Responses of wheat (Triticum aestium L.) constitutively expressing four different monolignol biosynthetic genes to Fusarium head blight caused by Fusarium graminearum

Authors: Funnell-Harris, Deanna; Sattler, Scott; DILL-MACKY, RUTH - University Of Minnesota; WEGULO, STEPHEN - University Of Nebraska; DURAY, ZACHARY - Illinois Crop Improvement Association; Oneill, Patrick; Gries, Tammy; Masterson, Steven; GRAYBOSCH, ROBERT - Retired ARS Employee; Mitchell, Robert

Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/13/2024
Publication Date: 9/10/2024
Citation: Funnell-Harris, D.L., Sattler, S.E., Dill-Macky, R., Wegulo, S.N., Duray, Z.T., Oneill, P.M., Gries, T.L., Masterson, S.D., Graybosch, R.A., Mitchell, R. 2024. Responses of wheat (Triticum aestium L.) constitutively expressing four different monolignol biosynthetic genes to Fusarium head blight caused by Fusarium graminearum. Phytopathology. 114:2096-2112. https://doi.org/10.1094/PHYTO-01-24-0005-R.
DOI: https://doi.org/10.1094/PHYTO-01-24-0005-R

Interpretive Summary: The fungus, Fusarium graminearum, causes the devastating disease Fusarium head blight (FHB) of wheat, and it also produces a toxin called DON, which can make the grain deadly to consume. Infected wheat has scabby kernels with high levels of DON, which cause grain elevators to reject entire harvests. The Crop Protection Network estimated that during 2021 alone, over 18 million bushels of U. S. wheat were lost to FHB. The American Phytopathological Society estimates that a total of $3 billion was lost to this wheat disease since 1990. Breeding for resistance to FHB requires research to determine how plants defend themselves against the fungus. The plant cell wall is the first line of defense, and the cell wall component lignin may play a critical role against this fungus. A series of experimental wheat lines were developed to augment lignin production through biotechnology. These wheats were screened for the ability of the fungus to initiate infection and to grow through the plant, infecting the kernels. Four lines were shown to resist the growth of the fungus through the plant even though lignin levels were not significantly increased in these plants. Further experiments will be done to determine why these wheat lines have improved resistance to FHB. This study shows the components of lignin production may be useful targets for breeding wheat with increased FHB resistance.

Technical Abstract: The Fusarium head blight (FHB) pathogen Fusarium graminearum produces the trichothecene mycotoxin deoxynivalenol (DON), and reduces wheat yield and grain quality. Spring wheat (Triticum aestivum L.) genotype CB037 was transformed with constitutive expression (CE) constructs containing sorghum (Sorghum bicolor L. (Moench)) genes encoding monolignol biosynthetic enzymes, caffeoyl-Coenzyme A (CoA) 3-O-methyltransferase (SbCCoAOMT), 4-coumarate-CoA ligase (Sb4CL), or coumaroyl shikimate 3-hydroxylase (SbC3’H), or monolignol pathway transcriptional activator, SbMyb60. Spring wheats were screened for Type I (resistance to initial infection, using spray inoculations) and Type II (resistance to spread within the spike, using single floret inoculations) resistances in the field (spray) and greenhouse (spray and single floret). Following field inoculations, Disease Index, percent Fusarium damaged kernels (FDK), and DON measurements of CE plants were similar to or greater than CB037. For greenhouse inoculations, the area under the disease progress curve (AUDPC) and FDK were determined. Following screens, focus was placed on two each, SbC3’H and SbCCoAOMT CE lines because of trends towards decreased AUDPC and FDK observed following single floret inoculations. These four lines were as susceptible as CB037 following spray inoculations. However, single floret inoculations showed that these CE lines had significantly reduced AUDPC (P<0.01) and FDK (P=0.02) compared with CB037, indicating improved Type II resistance. None of these CE lines had increased acid detergent lignin, as compared with CB037, indicating that lignin concentration may not be a major factor in FHB resistance. The SbC3’H and SbCCoAOMT CE lines are valuable for investigating phenylpropanoid-based resistance to FHB.