Genetic modulation of yield and phenotypic plasticity of yield in winter wheat

For winter wheat in the US Central Great Plains, phenotypic plasticity of yield is agronomically adaptive, that is, genotypes with higher plasticity have higher yield in high yielding environments with no tradeoff in stressful, low yielding environments. Using data from variety trials conducted between 2000 and 2022 and cultivars released between 1991 and 2022, we explored time trends in phenotypic plasticity and heritability of yield. Given that yield plasticity is agronomically adaptive in the Great Plains, we hypothesize that (i) newer cultivars will have higher yield plasticity; (ii) heritability of yield is declining in the time series; and (iii) genomic regions associated with yield depend on the environment and do not fully overlap with those associated with phenotypic plasticity of yield. Breeding for yield and agronomic adaptation increased phenotypic plasticity of yield at 0.5% year-1; broad sense heritability of yield decreased from 0.23 in 1993 to 0.15 in 2017. Genome-wide association analysis shows genomic regions associated with yield varied between high yielding and stressful environments and were partially independent of those associated with yield plasticity. Newer cultivars have a higher frequency of alleles associated with yield and its plasticity. We discuss implications for breeding and agronomy aimed at improving wheat phenotypes.