Fungal root endophytes of a wild barley species increase yield in a nutrient-stressed barley cultivar Brian R. Murphy & Fiona M. Doohan & Trevor R. Hodkinson Received: 20 November 2014 /Accepted: 15 January 2015 /Published online: 26 January 2015 # Springer Science+Business Media Dordrecht 2015 Abstract Overuse of chemical fertilisers in barley crops carries large economic and environmental costs and can lead to ecosystem degradation and loss of biodiversity. Methods of reducing chemical crop inputs using endophyte treatments have been demonstrated elsewhere. Here, we show that inoc- ulation with six different fungal root endophytes isolated from wild populations of Hordeum murinum ssp. murinum in- creased grain yield in a nutrient-starved barley cultivar by up to 29 %. Furthermore, we also show that inoculation with the isolates induced increases of up to 70 % in shoot dry weight in the nutrient-starved barley. The greatest increases in grain yield and shoot dry weight were achieved under the lowest nutrient input. Several of the isolates may be new species, and one particularly effective isolate has previously been shown to completely suppress seed-borne infections of barley. Our re- sults indicate that novel fungal root endophytes derived from a wild relative of barley may help to reduce fertiliser inputs while maintaining acceptable yields. If this potential can be realised in field crops it may result in more sustainable, eco- nomically cost-effective and environmentally friendly crop treatments and a reduction in chemical fertiliser use. Keywords Barley . Biofertilisation . Fungal root endophytes . Nutrient stress . Symbiosis 1 Introduction Barley (Hordeum vulgare L.) is the world’ s fourth most im- portant cereal crop, grown annually on 48 million hectares (CGIAR 2012), and like other food crops grown as monocul- tures, uses significant inputs of chemical fertilisers. Total glob- al fertiliser consumption reached 180 mt in 2012 (FAO 2012), and according to one estimate, application of N-P-K fertilisers to barley crops alone worldwide will be over 4 mt in 2014 (Rosas 2011), which represents large economic and environ- mental costs, along with ecosystem degradation and potential losses in biodiversity (Dobermann and Nelson 2013). Ways of reducing these costs whilst still maintaining acceptable yields are required if sustainable agricultural practices are to be wide- ly adopted. Inoculating barley with beneficial endophytic or- ganisms may provide part of the solution. Endophytes are microorganisms (bacteria, fungi and uni- cellular eukaryotes) which can live at least part of their life cycle inter- or intracellularly inside of plants usually without inducing pathogenic symptoms. This can include competent, facultative, obligate, opportunistic and passenger endophytes. Endophytes can have several functions and/or may change function during their lifecycle (Murphy et al. 2013). Fungal root endophytes (hereafter endophytes) have been shown to increase biomass in several globally important food crops, including cereals such as barley (Waqas et al. 2012). The model endophyte Piriformospora indica was first isolated from the roots of desert shrubs (Prosopis juliflora (Swartz) DC. and Zizyphus nummularia (Burm. fil.) Wt. & Arn.) in north-west India (Verma et al. 1998) and has been shown to increase grain yield in barley (Waller et al. 2005; Achatz et al. 2010; Murphy et al. 2014a, b). Although it has been shown to increase grain yield in cool-cultivated barley under some cir- cumstances (Murphy et al. 2014a, b), it may not generally be suitable for use in cooler growing conditions. There is also the danger of releasing this organism as an invasive species into B. R. Murphy (*) : T. R. Hodkinson School of Natural Sciences & Trinity Centre for Biodiversity Research, Trinity College Dublin, College Green, Dublin 2, Ireland e-mail: murphb16@tcd.ie F. M. Doohan UCD Earth Institute and School of Biology & Environmental Science, University College Dublin, Dublin 4, Ireland Symbiosis (2015) 65:1–7 DOI 10.1007/s13199-015-0314-6