A novel wheat q' allele identified by forward genetic in silico TILLING

The major wheat domestication allele Q (encoding an APETALA2 like transcription factor) is responsible for the free threshing and square-headed spikes of modern wheat. Wild type q and null q' alleles cause a reversal to the speltoid phenotype. Q pleiotropically affects additional yield and quality traits so genetic variation in Q and its interaction partners remain important for crop improvement. Here we report the discovery of a novel q' allele that contribute to the molecular characterization of Q. This induced mutation cause an Ala→Thr substitution at a highly conserved position in the first of two APETALA2 like domains of the Q protein. The mutation correlates with a speltoid phenotype as expected for a loss of Q function. Thus, it is demonstrated that the first APETALA2 like domain is essential for Q function. The phenotype was discovered in a mutant from an in silico TILLING population and the causative mutation could be identified in the existing sequence data. This report therefore provides an example of a forward genetic application of in silico TILLING.