Contact: Lukas.Foerter@ag.uni-giessen.de

Plant breeding has contributed to a steady yield progress in European winter wheat varieties released since the 1960s. This progress was particularly driven by improving sink-related traits like grain number per spike. However, since yield formation relies on complex source-sink interactions throughout the entire vegetation period, an additional investigation of source-related traits is essential for understanding and further improving yield progress in wheat breeding. Accumulation of stem water-soluble carbohydrates (SWSC) is one determinant for source capacity after the shift to generative growth and is known to be a key factor for yield formation.

To assess the SWSC concentration in the context of genotype-environment-interactions, 50 well-characterized, elite European winter wheat varieties representing the last five decades of breeding progress were sown in a field trial with two irrigation treatments (rainfed and additional irrigation) at our field station in Gross Gerau.

Plant samples were taken at four timepoints (flag leave, anthesis, milk/dough stage, maturity) to investigate temporal dynamics of SWSC under abiotic stress conditions. Besides classical chemical analysis of SWSC (anthrone method), NIR spectra of the plant samples were recorded in order to develop calibration equations for establishment of a high-throughput analysis method for samples from field trials in multiple years, locations and treatments.

As expected, preliminary results from the 2023 field trial confirmed the superior yield performance of modern varieties. Moreover, the SWSC concentration showed a similar linear improvement over time in relation to the year of cultivar registration and was correlated to grain yield under both irrigation treatments. In summary, modern varieties tend to have higher yields as well as a higher source capacity than older varieties.

We thus assume that SWSC, as a source-related trait, has been a key contributing factor to historical yield progress in winter wheat breeding. The findings are being validated with further sample analysis and multi-location field trials in 2024.

High-throughput phenotyping for SWSC via NIRS will enable collection of large datasets that provide valuable insight into the complex genotype-environment-interactions affecting SWSC and yield performance, especially under abiotic stress conditions. Ultimate, this will facilitate a more direct approach to selection for yield improvement in future wheat breeding programs.