Q gene variability in wheat species with different spike morphology

Q gene is the major domestication gene of wheat and many questions concerning Q gene genetics, including Q gene variability and its functional influence on phenotype, remain unanswered for the majority of wheat species. Here we crossed wheat species with dominant (Q) and recessive (q) alleles and confirmed that Q gene controls threshability, rachis fragility and spike shape traits. In the present study 18 new Q gene sequences were obtained and the Q gene sequences from 42 di- and polyploid wheat species with variable spike morphology were analyzed. We identified correlation between Q gene variability (coding mutation 329Val/Ile, promoter variability, microRNA172 binding site substitution) and threshability, rachis fragility and spike shape traits in polyploid wheat species. The analysis of 3D structures of q and Q proteins indicated that 329Val/Ile mutation does not affect overall protein structure and likely protein activity. We conclude that alterations in all three regions are essential for the formation of free-threshing non fragile normal phenotype in polyploid wheat.