Abstract: The potential of fungal root endophytes to suppress vertically transmitted infections in barley cultivars has only been studied in relatively few symbiotic associations, and is virtually unknown for endophytes derived from wild barley species. Here, we show that fungal root endophytes derived from wild populations of Hordeum murinum ssp. murinum L. suppressed the development of seed-borne infections in a barley cultivar when inoculated onto seed in combination and individually on a range of growth media. The plant sampling sites were characterised by relatively high soil pH, high soil salinity and low soil moisture content. The fungal endophytes isolated from plants growing in the most saline soil with the lowest moisture content and cultured in the medium with a pH most similar to the sampling sites were most successful in suppressing seed-borne infections. We further show that the two most effective endophytes were also the most persistent as re-emergents from infected roots, and are easily cultured and sporulate readily. To our knowledge, this is the first time that fungal root endophytes isolated from roots of Hordeum murinum ssp. murinum have been shown to control vertically transmitted barley infections. These results suggest that fungal root endophytes derived from a wild barley species may have potential as biocontrol agents and seed inoculants for barley cultivars growing in similar and previously unsuitable soils.