Epichloë Fungal Endophytes—From a Biological Curiosity in Wild Grasses to an Essential Component of Resilient High Performing Ryegrass and Fescue Pastures

Abstract

The relationship between Epichloë endophytes found in a wide range of temperate grasses spans the continuum from antagonistic to mutualistic. The diversity of asexual mutualistic types can be characterised by the types of alkaloids they produce in planta. Some of these are responsible for detrimental health and welfare issues of ruminants when consumed, while others protect the host plant from insect pests and pathogens. In many temperate regions they are an essential component of high producing resilient tall fescue and ryegrass swards. This obligate mutualism between fungus and host is a seed-borne technology that has resulted in several commercial products being used with high uptake rates by end-user farmers, particularly in New Zealand and to a lesser extent Australia and USA. However, this has not happened by chance. It has been reliant on multi-disciplinary research teams undertaking excellent science to understand the taxonomic relationships of these endophytes, their life cycle, symbiosis regulation at both the cellular and molecular level, and the impact of secondary metabolites, including an understanding of their mammalian toxicity and bioactivity against insects and pathogens. Additionally, agronomic trials and seed biology studies of these microbes have all contributed to the delivery of robust and efficacious products. The supply chain from science, through seed companies and retailers to the end-user farmer needs to be well resourced providing convincing information on the efficacy and ensuring effective quality control to result in a strong uptake of these Epichloë endophyte technologies in pastoral agriculture.

Antagonism to Plant Pathogens by Epichloë Fungal Endophytes—A Review

“…To the best of our knowledge, no published research documents the biological control of bacterial phytopathogens by Epichloë, although certain endophyte strains can influence the host plant's bacterial microbiota [39]. Furthermore, no correlation exists between the antifungal bioactivity expressed by these endophytes and their alkaloid profiles [40,41] and although several Epichloë-based grass products are marketed across the continents of Australia, North America and South America for their insect deterrent properties [30,31,42], none are marketed for their control of plant diseases. However, Epichloë endophytes can inhibit the growth and reproduction of other microorganisms, including economically important fungal phytopathogens [43].…”

Bioprospecting Desert Plants for Endophytic and Biostimulant Microbes: A Strategy for Enhancing Agricultural Production in a Hotter, Drier Future

“…Just as with endophyte-mediated pathogen resistance, endophyte-mediated pest resistance likely comes from a combination of secondary metabolite production and alteration of signaling pathways. In terms of secondary metabolite production, lipopeptides produced by bacteria can act as host defense inducers [198,199] or insecticidals [200], while the alkaloids produced by fungi are toxic to herbivores [194,[201][202][203]. For instance, Epichloë, a known producer of alkaloids, is a fungal endophyte of grasses [202][203][204].…”

“…In terms of secondary metabolite production, lipopeptides produced by bacteria can act as host defense inducers [198,199] or insecticidals [200], while the alkaloids produced by fungi are toxic to herbivores [194,[201][202][203]. For instance, Epichloë, a known producer of alkaloids, is a fungal endophyte of grasses [202][203][204]. A study by Qin et al [195] on Achnatherum sibiricum, a grass from the Mongolian steppe with inherently low alkaloid production, showed that infection with Epichloë endophytes reduced locust herbivory.…”

Insights into the soil microbiome and prospects for its manipulation for improved pasture resilience

“…A great example in New Zealand is the Epichloë endophytes for enhancing grass productivity and longevity. Decades of research have provided considerable understanding of the different alkaloids produced by different Epichloë strains and strain-ryegrass cultivar interactions, which has supported commercially successful use of these endophytes in improved pasture varieties (Johnson & Caradus 2019;Caradus & Johnson 2020). Similar effort applied to other potentially beneficial microorganisms would likely lead to equally successful advances.…”