Buying time – increasing yield potential in wheat by extending stem elongation duration

Abstract Extending the duration of the stem elongation (SE) phase between terminal spikelet (TS) and anthesis has often been proposed as an avenue to increase wheat yield. However, accurate determination of TS is labour intensive, and existing evidence is often based on a limited number of genotypes observed under controlled conditions. Here, a Buster x Charger population comprising 108 doubled haploid lines was grown across four year-sites under UK field conditions. TS was recorded through meristem dissection and SE duration was measured as the time between TS and ear emergence (EE). Mixed model analysis across year-sites revealed high heritabilities (H 2 yield = 0.66, H 2 TS = 0.93, H 2 SE = 0.89, H 2 EE = 0.95) and strong genetic correlations between yield and the phenology traits SE and EE ( r g = 0.56 and r g = 0.6, respectively). While SE duration was mainly driven by EE, independent QTL for TS suggest that SE could be modified without affecting EE. The positive effect of SE duration on yield was attributed to increased grain number per area as well as increased grain weight, through independent QTL. Although validation in broader genetic backgrounds is needed, these QTL may offer opportunities for further yield increase in a physiological breeding framework. Highlights Longer stem elongation duration increases grain number. Longer stem elongation duration increases grain weight. Independent QTL suggest the timing of stem elongation as well as its effect on yield components may be independently selectable.