Yield components and yield quality of old and modern wheat cultivars as affected by cultivar release date, N fertilization and environment in Germany

Wheat (Triticum aestivum L.) is the main staple crop worldwide. Understanding the genotype x management x environment (G x M x E) interaction is critical for breeding, yield, grain quality estimation and to develop sustainable production systems that meet food and feed demand. Many studies have explored grain yield changes and yield stability over time, as well as G x M x E (i.e., the effect of breeding progress), but limited studies have looked at these effects on yield components and grain quality parameters. A field experiment was conducted to understand the G x M x E interactions for yield components of winter wheat cultivars. The study was carried out for three seasons (2015-2018) using a split plot design with four replications, with nitrogen (N) fertilizer levels (0, 120 and 240 kg N ha-1), in the main plot and cultivars in the subplot. Three old cultivars (released before 1960), Heines II, Heines Rot, Heines VII and three modern cultivars (released after 1960), Jubilar, Sperber and Tommi, were selected. Total aboveground biomass (TAGB), grain yield, harvest index (HI), thousand kernel weight (TKW), grains m-2, grain protein and hectoliter weight (HLW) were collected at harvest. The three-way interaction was significant for most variables except for grain protein, but after applying the AIC method, the three-way interaction was just relevant for HI. The 0 N level always resulted in lowest TAGB, grain yield, grains m-2, grain protein and HLW for all cultivars. All cultivars showed a positive response in grain yield when applying 120 kg ha-1 of N but no significant further yield increase was observed with higher N levels. With regards to HI, cultivar differences were more apparent during the wettest year 2016. The HI tends to decrease with increasing N levels and was the highest in modern cultivars with Tommi and Sperber, though in 2017, also Heines VII showed one of the highest HI across treatments. Grain protein content progressively increased with N level, but newer cultivars like Tommi and Sperber, showed some of the lowest protein contents. Yield component contribution to grain yield has changed over time with grain number, grain size and HI, becoming more important for yield realization. Modern cultivars, especially Tommi, performed better than the rest of the cultivars under sufficient N supply. Optimal N-rates among cultivars differ for grain yield and grain protein, posing a challenge to maintain wheat supply to the increasing wheat demand in the future but also to meeting sustainability targets to reduce and optimize resource use.