DISTRIBUTION AND ACCUMULATION OF THE MYCOTOXIN LOLITREM-B IN NEOTYPHODIUM LOLII-INFECTED PERENNIAL RYEGRASS

The symbiotic relationship between perennial ryegrass and its endophyt ic fungus, Neotyphodium lolii, is of considerable agronomic significan ce in New Zealand. Livestock ingesting N. lolii-infected perennial rye grass may succumb to a neuromuscular condition, ryegrass staggers, th e probable cause of which has been identified as the endophyte-produce d indole-diterpenoid mycotoxin lolitrem B. The effects of plant compon ent, plant reproductive development, and plant management (clipping) o n the concentration and accumulation of lolitrem B were investigated. Eight different naturally occurring perennial ryegrass-N. lolii associ ations were cloned. They were either trimmed regularly to maintain the ir vegetative state (V clones) or not trimmed at all to enable full pl ant reproductive development (R clones). At times that corresponded ap proximately with the start, middle, and end of the plant reproductive phase, V and R clones of each grass-endophyte association were destruc tively harvested. After dissection into a number of plant components, harvested material was analyzed for lolitrem B content by HPLC. Analys es were also performed on all clippings taken from the V clones. Highe st lolitrem B concentrations in vegetative parts were found in older l eaf sheaths and dead leaves. Towards the end of the plant reprodutive phase, dead leaves also contained a large proportion of the total loli trem B content of the V clones. The highest concentration of lolitrem B was found in the seed, which accounted for nearly 60% of the total q uantity in R clones. Leaf blades, young leaf sheaths, roots, and crown s generally contained low to moderate concentrations. In late spring, mean concentrations in R and V clones were similar. By the time mature seed was present (mid-summer), mean concentrations in R clones were t hree times higher than in V clones. This difference was attributed lar gely to the contribution by the seed in the R clones. The implications of these findings in relation to ryegrass staggers in livestock are d iscussed.