Indirect early generation selection for yield in winter wheat

Early generation selection (EGS) aims to accelerate genetic yield gain by applying selection pressure for desirable traits at early generations within breeding programmes. This study was designed to evaluate single plant yield (SPY), harvest index (HI; SPY divided by aboveground biomass) and estimated fruiting efficiency (FEm; kernels per unit chaff weight) as EGS traits in predominantly F3 populations of winter wheat. Lines were sown as single plants and in plots of pooled family seed in northwest Victoria, Australia in 2018. From the single plant populations, 21-23 lines were selected for each EGS trait and 52 lines were selected at random to estimate true population mean; 25 lines were selected visually from pooled plots. Selected lines were sown in partially replicated plots in 2019. Lines selected for HI yielded 24% more than lines selected at random and 22% more than lines selected visually; selections made for SPY and FEm yielded the equivalent of HI selections, but not significantly higher than the random or visual treatments. In 2020, the 7 highest-yielding lines from the HI, random and visual selection treatments were sown in replicated plots. There was no significant difference in yield between treatments. Nevertheless, EGS for HI successfully culled low yielding lines, and enriched populations with high yielding lines prior to plot-level yield testing. Advancements in high-throughput phenotyping are required before widespread adoption but are anticipated in the near future.