Endophytic fungi live their whole life within host tissues usually without any visible symptoms. Their vertical transmission (seed-plant-seed) has been well described and documented. However, horizontal transmission (plant-plant) needs more clarification. The aim of this study was to assess the extent to which endophytes move vertically in ecotypes of perennial ryegrass and whether there is evidence for the horizontal transmission of endophytes. Ecotypes from grasslands in Poland were collected in the form of living plants and used for vertical transmission analysis. Plants, the seed collected from these plants and plants grown from this collected seed were tested for endophytic infection. Provided that all produced seeds were viable and able to germinate and produce seedlings, the vertical transmission of Neotyphodium endophytes in perennial ryegrass ecotypes was nearly complete. For the horizontal transmission experiment, endophyte-hosting plants (E+) and endophyte-free plants (E-) of four cultivars were planted in the field in close proximity on small plots that were frequently mown. These studies revealed that after 7 months of growth next to E+ plants, the characteristic Neotyphodium spp. mycelia were found in E- plants, which was especially true for plants growing in close proximity to the infected plants. The occurrence of horizontal transmission of endophytes has not been previously demonstrated.

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Background: The phenomenon of plant mutualistic symbiosis with microbes may have a positive effect on the improvement of plant tolerance to environmental stresses. The in uence of fungal endophyte of the Epichloë sp. (Clavicipitaceae) on perennial ryegrass (Lolium perenne L.) plants grown in presence of elevated concentration of heavy metal (HM) ions (Cd 2+ , Pb 2+ and Cu 2+) in soil was studied. Results: The presence of Epichloë in the host grass tissues resulted in increased accumulation of HM ions in aerial parts of plants and was dependent on host genotypes related to host plant origin. In plants with (E+) and without (E-) endophytes the hormesis effect was induced by the elevated concentration of Cu 2+ ions, resulting in better growth and photosynthesis, as examined by measurements of Chl a uorescence. The obtained results indicate that based on the laboratory evaluation of the e ciency of the symbiosis, we were able to choose the best associations of perennial ryegrass with endophytes for HM phytoremediation. Conclusions: The presence of Epichloë endophytes positively affected ryegrass ability to accumulate HM ions and this accumulation was associated with the origin of Epichloë-ryegrass symbionts.

The phenomenon of plant mutualistic symbiosis with microbes may have a positive effect on the improvement of plant tolerance to environmental stresses as well as on the ability of plants to accumulate heavy metal (HM) ions from soil. The influence of Epichloë fungal endophyte (Ascomycota, Clavicipitaceae) on perennial ryegrass (Lolium perenne L.) plants grown in the presence of elevated concentrations of HM ions (Cd2+, Pb2+, and Cu2+) in soil was studied. The presence of Epichloë in the host grass tissues resulted in different accumulation of HM ions in the aboveground parts of the plants. In some cases, endophyte infection positively affected ryegrass ability to accumulate HM ions from soil. In plants with (E +) and without (E −) endophytes, the hormesis effect was induced by the elevated concentration of Cu2+ ions, resulting in better growth and photosynthesis, as examined by measurements of Chl a fluorescence. The obtained results indicate that based on the laboratory evaluation of the efficiency of HM accumulation, we were able to choose the best associations of perennial ryegrass with endophytes for HM phytoremediation.

The rapid development of civilization increases the area of land exposed to the accumulation of toxic compounds, including heavy metals, both in water and soil. Endophytic fungi associated with many species of grasses are related to the resistance of plants to biotic and abiotic stresses, which include heavy metals. This paper reviews different aspects of symbiotic interactions between grass species and fungal endophytes from the genera Epichloë with special attention paid to the elevated concentration of heavy metals in growing substrates. The evidence shows the high resistance variation of plant endophyte symbiosis on the heavy metals in soil outcome. The fungal endophytes confer high heavy metal tolerance, which is the key feature in its practical application with their host plants, i.e., grasses in phytoremediation.