Plant population and genotype effects override the effects of Epichloë endophyte species on growth and drought stress response of Achnatherum robustum plants in two natural grass populations

Aims In cool-season grasses,systemic and vertically transmitted Epichloëinfections often provide a suite of benefits including increased growth,reproduction and competitive abilities.However,these effects of Epichloëendophytes on their hosts often depend upon host and endophyte genotype and environmental factors.Methods Achnatherum robustum(sleepygrass)harbors at least two Epichloëspecies within natural populations in the southwest USA.We tested the effects of endophyte infection and species,host population and plant genotype(by experimentally removing the endophyte),and soil moisture(a key limiting factor)on growth and drought stress response of infected A.robustum plants from two populations(Weed and Cloudcroft)in the sacremento mountains of New mexico,USA).Important Findingsalthough the two populations harbor distinct Epichloëspecies each with very different chemoprofiles,neither endophyte status(infected vs.uninfected)nor endophyte species affected most growth param-eters at 8 or 25 weeks of the experiment,except for leaf length.In high water treatment,infected plants from the Weed population had longer leaf length compared with uninfected plants.In contrast,the population of origin affected all growth parameters,including plant height,leaf number,length and width,tiller number and shoot and root biomass,as well as wilting time.grasses from the Cloudcroft population generally showed greater growth than grasses from the Weed population.Endophyte infection did affect wilting time,with infection in the Weed population generally reducing time to wilting under low and high water,whereas infection in the Cloudcroft population reduced time to wilting only under high water conditions.our results suggest that plant population and their associated plant genotypes may play a much larger role in endophyte-host grass interactions in varying environments than previously thought.asexual Epichloëspecies may be compatible with only specific host genotypes within populations such that the phenotypic effects due to population may be greater than phenotypic changes influenced by variation in the endophyte.

Neotyphodium fungal endophyte in tall fescue (Schedonorus phoenix): a comparison of three Northern European wild populations and the cultivar Kentucky-31

Pooideae grasses may be colonized by systemic fungal endophytes.The fitness of endophyte depends entirely on resources and seed transmission from the host plant,while colonized plants may gain increased survival,growth,and reproduction relative to their uncolonized conspecifics.Most research of endophyte-grass interactions have been carried out on few cultivars of tall fescue(Schedonorus phoenix)and their symbiont Neotyphodium coenophialum.Lack of studies using wild populations of tall fescue across the species natural distribution range,however,limits the understanding of the ecological and evolutionary role of the symbiosis in nature.We performed a common garden experiment in Southern Finland with three wild,tall fescue populations from northern Europe and the forage cultivar Kentucky-31(KY-31).For each population,we used naturally endophyte-colonized,naturally endophytecolonized but endophyte removed(decolonized),and naturally uncolonized plants to separate effects due to the host genotype from the endophyte.We evaluated growth variables and survival in four environmental treatments of varying water and nutrients.Supply of water and nutrients increased plant biomass and reproductive effort in all populations.This effect was higher for KY-31 plants which produced on average 55%more seeds than wild plants,indicating better adaptation to high resource environments.However,the higher incidence of Claviceps sp.and the low winter survival indicated KY-31 tall fescue is mal-adapted to Northern European conditions.Naturally colonized plants had greater plant biomass(≈12%),reproductive effort(≈22%)and seed mass(≈29%)than naturally uncolonized and decolonized plants.Nonetheless,endophyte colonization did not affect plant survival,and the effects of endophyte colonization on tiller number,panicle/tiller ratio and Claviceps sp.incidence depended on the population origin.In the wild populations,endophyte removal only reduced the number of tillers(≈29%lower),while the difference between naturally colonized and naturally uncolonized plants was not significant.Our results show that endophyte symbiont increases tall fescue performance in general,but the differences between wild populations and cultivars indicate adaptation to local habitats and agronomic management,respectively.The comparison of naturally endophyte-colonized and decolonized plants suggests certain plant genotype-endophyte combinations found within populations result from local selection pressures.