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.
Highlights
Plants and microbes have long been recognised to co-exist in a symbiotic relationship, and in some cases, they are known to provide benefit to each other in a mutualistic interaction
This study showed that for the NEA type endophytes, even though they express some level of ergovaline, they did not protect the host plant against root aphid
Epichloë endophytes have been found in a wide range of wild grasses across most temperate regions of the world
Summary
Plants and microbes have long been recognised to co-exist in a symbiotic relationship, and in some cases, they are known to provide benefit to each other in a mutualistic interaction. Asexual Epichloë endophytes exhibit the characteristics of mutualism, systemic infection, high host specificity, vertical (maternal) transfer, and an obligate lifestyle [8] that in many ways make this microbial technology unique and in part explains why as a commercial product, it has been so successful [12]. They are known to produce a large range of secondary metabolites of which the alkaloids are the most well characterised [3,13]. The aim here is to review this mutualistic relationship to determine (1) the origins of Epichloë strain variation, (2) reasons for its importance in many temperate grass pastures, (3) methods of managing its negative and positive characteristics, (4) how effective delivery of commercial Epichloë technologies has been achieved, and (5) how further research opportunities can continue to add value to this economically important relationship, which underpins sustainable pastoral farming practices in managed temperate grasslands
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