Forage production of grasslands composed by one, two or three varieties of perennial ryegrass
Résumé
The present study aimed at evaluating the effect of an increased genetic diversity on forage production of perennial ryegrass (Lolium perenne L.), increasing genetic diversity being achieved by mixtures of varieties. Mixtures of varieties with similar or different heading dates were sown in 2003 in a micro-plot experiment conducted at INRA of Lusignan. Nine varieties grown in pure stand and 10 mixtures of two or three varieties were analysed. Two defoliation regimes were applied (fast or slow). During 5 years, dry matter production was mesured in each cut. Considering plots composed by one, two or three varieties of the same heading date, no difference in annual forage production was noticed. Increased genetic diversity within a heading date group provided neither advantage nor disadvantage. The effect of heading date was highly significant on forage production. Mixtures of varieties of different heading dates had an intermediate forage production and never produced more than the highest yielding variety. Compared to positive effects of increased specific diversity on grassland production, increased genetic diversity was not related to any increased yield, but can be seen as a method to secure forage production while avoiding a poor production of a particular variety in a given environment.