Fusarium head blight (FHB) of wheat is caused by the devastating pathogen Fusarium graminearum, which can contaminate grain with the mycotoxin deoxynivalenol. To sustainably manage FHB, it is important to identify novel mechanisms of resistance to F. graminearum. Lignin, a product of monolignol biosynthesis in phenylpropanoid metabolism, rigidifies cell walls and may be a barrier to pathogen infection and spread. In sorghum, altered expression of some monolignol biosynthesis genes was shown to improve resistance to some Fusarium spp. Our goal was to determine if constitutive expression (CE) of the sorghum genes SbC3’H (coumaroyl shikimate 3-hydroxylase) and SbCCoAOMT (caffeoyl coenzyme A 3-O-methyltransferase) in the moderately susceptible spring wheat line CB037 improves resistance to FHB. In the greenhouse, Type II resistance (to pathogen spread) was determined on two CE lines for each gene and CB037, using the area under the disease progress curve (AUDPC) and Fusarium-damaged kernels (FDK). The CE line CCoAOMT413 had the lowest AUDPC and FDK as compared with the CE line, CCoAOMT421, both C3’H CE lines and CB037. RNA sequencing of F. graminearum or mock point-inoculated heads of CB037 and both SbCCoAOMT CE lines at 12 and 72 hours post inoculation (hpi) was performed. Principal component analysis showed that expression varied the most according to time-point then according to treatment and line. At 12 hpi, no mutually-expressed genes were significantly (p-value > 0.05) differentially regulated in the SbCCoAOMT CE lines as compared with CB037 (the recipient line). At 72 hpi, 474 mutually-expressed genes were significantly upregulated (p-value ≤ 0.05) in the SbCCoAOMT CE lines. Gene ontology (GO) enrichment included GO terms for chitin metabolism, regulation of jasmonic acid pathway, and defense response that might be associated with the observed moderate resistance in CCoAOMT413. Phloroglucinol staining of F. graminearum-inoculated rachis samples at 72 hpi showed that CCoAOMT413 was more darkly stained compared to CB037 and CCoAOMT421, indicating increased lignin accumulation in CCoAOMT413. We are examining targeted secondary metabolite accumulation in SbCCoAOMT CE and CB037 lines. Results from this research can be used to identify targets for development of novel resistance to FHB.

ACKNOWLEDGEMENT AND DISCLAIMER

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.