Evaluation of Trialling Efficiency of the Australian Wheatbelt

The Australian wheatbelt is divided into three main growing regions: the North (New South Wales and Queensland), the South (Victoria, South Australia and Tasmania), and the West (Western Australia). Using wheat yield data from the 2015-2022 multi-environmental trials (METs) conducted by the National Variety Trials (NVT), this study examines genotype-by-environment interactions (G×E) and trialling efficiencies, within and across regions. The North had the highest mean yield (390 gm-2) and the largest proportion of phenotypic variance explained by G×E (64%), while the West had the lowest yield (355 gm-2) and the lowest G×E contribution (44%). Despite regional differences, yield gains were approximately 1.4 gm-2 per year (or ∼ 0.5% annually) across all regions. The West also showed the highest repeatability (0.85 ± 0.02) and the lowest least significance difference (5% LSD, 22 gm-2 ± 1 gm-2) for a benchmark five-year MET, compared to the South (0.70 ± 0.04, 35 ± 1.4 gm-2) and the North (0.59 ± 0.05, 35 ± 1.4 gm-2). Modelling results were consistent across regions and indicated that 2 years of testing at 20 sites per year delivered efficiencies that could not be improved very much further.