Entomologia Experimentalis et Applicata (2008) 126, 138-147

Daniel A. Potter, J. Tyler Stokes, Carl T. Redmond, Christopher L. Schardl and Daniel G. Panaccione (2008)
Contribution of ergot alkaloids to suppression of a grass-feeding caterpillar assessed with gene knockout endophytes in perennial ryegrass
Entomologia Experimentalis et Applicata 126 (2), 138-147
Abstract: Neotyphodium and Epichloë species (Ascomycota: Clavicipitaceae) are fungal symbionts (endophytes) of grasses. Many of these endophytes produce alkaloids that enhance their hosts' resistance to insects or are toxic to grazing mammals. The goals of eliminating from forage grasses factors such as ergot alkaloids that are responsible for livestock disorders, while retaining pasture sustainability, and of developing resistant turf grasses, require better understanding of how particular alkaloids affect insect herbivores. We used perennial ryegrass Lolium perenne L. (Poaceae) symbiotic with Neotyphodium lolii × Epichloë typhina isolate Lp1 (a natural interspecific hybrid), as well as with genetically modified strains of Lp1 with altered ergot alkaloid profiles, to test effects of ergot alkaloids on feeding, growth, and survival of the black cutworm, Agrotis ipsilon (Hufnagel) (Lepidoptera: Noctuidae), a generalist grass-feeding caterpillar. Neonates or late instars were provided clippings from glasshouse-grown plants in choice and rearing trials. Wild-type endophytic grass showed strong antixenosis and antibiosis, especially to neonates. Plant-endophyte symbiota from which complex ergot alkaloids (ergovaline and lysergic acid amides such as ergine) or all ergot alkaloids were eliminated by endophyte gene knockout retained significant resistance against neonates. However, this activity was reduced compared to that of wild-type Lp1, providing the first direct genetic evidence that ergot alkaloids contribute to insect resistance of endophytic grasses. Similarity of larval response to the two mutants suggested that ergovaline and/or ergine account for the somewhat greater potency of wild-type Lp1 compared to the knockouts, whereas simpler ergot alkaloids contribute little to that added resistance. All of the endophyte strains also produced peramine, which was probably their primary resistance component. This study suggests that ergot alkaloids can be eliminated from an endophyte of perennial ryegrass while retaining significant insect resistance.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Christopher L. Schardl

Research topic(s) for pests/diseases/weeds:
biocontrol - natural enemies
Research topic(s) for beneficials or antagonists:
general biology - morphology - evolution
evaluation - screening - selection

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Pest and/or beneficial records:

Beneficial	Pest/Disease/Weed	Crop/Product	Country	Quarant.
	Agrotis ipsilon	Lolium (crop)
Epichloë festucae (entomopathogen)	Agrotis ipsilon	Lolium (crop)