Zhang Y. Maize breeding for smaller tassels threaten yield under a warming climate.

Breeding programs have increased the yields for major crops, including maize (Zea mays L.), but the suitability of optimized traits to future climates remains unclear. Here, by comparing the responses of 323 elite maize inbred lines from different breeding eras under natural field conditions, we show that while newer lines exhibit higher grain yield than the early released lines under standard growth, the bred trait of reduced tassel size increases the susceptibility of newly released lines to high temperature during flowering. We identified a potential threshold for spikelet/tassel (~700), over which maize can produce a stably high seed set ratio under warm conditions and show that small-tassel (<700 spikelet/tassel) genotypes are now unsuitable in 23.7% of global maize-growing regions. Our work highlights the need to consider possible climate change maladaptation resulting from breeding programs.