Crops under past diversification and ongoing climate change: more than just selection of nuclear genes for flowering.

The article focuses on the evolutionary changes in circadian clock genes and chloroplast genome diversity that have occurred during crop domestication and diversification, and their implications for breeding crops resilient to climate change. It details how mutations in core clock genes, such as PSEUDO-RESPONSE REGULATOR (PRR) and EARLY FLOWERING (EAM) genes, have enabled major crops like barley, rice, soybean, sorghum, and tomato to adapt flowering time and growth to new photoperiods and shorter growing seasons, particularly in the Northern Hemisphere. The review highlights the emerging recognition of chloroplast genome variation (plasmotype diversity) as a significant factor influencing circadian clock output plasticity and plant fitness under heat stress, suggesting that cytonuclear interactions should be integrated into breeding programs. It also emphasizes the potential of reintroducing wild alleles, including those affecting source–sink relationships and clock plasticity, to enhance crop robustness under abiotic stresses such as drought and high temperature.