Yield formation of Central-European winter wheat cultivars on a large scale perspective

Improvement of grain yield potential for winter wheat (Triticum aestivum) may become harder to achieve in the future because an increase of harvest index has been largely exploited by breeders. Therefore, it is of high interest to detect how the components of the yield equation GY=Q×LUE×HI (GY: grain yield, Q: radiation interception, LUE: light use efficiency, HI: harvest index) contribute to the explanation of yield differences of modern high yielding wheat varieties. To gain more insight in the variability of the parameters in the above equation and their contribution to grain yield, a field experiment was carried out in two seasons using a set of 9 recent German winter wheat cultivars (among them a hybrid cultivar and its parent lines).Beneath combine harvest, sequential harvests by hand were conducted (4 in the growing season 2013–2014, 5 in the growing season 2014–2015) to ascertain the above-ground biomass, the leaf area index and the harvest index (at the final harvest). Non-destructive measurements with a plant canopy analyzer to measure leaf area indices and mean tilt angles were conducted 4 times in 2014 and 9 times in 2015. Light absorption was calculated based on interpolated values of leaf area indices and mean tilt angles. Light use efficiency was calculated based on the linear relationship between above-ground biomasses at hand harvests and the related quantities of absorbed radiation.For all parameters of yield formation besides light use efficiency (P=0.073) statistically significant differences regarding the cultivars can be observed. Our results suggest that grain yield of modern German cultivars can be explained to a similar extent by differences in harvest indices (adj. r2: 0.77) and total biomass accumulation (adj. r2: 0.61). Variation in biomass accumulation partly can be explained by light use efficiency differences and to a lesser extent by differences in radiation interception. Most of the differences in biomass accumulation result, however, from differences in the accumulation of biomass from mid flowering to the final yield which for methodological reasons could not be further dissected to effects of light use efficiency and radiation interception. This information gap was described by the introduced parameter late performance. Various combinations of high and low performance, regarding the parameters of yield formation, exist in the analyzed set of cultivars.