The da1 mutation in wheat increases grain size under ambient and
elevated CO2 but not grain yield due to trade-off between grain size and
grain number
Abstract
Grain size is potentially yield-determining in wheat, controlled by the
ubiquitin pathway and negatively regulated by ubiquitin receptor DA1. We
analysed whether increased thousand grain weight in wheat da1 mutant is
translated into higher grain yield and whether additional carbon
provided by elevated (e)CO2 can be better used by the da1, displaying
higher grain sink strength and size. Yield-related, biomass, grain
quality traits and grain dimensions were analysed by two-factorial
analysis, regarding genotype and eCO2. da1 increased grain size but
reduced spikes and grains per plant, grains per spike and spikelets per
spike, independent of eCO2 treatment, leaving total grain yield
unchanged. eCO2 increased yield and grain number additively and
independently of da1, but did not overcome the trade-off between grain
size and number observed for da1. eCO2 but not da1 impaired grain
quality, strongly decreasing concentrations of several macro- and
micro-elements. In conclusion, intrinsic stimulation of grain sink
strength and grain size, achieved by da1, is not benefitting total yield
unless trade-offs between grain size and numbers can be overcome. The
results reveal interactions of yield components in da1-wheat under
ambient and eCO2, thereby uncovering limitations enhancing wheat yield
potential.