The role of TaMYB10-A1 of wheat (Triticum aestivum L.) in determining grain coat colour and dormancy phenotype

Grain dormancy is an important component of resistance to preharvest sprouting in wheat. Historically, red grain coat colour has been associated with this trait despite clear evidence of wide variation in dormancy amongst both red and white wheat varieties. Whereas the genes controlling red grain coat colour have been identified, the mechanism involved in their effect on dormancy has not been determined. This investigation confirmed that the R gene that controls colour in a single gene (Tamyb10-A1b) red wheat, AUS1490 is a Tamyb10 transcription factor. Mutation of Tamyb10-A1 resulted in a white grain coat as well as a reduction in dormancy that was manifest as an early release from dormancy during grain ripening. Red coat colour per se appeared to increase the time to dormancy release and had a cumulative effect in combination with other dormancy loci that are not linked to grain colour. In quantitative terms, the effect of the seed coat colour appeared to be equivalent to that of the dormancy loci present in AUS1490 that are not linked to grain colour. Dormancy release occurred earlier in isolated embryos compared with intact caryopses but was similar in both the mutants and the parental line. This suggests that a component of dormancy that is not associated with the red coat colour is expressed in the embryo and that it interacts with factors in the grain coat to generate the phenotype of the intact caryopsis.