NATURE PLANTS | VOL 2 | FEBRUARY 2016 | www.nature.com/natureplants 1 G lobal agriculture faces major challenges, two of them being the heavy use of synthetic pesticides and the changing envi- ronment brought about by climate change 1,2 . Microbial sym- bionts of crop plants could provide solutions for mitigating these problems by improving plant ftness and resistance to several stress- ors. Grasslands in particular are under pressure, as they represent 70% of the world’s agricultural area 3,4 , with approximately 58% and 70% of dairy- and meat-based dietary protein, respectively, being derived from grasslands 5 . Today, the productivity of intensive farming relies heavily on the use of chemical pesticides 6,7 . However, increased global con- cern about the impacts of synthetic plant protection substances on human and animal health is driving changes in agricultural produc- tion practices and related legislation 8 . For example, the European Union (EU) promotes use of less harmful chemicals in agriculture through the European Pesticide Regulation (EC) No. 1107/2009. Te substitution principle, that is, the use of the least hazardous alternatives, determined through comparative risk assessments of plant protection products, will be applied in the EU 9 , and stricter legislation has been implemented to ensure tighter control of pesti- cides in other parts of the world 10 . Tighter regulation of agrichemi- cals, in turn, poses challenges to plant production, as it can lead to reductions in crop yields. Consequently, there is a need for alterna- tive pest control methods, such as integrated pest management — a system-wide approach that minimizes the use of pesticides 2,7 . New synthetic solutions, such as the use of genetically modifed organ- isms (GMO), are not being put to use globally because of concern about their efect on health and the environment. Te EU has prob- ably the strictest regulations in the world for GM products 11 , but tight regulations on GMOs are also applied elsewhere, for example in Japan and New Zealand 12 . Instead of (or in conjunction with) man-made technologies, we could take advantage of naturally occurring agents to make agriculture more sustainable and envi- ronmentally friendly. Epichloë grass endophytes in sustainable agriculture Miia Kauppinen 1 *, Kari Saikkonen 2 , Marjo Helander 2,3 , Anna Maria Pirttilä 4 and Piippa R. Wäli 1 There is an urgent need to create new solutions for sustainable agricultural practices that circumvent the heavy use of fertilizers and pesticides and increase the resilience of agricultural systems to environmental change. Benefcial microbial symbionts of plants are expected to play an important role in integrated pest management schemes over the coming decades. Epichloë endophytes, symbiotic fungi of many grass species, can protect plants against several stressors, and could therefore help to increase the productivity of forage grasses and the hardiness of turf grasses while reducing the use of synthetic pesticides. Indeed, Epichloë endophytes have successfully been developed and commercialized for agricultural use in the USA, Australia and New Zealand. Many of the host grass species originate from Europe, which is a biodiversity hotspot for both grasses and endophytes. However, intentional use of endophyte-enhanced grasses in Europe is virtually non-existent. We suggest that the diversity of European Epichloë endophytes and their host grasses should be exploited for the development of sustainable agricultural, horticultural and landscaping practices, and potentially for bioremediation and bioenergy purposes, and for envi- ronmental improvement. In addition to the overuse of synthetic pesticides, climate change also sets challenges for today’s agriculture. Extreme weather condi- tions are expected to become more frequent, and increasing water scarcity, together with overgrazing and erosion, are threatening many agricultural regions, especially dry grasslands 1,13 . Although climate change may expand the extent of arable land area, there may also be a concomitant spread of new pests, pathogens and weed spe- cies 1 . Tus, there is a need to increase drought resistance of both for- age and crop plants, and to develop new plant protection methods and practices to enhance the resilience of agriculture to the poten- tial efects of climate change. Epichloë endophytes can contribute to the establishment of sustainable agricultural systems 14,15 , as they are natural fungal symbionts of many agriculturally important grass species and can improve the ftness of their hosts 16 . It is also possible to create new grass cultivars by inoculating grasses with endophytes. Compared with other plant-ftness-promoting microbes that can be used in agriculture and need to be continuously added to the production environment (such as mycorrhizal fungi 17 and rhizobacteria 18 ), systemic Epichloë endophytes are maternally inherited and persist in grass lines afer inoculation 19,20 . Te ability of these endophytes to improve agricultural and turf production is well acknowledged and taken into account in grass breeding, especially in the USA, Australia and New Zealand. In Europe, however, endophytes are largely ignored in grass breeding programs and in agriculture, even though they have been documented in many European cultivars 21,22 . Detailed reviews of plant breeding, development and the success of Epichloё endophytes are provided elsewhere 14,23,24,25 . Biology of Epichloë endophytes Epichloë endophytes are one of the most studied genera of the asco- mycete family Clavicipitaceae, and in endophyte research in gen- eral 26,27 . Tey are symbiotic fungi that inhabit above-ground plant tissues without causing apparent disease symptoms 16 . Epichloë 1 Department of Ecology, FI-90014 University of Oulu, Finland, 2 Natural Resources Institute Finland (Luke), Management and Production of Renewable Resources, Itäinen Pitkäkatu 3, 20520 Turku, Finland, 3 Section of Ecology, Department of Biology, FI-20014 University of Turku, Finland, 4 Department of Genetics and Physiology, FI-90014 University of Oulu, Finland. *e-mail: Miia.Kauppinen@oulu.f PERSPECTIVE PUBLISHED: 3 FEBRUARY 2016 | ARTICLE NUMBER: 15224 | DOI: 10.1038/NPLANTS.2015.224 © 2016 Macmillan Publishers Limited. All rights reserved