Diversity, Ecology, and Applications of Epichloë Fungal Endophytes of Grasses in South America

Abstract

Epichloë fungal endophytes are a conspicuous group of fungi (Ascomycota, Hypocreales, Clavicipitaceae) that form persistent symbiosis with certain cool-season grasses (Poöideae) worldwide. The symbiosis is not vital for the plants but it seems to be associated with fitness benefits, a basic condition for being favorable selected. Epichloë 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 North Hemisphere, where species with sexual or asexual stages are found, Epichloë in South America appears to present its own characteristics. Only asexual vertically transmitted Epichloë have been detected in South America from Venezuela to Argentina. Although research in genetic biodiversity of Epichloë 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 north hemisphere not found in this egion.Interestingly, a few strains or fungal species are associated to more than one host grass species, which contrasts with what is known from North 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 relative plant species also evidence for phylogenetic constrains. Fungal endophytes are being used in programs breeding 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). To know the diversity of Epichloë fungi, the host grasses they infect and the eco-physiological impact on plant fitness, open a big potential to advance ecofriendly tools for the development of a more sustainable agriculture.