Influence of water supply and endophyte infection (Neotyphodium spp.) on vegetative and reproductive growth of two Lolium perenne L. genotypes

To investigate how infection with Neotyphodium spp. affects vegetative and reproductive growth of Lolium perenne L., as influenced by water supply, two endophyte/plant associations were tested in a pot experiment. Clones of the originally infected plants were freed of the endophyte by fungicide treatment. For experimental purposes, the clones were planted separately into pots and subjected to three water supply levels: adequate (control), periodical reduced (drought) or periodical excessive (flooding). In the host genotype originally collected from a dry site, endophyte effects on vegetative and reproductive plant growth depended on water supply. In the drought treatment, endophyte infection did not affect vegetative plant growth, but significantly increased seed yield. In the control and flooding treatments endophyte-infected plants produced less shoot dry matter than the endophyte-free clones, and reproductive growth was not affected by the fungus. However, root dry weight and root/shoot ratio were higher when endophyte was present. Maintenance of low shoot growth and enhanced root growth can improve plant survival particularly in dry areas. Furthermore, water deficiency triggered positive endophyte effects on seed production. These effects were not observed in the genotype originating from a wet site. The results indicate that dry environmental conditions may favour selection of Neotyphodium/L. perenne associations with beneficial endophyte effects on plant persistence and seed production.