Photosynthesis-driven yield gains in global wheat breeding trials

Increasing wheat yields is critical to meet the demands of a growing population and ensure socioeconomic stability. Rising photosynthesis is being proposed as a promising avenue to increase wheat yields, but evidence for this is conflicting across studies. To test the viability of this hypothesis, here we report a systematic and quantitative literature review examining the association between historic yield increases due to breeding that occurred over 129 years (1890–2019) across the globe and light-saturated photosynthesis (A_sat) for 273 wheat commercial varieties released to farmers in five continents. A positive and highly significant relationship between trial-corrected grain yield and cultivars’ year of release (YOR) was found globally (R² = 0.56), with an annual rate of yield increase of 0.84%. Trial-corrected seed-fill A_sat increased globally at a pace of 0.58% year⁻¹, and this association was the strongest among the examined four phenological stages. Detrended (from YOR), trial-corrected grain yield and A_sat were found to be correlated, with this association being significant only during seed-fill. The analysis also suggests that historical yield gains may also have been achieved by an increase in water uptake during seed-fill, but it points to the need for more standardized protocols for measuring gas exchange in such vintage/era studies. Overall, these insights indicate that breeding for higher wheat yields was accompanied by physiological alterations to improve A_sat and, possibly, increase water use during the critical seed-fill period, two traits that are also likely to enhance wheat climate resilience.