To face the impending global food security challenges there is a pressing need to devise innovative breeding strategies for raising crop yields. Here we propose to contribute to this effort by developing strategies and materials that will improve photosynthetic efficiency. Crop yield is determined by the available solar irradiation energy (St), the radiation interception efficiency (εi), the light conversion efficiency (εc) and the harvest index (εp). From this factorial analysis photosynthetic efficiency emerges as the most potent factor for yield improvement. The project therefore aims at developing novel strategies for enhancing photosynthesis. An enhancement of crop photosynthesis would be an important step in improving yield, but in a sustainable manner without sacrificing more arable land for use in agriculture,

The first two subprojects target the leaf, the central organ of photosynthesis in angiosperms. They rely on recent strong experimental and theoretical evidence that leaf form and inner anatomy influence the photosynthetic output of this organ. The two subprojects aim to identify genes that affect leaf morphology and anatomy in a manner that is relevant to photosynthesis and to investigate how and to which degree these genes can be used to optimise the photosynthetic output of leaves. Both sub-projects pursue genetic approaches using well-established model systems (Arabidopsis and Cardamine) that have documented their suitability for an easy identification of genes and their functions. The two model species chosen belong to the Brassicaceae. Since photosynthesis and leaf differentiation are rather conserved in evolution, at least among the angiosperms, the transfer of knowledge from these model systems to the major crop species of this plant family, the Brassicas, should therefore be relatively straightforward.

The third subproject embarks on experimental evolution to improve photosynthesis in the crop species wheat (Triticum aestivum). Wheat has been selected, because breeding efforts in this crop are faced with the fundamental problem that the major bottleneck for increasing the yield potential, the light conversion efficiency has almost remained unaltered in modern wheat breeding. The evolutionary concept used in this subproject relies on the actual model of C4 evolution stating that the transition from C3 to C4 photosynthesis proceeded in modules and that each of the individual modules were adaptive implying that each step brought a small but detectable advantage in the photosynthetic capacity. By introducing mutations into wheat and using low CO2 concentration as the selection criterion mutant lines are to be expected with improvements in their photosynthetic capacity and which be classified under the broad category of C3-C4 intermediates. Candidate lines showing higher tolerance to low CO2 are also potential candidates with improved drought tolerance. Therefore, intermediate C3-C4 mutant lines are potentially of direct interest for breeding purposes.

The proposal brings together scientists with highly complementary interests and established track records in leaf physiology and its genetics (Westhoff), leaf developmental genetics (Tsiantis), crop genetics and breeding also in the private sector (Falk) and plant growth analysis coupled with unique expertise in the development and application of novel phenotyping methodologies (Fiorani). This team composition will allow us to deliver both concrete strategies and germplasm that will support increases of the efficiency in photosynthesis to a level that has tangible benefits in field conditions.