Physiological adaptive traits are a potential allele reservoir for maize genetic progress under challenging conditions

Phenomic and genomic approaches are required to evaluate the progress of breeding strategies. Here, the authors analyse 65 years of genetic progress in maize, showing that breeders have selected traits with stable effects on yield whereas not for adaptive traits key for climate change adaptation. Combined phenomic and genomic approaches are required to evaluate the margin of progress of breeding strategies. Here, we analyze 65 years of genetic progress in maize yield, which was similar (101 kg ha(-1) year(-1)) across most frequent environmental scenarios in the European growing area. Yield gains were linked to physiologically simple traits (plant phenology and architecture) which indirectly affected reproductive development and light interception in all studied environments, marked by significant genomic signatures of selection. Conversely, studied physiological processes involved in stress adaptation remained phenotypically unchanged (e.g. stomatal conductance and growth sensitivity to drought) and showed no signatures of selection. By selecting for yield, breeders indirectly selected traits with stable effects on yield, but not physiological traits whose effects on yield can be positive or negative depending on environmental conditions. Because yield stability under climate change is desirable, novel breeding strategies may be needed for exploiting alleles governing physiological adaptive traits.

Automated summary

Phenomic and genomic approaches are required to evaluate breeding strategies. The analysis of 65 years of genetic progress in maize shows that breeders have selected traits with stable effects on yield but not for adaptive traits. Simple physiological traits have been linked to yield gains, while traits related to stress adaptation have remained unchanged. New breeding strategies may be needed to exploit alleles governing physiological adaptive traits for yield stability under climate change.