Isolation of Novel Fungal Endophytes from Wild Relatives of Barley (Hordeum vulgare L.) and In Vitro Screening for Plant Growth Promotion and Antifungal Activity

There is an urgent demand for sustainable agricultural practices that minimize environmental impacts and reduce the reliance on synthetic pesticides and fertilizers. Endophytes represent a largely untapped resource of beneficial microorganisms with multiple potential applications as natural biocontrol agents and promoters of plant growth and development. This paper aimed at identifying new fungal strains and performing a series of preliminary in vitro screenings to evaluate their potential use for plant-growth promotion and antifungal activity. A total of 102 fungal endophytes were isolated from different plant tissues of seven wild relatives of barley (Brachypodium sylvaticum, Bromus hordeaceus, Bromus sterilis, Elymus farctus, Elymus repens, Leymus arenarius and Lolium perenne) that were sourced from 22 contrasting wild habitats. Fungal endophytes were isolated using standard culture-based methods and identified via DNA barcoding of the nrITS marker. Based on a literature search, a sub-group of endophytes were selected and evaluated for indole-3-acetic acid (IAA) synthesis, ammonia production and phosphorous (P) solubilization. From these, 15 endophytes were also tested for antifungal activity against Ramularia collo-cygni, Pyrenophora teres, and Gaeumannomyces tritici. All the endophytes were positive for ammonia production at variable rates, but no P solubilization nor IAA synthesis without L-tryptophan were observed. On the contrary, five promising isolates (2 Daldinia concentrica, Metapochonia suchlasporia, Chaetomium sp., and Ophiocordyceps sinensis) had mean pathogen growth inhibition rates above 80%, compared to the untreated negative controls. To the best of our knowledge, this study is the first published report that investigates natural antagonism against Ramularia collo-cygni and expands the list of endophytic strains with natural antagonism on the tested cereal pathogens. Results are discussed in the context of endophytes application to barley cultivation within the European regulatory framework.