Contrasting Effects of Grass - Endophyte Chemotypes on a Tri-Trophic Cascade

Abstract

Systemic grass-endophytes of the genus Epichloë symbiotically infect the above-ground plant parts of many grass species, where they produce alkaloids in a grass-and endophyte-specific manner that are toxic or deterrent to herbivores. An increasing number of studies show cascading negative effects of endophyte-derived alkaloids that extend to higher trophic levels, harming beneficial insects, including those that control aphid populations. Lacewings are one of the major biological aphid controls, and are especially resistant to insecticides and pollutants, but their susceptibility to endophyte infection in the food chain has never been studied. Our study found variability in aphid population growth depending on the endophyte-grass chemotype, where aphid population growth was lowest on chemotypes known for producing high amounts of loline alkaloids. We also showed that larval and pupal development and mortality of the Common Green Lacewing (Chrysoperla carnea) was, in a non-choice experiment, not affected by endophyte infection in the food chain. This is a first indication that lacewings might be resistant to endophyte-derived alkaloids and could be robust biocontrol agents when applied together with endophyte-infected grass, possibly replacing chemical pesticides.

Epichloë Endophytes Shape the Foliar Endophytic Fungal Microbiome and Alter the Auxin and Salicylic Acid Phytohormone Levels in Two Meadow Fescue Cultivars

“…Epichloë endophytes grow in the intercellular space of the leaves, stems, and reproductive tissue of several cool-season grasses and are typically absent in the roots [ 53 , 54 ], indicating that their effect on shaping fungal community structure is limited to aboveground plant parts. This is in agreement with our previous study, where Epichloë symbiosis in tall fescue ( Schedonorus phoenix ) impacted only the endophytic fungal community in leaves, not the bacterial community [ 38 ].…”

Epichloë Endophyte-Promoted Seed Pathogen Increases Host Grass Resistance Against Insect Herbivory

“…In line with our previous study, ergot alkaloid concentrations varied considerably among E+ plants in the present study. Similarly, many other studies with other grass species have revealed that the quantities of Epichloë alkaloids vary among geographic origin and genetic plant-fungus combinations and can be plastic during the growing season depending on environmental conditions (Siegel et al, 1990;Thom et al, 2014;Helander et al, 2016;König et al, 2018;Fuchs et al, 2020).…”

Management practice and soil properties affect plant productivity and root biomass in endophyte‐symbiotic and endophyte‐free meadow fescue grasses

“…Another reason may be the age of the plants or cultivar specific performance. Some studies have indicated that the beneficial effect of endophytes is frequently missing during the first year of plant establishment or highly strain specific (Fuchs et al, 2017b(Fuchs et al, , 2020König et al, 2018).…”