Three Lolium perenne L. genotypes collected from different natural habitats were tested for the effects of their fungal endophyte Neotyphodium spp. on plant growth and seed yield. Half the clones of the originally infected plants were subjected to fungicide treatment to eradicate the endophytes. In an experiment, the clones were planted separately into pots and were either watered adequately or subjected to drought stress. In the genotype collected from a dry site, the endophyte infection reduced plant growth at an adequate water supply, but increased regrowth under drought. In the genotype from a periodically either flooded or dry site, endophyte infection significantly promoted the development of reproductive tillers and seed production (effects which are associated with adaptation to drought). In contrast, the genotype that originated from a wet site showed higher sensitivity to drought stress when endophyte infection was present. The results suggest that environmental conditions in the original habitat of the plants may influence the symbiotic interaction between plant and fungus, probably through natural selection. However, endophyte-induced increases in root dry weight and root/shoot ratio were recorded for all three genotypes. These features could be beneficial for plant persistence, especially on sites where water is the growth-limiting factor.

Many wild and cultivated grasses live in mutualistic symbiosis with endophytic fungi of the genera Neotyphodium and Epichloe¨. These associations are of agronomic importance because endophytes may induce a range of beneficial effects for the host plant but also produce alkaloids detrimental to livestock. Conventional detection of endophytes by means of histological staining is time-consuming and not suited for large numbers of samples. Therefore, in order to simplify the detection of endophytic fungi the utility of tissue print immunoassay (TPIA) was studied and compared with the commonly used microscopic analysis. Ecotypes collected from natural grassland habitats and plants from field experiments were analyzed for endophyte infection. Both methods provided similar results. Based on stained or non-stained mycelium in tissue prints, endophyte-infected (E+) and endophyte-free (E-) tillers and inflorescences of Festuca pratensis, F. arundinacea and F. rubra were clearly distinguishable. Prints of cross sections of tillers allow the precise localization of endophyte infection within the plant tissues. Because TPIA allows the examination of endophytes in individual branches and segments of inflorescences it is a useful method for dissemination studies. Tissue print immunoassay appears to be a reliable method suited for routine work in research, practical grassland management and selection of defined E+ or E-material for breeding.

The aim of this study was to investigate whether Neoptyphodium spp. endophytes, fungal symbionts of cool‐season grasses, can be selected to improve plant growth and seed yield of perennial ryegrass (Lolium perenne L.). Endophyte‐infected (EI) and endophyte‐free (EF) clones of 13 L. perenne genotypes, collected from native habitats with stressful environmental conditions, were evaluated in a field experiment for symbiotic effects on plant growth (herbage yield, reproductive tiller number), seed production, and seed quality parameters [1000‐seed weight (TSW), germination] over 3 yr in an area with low rainfall (Halle, Germany). The results revealed high variability in endophyte effects on the investigated parameters. In seven genotypes, endophyte presence improved plant growth and seed production during the first harvest year. However, in four of these genotypes, endophyte effects were reversed in the following harvests. In the remaining six genotypes, endophyte infection reduced plant performance. The impact of the fungus on TSW was inconsistent, while seed germination was either improved or not affected by the endophyte. A positive endophyte effect was detectable for genotypes with low performance of EF clones, whereas genotypes with high‐yield EF clones were not, or negatively, affected by the endophyte. Genotypes originating from sites exposed to flooding and periodic drought showed consistent negative endophyte effects on herbage yield and seed production. Since reduced shoot growth is a drought avoidance mechanism, further studies are needed to determine whether endophytes in these genotypes improve adaptation to drought, or represent a “metabolic cost.” Our results indicate that some Neotyphodium endophytes have the potential to improve plant performance of L. perenne, but the selection of strains with consistent beneficial effects on plant growth is difficult.

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