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Description:
Wheat (Triticum aestivum L.) is one of the most important staple crops worldwide and there is an urgent need to develop high-yielding and resilient new cultivars and to elevate the breeding progress. This thesis presents a retrospective analysis of the breeding progress of the last 50 years aiming to identify innovations in physiological traits with great relevance for future breeding. Intercepting radiation and the radiation use efficiency (RUE) determine biomass production, which is the more promising influencing factor for total grain yield in comparison to biomass partitioning (harvest index). The first objective within this thesis was to discover the genetic variation in relative light interception and RUE and to understand the underlying architectural and physiological functions of the canopy determining the source of assimilate production. From another perspective, grain yield formation can also be seen as a constant interplay between sink and source components, as the assimilates produced by the source are allocated to the sink organs of the crop. Therefore, the second objective was an in-depth analysis of the interdependencies between sinks and sources and possible limiting factors within that network. Furthermore, a genetic analysis of the physiological and yield related traits was performed. The identification of the genetic regions relevant for the source compartments, which partly enabled the yield increase and their potential effect, was the third objective of this thesis. During three experimental seasons, canopy traits were assessed in the field by measuring the relative leaf chlorophyll content (via SPAD measurements), the proportion of green leaf material, light interception and leaf area index (LAI) non-destructively. Using these traits, relative light interception, RUE, green canopy duration (GCD), green leaf area integral and the light extinction coefficient were derived. The field trials were conducted with 220 cultivars of which 174 represent the German breeding history. For the evaluation ...