Extending the duration of the ear construction phase to increase the grain yield of wheat

We tested the hypothesis that lengthening of the duration between the terminal spikelet stage of development and anthesis, referred to here as the construction phase duration (CPD), will increase yield per unit area in wheat. Field experiments were undertaken at 17 sites across the high rainfall zone of south-eastern and Western Australia in 2014 and 2015. In total, 205 wheat genotypes were grown. Genetic material included a set of near-isogenic lines (NILs) varying in photoperiod and vernalisation alleles; commercial wheat cultivars and breeding lines; and lines selected from the Multiparent Advanced Generation Inter Cross (MAGIC) population. As such, this is the only comprehensive dataset where the effect of variation in CPD on grain yield in field plots has been evaluated in diverse field environments. Within an optimum anthesis window of 10 d, longer CPD significantly increased grain yield by >11% at three sites and tended to increase grain yield at another 10 sites, although this was not statistically significant. The average yield increase across these sites was 5.5%. There was no consistent trend where a specific yield component was responsible for the increase across sites. We suggest that CPD can be extended by genetic selection and by sacrificing some of the vegetative period without any detriment to gain yield. We also found that CPD is increased by extending the duration from sowing to flowering by sowing earlier, which may be associated with increased yields in some environments. We conclude that, for the same anthesis date, a longer CPD may be beneficial in moderately favourable rainfed environments with a relatively even distribution of rainfall. We explore the basis of these relationships and implications for growers and plant breeders.