Investigations on the Influence of Neotyphodium Endophytes on Plant Growth and Seed Yield of Lolium perenne Genotypes.

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. [ABSTRACT FROM AUTHOR]