Monolignol biosynthesis, part of the phenylpropanoid pathway, produces the lignin subunits and is associated with plant defense. We hypothesize that constitutive expression in wheat of sorghum genes involved in monolignol biosynthesis will increase resistance to FHB. The spring wheat variety CB037 (moderately susceptible) was transformed with constitutive expression constructs consisting of one of four sorghum genes: SbMyb60, encoding a transcriptional activator of monolignol biosynthesis, and, SbC3’H (coumaroyl shikimate 3-hydroxylase), SbCCoAOMT (caffeoyl coenzyme A 3-O-methyl transferase), or Sb4CL (4 coumarate:CoA ligase), that encode enzymes. In the field, the constitutive expression wheat lines were screened for Type-I resistance (initial infection) by determining disease index (DI), percent of Fusarium damaged kernels (FDK) and deoxynivalenol (DON) levels. In the greenhouse, two lines each constitutively expressing either SbC3’H or SbCCoAOMT, were tested for Type-I and Type-II resistance (spread of infection) by measuring FDK and the Area Under the Disease Progress Curve (AUDPC). In the field, a wheat line constitutively expressing SbMyb60 had significantly less FDK than CB037 (the recipient check), but Sumai 3 (moderately resistant check) had lower FDK than all the lines. The DI and DON levels in transgenic lines were similar to or greater than CB037, but the DON level of one SbC3’H constitutive expression line was not significantly different from Sumai 3. In the greenhouse, for Type-I resistance, AUDPC and FDK in transgenic lines were similar to or greater than those of CB037. When screened for Type-II resistance, lines constitutively expressing SbC3’H and SbCCoAOMT had significantly less FDK and AUDPC than CB037. To identify genes and pathways involved in conferring Type-II resistance in SbC3’H and SbCCoAOMT constitutive expression lines, a global gene expression study is underway. Greenhouse-grown heads of these lines and CB037 were collected at 12 hours post-inoculation (hpi), 24 hpi, and 72 hpi. Total RNA will be extracted, followed by high-throughput RNA sequencing and analysis. We hypothesize that expression of genes involved in defense hormone production is increased in the constitutive expression lines. This study will improve understanding of the genes and mechanisms involved in FHB resistance.

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.