PERENNIAL RYEGRASS (LOLIUM-PERENNE) ENDOPHYTE (ACREMONIUM-LOLII) RELATIONSHIPS - THE AUSTRALIAN EXPERIENCE

Perennial ryegrass is the main pasture grass used in temperate Australia and is established on over six million hectares. The main cultivars sown are old Australian ecotypes - 87% of the seed certified is of cultivar 'Victorian'. Infection with Acremonium lolii Latch, Christensen and Samuels is common in this cultivar, as is the incidence of ryegrass staggers in sheep in summer. Endophyte detection and incidence is discussed as are the effects of endophyte on seedling vigour, plant persistence, grass-clover relations, plant pathogens and sheep production and reproduction. The endophyte appears to aid ryegrass persistence in low rainfall sites and may exhibit allelopathic effects on legumes thereby reducing the overall productivity of pastures. Ewes grazing highly infected perennial ryegrass pasture have recorded higher losses amongst newborn lambs in some years. Ongoing endophyte research programs of a multidisciplinary nature aim to identify the mechanisms underlying the above observations and to evaluate the animal production potential of ryegrass infected with novel endophyte claimed to be a low producer of agents toxic to sheep.