Brown Midrib Research Articles

148 Effects of Kernel Processing of Corn Silage with and without the Brown Midrib Trait on Finishing Performance of Steers.

148 Effects of Kernel Processing of Corn Silage with and without the Brown Midrib Trait on Finishing Performance of Steers.

The Brown Midrib Leaf (bml) Mutation in Rice (Oryza sativa L.) Causes Premature Leaf Senescence and the Induction of Defense Responses.

Isolating and characterizing mutants with altered senescence phenotypes is one of the ways to understand the molecular basis of leaf aging. Using ethyl methane sulfonate mutagenesis, a new rice (Oryza sativa) mutant, brown midrib leaf (bml), was isolated from the indica cultivar ‘Zhenong34’. The bml mutants had brown midribs in their leaves and initiated senescence prematurely, at the onset of heading. The mutants had abnormal cells with degraded chloroplasts and contained less chlorophyll compared to the wild type (WT). The bml mutant showed excessive accumulation of reactive oxygen species (ROS), increased activities of superoxide dismutase, catalase, and malondialdehyde, upregulation of senescence-induced STAY-GREEN genes and senescence-related transcription factors, and down regulation of photosynthesis-related genes. The levels of abscisic acid (ABA) and jasmonic acid (JA) were increased in bml with the upregulation of some ABA and JA biosynthetic genes. In pathogen response, bml demonstrated higher resistance against Xanthomonas oryzae pv. oryzae and upregulation of four pathogenesis-related genes compared to the WT. A genetic study confirmed that the bml trait was caused by a single recessive nuclear gene (BML). A map-based cloning using insertion/deletion markers confirmed that BML was located in the 57.32kb interval between the L5IS7 and L5IS11 markers on the short arm of chromosome 5. A sequence analysis of the candidate region identified a 1 bp substitution (G to A) in the 5′-UTR (+98) of bml. BML is a candidate gene associated with leaf senescence, ROS regulation, and disease response, also involved in hormone signaling in rice. Therefore, this gene might be useful in marker-assisted backcrossing/gene editing to improve rice cultivars.

Inclusion of brown midrib dwarf pearl millet silage in the diet of lactating dairy cows

Brown midrib brachytic dwarf pearl millet (Pennisetum glaucum) forage harvested at the flag leaf visible stage and subsequently ensiled was investigated as a partial replacement of corn silage in the diet of high-producing dairy cows. Seventeen lactating Holstein cows were fed 2 diets in a crossover design experiment with 2 periods of 28 d each. Both diets had forage:concentrate ratios of 60:40. The control diet (CSD) was based on corn silage and alfalfa haylage, and in the treatment diet, 20% of the corn silage dry matter (corresponding to 10% of the dietary dry matter) was replaced with pearl millet silage (PMD). The effects of partial substitution of corn silage with pearl millet silage on dry matter intake, milk yield, milk components, fatty acid profile, apparent total-tract digestibility of nutrients, N utilization, and enteric methane emissions were analyzed. The pearl millet silage was higher in crude protein and neutral detergent fiber and lower in lignin and starch than the corn silage. Diet did not affect dry matter intake or energy-corrected milk yield, which averaged 46.7 ± 1.92 kg/d. The PMD treatment tended to increase milk fat concentration, had no effect on milk fat yield, and increased milk urea N. Concentrations and yields of milk protein and lactose were not affected by diet. Apparent total-tract digestibility of dry matter decreased from 66.5% in CSD to 64.5% in PMD. Similarly, organic matter and crude protein digestibility was decreased by PMD, whereas neutral- and acid-detergent fiber digestibility was increased. Total milk trans fatty acid concentration was decreased by PMD, with a particular decrease in trans-10 18:1. Urinary urea and fecal N excretion increased with PMD compared with CSD. Milk N efficiency decreased with PMD. Carbon dioxide emission was not different between the diets, but PMD increased enteric methane emission from 396 to 454 g/d and increased methane yield and intensity. Substituting corn silage with brown midrib dwarf pearl millet silage at 10% of the diet dry matter supported high milk production in dairy cows. When planning on farm forage production strategies, brown midrib dwarf pearl millet should be considered as a viable fiber source.

PERFORMANS COVER CROPS HIJAUAN PAKAN TERHADAP LEVEL PUPUK BOKASHI DAN KEPADATAN POPULASI

RESPONS OF FORAGES COVER CROPS ON LEVEL OF ORGANIC FERTILIZER BOKASHI AND PLANT POPULATION DENSITY. The objectives of this research was to asses the interaction of bokashi levels and plant population density on vegetative growth of sorghum Brown Midrib (BMR) and Leucaena leucocephala legume trees. Level bokashi were LB1 = 0 G; LB2 = 200 G; LB3 = 400 G and LB4 = 800 G pot-1 interact with plant population density of KP1 = 2 plants; KP2 = 4 plants and KPB3 = 6 plants pot-1 of BMR, and for Lamtoro plant density were KP1= 1 plat, KP2= 2 plant, KP3= 3 plant and KP4 = 4 plant pot-1. Treatments were arranged in a 4 x 3 factorial with 3 replications based on a Completely Randomized Design. Variable measured were leaf length of leaf, number of leafes and plant height. The results showed that the interaction of both treatment had significant effect on leaf length (P<0.05), but did not have significant effect (P>0,05) on number of leafs and plant height of BMR. On the otherhand the optimum plant density was 3 plant per pot. Based on this results can be concluded that to get optimal vegetative growth of sorghum BMR needs bokashi fertilizer by 400 G/polybag at density of 2 plants/polybag, but up to 3 plant per pot for lamtoro.Keywords:Bokashi level of chicken manure, plant population density level, growth sorghum, growth.

Bacterial and fungal communities, fermentation, and aerobic stability of conventional hybrids and brown midrib hybrids ensiled at low moisture with or without a homo- and heterofermentative inoculant

We evaluated the effects of adding a combination inoculant to 4 corn (Zea mays L.) hybrids harvested at low moisture on the nutritive value, fermentation profile, aerobic stability, bacterial and fungal populations, and community structure. The treatment design was the factorial combination of 4 corn hybrids ensiled with (INO) and without (CON) inoculant. The hybrids were TMF2R737 (MCN), F2F817 (MBR), P2089YHR (PCN), and PI144XR (PBR), ensiled at 44.0, 38.1, 42.0, and 41.3% of dry matter, respectively; MBR and PBR were brown midrib mutants. The inoculant contained Lactobacillus buchneri and Pediococcus pentosaceus (4 × 105 and 1 × 105 cfu/g of fresh corn). The experimental design was a complete randomized design with treatments replicated 6 times. Corn was chopped, treated or not with inoculant, packed into 7.6-L bucket silos, and stored for 100 d. At d 0, we found higher bacterial observed operational taxonomic units in the brown midrib mutants (MBR and PBR) relative to MCN and PCN (654 and 534 vs. 434 and 444 ± 15.5, respectively). The bacterial and fungal families with the highest relative abundance (RA) were Enterobacteriaceae (61.4%) and incertae sedis Tremellales (12.5%). At silo opening, we observed no effects of INO treatment on dry matter recovery (∼94.3 ± 1.07%), but aerobic stability was extended for all INO-treated hybrids (∼217 vs. ∼34.7 h), except for MBR (∼49 ± 38 h), due to a decreased yeast population (3.78 vs. 5.13 ± 0.440 log cfu/g of fresh corn) and increased acetic acid concentration (1.69 vs. 0.51 ± 0.132%) compared with the control. Furthermore, INO treatment reduced bacterial (61.2 vs. 276 ± 8.70) and increased fungal (59.8 vs. 43.6 ± 2.95) observed operational taxonomic units compared with CON. We observed that INO treatment increased the RA of Lactobacillaceae across all hybrids (∼99.1 vs. ∼58.9), and to larger extent MBR (98.3 vs. 34.3 ± 5.29), and decreased Enterobacteriaceae (0.614 vs. 23.5 ± 2.825%) among 4 other bacterial families relative to CON. For fungi, INO treatment increased the RA of Debaryomycetaceae (63.1 vs. 17.3 ± 8.55) and 5 other fungal families and decreased the RA of Pichiaceae (6.47 vs. 47.3 ± 10.95) and incertae sedis Saccharomycetales (8.47 vs. 25.9 ± 5.748) compared with CON. The bacterial and fungal community structures changed, due to ensiling, to a distinct and more stable community dominated by Lactobacillaceae and Debaryomycetaceae, respectively, when INO treatment was applied relative to CON. In conclusion, the INO treatment used in this study improved low-moisture whole-crop corn silage quality because of a shift in the bacterial and fungal community composition during ensiling.

Performance of bmr 6 and 12 Sorghum Mutants in Different Wild Backgrounds Under Salinity

Sorghum is one of the bioenergy crops, with considerable tolerance to salinity. The current work was undertaken to assess the salinity tolerance of brown midrib (bmr) mutant lines and wild parents for biomass composition and potential theoretical ethanol yield (TEY). The variation for salinity levels in field plots was significant; hence, salinity screening under controlled environment was performed. The mutant line N 600 (bmr-12) had performed better under field screening (at 10 dS m−1) with fresh stalk yield of 17.3 t ha−1, dry stalk yield of 7.4 t ha−1, and grain yield of 2.0 t ha−1. The performance of bmr-6 and bmr-12 mutant alleles showed that bmr-12 allele, i.e., N 597 and N 600 had performed better than its wild types EHS and Atlas, respectively, for relative fresh and dry biomass index at 20, 40 and 80 days after imposing 150 mM salinity stress. The lines N 597 (13.05 cm2 g−1), N 596 (6.84 cm2 g−1) and N 593 (7.39 cm2 g−1) recorded the highest specific leaf area at 20, 40 and 80 days of stress, respectively. High membrane stability index was recorded in mutants N 596 (bmr-6-85.33%) and N 597 (bmr-12-84.78%) with EHS though under different genetic background under stress. Higher TEY was recorded in N 597 (2219.82 L ha−1), N 600 (2159.79 L ha−1), N 595 (2019.03 L ha−1) and N 598 (1945.33 L ha−1) under stressed conditions, with a moderate reduction of 47.85 and 47.50% in 2014 and 2015, respectively, in TEY.

Ruminal degradability of brown-midrib sorghum-sudangrass hybrids for cutting and grazing

Greater ruminal degradability has been reported in mutant plants with brown midrib (bmr). The aim of this study was to evaluate the in situ degradability of dry matter (DM), neutral detergent fibre (NDF) and crude protein (CP) in the experimental sorghum-sudangrass bmr hybrids BR007 x Tx2784bmr and Tx635x Tx2785bmr, conventional experimental hybrids CMSxS206 x Tx2784 and Tx636 x Tx2785, and the control hybrid BRS801, harvested 51 days after planting. Three sheep with ruminal cannulae were used. The experimental design was of randomised complete blocks in subdivided lots. The mean values for DM and NDF disappearance were higher in the bmr hybrids after 6 h incubation. These plants had a higher rate of degradation (mean value of 6.93%/h) for fraction b of the DM compared to conventional plants (mean value of 5.73%/h), and greater effective DM degradability. The mean values for effective NDF degradability at passage rates of 2, 5 and 8%/h were 72.7% and 62.0%, 56.1% and 45.6%, and 47.1% and 37.3% for the bmr and conventional hybrids respectively. The experimental mutant hybrids showed higher values for effective CP degradability in relation to the remainder, however, the differences were more subtle in relation to those seen for DM and NDF. The results of the present work show the potential of using sorghum-sudangrass bmr hybrids in systems of ruminant production with high nutritional requirements.

PENGARUH LEVEL PUPUK BOKASHI KOTORAN AYAM TERHADAP PERTUMBUHAN SORGUM BROWN MID RIB (BMR)

EFFECT OF BOKASHI FERTILIZER LEVEL CHICKEN MANURE ON THE GROWHTH OF BROWN MID RIB (BMR) SORGHUM. The purpose of the present research was to determine effect of bokashi fertilizer level chicken manure on the growhth of brown mid rib (bmr) sorghum. The research was used in a completely randomized design arrangement, with 4 treatments and 7 replications. Treatments were formulated as follow : b1 = 0 g/polybag, b2 = 200 g/polybag, b3 = 400 g/polybag, b4 = 800 g/polybag. Parameters measured were : plant height, number of leaves length of leaves. Research result showed that, bokashi fertilizer of chicken manure gave a significant different (p<0,05) on plant height, number of leaves leaves length of brown mid rib sorghum. Based on the research result, it can be concluded that, the utilization of bokashi fertilizer level chicken manure with 200 g/polybag, enough to support the growth of plant height, number of leaves and leaves length of brown mid rib sorghum.Keywords : Bokashi Fertilizer Level Chicken Manure, Brown Mid Rib Sorghum, Growth.

PENGARUH LEVEL BOKASHI KOTORAN AYAM DAN TINGKAT KEPADATAN POPULASI TANAMAN TERHADAP PERTUMBUHAN VEGETATIF SORGUM BROWN MIDRIB (BMR)

EFFECT OF LEVEL BOKASHI CHICKEN MANURE AND PLANT POP­ULATION DENSITY ON VEGETATIVE GROWTH OF BROWN MIDRIB (BMR) SORGUM. The aims of this experiment was to study the interaction of bokashi chicken manure and plant population density on vegetative growth of sorghum Brown Midrib (BMR). Level bokashi were A1 = 0 G; A2 = 200 G; A3 = 400 G and A4 = 800 G/polybag interact with plant population density B1 = 2 plants; B2 = 4 plants and B3 = 6 plants/polybag. Treatments were arranged in a 4 x 3 factorial with 3 replications based on a Completely Randomized Design (CRD). Variable measured were leaf length of leaf, number of leafes and plant height. The results showed that the interaction of treatment had significant effect on leaf length (P<0.05), but did not have significant effect (P>0,05) on number of leafs and plant height. Each treatment gave significant different effect on these both variable (P<0.05). Based on this results can be concluded that to get optimal vegetative growth of sorghum BMR needs bokashi fertilizer by 400 G/polybag at density of 2 plants/polybag. Keywords: Bokashi level of chicken manure, plant population density level, growth sorghum, growth

PENGARUH LEVEL BOKASHI KOTORAN AYAM TERHADAP PERTUMBUHAN VEGETATIF SORGUM BROWN MIDRIB (BMR) PADA KONDISI TERNAUNG

THE INFLUENCE CHICKEN MANURE BOKASHI ON VEGETATIVE GROWTH OF BROWN MIDRIB SORGHUM (BMR) UNDER SHADE. The aim of this experiment was to study the effects of application of chicken manure bokashi on the vegetative growth of Brown Midrib (BMR) sorghum. Completely Randomized Design (CRD) has been used according to Steel and Torrie (1995). The treatments were level of chicken manure bokashi as follows B1= 0 gram; B2= 200 gram; B3= 400 gram and B4= 800 gram/polybag, with 7 replications to form 28 numbers of observations. The variables measured were plant height, leaf number and length of leaf. Analysis of Variance showed that treatments effected significanly different (P<0.05) on plant height, leaf number and length of leaf. Result of Tuckey Simultenaus Test showed that between treatment B3 and B4 were not significant different (P>0.05) on all variable measured, but both treatments gave a good performance of all variable measured significantly (P<0,05) better than treatments B2 and B1. Based on this research result it can be concluded that utilization of chicken manure bokashi up to 400 gram/polybag could provide nutrients requirement to support vegetative growth of sorghum BMR in term of height of plant, leaf number and length of leaf. Keywords: Bokashi, chicken manure, growth, BMR sorghum, shaded.

Rendimiento y calidad de forraje de maíz y sorgo de temporal a cuatro y seis hileras en Aguascalientes, México

El sorgo (Sorghum bicolor L. Moench) de nervadura café presenta características de adaptación y calidad de forraje de potencial importancia para la zona de temporal de Aguascalientes. En este estudio se evaluó el rendimiento y calidad de forraje en tres métodos de siembra: a) surco de 0.76 m en hilera sencilla para maíz y sorgo, b) camas de 1.6 m a cuatro hileras para maíz (Zea mays L.) “Cafime” y c) camas de 1.6 m a seis hileras para “sorgo de nervadura café. La unidad experimental consistió de 15 surcos a 0.76 m, y 8 camas de 1.6 m de ancho por cultivo, y 160 m de longitud con una separación de 0.76, 0.30 y 0.20 m para la siembra sencilla, cuatro y seis hileras, respectivamente. El estudio se hizo en el Sitio Experimental Sandovales, del INIFAP (El Llano, Aguascalientes, México) durante el verano de 2014. Se determinó la evapotranspiración y las unidades calor; a la madurez fisiológica se estimó el rendimiento de materia seca (MS), calidad de forraje en términos de proteína cruda (PC), fibra detergente neutro (FDN) y fibra detergente ácida (FDA) y la eficiencia en el uso del agua de lluvia. El rendimiento de materia seca obtenido fue mayor en camas de 1.60 m para maíz y sorgo a cuatro y seis hileras, respectivamente. El sorgo superó al maíz en los dos métodos de siembra (surcos y camas). Lo anterior determina que el cultivo de sorgo bajo la siembra en camas de 1.60 m con seis hileras es una alternativa de producción de forraje para esta zona de temporal deficiente, con respecto a la siembra convencional a 0.76 m. En calidad de forraje, el sorgo tuvo un mayor contenido de PC (14.5%) que el maíz (12.9%); sin embargo, su valor de FDA fue mayor, lo cual sugiere que presentó una menor proporción de fibra potencialmente digestible que el maíz. El sorgo presentó mayor eficiencia en el uso de agua de lluvia que el maíz sembrado en camas con cuatro hileras y en surco sencillo y, en consecuencia, mayor rendimiento de MS.

Expression of brown-midrib in a spontaneous sorghum mutant is linked to a 5\u2032-UTR deletion in lignin biosynthesis gene SbCAD2

Brown midrib (bmr) mutants in sorghum (Sorghum bicolor (L.) Moench) and several other C4 grasses are associated with reduced lignin concentration, altered lignin composition and improved cell wall digestibility, which are desirable properties in biomass development for the emerging lignocellulosic biofuel industry. Studying bmr mutants has considerably expanded our understanding of the molecular basis underlying lignin biosynthesis and perturbation in grasses. In this study, we performed quantitative trait locus (QTL) analysis, identified and cloned a novel cinnamyl alcohol dehydrogenase allele (SbCAD2) that has an 8-bp deletion in its 5′-untranslated region (UTR), conferring the spontaneous brown midrib trait and lignin reduction in the sorghum germplasm line PI 595743. Complementation test and gene expression analysis revealed that this non-coding region alteration is associated with the significantly reduced expression of the SbCAD2 in PI 595743 throughout its growth stages. Moreover, a promoter-GUS fusion study with transgenic Arabidopsis thaliana plants found that SbCAD2 promoter is functionally conserved, driving a specific expression pattern in lignifying vascular tissues. Taken together, our results revealed the genetic basis of bmr occurrence in this spontaneous sorghum mutant and suggested the regulatory region of the SbCAD2 can be a target site for optimizing lignin modification in sorghum and other bioenergy crops.

Differences in Fusarium Species in brown midrib Sorghum and in Air Populations in Production Fields

Several Fusarium spp. cause sorghum (Sorghum bicolor) grain mold, resulting in deterioration and mycotoxin production in the field and during storage. Fungal isolates from the air (2005 to 2006) and from leaves and grain from wild-type and brown midrib (bmr)-6 and bmr12 plants (2002 to 2003) were collected from two locations. Compared with the wild type, bmr plants have reduced lignin content, altered cell wall composition, and different levels of phenolic intermediates. Multilocus maximum-likelihood analysis identified two Fusarium thapsinum operational taxonomic units (OTU). One was identified at greater frequency in grain and leaves of bmr and wild-type plants but was infrequently detected in air. Nine F. graminearum OTU were identified: one was detected at low levels in grain and leaves while the rest were only detected in air. Wright's F statistic (FST) indicated that Fusarium air populations differentiated between locations during crop anthesis but did not differ during vegetative growth, grain development, and maturity. FST also indicated that Fusarium populations from wild-type grain were differentiated from those in bmr6 or bmr12 grain at one location but, at the second location, populations from wild-type and bmr6 grain were more similar. Thus, impairing monolignol biosynthesis substantially effected Fusarium populations but environment had a strong influence.

Yield, Nutritive Value, and Preference of Annual Warm‐Season Grasses Grazed by Horses

Core Ideas Teff, sudangrass, and sorghum sudangrass have potential as pasture forage for horses. Japanese and Siberian millet have little regrowth and are not ideal for pastures. Inverted Ca/P and high NO3–N were observed and should be determined prior to grazing. Annual warm‐season grasses have the potential to provide forage, but are rarely evaluated under horse (Equus caballus) grazing. The objectives were to determine yield, forage nutritive values, and preference of annual warm‐season grasses at different maturities under horse grazing. Horses grazed Japanese millet [Echinochloa esculenta (A. Braun) H. Scholz], Siberian millet (E. frumentacea L.), teff [Eragrostis tef (Zucc.) Trotter], sorghum sudangrass brown midrib (BMR) (Sorghum bicolor × S. bicolor L. var. sudanese), sudangrass [S. bicolor (L.) Moench ssp. drummondii], and annual ryegrass (Lolium multiflorum Lam.) at vegetative and mature stages in Minnesota; annual ryegrass served as a control. Sudangrass had the highest yield (P ≤ 0.01), producing ≥5.5 Mg ha−1 at the vegetative stage and ≥9.7 Mg ha−1 at the mature stage. Siberian millet produced the lowest yields at the vegetative (≤2.5 Mg ha−1) and mature (≤6.0 Mg ha−1) stages. While all grasses met the nutritional requirements of many classes of adult horses, an inverted Ca to P ratio and high nitrate‐nitrogen (NO3–N) levels were observed. Annual ryegrass was most preferred (P ≤ 0.01) with ≥60% removal at the vegetative stage and ≥40% removal at the mature stage. Siberian millet was least preferred with ≤40% removal at the vegetative stage and ≤5% removal at the mature stage. Based on maximizing yield, forage nutritive values, and preference, teff, sudangrass, and sorghum sudangrass show potential as annual warm‐season horse pasture forages; however, Ca/P and NO3–N should be determined before initiating grazing.

Effect of lignin linkages with other plant cell wall components on in vitro and in vivo neutral detergent fiber digestibility and rate of digestion of grass forages

The objective of this study was to correlate in vitro and in vivo neutral detergent fiber (NDF) digestibility (NDFD) with the chemical composition of forages and specific chemical linkages, primarily ester- and ether-linked para-coumaric (pCA) and ferulic acids (FA) in forages fed to dairy cattle. The content of acid detergent lignin (ADL) and its relationship with NDF does not fully explain the observed variability in NDFD. The ferulic and p-coumaric acid linkages between ADL and cell wall polysaccharides, rather than the amount of ADL, might be a better predictor of NDFD. Twenty-three forages, including conventional and brown midrib corn silages and grasses at various stages of maturity were incubated in vitro for measurement of 24-h and 96-h NDFD. Undigested and digested residues were analyzed for NDF, acid detergent fiber (ADF), ADL, and Klason lignin (KL); ester- and ether-linked pCA and FA were determined in these fractions. To determine whether in vitro observations of ester- and ether-linked pCA and FA and digestibility were similar to in vivo observations, 3 corn silages selected for digestibility were fed to 6 ruminally fistulated cows for 3 wk in 3 iso-NDF diets. Intact samples and NDF and ADF residues of diet, rumen, and feces were analyzed for ester- and ether-linked pCA and FA. From the in vitro study, the phenolic acid content (total pCA and FA) was highest for corn silages, and overall the content of ester- and ether-linked pCA and FA in both NDF and ADF residues were correlated with NDF digestibility parameters, reflecting the competitive effect of these linkages on digestibility. Also, Klason lignin and ADL were negatively correlated with ether-linked ferulic acid on an NDF basis. Overall, esterified FA and esterified pCA were negatively correlated with all of the measured fiber fractions on both a dry matter and an NDF basis. The lignin content of the plant residues and chemical linkages explained most of the variation in both rate and extent of NDF digestion but not uniformly among forages, ranging from 56 to 99%. The results from the in vivo study were similar to the in vitro data, demonstrating the highest total-tract aNDF digestibility (70%; NDF analysis conducted with α-amylase and sodium sulfite) for cows fed the corn silage with the lowest ester- and ether-linked pCA content in the NDF fraction. In this study, digestibility of forage fiber was influenced by the linkages among lignin and the carbohydrate moieties, which vary by hybrid and species and most likely vary by the agronomic conditions under which the plant was grown.

617 Microbial community structure of conventional and brown midrib corns ensiled at low dry matter concentrations with and without a combo inoculant

617 Microbial community structure of conventional and brown midrib corns ensiled at low dry matter concentrations with and without a combo inoculant

274 Growth stage at harvest influences forage quality and yield of brown midrib forage sorghum

274 Growth stage at harvest influences forage quality and yield of brown midrib forage sorghum

The Enzyme Activity and Substrate Specificity of Two Major Cinnamyl Alcohol Dehydrogenases in Sorghum (Sorghum bicolor), SbCAD2 and SbCAD4.

Cinnamyl alcohol dehydrogenase (CAD) catalyzes the final step in monolignol biosynthesis, reducing sinapaldehyde, coniferaldehyde, and p-coumaraldehyde to their corresponding alcohols in an NADPH-dependent manner. Because of its terminal location in monolignol biosynthesis, the variation in substrate specificity and activity of CAD can result in significant changes in overall composition and amount of lignin. Our in-depth characterization of two major CAD isoforms, SbCAD2 (Brown midrib 6 [bmr6]) and SbCAD4, in lignifying tissues of sorghum (Sorghum bicolor), a strategic plant for generating renewable chemicals and fuels, indicates their similarity in both structure and activity to Arabidopsis (Arabidopsis thaliana) CAD5 and Populus tremuloides sinapyl alcohol dehydrogenase, respectively. This first crystal structure of a monocot CAD combined with enzyme kinetic data and a catalytic model supported by site-directed mutagenesis allows full comparison with dicot CADs and elucidates the potential signature sequence for their substrate specificity and activity. The L119W/G301F-SbCAD4 double mutant displayed its substrate preference in the order coniferaldehyde > p-coumaraldehyde > sinapaldehyde, with higher catalytic efficiency than that of both wild-type SbCAD4 and SbCAD2. As SbCAD4 is the only major CAD isoform in bmr6 mutants, replacing SbCAD4 with L119W/G301F-SbCAD4 in bmr6 plants could produce a phenotype that is more amenable to biomass processing.

Forage Mass, Nutritive Value, and In situ Degradation of Sorghum Silage Treated with Fibrolytic Enzymes

Core Ideas Xylanase and cellulase treatment of sorghum silage did not affect sorghum silage nutritive value. The brown midrib trait and harvest timing have more influence on silage quality than fibrolytic enzymes. Sorghum [Sorghum bicolor (L.) Moench.] and sorghum‐sudangrass (S. bicolor × S. bicolor drummondii) silage utilization in cattle diets has increased in recent years. The objectives of this study were to compare the forage mass and nutritive value of photoperiod‐sensitive (PS) sorghum and hybrid sister lines with or without the BMR trait, and determine if fibrolytic enzymes would improve the rate and extent of in situ disappearance of PS forage sorghum (FS) and PS sorghum‐sudagrass (SS) silage varieties with or without the brown midrib (BMR) trait (i.e., FS‐PS, FS‐PS/BMR, SS‐PS, and SS‐PS/BMR). This experiment was a 2 × 2 × 2 factorial arrangement whereby the crop was grown, chopped, and ensiled and inoculated with or without (control) the enzyme mixture. Yield was at least 1.6 ton/acre and nutritive value similar to that of similar cultivars. Mini‐silo buckets were sealed for 150 days, and dried silage material weighed into duplicate Dacron bags for in situ incubation for 0, 4, 8, 16, 24, 48, or 72 h in three ruminally cannulated Angus steers (679 ± 52.9 lb body weight [BW]) to determine rate and extent of dry‐matter (DM) disappearance. The addition of fibrolytic enzymes had little effect on the nutritive value of ensiled forage. Non‐BMR silage had a greater potentially degradable fraction; however, BMR varieties had a greater wash loss and extent of digestion. Based on our results, selecting a sorghum variety with the BMR trait may be more important than using a fibrolytic enzyme to improve silage degradation characteristics.

The effects of ultraviolet radiation on the brown midrib mutants of Zea mays and Sorghum bicolor

The brown-midrib varieties (bm/bmr) of corn (Zea mays) and sorghum (Sorghum bicolor) have gained attention as both forage material and feedstock for biofuel. These varieties are attractive due to their low-lignin content resulting from alterations in the phenylpropanoid pathway. These bm/bmr varieties have impaired activity of cinnamyl alcohol dehydrogenase (CAD) or caffeate/5 hydroxyferulate O-methyl transferase (COMT) enzymes. We examined the effects of ultraviolet-B radiation (UV-B; 280–320 nm) on bm3 corn and bmr6 sorghum growing in a UV-transparent greenhouse in southern Minnesota. Plants grew under filters that either transmitted 2.8% (mylar) or 90% (aclar) of UV-B for 71 days. We monitored UV-screening effectiveness and chlorophyll fluorescence of leaves with pulse-amplitude modulated fluorometers. In order to explain differences in UV-screening effectiveness, we estimated concentrations of bulk-soluble UV-absorbing compounds (λ = 300 and 370 nm). We also measured final cellulose, hemicellulose and lignin concentrations of plants using a fiber analyzer. Epidermal transmittance of UV was reduced under aclar filters in both species and decreased from 41.6 to 1.9% in corn and 66.4 to 0.98% in sorghum. Increased epidermal screening may be related to the 35–39 and 37–54% higher concentrations of UV-absorbing compounds in plants growing under aclar. Concentrations of lignin were 1.7% lower in corn and 1.1% higher in sorghum in plants under aclar treatments. These contrasting results may be the result of alterations in the phenylpropanoid pool associated with each bm/bmr variety.