Elite UK winter wheat cultivars differ in their ability to support the colonization of beneficial root-infecting fungi

Fungal Endophytes Isolated from Elymus repens, a Wild Relative of Barley, Have Potential for Biological Control of Fusarium culmorum and Pyrenophora teres in Barley

Twenty-four fungal endophytes, isolated from a wild relative of barley, Elymus repens, were screened in barley against an isolate of Fusarium culmorum and an isolate of Pyrenophora teres under controlled conditions. In all experiments, the endophytes were applied individually as seed dressings. Five endophytes could significantly reduce symptoms of Fusarium culmorum (Periconia macrospinosa E1 and E2, Epicoccum nigrum E4, Leptodontidium sp. E7 and Slopeiomyces cylindrosporus E18). In particular, treatment with Periconia macrospinosa E1 significantly reduced Fusarium symptoms on roots by 29–63% in two out of four experiments. Using, a gfp transformed isolate of P. macrospinosa E1, it was possible to show that the fungus was present on roots 14 days after sowing, coinciding with the disease scoring. To test for a potential systemic effect of the seed treatment, eight endophyte isolates were tested against the leaf pathogen Pyrenophora teres. Three isolates could significantly reduce symptoms of P. teres (Lasiosphaeriaceae sp. E10, Lindgomycetaceae sp. E13 and Leptodontidium sp. E16). Seed treatment with Lasiosphaeriaceae sp. E10 reduced net blotch leaf lesion coverage by 89%, in one out of three experiments. In conclusion, specific endophyte isolates exerted varying degrees of protection in the different experiments. Nevertheless, data suggest that endophytic strains from E. repens in a few cases are antagonistic against F. culmorum and P. teres, but otherwise remain neutral when introduced to a barley host in a controlled environment.

Significance of the Diversification of Wheat Species for the Assembly and Functioning of the Root-Associated Microbiome

Wheat, one of the major crops in the world, has had a complex history that includes genomic hybridizations between Triticum and Aegilops species and several domestication events, which resulted in various wild and domesticated species (especially Triticum aestivum and Triticum durum), many of them still existing today. The large body of information available on wheat-microbe interactions, however, was mostly obtained without considering the importance of wheat evolutionary history and its consequences for wheat microbial ecology. This review addresses our current understanding of the microbiome of wheat root and rhizosphere in light of the information available on pre- and post-domestication wheat history, including differences between wild and domesticated wheats, ancient and modern types of cultivars as well as individual cultivars within a given wheat species. This analysis highlighted two major trends. First, most data deal with the taxonomic diversity rather than the microbial functioning of root-associated wheat microbiota, with so far a bias toward bacteria and mycorrhizal fungi that will progressively attenuate thanks to the inclusion of markers encompassing other micro-eukaryotes and archaea. Second, the comparison of wheat genotypes has mostly focused on the comparison of T. aestivum cultivars, sometimes with little consideration for their particular genetic and physiological traits. It is expected that the development of current sequencing technologies will enable to revisit the diversity of the wheat microbiome. This will provide a renewed opportunity to better understand the significance of wheat evolutionary history, and also to obtain the baseline information needed to develop microbiome-based breeding strategies for sustainable wheat farming.

Take-All Disease: New Insights into an Important Wheat Root Pathogen

Take-all disease, caused by the fungal root pathogen Gaeumannomyces tritici, is considered to be the most important root disease of wheat worldwide. Here we review the advances in take-all research over the last 15 years, focusing on the identification of new sources of genetic resistance in wheat relatives and the role of the microbiome in disease development. We also highlight recent breakthroughs in the molecular interactions between G. tritici and wheat, including genome and transcriptome analyses. These new findings will aid the development of novel control strategies against take-all disease. In light of this growing understanding, the G. tritici-wheat interaction could provide a model study system for root-infecting fungal pathogens of cereals.