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Funnell-Harris D.L.,Forage and Bioenergy Research Unit | Funnell-Harris D.L.,University of Nebraska - Lincoln | Pedersen J.F.,University of Nebraska - Lincoln | Sattler S.E.,University of Nebraska - Lincoln
Phytopathology | Year: 2010

To improve sorghum for bioenergy and forage uses, brown midrib (bmr)6 and -12 near-isogenic genotypes were developed in different sorghum backgrounds. The bmr6 and bmr12 grain had significantly reduced colonization by members of the Gibberella fujikuroi species complex compared with the wild type, as detected on two semiselective media. Fusarium spp. were identified using sequence analysis of a portion of the translation elongation factor (TEF) 1-α gene. The pathogens Fusarium thapsinum, F. proliferatum, and F. verticillioides, G. fujikuroi members, were commonly recovered. Other frequently isolated Fusarium spp. likely colonize sorghum asymptomatically. The χ2 analyses showed that the ratios of Fusarium spp. colonizing bmr12 grain were significantly different from the wild type, indicating that bmr12 affects colonization by Fusarium spp. One F. incarnatum-F. equiseti species complex (FIESC) genotype, commonly isolated from wild-type and bmr6 grain, was not detected in bmr12 grain. Phylogenetic analysis suggested that this FIESC genotype represents a previously unreported TEF haplotype. When peduncles of wild-type and near-isogenic bmr plants were inoculated with F. thapsinum, F. verticillioides, or Alternaria alternata, the resulting mean lesion lengths were significantly reduced relative to the wild type in one or both bmr mutants. This indicates that impairing lignin biosynthesis results in reduced colonization by Fusarium spp. and A. alternata.

Paudel B.,South Dakota State University | Das A.,South Dakota State University | Das A.,Texas A&M University | Tran M.,South Dakota State University | And 6 more authors.
Frontiers in Plant Science | Year: 2016

Senescence in biofuel grasses is a critical issue because early senescence decreases potential biomass production by limiting aerial growth and development. 2-Dimensional, differential in-gel electrophoresis (2D-DIGE) followed by mass spectrometry of selected protein spots was used to evaluate differences between leaf proteomes of early (ES)- and late- senescing (LS) genotypes of Prairie cordgrass (ES/LS PCG) and switchgrass (ES/LS SG), just before and after senescence was initiated. Analysis of the manually filtered and statistically evaluated data indicated that 69 proteins were significantly differentially abundant across all comparisons, and a majority (41%) were associated with photosynthetic processes as determined by gene ontology analysis. Ten proteins were found in common between PCG and SG, and nine and 18 proteins were unique to PCG and SG respectively. Five of the 10 differentially abundant spots common to both species were increased in abundance, and five were decreased in abundance. Leaf proteomes of the LS genotypes of both grasses analyzed before senescence contained significantly higher abundances of a 14-3-3 like protein and a glutathione-S-transferase protein when compared to the ES genotypes, suggesting differential cellular metabolism in the LS vs. the ES genotypes. The higher abundance of 14-3-3 like proteins may be one factor that impacts the senescence process in both LS PCG and LS SG. Aconitase dehydratase was found in greater abundance in all four genotypes after the onset of senescence, consistent with literature reports from genetic and transcriptomic studies. A Rab protein of the Ras family of G proteins and an s-adenosylmethionine synthase were more abundant in ES PCG when compared with the LS PCG. In contrast, several proteins associated with photosynthesis and carbon assimilation were detected in greater abundance in LS PCG when compared to ES PCG, suggesting that a loss of these proteins potentially contributed to the ES phenotype in PCG. Overall, this study provides important data that can be utilized toward delaying senescence in both PCG and SG, and sets a foundational base for future improvement of perennial grass germplasm for greater aerial biomass productivity. © 2016 Paudel, Das, Tran, Boe, Palmer, Sarath, Gonzalez-Hernandez, Rushton and Rohila.

Saathoff A.J.,Forage and Bioenergy Research Unit | Sarath G.,Forage and Bioenergy Research Unit | Chow E.K.,Genomics and Gene Discovery Research Unit | Dien B.S.,Bioenergy Research Unit | Tobias C.M.,Genomics and Gene Discovery Research Unit
PLoS ONE | Year: 2011

Cinnamyl alcohol dehydrogenase (CAD) catalyzes the last step in monolignol biosynthesis and genetic evidence indicates CAD deficiency in grasses both decreases overall lignin, alters lignin structure and increases enzymatic recovery of sugars. To ascertain the effect of CAD downregulation in switchgrass, RNA mediated silencing of CAD was induced through Agrobacterium mediated transformation of cv. "Alamo" with an inverted repeat construct containing a fragment derived from the coding sequence of PviCAD2. The resulting primary transformants accumulated less CAD RNA transcript and protein than control transformants and were demonstrated to be stably transformed with between 1 and 5 copies of the TDNA. CAD activity against coniferaldehyde, and sinapaldehyde in stems of silenced lines was significantly reduced as was overall lignin and cutin. Glucose release from ground samples pretreated with ammonium hydroxide and digested with cellulases was greater than in control transformants. When stained with the lignin and cutin specific stain phloroglucinol-HCl the staining intensity of one line indicated greater incorporation of hydroxycinnamyl aldehydes in the lignin.

Schmer M.R.,Agroecosystem Management Research Unit | Vogel K.P.,Forage and Bioenergy Research Unit | Mitchell R.B.,Forage and Bioenergy Research Unit | Dien B.S.,University St | And 2 more authors.
Agronomy Journal | Year: 2012

Information on temporal and spatial variation in switch grass (Panicum virgatum L.) biomass composition as it affects ethanol yield (L Mg -1) at a biorefinery and ethanol production (L ha -1) at the field-scale has previously not been available. Switch grass biomass samples were collected from a regional, on-farm trial and biomass composition was determined using newly developed near-infrared reflectance spectroscopy (NIRS) prediction equations and theoretical ethanol yield (100% conversion efficiency) was calculated. Total hexose (cell wall polysaccharides and soluble sugars) concentration ranged from 342 to 398 g kg -1 while pentose (arabinose and xylose) concentration ranged from 216 to 245 g kg -1 across fields. Theoretical ethanol yield varied signifycantly by year and field, with5 yr means ranging from 381 to 430 L Mg -1. Total theoretical ethanol production ranged from 1749 to 3691 L ha -1 across fields. Variability (coefficient of variation) within established switch grass fields ranged from 1 to 4% for theoretical ethanol yield (L Mg -1) and 14 to 38% for theoretical ethanol production (L ha -1). Most fields showed a lack of spatial consistency across harvest years for theoretical ethanol yield or total theoretical ethanol production. Switch grass biomass composition from farmer fields can be expected to have significant annual and field-to-field variation in a production region, and this variation will significantly affect ethanol or other liquid fuel yields per ton or hectare. Cellulosic biorefineries will need to consider this potential variation in biofuel yields when developing their business plans. © 2012 by the American Society of Agronomy.

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