Beyond Averaging: Pleiotropic effects of Dry2.2 expose the evolution of growth bet-hedging in barley

Abstract

RationaleDeveloping 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. MethodsWe 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. ResultsSpecific 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. ConclusionImproving 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.