wheat. Based on these results, we discuss the possibilities for utilizing the genetic variation of exotic Triticeae species for breeding improved quality traits in wheat.