The contribution of spike photosynthesis to wheat yield needs to be considered in process-based crop models

•Contribution of spikes photosynthesis to grain yield of wheat was 20%.•No current models explicitly consider contribution of spike photosynthesis to grain.•Simulation results of excluding & including spike contributions are investigated.•APSIM overestimated leaf contribution to compensate neglection of spike contribution.•Most current models may simulate wheat yield correctly partly for the wrong reasons.