Distribution and accumulation of the alkaloid peramine in Neotyphodium lolii-infected perennial ryegrass

Through the production of alkaloids and mycotoxins, the endophytic fungus of perennial ryegrass, Neotyphodium lolii, confers resistance to the host grass against several insect pasture pests and causes health problems in livestock. The effects of plant component, plant reproductive development, and plant management (trimming) on the concentration and accumulation of peramine, the alkaloid thought to be most important for conferring resistance against Argentine stem weevil, were investigated. Clones of eight different naturally occurring perennial ryegrass-N. lolii associations were used in the experiment, which was conducted during spring-summer, which corresponded with the height of plant reproductive activity. Clones were either trimmed regularly to maintain them in a vegetative state (V clones) or not trimmed, allowing them to become fully reproductive (R clones). V and R clones of each grass/endophyte association were destructively harvested at times that corresponded roughly with the start, middle, and end of the plant reproductive phase. Harvested material was dissected into a number of plant components that were analyzed for peramine concentration by HPLC. All clippings from the V clones were also analyzed. Peramine concentrations were usually similar in leaf sheaths and leaf blades, but they decreased as leaf age increased. The seed from R clones and younger sheaths and blades of leaves from vegetative tillers contained the highest concentrations, while the root, crown, and dead leaf tissue contained the lowest. During the inflorescence phase, tissues from reproductive tillers generally contained lower concentrations than corresponding tissues from vegetative tillers. Also at this time, mean peramine concentrations were higher in V clones than in R clones. By the end of the plant reproductive phase, at the mature seed stage, mean peramine concentrations in R and V clones were similar. The seed component, which contained approximately 75% of the total peramine present in the plant (at a mean concentration of 63.7 mu g/g), probably accounted for much of the recovery in the R clones.