Heterosis in F1 hybrids derived from crosses of adapted Australian wheats

Data on the level of heterosis for grain yield under Australian dryland wheat growing conditions is essential before any decision can be made to commit resources to hybrid wheat breeding. Experiments were conducted at Narrabri, N.S.W., to determine the level and stability of heterosis for grain yield expressed by F1 hybrids derived from crosses of adapted Australian varieties. The hybrids and their parents were grown in hill plots in replicated experiments at three sowing times for two years (six environments). The hybrids outyielded their parents in each of the six environments with levels of mid- and high-parent heterosis up to 31.5 and 26.8%, respectively. The best hybrid outperformed the best check variety by an average yield margin of 18.2%. The hybrids were marginally but not significantly more stable in their yield performance across environments than their parents. While heterosis for grain protein content was generally negative, some hybrids were superior to the check varieties for both grain yield and protein content. Yield component analysis revealed no consistent pattern by which the best hybrids obtained their yield advantage over their parents. The levels of heterosis and the absolute yield advantage displayed by the hybrids over the best pure line check varieties were sufficient to sustain the commercial production of hybrid wheats in northern N.S.W.