Is synthetic hexaploid wheat a useful germplasm source for increasing grain size and yield in bread wheat breeding

Bread wheat (Triticum aestivum L.) evolved from limited hybridisations between Triticum turgidum L. and Aegilops tauschii Coss., restricting genetic diversity.Human-assisted crossing between these progenitors can be used to create synthetic hexaploid wheat that readily hybridises with bread wheat cultivars, providing an additional source of genetic diversity for breeding.Synthetic hexaploids have been reported to be useful for increasing both grain size and grain yield in bread wheat breeding.The objective of this study was to investigate variation in grain size and yield potential of syntheticderivatives under south-eastern Australian conditions.Twenty-seven synthetic hexaploids were backcrossed to Yitpi, an elite south-eastern Australian bread wheat, with the resulting progeny developed into 27 families of 15 to 48 BC 1 F 4:6 lines.Evaluated at a typically high yielding environment in south-eastern Australia in 2006, under rainfed conditions, mean thousand grain weights of all 27 families were found to be similar to or higher than that of the recurrent parent Yitpi.One family had a thousand grain weight 9.8% above that of Yitpi.Mean grain yields of the families were all lower than that of Yitpi.As 2006 was a drought year, these results indicate that synthetic hexaploids can contribute to increased grain size under a water stressed environment, but further evaluation is required to understand whether significant increases in grain yield can be achieved.