Co-Evolution of Sink and Source in the Recent Breeding History of Winter Wheat in Germany

Abstract

Optimizing the interplay between sinks and sources is of crucial importance for breeding progress in winter wheat. However, the physiological limitations of yield from source (e.g. green canopy duration, GCD) and sink (e.g. grain number) are still unclear. Furthermore, there is little information on how the source traits have been modified during the breeding history of winter wheat. This study analyzed the breeding progress of sink and source components and their relationships to yield components. Field trials were conducted over three years with 220 cultivars representing the German breeding history of the past five decades. In addition, genetic associations of QTL for the traits were assessed with genome-wide association studies. Breeding progress mainly resulted from an increase in grain numbers per spike, a sink component, whose variations were largely explained by the photosynthetic activity around anthesis, a source component. Surprisingly, despite significant breeding progress in GCD and other source components, they showed no direct influence on thousand grain weights, indicating that grain filling was not limited by the source strength. Our results suggest that, 1) the potential longevity of the green canopy is predetermined at the time point that the number of grains is fixed; 2) a coevolution of source and sink strength during the breeding history contribute to the yield formation of the modern cultivars. For future breeding we suggest to choose parental lines with high grain numbers per spike on the sink side, and high photosynthetic activity around anthesis and canopy duration on the source side, and to place emphasis on these traits throughout selection.

Detection of breeding signatures in wheat using a linkage disequilibrium-corrected mapping approach

“…These cultivars were selected based on their economic and historic importance. The composition of the utilized population was described in Voss-Fels, et al 37 and Lichthardt, et al 38 . Seeds of the bread wheat cultivars were provided by Leibniz Institute of Plant Genetics and Crop Plant Research (IPK) by accepting the terms and conditions of the Standard Material Transfer Agreement (SMTA) of the International Treaty on Plant Genetic Resources for Food and Agriculture ( http://www.fao.org/plant-treaty ).…”

“…Genotyping and data processing. The accessions of the diversity panel were genotyped at SGS Trait-Genetics GmbH (Gatersleben, Germany) using the Infinium iSelect 15 K single nucleotide polymorphism (SNP) bead array, which comprises 13 006 polymorphic loci 39 , as well as by the 135 K Axiom Exome Capture Array carrying 136 780 SNP markers 38 .…”

“…Moreover, modern cultivars outperform older cultivars with respect to morphological, physiological as well as agronomic traits under low-input conditions e.g. without fungicide treatment 37,38 .…”

“…This is mainly due to the complexity of the wheat genome: wheat is an allohexaploid with three closely related subgenomes, a large genome size of (~ 16 Gb) and > 85% repetitive element content 25 . However, analyzing a set of winter wheat cultivars representing 50 years of German breeding history, Lichthardt et al (2020) were able to identify a co-evolution effect determining sink and source allocation in plants which consequently affected grain yield potential. Large-scale field experiments with the same association panel also revealed that modern cultivars consistently outperform older varieties with respect to yield parameters, grain quality, nutrient use efficiency and disease resistance (Voss-Fels et al 2019).…”

Crop adaptation to climate change as a consequence of long-term breeding

“…Selection for performance and yield stability under the expected stress scenarios that occur commonly in a particular target region may be the best way to maintain crop performance while mitigating risks. Yield selection in target environments also improves complex stress response traits and yield stability (Voss-Fels et al 2019b) expected positive impact on grain yield: Instead, such genotypes often show sink deficits in terms of irregular grain formation, spatio-temporal variability for grain development or other source-sink trade-offs (Lichthardt et al 2020).…”