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The USDA‐ARS and North Dakota State University Agricultural Experiment Station jointly released the Fusarium head blight (FHB)‐resistant spring wheat (Triticum aestivum L.) germplasm WGC002 (Reg. no. GP‐1089, PI 702949) in May 2023. WGC002 is a wheat‐Thinopyrum elongatum 7B‐7E translocation line, designated 7BS·7BL‐7EL, with the wheat chromosome 7BL terminal region replaced by the homoeologous counterpart of the Th. elongatum chromosome 7EL that contains the novel FHB resistance gene Fhb7The2. WGC002 was developed from the Chinese Spring (CS) wheat‐Th. elongatum disomic substitution line DS 7E(7B) using our genomics‐enabled chromosome engineering pipeline. The pedigree of WGC002 is DS 7E(7B)/2*CS ph1b mutant//DS 7E(7B). WGC002 has consistently exhibited resistance to FHB in inoculations of greenhouse grown plants. WGC002 does not contain the yellow flour pigment gene in the Fhb7The2 haplotype present on the terminal 7EL segment of the 7BS·7BL‐7EL translocation and has not exhibited any obvious linkage drag on the 7EL segment. Therefore, WGC002 is ready for immediate use in wheat breeding. One sequence‐tagged site (STS) and two polymerase chain reaction allelic competitive extension markers were developed specifically for Fhb7The2 and validated in different wheat genotypes. They are highly diagnostic for Fhb7The2 and extremely useful in marker‐assisted introgression of Fhb7The2 in wheat breeding. In summary, WGC002 is a new wild grass‐derived FHB‐resistant spring wheat germplasm with diagnostic DNA markers available to conduct marker‐assisted selection of Fhb7The2, that will enhance and diversify FHB resistance of wheat. Core Ideas: We developed an FHB‐resistant wheat germplasm, WGC002, which contains the wild grass‐derived resistance gene Fhb7The2.Fhb7The2 was incorporated into wheat through a 7B‐7E translocation by chromosome engineering. The chromosome 7E segment containing Fhb7The2 does not carry the gene for yellow flour pigment in WGC002.We developed the STS and PACE markers specific for Fhb7The2. [ABSTRACT FROM AUTHOR]

Sorghum (Sorghum bicolor) is drought‐tolerant and has diverse germplasm for food, feed, forage and bioenergy. However, stalk diseases reduce quality and yield of biomass and grain, especially under drought. Previously, brown midrib (bmr) mutations in monolignol biosynthesis were shown to reduce lignin content and alter composition but were not more susceptible to stalk diseases than wild‐type lines. Recently characterized bmr mutations were shown to affect flavonoid biosynthesis (chalcone isomerase; bmr30‐1) or 1‐carbon metabolism (folylpolyglutamate synthase; bmr19‐1107, bmr19‐1168 and bmr19‐1937). Two other mutations, bmr29‐1 and bmr31‐1, have not yet been characterized. The six mutations were incorporated into elite genetic backgrounds (RTx430, BTx623 and BWheatland) to develop near‐isogenic lines containing each mutation. Using peduncle inoculations with Fusarium thapsinum and F. proliferatum (Fusarium stalk rot) and Macrophomina phaseolina (charcoal rot) under well‐watered conditions, most bmr lines were at least as resistant as the corresponding wild type, except for RTx430 bmr19‐1937 that had significantly longer mean lesion lengths when inoculated with M. phaseolina. Based on significantly reduced lesion lengths following inoculations with F. proliferatum and F. thapsinum, respectively, bmr29‐1 and bmr31‐1 lines were screened using basal stalk inoculations under well‐watered and water‐deficit conditions. The bmr lines were at least as resistant as the corresponding wild‐type lines. Wild‐type BTx623 was highly susceptible to M. phaseolina under water deficit, but near‐isogenic bmr29‐1 and bmr31‐1 lines had significantly shorter mean lesion lengths. Incorporation of these mutations can increase resistance to stalk pathogens in cultivar and hybrid development for feed, bioenergy and production of biomass‐based green chemicals. [ABSTRACT FROM AUTHOR]

Few transcription factors have been identified in C4 grasses that either positively or negatively regulate monolignol biosynthesis., Previously, the overexpression of SbMyb60 in sorghum ( Sorghum bicolor) has been shown to induce monolignol biosynthesis, which leads to elevated lignin deposition and altered cell wall composition. To determine how SbMyb60 overexpression impacts other metabolic pathways, RNA-Seq and metabolite profiling were performed on stalks and leaves., 35S::SbMyb60 was associated with the transcriptional activation of genes involved in aromatic amino acid, S-adenosyl methionine ( SAM) and folate biosynthetic pathways. The high coexpression values between SbMyb60 and genes assigned to these pathways indicate that SbMyb60 may directly induce their expression. In addition, 35S::SbMyb60 altered the expression of genes involved in nitrogen (N) assimilation and carbon (C) metabolism, which may redirect C and N towards monolignol biosynthesis. Genes linked to UDP-sugar biosynthesis and cellulose synthesis were also induced, which is consistent with the observed increase in cellulose deposition in the internodes of 35S::SbMyb60 plants. However, SbMyb60 showed low coexpression values with these genes and is not likely to be a direct regulator of cell wall polysaccharide biosynthesis., These findings indicate that SbMyb60 can activate pathways beyond monolignol biosynthesis, including those that synthesize the substrates and cofactors required for lignin biosynthesis. [ABSTRACT FROM AUTHOR]

The presence of lignin reduces the quality of lignocellulosic biomass for forage materials and feedstock for biofuels. In C4 grasses, the brown midrib phenotype has been linked to mutations to genes in the monolignol biosynthesis pathway. For example, the Bmr6 gene in sorghum ( Sorghum bicolor) has been previously shown to encode cinnamyl alcohol dehydrogenase (CAD), which catalyzes the final step of the monolignol biosynthesis pathway. Mutations in this gene have been shown to reduce the abundance of lignin, enhance digestibility, and improve saccharification efficiencies and ethanol yields. Nine sorghum lines harboring five different bmr6 alleles were identified in an EMS-mutagenized TILLING population. DNA sequencing of Bmr6 revealed that the majority of the mutations impacted evolutionarily conserved amino acids while three-dimensional structural modeling predicted that all of these alleles interfered with the enzyme's ability to bind with its NADPH cofactor. All of the new alleles reduced in vitro CAD activity levels and enhanced glucose yields following saccharification. Further, many of these lines were associated with higher reductions in acid detergent lignin compared to lines harboring the previously characterized bmr6-ref allele. These bmr6 lines represent new breeding tools for manipulating biomass composition to enhance forage and feedstock quality. [ABSTRACT FROM AUTHOR]

The phenylpropanoid biosynthetic pathway that generates lignin subunits represents a significant target for altering the abundance and composition of lignin. The global regulators of phenylpropanoid metabolism may include MYB transcription factors, whose expression levels have been correlated with changes in secondary cell wall composition and the levels of several other aromatic compounds, including anthocyanins and flavonoids. While transcription factors correlated with downregulation of the phenylpropanoid biosynthesis pathway have been identified in several grass species, few transcription factors linked to activation of this pathway have been identified in C4 grasses, some of which are being developed as dedicated bioenergy feedstocks. In this study we investigated the role of SbMyb60 in lignin biosynthesis in sorghum ( Sorghum bicolor), which is a drought-tolerant, high-yielding biomass crop. Ectopic expression of this transcription factor in sorghum was associated with higher expression levels of genes involved in monolignol biosynthesis, and led to higher abundances of syringyl lignin, significant compositional changes to the lignin polymer and increased lignin concentration in biomass. Moreover, transgenic plants constitutively overexpressing SbMyb60 also displayed ectopic lignification in leaf midribs and elevated concentrations of soluble phenolic compounds in biomass. Results indicate that overexpression of SbMyb60 is associated with activation of monolignol biosynthesis in sorghum. SbMyb60 represents a target for modification of plant cell wall composition, with the potential to improve biomass for renewable uses. [ABSTRACT FROM AUTHOR]