Phenotypic plasticity of grain and hay quality in varieties and advanced lines from the Australian oat breeding program

The profitability of oat crops depends on quality attributes in relation to milling and hay marketing standards. The aims of this paper were to (i) quantify grain and hay quality traits in varieties and advanced grain, hay and grazing oat lines, and (ii) analyse the effect of line, environment and their interaction from the viewpoint of phenotypic plasticity. The experiment included 29 lines grown in the winter-rainfall region of South Australia. Grain traits included hectolitre weight, screenings, groat percentage, brightness and concentration of oil and protein. Hay traits, measured at GS71, included digestibility, crude protein, water soluble carbohydrates, acid detergent fibre, and neutral detergent fibre. High temperature, high vapour pressure deficit, and water deficit in the developmental window from GS31 to 200 degrees Cd after GS60 reduced hectolitre weight and groat percentage, and increased screenings. For hay, the proportion of water soluble carbohydrates declined, the proportion of both acid detergent fibre and neutral detergent fibre increased, and digestibility decreased with higher minimum temperature in a window from approx. -500 to +500 degrees Cd centred at anthesis. For both grain and hay, current lines returned high yield and high quality in favourable environments, where further improvement could focus on yield and maintenance of quality. In stressful environments, trade-offs between yield and quality were important; water soluble carbohydrates were the crux of these trade-offs. For grain, high concentration of water soluble carbohydrates favoured high hectolitre weight, low screenings and high groat percentage, at the expense of yield. For hay, high concentration of water soluble carbohydrates associated with higher digestibility and lower fibre, at the expense of yield. Nitrogen adds a layer of complexity to these relations, which were partially captured by leaf greenness measured with SPAD. Greener leaves associated with lower concentration of water soluble carbohydrates, hence capturing the established negative correlation between nitrogen and water soluble carbohydrates. Greener leaves associated positively with yield and protein concentration in grain and hay, lower digestibility and higher neutral (and acid) detergent fibre. Whereas the breeding program targets specialist phenotypes for grain and fodder, quality traits meeting market standards were spread across types. Generalist phenotypes can accommodate multiple agronomic uses but specialists are required where trade-offs are involved.