Genetic variation for quality traits in synthetic wheat germplasm

Synthetic hexaploid wheats offer breeders ready access to potentially novel genetic variation associated with the D genome of Aegilops tauschii. In order to assess the application of this germplasm to wheat quality improvement, collections of primary and derived synthetic hexaploid wheat lines were surveyed for traits that determine colour and colour stability in Asian noodles and the frequency of a genetic defect know as late maturity alpha-amylase ( LMA). The range of variation was then compared with bread wheat and durum wheat cultivar collections. Primary synthetics contained substantial genetic variation for quality traits associated with colour and colour stability of Asian noodles including near-zero extremes for polyphenol oxidase and lipoxygenase. These extremes represent a significant advantage compared with current bread wheat cultivars and are similar to the best durum wheats. While alternative strategies for reducing polyphenol oxidase and lipoxygenase are available, the synthetics nevertheless provide a useful resource for wheat breeders attempting to develop improved wheat cultivars for the Asian noodle market. Unfortunately, however, most primary synthetics were prone to late maturity alpha-amylase and mature grain contained unacceptably high levels of alpha-amylase. Elimination of this genetic defect, or selection within breeding populations for low or non-LMA, is both time consuming and labour intensive and presents a significant obstacle to exploitation of variation for other traits. As proof of concept, near-zero polyphenol oxidase (PPO) lines, free from LMA, were recovered from backcross populations involving a high LMA primary synthetic.