Novel resistance to pre-harvest sprouting in Australian wheat from the wild relative Triticum tauschii

The diploid D-genome progenitor of hexaploid wheat, Triticum tauschii (Coss.) Schmahl., was screened to identify mechanisms for resistance to pre-harvest sprouting. A number of promising mechanisms were identified, and transferred to hexaploid wheat via wide-hybridisation. One identified mechanism, an inhibitory phenolic compound present in the bracts surrounding the grain, has been shown to function effectively in synthetic hexaploid wheats. A number of seed-borne dormancy mechanisms were also identified. Expression of embryo dormancy in synthetic hexaploid wheats was demonstrated when compared with non-dormant hexaploid wheat. Effects of the seed coat on dormancy were also studied, with the seed coat of synthetic hexaploids accelerating rather than inhibiting germination. Embryo dormancy was also demonstrated in two `direct-cross' hybrids. The results suggest that a combination of the described mechanisms may produce white wheats with resistance to pre-harvest sprouting adequate for most Australian climatic conditions.