Previous studies investigation the breeding history of winter wheat (Triticum aestivum L.) have identified distinct sink and source characteristics as causal agents for the progress in yield. Due to functional interdependencies, co-evolutionary development between sinks and sources can be assumed. Source limitations prior to and around anthesis affect grain number per spike (GPS), but it is unclear whether an extended source persistence (stay-green) influences grain weight or whether it is a consequence of grain number. Furthermore, the role of stay-green in the breeding progress needs to be clarified. This study therefore aimed to identify the interdependencies of sink and source characteristics in the course of the German winter wheat breeding history, especially focusing on leaf longevity by assessing the green canopy duration (GCD).

Field trials were conducted in three years with 220 cultivars representing the German breeding history from 1966 – 2013. All yield components and a selection of source characteristics (maximal LAI, chlorophyll content (SPAD) around anthesis and stay-green-parameters) were analysed. Stay green was estimated as GCD, i.e. the time from anthesis to 50 % senescence, and by leaf area duration, i.e. GCD weighted with the leaf area index (LAI). A genome wide association study (GWAS) was conducted for all traits to detect quantitative-trait-loci (QTL).

We found that the chlorophyll content around anthesis influences GPS which then affect the GCD. By that, GCD explains 30% of the variation in grain yield. Considering the breeding progress, yield increase of winter wheat has been realised by increasing the number of grains per spike which entail an increased canopy longevity to fill these grains. The GWAS underpinned the dependencies: GCD and grain yield share a common QTL and several more QTL co-localise. None of the source characteristics could be linked to thousand grain weight apparently grain filling was not affected by the source traits. In fact, the stages related to floret fertility and abortion were identified as the critical link for the dependency of yield and stay-green. The GWAS indicated a possible linkage drag of genetic regions relevant for yield and source characteristics. In-depth analyses of the associations with candidate genes and known QTL will help to answer to elucidate the connection between GCD and yield.