Oat genetic gain and phenotypic plasticity of yield and grain quality traits over five decades of breeding in Australia

Globally, oat is a small crop; with modest investments, breeders target multiple phenotypes to meet diverse uses. Here we analyse yield and grain quality data from Australian breeding trials conducted over the continent between 2011 and 2020. Our aims were to establish rates of genetic gain in yield, associated yield components and grain quality traits, and to analyse the interaction between genotype and environment from the perspective of phenotypic plasticity. Over 56 years, the rate of genetic gain in grain yield has averaged 10.3 ± 0.7 kg ha-1 yr-1, ranging from 19.6 ± 1.2 kg ha-1 yr-1 for milling varieties to negligible for varieties with other end uses. Genetic gain in yield was higher in high-yielding environments, reaching up to 40 kg ha-1 yr-1. Rates of genetic change in grain quality traits were significant, small and end-use dependent. A dataset combining 128 genotypes and 106 environments returned a 32-fold variation in yield, a 19-fold variation in grain number and a 3.6-fold variation in grain weight. Phenotypic plasticity of yield was agronomically adaptive: phenotypes with higher plasticity had higher yields in high-yielding conditions. We identified the following breeding strategies to improve oat grain yield in Australian environments: 1) adoption of technologies to shorten the seed-to-seed interval; 2) a focus on high-yielding environments; 3) targeting both yield and its phenotypic plasticity; and 4) selection for grain composition favouring starch and/or protein at the expense of energetically more expensive oil.