Luxiang Liu: liuluxiang@caas.cn; Hongchun Xiong: xionghongchun@caas.cn

The agronomic traits such as heading date (HD) and grain-related traits are very important factors affecting yield potential in wheat. Based on an early heading (eh1) wheat mutant, we constructed an RIL population and identified a minor QTL for HD on the short arm of chromosome 2A by Bulked Segregant Analysis (BSA). Gene fine mapping using a segregating population of 4894 individuals further delimited it to a 1.70-Mb physical interval which contains 16 high-confidence genes based on IWGSC RefSeq v1.0.

Gene sequences and expression analysis indicated that TraesCS2A02G181200 encoding a C2H2-type zinc finger protein is the best candidate gene that affects HD. Screening our TILLING mutant resource (http://jing411.molbreeding.com) validated the function of TraesCS2A02G181200 in controlling HD. We also analyzed the variations of its putative regulatory sites in wheat natural accession, and identified the allele which was positively selected during wheat breeding.

Meanwhile, we identified a round grain 1 (rg1) wheat mutant with flag leaf morphology change, and found that the gene encodes von Willebrand factor type A (vWA)-/Vwaint domain-containing protein affecting grain size and weight, and flag leaf morphology by map-based cloning. Various missense mutations at sites in the Vwaint domain required for RG1 protein folding result in round grains and short flag leaves with a yellow, degraded apex.

Further protein-protein interaction experiments indicate that RG1 could interact with the key enzyme for biosynthesis of gibberellin/abscisic acid precursor, MCT, and their corresponding levels were decreased in rg1 plants, potentially contributing to round grain and short flag leaf phenotype. Moreover, we have cloned the important dwarfing gene Rht8 from wheat mutants and identified the new allele in Rht8-B1 for regulating plant height.

These studies provide important genetic resources for improving the associated agronomic traits, and therefore facilitating yield enhancement in wheat breeding programs.