Endophyte symbiosis benefits a rare grass under low water availability

Abstract

Summary 1.Symbiotic relationships with microbes may influence how plant species respond to environmental change. Here, we investigated how a fungal endophyte symbiosis affects the growth and survival of a rare, mid-western United States grass species under altered water availability. In a 12-week long greenhouse experiment, we compared the performance of endophyte-infected and endophytedisinfected grove bluegrass ( Poa alsodes , Poaceae) subjected to two levels of water availability. Gravimetric water measurements indicated that the low water treatment had 24% less soil moisture than the high water treatment. 2. In the high water treatment, the performance of endophyte-infected plants and disinfected plants was similar. However, under low water, endophyte-infected plants had 17% more total biomass than disinfected plants. Despite localization of the endophyte in above-ground plant tissues, effects of the endophyte were stronger below-ground: Under low water, endophyte-infected plants produced 24% more root biomass, but just 14% more shoot biomass than disinfected plants. When water-limited, disinfected plants had 29% greater leaf senescence than endophyte-infected plants. 3. We investigated several plant traits that may underlie benefits of symbiosis. Under low water, disinfected plants had significantly higher relative leaf water content than endophyte-infected plants, consistent with the hypothesis that endophytes cause plants to up-regulate water conservation mechanisms faster in response to drought. There were no strong differences between endophyteinfected and disinfected plants in root morphology, leaf area or water use efficiency, although plants with the endophyte had slightly shorter leaves. 4. Our results suggest that endophyte symbiosis may ameliorate the negative effects of drought stress for grove bluegrass. The heritable transmission of endophytes from plants to seeds provides opportunities for environmental change to influence selection on native grass-endophyte symbioses.

Benefits of a symbiotic association with endophytic fungi are subject to water and nutrient availability in Achnatherum sibiricum

“…By understanding how complex interactions between plants and their associated symbionts vary with stress, we can make better predictions about how climate change will influence species distributions and abundances in the future (Kannadan and Rudgers 2008). For A. sibiricum, we predict that enhanced N supply will result in greater benefits of the symbiosis for plant growth.…”

“…Plants were grown in the greenhouse for about 5 months prior to cloning. This procedure allowed the subsequent assessment of plant performance to be separated from the initial heat treatment by a round of vegetative reproduction, and is commonly used in endophyte studies (Morse et al 2007;Kannadan and Rudgers 2008). On June 1, 2009, we moved the plants out to the experimental field.…”

“…To eliminate the endophyte, we heat-treated a subset of randomly chosen seeds in a convection drying oven according to Kannadan and Rudgers (2008). Because disinfection procedures have not been established for this species, we initially treated seeds for 0, 5, 10, 15, 20, 25 or 30 days at 60°C to determine optimal treatment time.…”

“…Symbiotic relationships may influence how plants respond to environmental change (Kannadan and Rudgers 2008). It has been well documented that endophytic fungi can improve drought resistance in a few species of agronomically important forage and turf grasses, namely perennial ryegrass (Lolium perenne L.) and tall fescue (Lolium arundinaceum Darbyshire ex.…”

Water availability alters the tri-trophic consequences of a plant-fungal symbiosis

“…This result contributes to a growing body of literature demonstrating benefits of fungal endophytes in native grasses (see also Bazely et al 1997;Clement et al 2005;Gonthier et al 2008;Kannadan and Rudgers 2008;Crawford et al 2010). However, the benefit to P. autumnalis was highly contextdependent, and only present when water availability was low.…”