Allelopathic effects of endophyte-infected perennial ryegrass extracts on white clover seedlings

Abstract

Two glasshouse experiments were conducted to evaluate possible allelopathic effects of perennial ryegrass/endophyte (Lolium perennel Neotyphodium lolii) associations on white clover (Trifolium repens). The influence of between-species competition, environmental stress, and soil fauna was eliminated by the use of a sterile sand nutrient culture technique to sustain potted clover seedlings, to which aqueous extracts from moisture-stressed perennial ryegrass pseudostem were applied. In Experiment 1, extracts from two ryegrass cultivars ('Grasslands Pacific’ and ‘Grasslands Nui'), each hosting in separate seed lines two endophyte strains (ES, WT), suppressed clover growth (mean suppression 22% at 100% concentration) relative to extracts from endophyte-free lines of the same cultivars. The degree of suppression increased with increasing extract concentration, differed between cultivars, but did not differ between endophyte strains. In Experiment 2, extracts at 100% concentration from a third ryegrass cultivar ('Grasslands Ruanui'), hosting in separate seed lines three endophyte strains (AR4, ES, WT), suppressed clover growth by a mean of 27% relative to extracts from an endophyte-free line of this cultivar (range 11 to 47%), with significant differences between strains. The endophyte strains differed in three known endophyte alkaloids, viz peramine, ergovaline, lolitrem B, but in this study none of these alkaloids could solely account for the allelopathic response. The suppression of clover by all ryegrass cultivar/endophyte strain associations tested indicates that clover suppression is not confined to the specific associations used in previous studies, and that further testing of new associations is warranted as variation in the degree of allelopathy existed, being dependant on endophyte strain and host ryegrass cultivar. © 1999 Taylor & Francis Group, LLC.