Will C3 crops enhanced with the C4 CO2-concentrating mechanism live up to their full potential (yield)?

Sustainably feeding the worlds growing population in future is a great challenge and can be achieved only by increasing yield per unit land surface. Efficiency of light interception and biomass partitioning into harvestable parts (harvest index) has been improved substantially via plant breeding in modern crops. The conversion efficiency of intercepted light into biomass still holds promise for yield increase. This conversion efficiency is to a great extent constrained by the metabolic capacity of photosynthesis, defined by the characteristics of its components. Genetic manipulations are increasingly applied to lift these constraints, by improving CO2 or substrate availability for the photosynthetic carbon reduction cycle. Although these manipulations can lead to improved potential growth rates, this increase might be offset by a decrease in performance under stress conditions. In this review, we assess possible positive or negative effects of the introduction of a CO2-concentrating mechanism in C-3 crop species on crop potential productivity and yield robustness.