The fungal pathogen Fusarium graminearum causes Fusarium head blight (FHB) on wheat and barley and contaminates grain with trichothecene mycotoxins. In the presence of microbes, plants perceive microbe-associated molecular patterns (MAMPs). The production of reactive oxygen species (ROS) is a hallmark of plant defense responses during plant and pathogen interactions. Cell walls of filamentous fungi consist of two main components: chitin and β-glucans. Although the chitin-mediated immunity is well studied, less information is available about the role of β-glucans during plant and pathogen interactions. In this study, we investigated ROS production in wheat and barley tissues treated with laminarin, an essentially linear glucan composed of ca. 33 β-1,3-linked Glc residues. Using luminol-based chemiluminescent assays, we showed that laminarin did not induce ROS bursts in leaves from eight tested wheat varieties but induced a high and broad ROS burst in barley leaves. Our prior study found that chitin induced ROS bursts in wheat head tissues including rachis nodes. Therefore, we compared ROS production induced by laminarin and chitin in wheat head tissues. In lemmas and paleae, a ROS burst was barely induced by chitin, but highly induced by laminarin. In rachises and rachis nodes, a high and broad ROS peak was induced by laminarin. Overall, significantly higher ROS were induced in all tested tissues by laminarin compared to chitin. Furthermore, we determined that plant defense genes were upregulated in wheat heads treated with laminarin. Currently, we are investigating the effects of chitin or laminarin treatments on FHB severity and mycotoxin contamination.

This material is based upon work supported by the U.S. Department of Agriculture. This is a cooperative project with the U.S. Wheat & Barley Scab Initiative. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.