Isolation of feeding deterrents to Argentine stem weevil in cultures of endophytes of perennial ryegrass and tall fescue

Abstract

Bioassays showed that a feeding deterrent to adult Argentine stem weevil (Listronotus bonariensis (Kuschel)) was produced in broth cultures of 4 strains of the endophyte Acremonium loliae (Latch, Christensen & Samuels) isolated from perennial ryegrass (Lolium perenne L.), and one strain of an endophyte isolated from tall fescue (Festuca arundinacea L.). Weevils could detect the deterrent when 0.05% w/w mycelium was incorporated in an agar-based diet, suggesting that it may be practical to maintain stem weevil resistance to ryegrass at low levels of endophyte infection per plant and thereby reduce the ryegrass staggersinducing component. Bioassays of chemical fractions have shown the deterrent to be very active, strongly hydrophilic, and present in both fungus mycelium and the supernatant broth. The behaviour of the active component suggests that it is a polar organic compound and possibly amphoteric in nature.

Keywords:

• Listronotus bonariensis Kuschel
• bioassays
• Acremonium loliae Latch, Christensen & Samuels
• cultures
• Lolium perenne L.
• Festuca arundinacea L.
• feeding deterrents
• chemical analysis