[Show abstract][Hide abstract] ABSTRACT: Maize (Zea mays L.) stover and cobs are potential feedstock sources for cellulosic ethanol production. Nitrogen (N) fertilization is an important management decision that influences cellulosic biomass and grain production, but its effect on cell wall composition and subsequent cellulosic ethanol production is not known. The objectives of this study were to quantify the responses of maize stover (leaves, stalks, husks, and tassel) and cob cell wall composition and theoretical ethanol yield potential to N fertilization across a range of sites. Field experiments were conducted at rainfed and irrigated sites in Minnesota, USA, over a 2-year period. Stover cell wall polysaccharides, pentose sugar concentration, and theoretical ethanol yield decreased as N fertilization increased. Stover Klason lignin increased with N fertilization at all sites. Cob cell wall composition was less sensitive to N fertilization, as only pentose and Klason lignin decreased with N fertilization at two and one site(s), respectively, and hexose increased with N fertilization at one of eight sites. Cob theoretical ethanol yield was not affected by N fertilization at any site. These results indicate variation in stover cellulosic ethanol production is possible as a result of N management. This study also demonstrated that cell wall composition and subsequent theoretical ethanol yield of maize cobs are generally more stable than those with stover because of overall less sensitivity to N management.
Full-text · Article · Mar 2015 · BioEnergy Research
[Show abstract][Hide abstract] ABSTRACT: There is strong evidence to suggest that cross-linking of cell wall polymers through ester-linked diferulates has a key role in plant resistance to pests; however, direct experimentation to provide conclusive proof is lacking. This study presents an evaluation of the damage caused by two corn borer species on six maize populations particularly selected for divergent diferulates concentrations in pith stem tissues. Maize populations selected for high total diferulates concentration had 31% higher diferulates than those selected for low diferulates. Stem tunneling by corn borers species was 29% greater in the population with the lowest diferulates than in the population with the highest diferulates (31.7 cm vs. 22.6 cm), whereas total diferulates concentration was negatively correlated with stem tunneling by corn borers. Moreover, orthogonal contrasts between groups of populations evaluated showed that larvae fed in laboratory bioassays on pith stem tissues from maize populations with higher diferulates had 30-40% lower weight than larvae fed on same tissues from maize populations with lower diferulates. This is the first report that shows a direct relationship between diferulate deposition in maize cell walls and corn borer resistance. Current findings will help to develop adapted maize varieties with an acceptable level of resistance against borers and useful in special kinds of agriculture such as organic farming.
No preview · Article · Jan 2015 · Journal of Agricultural and Food Chemistry
[Show abstract][Hide abstract] ABSTRACT: High concentration and low digestibility of stem fiber constituents in herbage of alfalfa (Medicago sativa L.) can limit dry matter intake and energy availability in ruminant (dairy and beef) production systems. Stem neutral detergent fiber (NDF), acid detergent lignin (ADL), and stem in vitro neutral detergent fiber digestibility (IVNDFD) are impacted by the environment. We identified 45 individual alfalfa plants that differed in stem NDF and ADL concentrations, ADL as a proportion of NDF (ADL/NDF), and stem IVNDFD after 16 and 96 h of digestion. All plants were vegetatively propagated and established in replicated trials and sampled 12 times (spring and early and late summer harvests for 2 yr at two field locations). A subset of clones were evaluated in two greenhouses and harvested for two regrowth cycles. Stability analyses demonstrated that stem ADL/NDF, NDF, and 96-h IVNDFD were more environmentally stable among the alfalfa clones in the field environments tested than stem 16-h IVNDFD or ADL. All stem fiber quality traits were considered consistent between the two field environments, but no relationship in trait responses were demonstrated between field and greenhouse environments. These results suggested that stem 96-h IVNDFD, NDF, and ADL/NDF would be the traits to use in a field selection program to develop alfalfa with improved nutrient value.
[Show abstract][Hide abstract] ABSTRACT: An alfalfa (Medicago sativa L) biomass energy production system would produce two products. Leaves would be separated from stems to produce a protein feed for livestock while stems would be processed to produce ethanol. Therefore, maximum yields of both leaves and stems are essential for profitability of this biomass production system. Our objective was to evaluate the impact of growth environment (locations, years and plant density) and harvest maturity stage (early bud (4 annual cuts) and late flower (3 annual cuts)) on leaf crude protein and potential ethanol yields for four alfalfa germplasms, two with high forage quality, and two non-lodging biomass types. Potential ethanol yield was greater at late flower compared to early bud, while leaf crude protein concentration was similar at the two harvest maturity stages at both locations. Leaf crude protein yield was greater at the Minnesota (MN) site compared to Wisconsin (WI) site. The two non-lodging biomass germplasms had greater potential ethanol yield compared to the high forage quality cultivars in WI, but no differences among the alfalfa germplasms were found for ethanol yield at MN. In WI, no differences were found among the germplasms for leaf crude protein yield, but the high quality cultivars had greater leaf crude protein yield than the non-lodging germplasms in MN. While germplasm differences were found for leaf crude protein and potential ethanol yields, the environmental influences of harvest date and locations had the greatest impact on these two alfalfa biomass energy products.
No preview · Article · Apr 2014 · Biomass and Bioenergy
[Show abstract][Hide abstract] ABSTRACT: Genomewide selection (GWS) is marker-assisted selection without identifying markers with significant effects. Our previous work with the intermated B73 x Mo17 maize (Zea mays L.) population revealed significant variation for grain yield and stover-quality traits important for cellulosic ethanol production. Our objectives were to determine (i) if realized gains from selection are larger with GWS than with marker-assisted recurrent selection (MARS), which involves selection for markers with significant effects; and (ii) how multiple traits respond to multiple cycles of GWS and MARS. In 2007, testcrosses of 223 recombinant inbreds developed from B73 x Mo17 (Cycle 0) were evaluated at four Minnesota locations and genotyped with 287 single nucleotide polymorphism markers. Individuals with the best performance for a Stover Index and a Yield + Stover Index were intermated to form Cycle 1. Both GWS and MARS were then conducted until Cycle 3. Multilocation trials in 2010 indicated that gains for the Stover Index and Yield + Stover Index were 14 to 50% larger (significant at P = 0.05) with GWS than with MARS. Gains in individual traits were mostly nonsignificant. Inbreeding coefficients ranged from 0.28 to 0.38 by Cycle 3 of GWS and MARS. For stover-quality traits, correlations between wet chemistry and near-infrared reflectance spectroscopy predictions decreased after selection. We believe this is the first published report of a GWS experiment in crops, and our results indicate that using all available markers for predicting genotypic value leads to greater gain than using a subset of markers with significant effects.
[Show abstract][Hide abstract] ABSTRACT: Cross-linking of grass cell wall components through diferulates (DFAs) has a marked impact on cell wall properties. However, results of genetic selection for DFA concentration have not been reported for any grass species. We report here the results of direct selection for ester-linked DFA concentration in maize stalk pith tissues and the associated changes in cell wall composition and biodegradability. After two cycles of divergent selection, maize populations selected for higher total DFA (DFAT) content (CHs) had 16% higher DFAT concentrations than populations selected for lower DFAT content (CLs). These significant DFA concentration gains suggest that DFA deposition in maize pith parenchyma cell walls is a highly heritable trait that is genetically regulated and can be modified trough conventional breeding. Maize populations selected for higher DFAT had 13% less glucose and 10% lower total cell wall concentration than CLs, suggesting that increased cross-linking of feruloylated arabinoxylans results in repacking of the matrix and possibly in thinner and firmer cell walls. Divergent selection affected esterified DFAT and monomeric ferulate ether cross link concentrations differently, supporting the hypothesis that the biosynthesis of these cell wall components are separately regulated. As expected, a more higher DFA ester cross-coupled arabinoxylan network had an effect on rumen cell wall degradability (CLs showed 12% higher 24-h total polysaccharide degradability than CHs). Interestingly, 8-8-coupled DFAs, previously associated with cell wall strength, were the best predictors of pith cell wall degradability (negative impact). Thus, further research on the involvement of these specific DFA regioisomers in limiting cell wall biodegradability is encouraged.
[Show abstract][Hide abstract] ABSTRACT: Improving digestibility of roughage cell walls will improve ruminant animal performance and reduce loss of nutrients to the environment. The main digestibility impediment for dicotyledonous plants is highly lignified secondary cell walls, notably in stem secondary xylem, which become almost non-digestible. Digestibility of grasses is slowed severely by lignification of most tissues, but these cell walls remain largely digestible. Cell wall lignification creates an access barrier to potentially digestible wall material by rumen bacteria if cells have not been physically ruptured. Traditional breeding has focused on increasing total dry matter digestibility rather than cell wall digestibility, which has resulted in minimal reductions in cell wall lignification. Brown midrib mutants in some annual grasses exhibit small reductions in lignin concentration and improved cell wall digestibility. Similarly, transgenic approaches down-regulating genes in monolignol synthesis have produced plants with reduced lignin content and improved cell wall digestibility. While major reductions in lignin concentration have been associated with poor plant fitness, smaller reductions in lignin provided measurable improvements in digestibility without significantly impacting agronomic fitness. Additional targets for genetic modification to enhance digestibility and improve roughages for use as biofuel feedstocks are discussed; including manipulating cell wall polysaccharide composition, novel lignin structures, reduced lignin/polysaccharide cross-linking, smaller lignin polymers, enhanced development of non-lignified tissues, and targeting specific cell types. Greater tissue specificity of transgene expression will be needed to maximize benefits while avoiding negative impacts on plant fitness.cauliflower mosiac virus (CaMV) 35S promoter.
[Show abstract][Hide abstract] ABSTRACT: Evaluation of biomass crops for breeding or pricing purposes requires an assay that predicts performance in the bioenergy
conversion process. Cell wall polysaccharide hydrolysis was compared for a dilute sulfuric acid pretreatment at 121°C followed
with cellulase hydrolysis for 72h conversion assay (CONV) with in vitro rumen microflora incubation for 72h (RUMEN) for
a set of maize (Zea mays L.) stover samples with a wide range in cell wall composition. Residual polysaccharides from the assays were analyzed for
sugar components and extent of hydrolysis calculated. Cell wall polysaccharide hydrolysis was different for all sugar components
between the CONV and RUMEN assays. The CONV assay hydrolyzed xylose-, arabinose-, galactose-, and uronic acid-containing polysaccharides
to a greater degree than did the RUMEN assay, whereas the RUMEN assay was more effective at hydrolyzing glucose- and mannose-containing
polysaccharides. Greater hydrolysis of hemicelluloses and pectins by CONV can be attributed to the acid hydrolysis mechanism
of the CONV assay for noncellulosic polysaccharides, whereas the RUMEN assay was dependent on enzymatic hydrolysis. While
CONV and RUMEN hydrolysis were correlated for most polysaccharide components, the greatest correlation was only r = 0.70 for glucose-containing polysaccharides. Linear correlations and multiple regressions indicated that polysaccharide
hydrolysis by the RUMEN assay was negatively associated with lignin concentration and ferulate ether cross linking as expected.
Corresponding correlations and regressions for CONV were less consistent and occasionally positive. Use of rumen microbial
hydrolysis to characterize biomass performance in a conversion process may have some limited usefulness for genetic evaluations,
but such assays would be unreliable for biomass pricing.
KeywordsMaize stover–Cell wall polysaccharide–Hydrolysis–Conversion–Rumen
No preview · Article · Jun 2011 · BioEnergy Research
[Show abstract][Hide abstract] ABSTRACT: Knowledge about adverse symptoms over time from fiber supplementation is lacking.
The aim of this study was to compare the severity of adverse gastrointestinal (GI) symptoms during supplementation with dietary fiber or placebo over time in adults with fecal incontinence. A secondary aim was to determine the relationship between symptom severity and emotional upset and their association with study attrition and reducing fiber dose.
Participants (N = 189; 77% female; 92% White; age, M = 58 years, SD = 14 years) with fecal incontinence were randomly assigned to a placebo or a supplement of 16 g total dietary fiber per day from 1 of 3 sources: gum arabic, psyllium, or carboxymethylcellulose. They reported GI symptoms daily during baseline (14 days), incremental fiber dosing (6 days), and 2 segments of steady full fiber dose (32 days total).
Severity of symptoms in all groups was minimal. Adjusting for study segment and day, a greater feeling of fullness in the psyllium group was the only symptom that differed from symptoms in the placebo group. The odds of having greater severity of flatus, belching, fullness, and bloating were 1.2-2.0 times greater in the steady dose segment compared with baseline. There was a positive association between symptom severity and emotional upset. Participants with a greater feeling of fullness or bloating or higher scores for total symptom severity or emotional upset were more likely to withdraw from the study sooner or reduce fiber dose.
Persons with fecal incontinence experience a variety of GI symptoms over time. Symptom severity and emotional upset appear to influence fiber tolerance and study attrition. Supplements seemed well tolerated.
[Show abstract][Hide abstract] ABSTRACT: Alfalfa, [Medicago sativa (L.) sativa], a widely-grown perennial forage has potential for development as a cellulosic ethanol feedstock. However, the genomics of alfalfa, a non-model species, is still in its infancy. The recent advent of RNA-Seq, a massively parallel sequencing method for transcriptome analysis, provides an opportunity to expand the identification of alfalfa genes and polymorphisms, and conduct in-depth transcript profiling.
Cell walls in stems of alfalfa genotype 708 have higher cellulose and lower lignin concentrations compared to cell walls in stems of genotype 773. Using the Illumina GA-II platform, a total of 198,861,304 expression sequence tags (ESTs, 76 bp in length) were generated from cDNA libraries derived from elongating stem (ES) and post-elongation stem (PES) internodes of 708 and 773. In addition, 341,984 ESTs were generated from ES and PES internodes of genotype 773 using the GS FLX Titanium platform. The first alfalfa (Medicago sativa) gene index (MSGI 1.0) was assembled using the Sanger ESTs available from GenBank, the GS FLX Titanium EST sequences, and the de novo assembled Illumina sequences. MSGI 1.0 contains 124,025 unique sequences including 22,729 tentative consensus sequences (TCs), 22,315 singletons and 78,981 pseudo-singletons. We identified a total of 1,294 simple sequence repeats (SSR) among the sequences in MSGI 1.0. In addition, a total of 10,826 single nucleotide polymorphisms (SNPs) were predicted between the two genotypes. Out of 55 SNPs randomly selected for experimental validation, 47 (85%) were polymorphic between the two genotypes. We also identified numerous allelic variations within each genotype. Digital gene expression analysis identified numerous candidate genes that may play a role in stem development as well as candidate genes that may contribute to the differences in cell wall composition in stems of the two genotypes.
Our results demonstrate that RNA-Seq can be successfully used for gene identification, polymorphism detection and transcript profiling in alfalfa, a non-model, allogamous, autotetraploid species. The alfalfa gene index assembled in this study, and the SNPs, SSRs and candidate genes identified can be used to improve alfalfa as a forage crop and cellulosic feedstock.
[Show abstract][Hide abstract] ABSTRACT: European and Mediterranean corn borers are two of the most economically important insect pests of maize (Zea mays L.) in North America and southern Europe, respectively. Cell wall structure and composition were evaluated in pith and rind tissues of resistant and susceptible inbred lines as possible corn borer resistance traits. Composition of cell wall polysaccharides, lignin concentration and composition, and cell wall bound forms of hydroxycinnamic acids were measured. As expected, most of the cell wall components were found at higher concentrations in the rind than in the pith tissues, with the exception of galactose and total diferulate esters. Pith of resistant inbred lines had significantly higher concentrations of total cell wall material than susceptible inbred lines, indicating that the thickness of cell walls could be the initial barrier against corn borer larvae attack. Higher concentrations of cell wall xylose and 8-O-4-coupled diferulate were found in resistant inbreds. Stem tunneling by corn borers was negatively correlated with concentrations of total diferulates, 8-5-diferulate and p-coumarate esters. Higher total cell wall, xylose, and 8-coupled diferulates concentrations appear to be possible mechanisms of corn borer resistance.
[Show abstract][Hide abstract] ABSTRACT: Recruitment of participants to clinical trials remains a significant challenge, especially for research addressing topics of a sensitive nature such as fecal incontinence (FI). In the Fiber Study, a randomized controlled trial on symptom management for FI, we successfully enrolled 189 community-living adults through collaborations with specialty-based and community-based settings, each employing methods tailored to the organizational characteristics of their site. Results show that using the two settings increased racial and ethnic diversity of the sample and inclusion of informal caregivers. There were no differential effects on enrollment, final eligibility, or completion of protocol by site. Strategic collaborations with complementary sites can achieve sample recruitment goals for clinical trials on topics that are sensitive or known to be underreported.
Full-text · Article · Dec 2010 · Research in Nursing & Health
[Show abstract][Hide abstract] ABSTRACT: Bermuda grass is an attractive candidate as a feedstock for biofuel production because over four million hectares of Bermuda
grass are already grown for forage in the Southern USA. Because both rumen digestion and biochemical conversion to ethanol
depend upon enzymatic conversion of the cell wall polysaccharides into fermentable sugars, it is probable that grasses bred
for increased forage quality would be more amenable for ethanol production. However, it is not known how variation in rumen
digestibility and cell wall/fiber components correlates with efficiency of conversion to ethanol via fermentation. The objective
of this research was to determine relationships between ethanol production evaluated by simultaneous saccharification and
fermentation (SSF), 72-h in vitro ruminal dry matter digestibility (IVDMD), in vitro ruminal gas production after 24 and 96h,
and biomass composition for 50 genetically diverse Bermuda grass accessions. The Bermuda grass samples were subjected to standard
72-h IVDMD and forage fiber analyses. Also, in separate labs, gas production was measured in sealed volume-calibrated vials
after 24 (NNG24) and 96h (NNG96) of in vitro fermentation by ruminal fluid; ethanol and pentose sugar productions were measured
from a bench-top SSF procedure; cell wall constituents were determined by the Uppsala Dietary Fiber Method; and total nitrogen,
carbon, and ash concentrations were determined by using the LECO combustion method. Ethanol production was moderately correlated
with IVDMD (r = 0.55) and NNG96 (r = 0.63) but highly correlated with NNG24 (r = 0.93). Ethanol was negatively correlated with neutral detergent fiber (NDF; r = −0.53) and pentose sugars (r = −0.60), but not correlated with glucose content. Regression models indicated that NDF and cell wall pentose sugar concentrations
had significant negative effects on ethanol production. Variation among entries for IVDMD was affected by variability of NDF,
pentose sugar concentrations, and biomass nitrogen content. Variation in Klason lignin content had only minor negative impacts
on ethanol production and IVDMD. Biochemical conversion efficiency of Bermuda grass by SSF can be best estimated by NNG24
but not by IVDMD.
KeywordsBermuda grass-Biochemical conversion-Fiber components-In vitro gas production-Simultaneous saccharification and fermentation
No preview · Article · Sep 2010 · BioEnergy Research
[Show abstract][Hide abstract] ABSTRACT: The GeneChip(R) Medicago Genome Array, developed for Medicago truncatula, is a suitable platform for transcript profiling in tetraploid alfalfa [Medicago sativa (L.) subsp. sativa]. However, previous research involving cross-species hybridization (CSH) has shown that sequence variation between two species can bias transcript profiling by decreasing sensitivity (number of expressed genes detected) and the accuracy of measuring fold-differences in gene expression.
Transcript profiling using the Medicago GeneChip(R) was conducted with elongating stem (ES) and post-elongation stem (PES) internodes from alfalfa genotypes 252 and 1283 that differ in stem cell wall concentrations of cellulose and lignin. A protocol was developed that masked probes targeting inter-species variable (ISV) regions of alfalfa transcripts. A probe signal intensity threshold was selected that optimized both sensitivity and accuracy. After masking for both ISV regions and previously identified single-feature polymorphisms (SFPs), the number of differentially expressed genes between the two genotypes in both ES and PES internodes was approximately 2-fold greater than the number detected prior to masking. Regulatory genes, including transcription factor and receptor kinase genes that may play a role in development of secondary xylem, were significantly over-represented among genes up-regulated in 252 PES internodes compared to 1283 PES internodes. Several cell wall-related genes were also up-regulated in genotype 252 PES internodes. Real-time quantitative RT-PCR of differentially expressed regulatory and cell wall-related genes demonstrated increased sensitivity and accuracy after masking for both ISV regions and SFPs. Over 1,000 genes that were differentially expressed in ES and PES internodes of genotypes 252 and 1283 were mapped onto putative orthologous loci on M. truncatula chromosomes. Clustering simulation analysis of the differentially expressed genes suggested co-expression of some neighbouring genes on Medicago chromosomes.
The problems associated with transcript profiling in alfalfa stems using the Medicago GeneChip as a CSH platform were mitigated by masking probes targeting ISV regions and SFPs. Using this masking protocol resulted in the identification of numerous candidate genes that may contribute to differences in cell wall concentration and composition of stems of two alfalfa genotypes.
[Show abstract][Hide abstract] ABSTRACT: Switchgrass (Panicum virgatum L.) and reed canarygrass (Phalaris arundinacea L.) were pretreated under ambient temperature and pressure with sulfuric acid and calcium hydroxide in separate experiments. Chemical loadings from 0 to 100g (kg DM)(-1) and durations of anaerobic storage from 0 to 180days were investigated by way of a central composite design at two moisture contents (40% or 60% w.b.). Pretreated and untreated samples were fermented to ethanol by Saccharomyces cerevisiae D5A in the presence of a commercially available cellulase (Celluclast 1.5L) and beta-glucosidase (Novozyme 188). Xylose levels were also measured following fermentation because xylose is not metabolized by S. cerevisiae. After sulfuric acid pretreatment and anaerobic storage, conversion of cell wall glucose to ethanol for reed canarygrass ranged from 22% to 83% whereas switchgrass conversions ranged from 16% to 46%. Pretreatment duration had a positive effect on conversion but was mitigated with increased chemical loadings. Conversions after calcium hydroxide pretreatment and anaerobic storage ranged from 21% to 55% and 18% to 54% for reed canarygrass and switchgrass, respectively. The efficacy of lime pretreatment was found to be highly dependent on moisture content. Moreover, pretreatment duration was only found to be significant for reed canarygrass. Although significant levels of acetate and lactate were observed in the biomass after storage, S. cerevisiae was not found to be inhibited at a 10% solids loading.
Preview · Article · Mar 2010 · Bioresource Technology
[Show abstract][Hide abstract] ABSTRACT: In cellulosic ethanol production, the efficiency of converting maize (Zea mays L.) stover into fermentable sugars partly depends on the stover cell wall structure. Breeding for improved stover quality for cellulosic ethanol may benefit from the use of molecular markers. However, limited quantitative trait loci (QTL) studies have been published for maize stover cell wall components, and no QTL study has been published for glucose release (GLCRel) from stover by a cellulosic ethanol conversion process. Our objectives were to characterize the relationships among stover cell wall components and GLCRel, and to identify QTL with major effects, if any, influencing stover cell wall composition and GLCRel. Testcrosses of 223 intermated B73 x Mo17 recombinant inbreds and the parent lines were analyzed for cell wall composition and GLCRel after acid pretreatment and enzymatic hydrolysis. As expected, glucose (GLC), xylose (XYL), and Klason lignin (KL) composed the bulk (72%) of the stover dry matter. Significant genetic variance and moderate heritability were observed for all traits. Genetic and phenotypic correlations among traits were generally in the favorable direction but also reflected the complexity of maize stover cell wall composition. We found 152 QTL, mostly with small effects, for GLCRel and cell wall components on both a dry matter and cell wall basis. Because no major QTL were found, methods that increase the frequency of favorable QTL alleles or that predict performance based on markers would be appropriate in marker-assisted breeding for maize stover quality for cellulosic ethanol.
[Show abstract][Hide abstract] ABSTRACT: Corn (Zea mays L.) stover, the residue left after harvest, is an abundant biomass source for producing cellulosic ethanol in the United States. Corn has been bred for increased grain yield but not for stover quality for cellulosic ethanol production. Our objective in this study was to assess the feasibility of breeding corn for grain yield and agronomic traits as well as stover quality traits for cellulosic ethanol production. Testcrosses of 223 B73 x Mo17 recombinant inbreds were evaluated at four Minnesota locations in 2007. Three stover quality traits were measured: concentration of cell wall glucose in dry stover ("Glucose"); cell wall glucose released from the stover by thermochemical pretreatment and enzymatic saccharification ("Glucose Release"); and concentration of lignin on a cell wall basis ("Lignin"). Genetic variances were significant for grain yield, moisture, stalk and root lodging, plant height, and all three stover quality traits. Heritabilities of the stover quality traits were 0.57 for Glucose, 0.63 for Glucose Release, and 0.68 for Lignin. Phenotypic and genetic correlations were favorable or neutral among grain yield, agronomic traits, Glucose, Glucose Release, and Lignin. Lines selected with a multiple-trait index for grain yield, agronomic traits, and stover quality traits had improved means for each trait in the index. Current corn breeding programs should be able to incorporate stover quality for cellulosic ethanol as a breeding objective, without having to use unadapted or exotic germplasm and without adversely affecting genetic gains for grain yield and agronomic traits.
[Show abstract][Hide abstract] ABSTRACT: Advances in alfalfa [Medicago sativa (L.) subsp. sativa] breeding, molecular genetics, and genomics have been slow because this crop is an allogamous autotetraploid (2n = 4x = 32) with complex polysomic inheritance and few genomic resources. Increasing cellulose and decreasing lignin in alfalfa stem cell walls would improve this crop as a cellulosic ethanol feedstock. We conducted genome-wide analysis of single-feature polymorphisms (SFPs) of two alfalfa genotypes (252, 1283) that differ in stem cell wall lignin and cellulose concentrations. SFP analysis was conducted using the Medicago GeneChip (Affymetrix, Santa Clara, CA) as a cross-species platform. Analysis of GeneChip expression data files of alfalfa stem internodes of genotypes 252 and 1283 at two growth stages (elongating, post-elongation) revealed 10,890 SFPs in 8230 probe sets. Validation analysis by polymerase chain reaction (PCR)-sequencing of a random sample of SFPs indicated a 17% false discovery rate. Functional classification and over-representation analysis showed that genes involved in photosynthesis, stress response and cell wall biosynthesis were highly enriched among SFP-harboring genes. The Medicago GeneChip is a suitable cross-species platform for detecting SFPs in tetraploid alfalfa.
[Show abstract][Hide abstract] ABSTRACT: Alfalfa (Medicago sativa L.) is a promising bioenergy and bioproduct feedstock because of its high yield, N-fixation capacity, potential for planting in rotation with corn (Zea mays L.), and valuable protein co-product (leaf meal). Our objective was to examine the effect of growth environment on biomass yield, cellulosic ethanol traits, and paper pulp fiber characteristics of alfalfa stems. Landscape position (summit and mild slope), season of harvest (four harvests per season), and multiple years (2005 and 2006) provided environmental variation. Alfalfa stem samples were analyzed for cell wall carbohydrate and lignin concentration. Stems were subjected to dilute acid pre-treatment, enzymatic saccharification, and pulping processes to measure relevant cellulosic ethanol and paper production traits. Landscape position was not a significant source of variation for yield or any biomass quality trait. Yields varied among harvests in 2005 (1,410-3,265 kg ha⁻¹) and 2006 (1,610-3,795 kg ha⁻¹). All cell wall, conversion test, and paper production traits exhibited year by harvest interactions with no clear pattern. Total carbohydrates and lignin ranged from 440 to 531 g kg⁻¹ DM and from 113 to 161 g kg⁻¹ DM, respectively. Release of cell wall sugars by the conversion test ranged widely (419 to 962 g kg⁻¹ DM). Fiber traits were similarly variable with length and fine content ranging from 1.24 to 1.59 mm and from 15.2% to 21.9%, respectively. Utilizing alfalfa biomass for cellulosic ethanol and paper pulp production will involve dealing with significant feedstock quality variation due to growth environment.
[Show abstract][Hide abstract] ABSTRACT: BACKGROUND: In previous research, we demonstrated that cell wall polysaccharide (CWP) levels of soybean (Glycine max L.) cotyledons are negatively correlated with the sum of seed oil and protein content. Although the results suggest that reducing cotyledon CWP levels would be desirable, it is not known whether CWP are mobilized during early seedling growth and, if so, to what extent mobilization contributes to seed reserves.RESULTS: Ungerminated (dry) seeds contained equivalent amounts [approximately 20 mg (cotyledon pair)⁻¹] of non-cell wall carbohydrates (NCWC) and CWP. Galactose and arabinose accounted for 47% of total CWP in cotyledons of dry seeds. Measured 14 days after planting (DAP), the levels of NCWC and CWP were reduced 98% and 34%, respectively, in cotyledons of seedlings grown under a 16-h photoperiod. Measured 14 DAP, greater than 85% of cotyledon cell wall galactose plus arabinose was mobilized. The transformation of the cotyledon to a photosynthetic organ was associated with restructuring of the cell wall involving increases in uronic acids, glucose and rhamnose.CONCLUSION: CWP of soybean cotyledons are modified during early seedling growth due to mobilization and cell wall restructuring triggered by light. The amount of carbon mobilized makes only a small contribution to total cotyledon reserves.
Preview · Article · Aug 2009 · Journal of the Science of Food and Agriculture