Effects Of Endophytic Species, Host Genotype And Water/Nutrient Supply On The Performance Of Grass-endophyte Symbionts

Endophyte was widespread in native grasses and had a broad impact. However, a vast majority of research were focus on agronomic grasses, with less of native grasses as the target. In some studies, endophyte infection could benefit their hosts, while in other studies, endophyte-infected grasses did not appear to be competitive over those that were endophyte-free. It was reported that in native grass populations, endophytic fungal communities might be more diverse and variable than that of agronomicly and economically important species. The reason might be related to the endophyte species, plant genotype and also habitat factors. However, few studies concerned all factors together because of the immature technology, especially considering the endophyte species, host plant genotype, and the effect of habitat factors on the symbiotic relationship. Host plant genotype was an important factor, which was difficult to control in experiment. In our study, we selected three different natural grasses Achnatherum sibiricum, Achnatherum robustum and Festuca arizonica as our research objects with re-inocultion method. The effects of endophytic species, host genotype and water/nutrient supply on the performance of grass-endophyte symbionts were reported in our experiments. We studied host genotype and endophyte infection effects on growth and physiology of Achnatherum sibiricum and Festuca arizonica with re-inoculation method; and we also stuied the effects of plant genotype and endophyte species on growth and drought stress response of Festuca arizonica and Achnatherum robustum plants, which were from two natural grass populations. Several main conclusions were drawn as follows:(1) In our study, the prominent host genotype-endophyte infection interactions detected in A. sibiricum indicates that, for many growth and storage traits, endophyte infection had few effects. However, there is no overriding consistently positive effect of the endophyte on growth or storage in A. sibiricum before or after clipping. Our study showed that the interaction between endophyte and host grasses was highly contingent on plant genotypes. We found host genotype overrode fungal endophyte infection in influencing tiller number and photosynthetic properties of A. sibiricum before clipping. After clipping, host genotype accounted for more of the variation in re-growth and above-ground biomass of A. sibiricum than endophyte infection. Our study showed that host genotype affected the total nonstructural carbohydrates of A. sibiricum before and after clipping, whereas endophyte infection increased the carbon content after clipping.(2) The difference of growth parameters and physiological parameters dependent on the different transmission mode among plants.Neotyphodium infection had a significant positive effect on both leaf length and plant height of Achnatherum sibiricum, but this difference was significantly negative in Epichloe infection plants. Maximum net photosynthetic was significantly higher for endophyte-free plants than for Neotyphodium and Epichloe plants. In endophyte infection plants, Neotyphodium infection plants have a significantly higher maximum net photosynthetic than that of Epichloe plants. Neotyphodium infection accumulated more soluble sugar in host plant than endophyte-free plants.(3) In high water treatment, infected plants of sleepygrass from the Weed population had longer leaf length compared with uninfected plants. In contrast, plant population 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.(4) For Arizona festuca, the symbiotic relationship also depended on specific combination of host plant genotype and endophyte species in addition to the influence of water and nutrient conditions. In low water and low nutrient treatment, hybrid plant genotype of Arizona fescue has higher tiller number and root:shoot than non-hybrid plant genotype. In high water and high nutrient treatment, hybrid endophyte significantly increased the biomass of host plants, while non-hybrid endophyte had higher root:shoot. In these two treatments, hybrid endophyte significantly improved the tiller number and root dry weight of Arizona fescue.These conclusions provided some experimental basis for further understanding the complex symbiotic relationship. It also provided a basis for the conservation and sustainable use of biological resources.