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Epichloe fungal endophytes are a conspicuous group of fungi (Ascomycota, Hypocreales, Clavicipitaceae) that form persistent symbiosis with certain cool-season grasses (Pooideae) worldwide. The symbiosis is not vital for the plants, but it seems to be associated with fitness benefits, a basic condition for being favorably selected. Epichloe endophytes infect systemically green tissues, and while sexual stages reduce fertility of the host plant, their asexual forms persist asymptomatically through generations by means of vertical transmission (from plant to seeds). Host plants are endowed by a suite of fungal alkaloids that can be toxic to livestock (such as ergot alkaloids and lolitrem B) or protect plants against herbivorous insects (lolines and peramine). Mainly studied in the Northern Hemisphere, where species with sexual or asexual stages are found, Epichloe in South America appears to present its own characteristics. Only asexual vertically transmitted Epichloe has been detected in South America from Venezuela to Argentina. Although research in genetic biodiversity of Epichloe fungi in South America is in the dawn and mostly restricted to Argentina, we know that most of the endophytes from South America evolved from hybridization events among species from the Northern Hemisphere not found in this region. Interestingly, a few strains or fungal species are associated to more than one host grass species, which contrasts with what is known from the Northern Hemisphere. Regional surveys of grass-endophyte associations indicate that some environmental conditions promote the symbiosis while others don’t (e.g., aridity). However, variation among closely related plant species also evidences phylogenetic constrains. Fungal endophytes are being used in breeding programs of forage crops with two main goals: (i) replace those wild toxic endophytes and (ii) inoculate endophytes that protect host plants against agricultural plagues (as agents of biological control). The knowledge of the diversity of Epichloe fungi, the host grasses they infect, and the ecophysiological impact on plant fitness opens a big potential to advance eco-friendly tools for the development of a more sustainable agriculture.

This study compares the culturable fungal endophytic community inhabiting leaves of Epichloë-infected (E+) and Epichloë-free (E-) plants of Poa bonariensis. Plants were collected from a wild population (dioecious species) where E+ and E- plants co-exist. Fungal endophytes were isolated and then morphology and ribosomal DNA internal transcribed spacer sequences were used for the identification of isolates. In total 24 different taxa of non-Epichloë (NE) endophytes were identified. No significant differences were found in richness and diversity indexes of NE-endophytes between E+ and E- plants, or between pistillate (P) and staminate (S) plants. When we analyzed these effects based on the count of the most abundant genera, Alternaria and Stemphylium infection frequencies decreased in S plants, while in E+ plants, this tendency was observed for Alternaria. Our results suggest that Epichloë and the sex of the host plant may modulate some of the dominant foliar endophytic fungal taxa. Fil: Mc Cargo, Patricia Débora. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Micología y Botánica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Micología y Botánica; Argentina Fil: Iannone, Leopoldo Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Micología y Botánica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Micología y Botánica; Argentina Fil: Soria, Marcelo. Universidad de Buenos Aires. Facultad de Agronomía; Argentina Fil: Novas, María Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Micología y Botánica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Micología y Botánica; Argentina

Neotyphodium endophytes and arbuscular mycorrhizal (AM) fungi are common constituents of natural grasslands. The plant?endophyte symbiosis can introduce changes in soil conditions that affect the density and activity of different functional groups of soil organisms. A few experiments have reported that leaf endophytes can reduce mycorrhizal sporulation and colonization of host roots in agronomic hosts, contrasting with the studies we have conducted in native grasses from Argentina. In the present work we performed in vitro assays to evaluate the effect of root and endophyte exudates on the pre-infective state of mycorrhizal fungi (Gigaspora margarita and G. rosea). Plant roots of Bromus setifolius, from populations of Patagonia and four strains of Neotyphodium were used to obtain the exudates. Root exudates of infected plants, at a high concentration, significantly increased AMF hyphal branches and length. The effect of endophyte exudates on AMF mycelia lenght, varied depending on strain and the concentration used, suggesting a differential interaction between endophyte and AMF species. AMF hyphal branches were increased by fungal exudates in both mycorrhizal species. This study reports the direct and positive effect of Neotyphodium endophytes on AMF pre-infective state, supporting previous information on native grasses. Fil: Novas, María Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Micología y Botánica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Micología y Botánica; Argentina Fil: Iannone, Leopoldo Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Micología y Botánica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Micología y Botánica; Argentina Fil: Godeas, Alicia Margarita. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones en Biociencias Agrícolas y Ambientales. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones en Biociencias Agrícolas y Ambientales; Argentina Fil: Scervino, Jose Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones en Biociencias Agrícolas y Ambientales. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones en Biociencias Agrícolas y Ambientales; Argentina

Background and aims: Plants often establish multiple simultaneous symbiotic associations with different micro-organisms; however, the way in which each symbiont affects the other symbionts and the effects of these multiple interactions on plant performance are not well understood. The aim of this study was to evaluate how two different asexual Epichloë species modulate the establishment of arbuscular mycorrhizal fungi (AMF) in a wild forage grass under different soil fertilization levels. Methods: We performed a completely randomized 12-month-long field experiment to evaluate the effect of two B. auleticus-endophyte ecotypes and two soil fertilization levels on the colonization of AMF, in seedlings and adult plants. Plant biomass and reproductive tillers production were also measured. Results: The symbiosis, measured as the total extent of AM fungal colonization and frequency of arbuscules was significantly higher in Epichloë-infected plants and was not affected by fertilization either in seedlings or in adult plants. Plant biomass was increased by fertilization but no differences were observed due to the endophytic status. However, E+ plants produced more panicles than their E− counterparts. Conclusions: Our findings strongly support the hypothesis of positive association between Epichloë endophytes and AMF in wild grasses, making this model important for agronomic improvement. Fil: Vignale, Maria Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Micología y Botánica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Micología y Botánica; Argentina Fil: Iannone, Leopoldo Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Micología y Botánica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Micología y Botánica; Argentina Fil: Pinget, Albertina Daniela. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Entre Ríos. Estación Experimental Agropecuaria Concepción del Uruguay; Argentina Fil: De Battista, José P.. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Entre Ríos. Estación Experimental Agropecuaria Concepción del Uruguay; Argentina Fil: Novas, María Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Micología y Botánica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Micología y Botánica; Argentina

The interaction between mycorrhiza and leaf endophytes (Neotyphodium sp.) was studied in three Poa bonariensis populations, a native grass, differing significantly in endophyte infection. The association between endophytes and mycorrhizal fungi colonisation was assessed by analysing plant roots collected from the field. We found that roots from endophyte-infected populations showed a significantly higher frequency of colonisation by mycorrhizal fungi and that soil parameters were not related to endophyte infection or mycorrhiza colonization. In addition, we did not observe significant differences in the number of AM propagules in soils of the three populations sites. We also report the simultaneous development of Paris-type and Arum-type mycorrhiza morphology within the same root systems of P. bonariensis. The co-occurrence of both colonisation types in one and the same root system found in the three populations, which differed in Neotyphodium infection, suggests that foliar endophytes do not determine AM morphology. The percentage of root length colonised by different types of fungal structures (coils, arbuscules, longitudinal hyphae and vesicles) showed significant and positive differences in arbuscular frequency associated with endophyte infection, whereas the much smaller amounts of vesicles and hyphal coils did not differ significantly. Fil: Novas, María Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Micología y Botánica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Micología y Botánica; Argentina Fil: Iannone, Leopoldo Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Micología y Botánica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Micología y Botánica; Argentina Fil: Godeas, Alicia Margarita. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Biodiversidad y Biología Experimental y Aplicada. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biodiversidad y Biología Experimental y Aplicada; Argentina Fil: Cabral, Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Micología y Botánica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Micología y Botánica; Argentina