No abstract

No abstract

Identifying the physiological traits indirectly selected during the search for high yielding maize hybrids would be useful to guide further improvements. To investigate these traits we focused on the critical period of kernel formation because kernel number is the main yield component affected by breeding. We show that breeding has increased the number of florets per ear and ear growth rate but not vegetative shoot growth rate, suggesting localised effects around the ear. Consistently with this possibility, breeding has increased the net CO2-exchange of the ear leaf in field-grown crops grown at high population densities. This response was largely accounted for by the stronger light interception (which increased photosynthesis) and the reduced rates of respiration of the ear leaf of modern, compared to older hybrids. Modern hybrids showed increased ear leaf area per unit leaf dry matter (specific leaf area), which accounts for the reduced respiratory load per unit leaf area. These observations are consistent with a model where the improved ear leaf CO2-exchange helps the additional florets produced by modern hybrids to survive the critical period of high susceptibility to stress and produce kernels.

No abstract

No abstract