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 wit hout (E-) infection with the fungal endophyte Acremonium lolii were es tablished in spaced-plant nurseries and trial plots in 1989 and 1990 a t eight locations in France. In the nurseries, families were scored vi sually 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 nurser ies, and in all cases there was a positive response to A. lolii infect ion. In the nurseries, the traits showing the greatest number of signi ficant responses to infection were spring growth (3/28 comparisons) an d autumn vigour (3/26 comparisons). In trial plots, E+ families had a significantly (P < 0.05) higher yield than E- families at three dry lo cations (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 sowing s when different families were studied, endophyte infection had no eff ect on yield at the driest location. Therefore it is concluded that in fection of perennial ryegrass with some strains of A. lolii seems to b enefit the host in stressful conditions. However, in Europe generally, climatic conditions are not often stressful for perennial ryegrass an d the chances of E+ plants being favoured by either natural or artific ial selection seem to be low.