INFLUENCE OF THE FUNGAL ENDOPHYTE ACREMONIUM-LOLII ON AGRONOMIC TRAITS OF PERENNIAL RYEGRASS IN FRANCE

Four sets of half-sib families of perennial ryegrass with (E+) and without (E-) infection with the fungal endophyte Acremonium lolii were established in spaced-plant nurseries and trial plots in 1989 and 1990 at eight locations in France. In the nurseries, families were scored visually for six agronomic traits; in trial plots, dry matter yields or visual scores were obtained for eleven traits in the planting year and in the following two years. Significant differences between E- and E+ families in each set were more frequent in trial plots than in nurseries, and in all cases there was a positive response to A. lolii infection. In the nurseries, the traits showing the greatest number of significant responses to infection were spring growth (3/28 comparisons) and autumn vigour (3/26 comparisons). In trial plots, E+ families had a significantly (P < 0.05) higher yield than E- families at three dry locations (5/7 comparisons at Clermont-Ferrand, 3/9 at Montours, and 4/7 at Verneuil l'Etang) in the 1989 sowings. However, in the 1990 sowings when different families were studied, endophyte infection had no effect on yield at the driest location. Therefore it is concluded that infection of perennial ryegrass with some strains of A. lolii seems to benefit the host in stressful conditions. However, in Europe generally, climatic conditions are not often stressful for perennial ryegrass and the chances of E+ plants being favoured by either natural or artificial selection seem to be low.