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. Data included 144 Lolium perenne and 69 Lolium multiflorum candidate varieties, plus 'Vigor' and 'Lemtal', two varieties which were always included in the Value of Cultivation and Use (VCU) trials. As 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 ryegrasses varied around 100% relative to 'Vigor' or 'Lemtal'. After 1990, an annual increase of 3.6% against these standard varieties was found.