Tiller Mortality in Mixtures of Endophyte-Free Ryegrass and Ryegrass Infected with Two Different Endophytes

Abstract

Because of the mammalian toxicity caused by the presence of the alkaloids, ergovaline and lolitrem B, in perennial ryegrass (Lolium perenne) pastures infected with a wildtype endophyte (Neotyphodium sp.) in New Zealand, different strains of endophytes have been sought which do not produce these two alkaloids but do produce peramine, the highly active deterrent to the important pasture pest, Argentine stem weevil (ASW) (Listronotus bonariensis). Such endophytes once inoculated into New Zealand ryegrass cultivars undergo extensive testing to ensure that resistance to ASW is not compromised by the absence of ergovaline and lolitrem B. Initial work with one of these endophytes, ARI, suggested that it had little resistance to ASW larval attack, although there was resistance to adult feeding and oviposition (Popay and Wyatt 1995). To further assess its potential for control of ASW, perennial ryegrass infected with this endophyte was planted in mixtures with endophyte-free ryegrass or ryegrass with the wildtype endophyte. In this paper the tiller mortality of these plants is described.