Analysis of sink/source relations in bread wheat recombinant inbred lines and commercial cultivars under a high yield potential environment

•Under non-limiting growing conditions, grain yield in bread wheat is highly associated with sink capacity.•Yield:sink capacity falls from the expected 1:1 ratio above ∼8 tons ha−1, indicating source limitation for grain filling.•Sink limitation during grain filling in wheat seems more a consequence of breeding/environment than a ubiquitous attribute.•Source limitations that might arise from further improvement of grain number per unit area should not be disregarded.