New research reveals how genetic changes in the barley MKK3 gene fine-tune seed dormancy, determining whether grains stay dormant or sprout too soon. The findings offer breeders new genetic tools to balance seed dormancy and crop resilience under changing climate conditions. The rise of agriculture was driven by the intentional selection of crops with improved traits. One key trait under selection, particularly in cereal crops, is grain dormancy – the period before which a seed can germinate. In wild cereals, grain dormancy helps ensure plant survival under unpredictable conditions. During domestication, human selection shortened dormancy enabling quick and uniform crop establishment and greater yield. However, shorter dormancy also makes modern cereals like barley more vulnerable to pre-harvest sprouting (PHS), where grains germinate prematurely during warm, wet weather, which can lead to major agricultural losses. As global temperatures rise and extreme weather becomes more frequent, the incidence of PHS and associated crop loss will likely increase.
Despite the importance of grain dormancy to global food security, the evolutionary and molecular mechanisms underlying this trait remain poorly understood. Previous research has shown that variation in the Mitogen-activated protein kinase kinase 3 (MKK3) gene plays a major role in controlling grain dormancy. Morten Jøgensen and colleagues investigated genetic variation in MKK3 across wild and domesticated barley and found that slight amino acid changes in the MKK3 protein lead to big differences in dormancy and PHS resistance. Detailed genetic and molecular analyses revealed that domesticated barley, unlike its wild ancestor, often carries multiple copies of the MKK3 gene, and that this copy number variation in combination with amino acid changes that alter kinase activity is what fine-tunes grain dormancy traits in barley. According to the findings, distinct MKK3 haplotypes have evolved around the world in response to local climates and agricultural practices. For example, hyperactive variants emerged in northern Europe, where barley with low dormancy was favored for malting and beer brewing, while more dormant types persisted in humid and monsoon-prone regions of East Asia to prevent PHS. Although certain MKK3 haplotypes have become regionally prominent by enhancing productivity and grain quality for certain uses and within certain growing conditions, their genetic complexity poses challenges for traditional crossbreeding programs. Jørgensen et al. note that this illustrates the value of pangenomic approaches in identifying variants that could, when introduced into modern genotypes, promote sustainable and resilient crops under changing climate conditions.
