Postdomestication selection of MKK3 shaped seed dormancy and end-use traits in barley.

Anthropogenic selection of grain traits such as dormancy has shaped the developmental trajectories of crops. In cereals, shortening dormancy provides rapid and even postharvest germination, but increases the risk of weather-induced preharvest sprouting, with yearly harvest losses beyond 1 billion dollars. Our understanding of how, why, when, and where cereal dormancy diversification arose is fragmentary. Here, we show in the founder crop barley (Hordeum vulgare) that dormancy is primarily regulated through a mosaic of locus haplotypes comprising copy number variation and inherent kinase activity of Mitogen-activated protein kinase kinase 3 (MKK3). We provide evidence supporting the historical selection of specific MKK3 haplotypes that shaped dormancy levels according to changing climatic pressures and outline a genetic framework for breeders to balance grain dormancy and preharvest sprouting avoidance. Editor's summary: Short seed dormancy durations have been selected during cereal domestication to allow fast and even germination after sowing. However, when dormancy duration is too short, seeds can begin germinating while still attached to the parent plant, a phenomenon known as preharvest sprouting. Jørgensen et al. explored variation in sequences and copy number of barley MKK3, a kinase involved in dormancy regulation. Domesticated barley had more copies of MKK3 than its wild relatives, which generally only had one copy. Additional copies of MKK3 increased transcript levels, whereas sequence variation affected kinase activity. Together, these variations correlate with dormancy duration and preharvest sprouting across global growing regions. This research may help with grain selection for plants suited to their local climate, particularly in regions where preharvest sprouting is common or may become more common with climate change. —Madeleine Seale [ABSTRACT FROM AUTHOR]