Epichloë − a lifeline for temperate grasses under combined drought and insect pressure

Fungal Epichloëendophytes form symbiotic associations with many temperate grasses,such as Lolium and Festuca,giving their host grasses an ecological advantage.The importance of specific Epichloëendophytes in providing varying levels of protection against invertebrate pests has been well documented.Similarly,but with fewer studies,the benefits of Epichloëto host grasses in drought events has been shown.Endophyte-infected grasses show an improved persistence against herbivore insect attack as well as resilience under drought.However,there are relatively few studies that investigate the interaction between drought and insect pressure,and yet it is these combined pressures that can prove detrimental for a ryegrass or fescue crop.This review examines the current state of knowledge on the effects of Epichloëon the interactions of insects and drought in temperate grasses.

Costs and benefits of hosting Epichloë endophytes: a comparison of three haplotypes in Lolium perenne with contrasting effects on two herbivores

The symbiotic relationship between Lolium perenne and Epichloëfestucae var.lolii,a fungal endophyte that lives asymptomatically in its above-ground parts,benefits both the host and fungus.In an outdoor container experiment,the effects of three distinct endophyte haplotypes(AR1,AR37 and CT)on natural infestations of a root aphid,Aploneura lentisci and a mealybug Phenococcus graminicola were compared with an endophyte-free(Nil)control.Populations of these insects were suppressed in a genetically identical set of plants treated with insecticide.Over 18 months,foliar and root growth,tiller numbers and plant mortality were compared between the different endophyte treatments and between insecticide-treated and untreated plants.Hyphal densities were recorded once during the trial.Untreated plants infected with AR37 had the lowest populations of A.lentisci and P.graminicola,and the highest root and foliar growth compared with other treatments.Growth parameters of untreated plants infected with CT often exceeded that of AR1 and Nil due to low infestations of P.graminicola and lower populations of A.lentisci.Growth of Nil,AR1 and CT plants were higher in insecticide-treated than in corresponding untreated plants but was unaffected in AR37.Untreated Nil and AR1 plants had a lower survival than AR37 and CT plants.Cumulative root outgrowth for treated AR37 plants was significantly lower than for treated AR1 on three sampling occasions.These Epichloëhaplotypes are primarily mutualists,although there are circumstances when they may be disadvantageous to their host.Opposing outcomes likely originate in the ecosystems in which associations evolved.

The exploitation of epichloae endophytes for agricultural benefit

Epichloae endophytes of family Clavicipitaceae(comprising genera Epichloëand Neotyphodium)are fungal symbionts of Pooideae grasses.The associations formed,range from mutually beneficial to antagonistic and the nature of this relationship is dependent upon the importance of vertical(via host seeds)versus horizontal(ascospore mediated)transmission of the fungus.These endophytes can enhance their hosts’survival through protection from abiotic and biotic stresses and can thus be utilized in an agricultural context.Animal-safe grass-endophyte associations that confer bio-protective properties for increased pasture persistence and productivity have been developed and commercialized.One of the crucial drivers underpinning the selection of epichloae strains for commercial development is endophyte derived bioactivity.The potential of next generation endophytes is determined by testing a number of attributes such as agronomic fitness,animal and food safety as well as compatibility with host plants of interest.Strategic research supports these activities by focusing on elucidating mechanisms of compatibility between host and fungal symbiont,as well as investigating other molecular drivers of symbiosis such as siderophore mediated iron-uptake,fungal signalling,fungal growth in host plants and fungal secondary metabolism.This review weaves together the different strands of multidisciplinary research aimed at ultimately exploiting epichloae endophytes for increased pasture performance.