Wheat is a critical component of food security. Yield must be increased at a much faster rate than it has been increasing in the last decades. In this project we analyse aspects crop physiology not analysed much so far (due to the difficulties involved). A primary requisite for using any physiological trait in realistic breeding is to count with variability within elite material. These materials are frequently well characterised for the most commonly analysed yield determinants. The main specific objectives of the project are (i) to quantify genetic variation for the partitioning of phenological time between phases occurring before and after the onset of stem elongation, (ii) to evaluate genotypic differences in fruiting efficiency as well as the physiological causes of such differences, (iii) to determine the dynamics of floret development (floret primordia initiation and degeneration) for the different genotypes, (iv) to analyse the relationships between grain number and grain weight by studying the physiological causes behind the relationship, and (v) to identify genotypes exhibiting superior nutritional quality for particular grain number as well as those not having penalties in nutritional quality in response to improved grain number. The focal approach is to identify (and understand physiological bases of) genetic differences within elite material for breeding programmes and consistency of these differences. This is relevant in the likely impact of the work proposed. Overall, we aim to improve our understanding on these alternative traits as driven by genetic variation (on the side of the academic ambition of the research group) as well as to deliver well characterised elite material for these traits in terms of magnitude of differences, consistency across environments and lack of trade-offs (on the side of the translational expectation of the research conducted).