title: High nitrogen supply and carbohydrate content reduce fungal endophyte and alkaloid concentration in Lolium perenne.
abstract: The relationship between cool-season grasses and fungal endophytes is widely regarded as mutualistic, but there is growing uncertainty about whether changes in resource supply and environment benefit both organisms to a similar extent. Here, we infected two perennial ryegrass (Lolium perenne) cultivars (AberDove, Fennema) that differ in carbohydrate content with three strains of Neotyphodium lolii (AR1, AR37, common strain) that differ intrinsically in alkaloid profile. We grew endophyte-free and infected plants under high and low nitrogen (N) supply and used quantitative PCR (qPCR) to estimate endophyte concentrations in harvested leaf tissues. Endophyte concentration was reduced by 40% under high N supply, and by 50% in the higher sugar cultivar. These two effects were additive (together resulting in 75% reduction). Alkaloid production was also reduced under both increased N supply and high sugar cultivar, and for three of the four alkaloids quantified, concentrations were linearly related to endophyte concentration. The results stress the need for wider quantification of fungal endophytes in the grassland-foliar endophyte context, and have implications for how introducing new cultivars, novel endophytes or increasing N inputs affect the role of endophytes in grassland ecosystems.
authors.affiliation: AgResearch, P.B. 11008, Palmerston North, New Zealand.
authors.forename: Susanne
authors.initials: S
authors.lastname: Rasmussen
authors.affiliation: AgResearch, P.B. 11008, Palmerston North, New Zealand.
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Parsons
authors.affiliation: AgResearch, P.B. 11008, Palmerston North, New Zealand.
authors.forename: Shalome
authors.initials: S
authors.lastname: Bassett
authors.affiliation: AgResearch, P.B. 11008, Palmerston North, New Zealand.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Christensen
authors.affiliation: AgResearch, P.B. 11008, Palmerston North, New Zealand.
authors.forename: David E
authors.initials: DE
authors.lastname: Hume
authors.affiliation: AgResearch, P.B. 11008, Palmerston North, New Zealand.
authors.forename: Linda J
authors.initials: LJ
authors.lastname: Johnson
authors.affiliation: AgResearch, P.B. 11008, Palmerston North, New Zealand.
authors.forename: Richard D
authors.initials: RD
authors.lastname: Johnson
authors.affiliation: AgResearch, P.B. 11008, Palmerston North, New Zealand.
authors.forename: Wayne R
authors.initials: WR
authors.lastname: Simpson
authors.affiliation: AgResearch, P.B. 11008, Palmerston North, New Zealand.
authors.forename: Christina
authors.initials: C
authors.lastname: Stacke
authors.affiliation: AgResearch, P.B. 11008, Palmerston North, New Zealand.
authors.forename: Christine R
authors.initials: CR
authors.lastname: Voisey
authors.affiliation: AgResearch, P.B. 11008, Palmerston North, New Zealand.
authors.forename: Hong
authors.initials: H
authors.lastname: Xue
authors.affiliation: Department of Environmental Biology, University of Guelph, Ontario, Canada N1G 2W1.
authors.forename: Jonathan A
authors.initials: JA
authors.lastname: Newman
mesh_terms: D000470:Alkaloids / Q000378:metabolism*; D002241:Carbohydrates / Q000032:analysis; D005658:Fungi / Q000235:genetics / Q000378:metabolism*; D008129:Lolium / Q000737:chemistry / Q000378:metabolism* / Q000382:microbiology*; D009584:Nitrogen / Q000378:metabolism*; D010940:Plant Proteins / Q000032:analysis; D016133:Polymerase Chain Reaction
chemical_list: D000470:Alkaloids; D002241:Carbohydrates; D010940:Plant Proteins; D009584:Nitrogen