Potential contribution of increased photosynthetic efficiency to increased yield potential of maize

Rapidly growing global demand for food and feed maize must be met by increased crop production per unit of land area under cultivation. This requires closing the gap between farm and potential yields, as well as continued improvement in potential crop yield. • Over recent decades, conventional breeding has increased maize crop yield mainly by improving the crop’s tolerance to intensification. • Incremental increases in yield of newly released maize lines have been achieved by improving dry matter accumulation as a result of more erect canopy architecture and slower decline of photosynthetic rates during grain-filling. • Breeding has increased maize crop yield without affecting harvest index, maximal photosynthetic capacity or potential yield under non-limiting resources. • Recent maize yield increases resulting from higher biomass accumulation suggest that there is scope for achieving further yield increases by selectively improving maize photosynthetic capacity. • Possible avenues for improving photosynthetic capacity in maize include: (1) breaking the leaf photosynthetic capacity – leaf size paradigm; (2) up-regulating the activity of sedoheptulose-1,7-bisphosphatase in the mesophyll and the capacity for electron transport in the bundle sheath; (3) improving Rubisco turnover rates of high-yielding maize crops; and (4) improving drought tolerance of maize crops