Change in Agronomic Performance of Lolium perenne and Lolium multiflorum Varieties in the Past 40 Years Based on Data from Belgian VCU Trials

By using data of Belgian trials for Value of Cultivation and Use (1963 2007) the change in agronomic performance of ryegrass varieties was quantified. Since the genetics of 'Vigor' and 'Lemtal' have remained identical to those in 1963, these were used as constant standards to measure improvements of new varieties. Dry matter yield (DMY) of 'Vigor' and 'Lemtal' varied annually but did not show a progressive change, indicating that cultural changes in VCU trials of ryegrasses were small. By expressing DMY, persistency and rust resistance of the candidate varieties relative to Vigor and 'Lemtal', the change in agronomic performance due to breeding was determined. DMY increased with 0.3% of 'Vigor' and 'Lemtal' annually. Persistency showed an annual increase around 0.5% of the standard varieties. Before 1990, rust resistance of ryegrass varieties varied around 100, and only after 1990, an annual increase of 3.6% relative to 'Vigor' and 'Lemtal' was found.