Crops under past diversification and ongoing climate change: More than selection on nuclear genes for flowering.

Abstract

Diversification and breeding following domestication and current climate change across the globe are the two most significant events experienced by major crops. Diversification of crops from their wild ancestors has favored dramatic changes in the plant's sensitivity to environment, significantly in transducing light inputs to the circadian clock, which allowed the growth of major crops in the shorter growing season in the Northern hemisphere. Historically, mutants and quantitative trait loci (QTL) mapping have facilitated the identification and cloning of genes underlying major changes of the clock and flowering regulation. Recent studies suggest that thermal plasticity of circadian clock output, not just the core genes that follow temperature compensation, was also under selection during diversification and breeding. Wild alleles that accelerate output rhythmicity could be beneficial for crop resilience. Furthermore, wild alleles with beneficial and flowering-independent effects under stress indicate their possible role in maintaining a balanced source-sink relationship, allowing productivity under climatic change. Because the chloroplast genome also regulates the plasticity of the clock output, mapping populations including cytonuclear interactions should be utilized in an integrated field and clock phenomics framework. We highlight the need to integrate physiological and developmental approaches (Physio-Devo) to gain a better understanding while re-domesticating wild gene alleles into modern cultivars to increase their robustness under abiotic heat and drought stresses.