Beyond Averaging: Pleiotropic effects of Dry2.2 expose the evolution of growth bet-hedging in barley
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Rationale
Developing climate-resilient crops requires understanding the developmental and physiological mechanisms governing responses to unpredictable environmental stresses. While agricultural selection historically favored phenotypic uniformity, highly volatile conditions can favor risk-spreading “bet-hedging”. However, because standard genetic mapping relies on shifting plot-level averages, loci controlling population-level variance remain cryptic.
Methods
We investigated the pleiotropic effects of the Dry2.2 quantitative trait locus (candidate gene HvCEN ) using an allelic series of wild barley ( Hordeum vulgare ssp. spontaneum ) introgressions housed in distinct cultivated backgrounds, evaluated via high-resolution single-plant physiological phenotyping and mini-plot field trials.
Results
Specific wild alleles confer robust developmental canalization under water limitation, maintain harvest traits, stabilize vascular lignification, and drive a uniform senescence escape strategy. Conversely, carriers of cultivated alleles deploy a bet-hedging strategy under stress, more than doubling inter-plant developmental variation (volume, maturity timing). This variance-driven strategy relies on epistatic interactions, rendering Dry2.2 invisible to traditional mean-centric GWAS plots.
Conclusion
Improving crop resilience in volatile climates requires expanding selection focus beyond static, plot-level averages to include the active genetic design of population-level variance strategies.
