COS 24-2 - Host genotype and Fusarium head blight act as biotic filters for microbiome assembly in a barley breeding population

Abstract: Fusarium head blight (FHB) is a devastating disease of barley and wheat that affects both small grain yield and quality via contamination with mycotoxins. Breeding for FHB resistance in barley has made little progress in overcoming disease and conventional management of FHB with fungicides has led to the emergence of resistant fungal strains. Biological control agents, or living microorganisms that antagonize the pathogen, have emerged as an alternative management strategy for FHB. However, it has proven difficult to translate biocontrols to field settings due to their inability to thrive in “real world” environments, where they must compete for residence with native plant microbiota which are better adapted to the environment and genotype of their plant hosts. To tackle this dilemma, we hypothesized that selective breeding may be used as an alternative method to identify microbiota that are both recruited under FHB biotic stress and responsive to plant genotype. We analyzed the composition of the barley head (inflorescence) microbiome during FHB disease onset in ten genotypes from a barley breeding population across four FHB misted nurseries located in Idaho, Minnesota, North Dakota, and New York. Amplicon sequencing was used to assess both bacterial and fungal responsiveness to FHB disease and barley genotype. The bacterial microbiome was structured by a significant genotype by disease interaction at three locations (ID, MN, and ND), while the fungal microbiome was structured by a significant genotype by disease interaction at one location (MN). Barley genotype had a significant effect on bacterial community composition at each location but only had a significant effect on fungal community composition at one location (ID). In addition, the microbiome at each location consisted of several taxa that are known to have plant beneficial effects, including: Cladosporium, Nigrospora, Pantoea, Papiliotrema, Pseudomonas, Sarocladium, Sphingomonas, and Trichoderma, among others. Our research highlights the potential for barley genotypes to recruit potentially beneficial microbiota, particularly bacteria, in response to biotic stresses such as FHB.