Hybrid Miscanthus Research Articles

Yield development and nutrient offtake in contrasting miscanthus hybrids under green and brown harvest regimes

AbstractHarvest time is an important variable that determines the yield of miscanthus biomass, its possible end uses, and the nutrient offtake from the field. Green harvests result in a higher yield and greater nutrient removal from the field. Brown miscanthus harvests, carried out in late winter or early spring, result in lower yields and a lower nutrient offtake, whereby the harvested biomass is better suited to use in combustion. To look at the long‐term impact of green harvests on miscanthus, this experiment followed the yield development of two miscanthus hybrids subjected to green and brown harvests over a period of seven years at one site in Southern Germany. The standard commercial hybrid Miscanthus × giganteus (Mxg) was compared with a novel late‐ripening Miscanthus sinensis hybrid: Syn55. Average yields of Mxg were 19.9 t ha−1 for green harvests and 13.2 t ha−1 for brown harvests compared to 13.9 and 12.9 t ha−1 for green and brown harvested Syn55, respectively. Yields of Mxg were very different for green and brown harvests; green harvested Mxg had very high nutrient offtake, while brown harvested Mxg had the lowest nutrient offtakes of all treatments. Syn55 showed a less marked difference between green and brown harvests likely due to its tendency to retain its leaves over winter. Syn55 was however not tolerant of a green harvest, with yields of brown harvested stands surpassing the yield of green harvested stands in several years. Although Mxg demonstrated consistently high yields when harvested in October, some signs of yield decline were detected in both hybrids when harvested green, which was due to insufficient carbohydrate relocation. Alternating green and brown harvests are recommended to allow stands to replenish carbohydrate stores and to form a litter layer.

Species selection determines carbon allocation and turnover in Miscanthus crops: Implications for biomass production and C sequestration

Growing Miscanthus species and hybrids has received strong scientific and commercial support, with the majority of the carbon (C) modelling predictions having focused on the high-yield, sterile and noninvasive hybrid Miscanthus × giganteus. However, the potential of other species with contrasting phenotypic and physiological traits has been seldom explored. To better understand the mechanisms underlying C allocation dynamics in these bioenergy crops, we pulse-labelled (13CO2) intact plant-soil systems of Miscanthus × giganteus (GIG), Miscanthus sinensis (SIN) and Miscanthus lutarioriparius (LUT) and regularly analysed soil respiration, leaves, stems, rhizomes, roots and soils for up to 190 days until leaf senescence. A rapid isotopic enrichment of all three species was observed after 4 h, with the amount of 13C fixed into plant biomass being inversely related to their respective standing biomass prior to pulse-labelling (i.e., GIG < SIN < LUT). However, both GIG and LUT allocated more photoassimilates in the aboveground biomass (leaves+stems = 78 % and 74 %, respectively) than SIN, which transferred 30% of fixed 13C in its belowground biomass (rhizomes+roots). Although less fixed 13C was recovered from the soils (<1 %), both rhizospheric and bulk soils were signficantly more enriched under SIN and LUT than under GIG. Importantly, the soils under SIN emitted less CO2, which suggests it could be the best choice for reaching C neutrality. These results from this unique large-scale study indicate that careful species selection may hold the success for reaching net GHG mitigation.

Improving combustion quality of Miscanthus by adding biomass from perennial flower-rich wild plant species

Miscanthus (ANDERSSON) is considered a promising perennial industrial crop for providing biomass in a growing bioeconomy. One approach to increasing the biodiversity-enhancing ecosystem services of Miscanthus is the co-cultivation of flower-rich native wild plant species (WPS), for example, the perennial WPS common tansy (Tanacetum vulgare L.) and mugwort (Artemisia vulgaris L.), as well as the biennial WPS wild teasel (Dipsacus fullonum L.) and yellow melilot (Melilotus officinalis L.). This study tested whether these selected WPS would be as suitable for combustion as Miscanthus, in this case the sterile hybrid Miscanthus x giganteus Greef et Deuter, allowing for a mixing of the biomasses. By doing so, no additional value chain (e.g. biogas production) would be necessary to economically exploit the diversification of the agricultural system for bioenergy production. Feedstock samples of Miscanthus and the four above-mentioned WPS from a field trial in southwest Germany were used to investigate the combustion characteristics as well as the higher heating value (HHV). It was found that all WPS exhibited better combustion properties than Miscanthus with respect to ash melting behavior at similar HHVs of 16.3–17.5 MJ kg−1. From an admixture of >30% WPS to the Miscanthus biomass, a significant increase in the ash melting temperature by 20% from 1000 to 1200 °C was shown. Thus, the mixture of WPS and Miscanthus could potentially improve the combustion quality, leading to reduced costs in the incineration plant operation process. However, the reduced costs of incineration should be greater than the loss in productivity due to the lower biomass yields from the WPS. This is highly dependent on the particular site conditions and the establishment success of the WPS and needs to be investigated in long-term studies.

Design, instrumentation, and operation of a standard downdraft, laboratory-scale gasification testbed utilising novel seed-propagated hybrid Miscanthus pellets

Biomass gasification remains an attractive option to impact climate chaos; however, the technology presents challenges in tolerance to feedstock variability and tar production, which can limit the overall process efficiency, gasifier performance, durability and downstream syngas utilisation. The primary objectives of this study were to compare two gasifier design approaches using different reaction kinetics, based on multiple or singular oxidation and gasification reactions, and build and test a novel, flexible, laboratory-scale downdraft gasifier to convert pellets from UK hybrid Miscanthus into syngas, whilst deploying inexpensive instrumentation methods. The experimental gasification parameters studied were carbon conversion efficiency, gas yield, cold gas efficiency and gas heating values. The performance study shows that the system achieved good average temperature (842–866 °C) in the reduction zones for equivalence ratios between 0.25 and 0.35. The optimum values for carbon conversion efficiency, cold gas efficiency, heating values (HHV) of product gas and gas yield were 74%, 32%, 4.17 MJ/m3 and 1.32 m3/kg(biomass), respectively. The reported performance parameters for the new seed-propagated hybrid Miscanthus in the present study were comparable to those from conventional Miscanthus pellet gasification in downdraft gasifiers but these new hybrid varieties offer advantages in productivity over broader climatic regions compared to conventional varieties.

Stress Response of Miscanthus Plants and Soil Microbial Communities: A Case Study in Metals and Hydrocarbons Contaminated Soils

Second-generation biofuel crop miscanthus is one of the most promising plants tested for phytomanagement of contaminated sites. In this preliminary pot case study, the most used hybrid Miscanthus x giganteus was cultivated in three different real contaminated soils: agricultural soil contaminated with Cd; post-military soil slightly contaminated with Zn, Pb and Cd; and soil contaminated by petroleum industry with metals and hydrocarbons. The stress response of plants and soil microbial communities was monitored to receive data that are important for successful phytomanagement application. With metals only, the plant grew well, and chlorophyll fluorescence measurement proved their good vitality. Changes in leaf anatomy (leaf thickness and sclerenchyma cells area) were additionally determined in post-military soil compared to agricultural. On the contrary, in petroleum-contaminated soil, the biomass yield was too reduced and also physiological parameters were significantly decreased. The response of microbial communities also differed. In agricultural soil, no microbial stress was determined. In post-military soil, it became reduced during the experiment, and in petroleum contamination, it increased year-on-year. It could be concluded that miscanthus is suitable for cultivation in metals contaminated soils with potential for microbial communities support, but in soil contaminated by the petroleum industry, its application did not seem meaningful.

Allelopathic and intraspecific growth competition effects establishment of direct sown Miscanthus.

High yielding perennial crops are being developed as a sustainable feedstock for renewable energy and bioproducts. Miscanthus is a leading biomass crop, but most plantations comprise a sterile hybrid Miscanthus × giganteus that is clonally propagated. To develop new varieties across large areas, rhizome cloning is inefficient, time consuming and expensive. Alternative approaches use seed, and in temperate regions, this has been successfully applied by raising seedlings as plug plants in glasshouses before transfer to the field. Direct sowing has yet to be proven commercially viable because poor germination has resulted in inconsistent stand establishment. Oversowing using seed clusters is a common approach to improve the establishment of crops and it was hypothesized that such an approach will improve uniformity of density in early Miscanthus stands and thereby improve yield. Sowing multiple seeds creates potential for new interactions, and we identified at least two inhibitory mechanisms related to seed numbers. Germinating seed produced allelopathic effects on nearby seed thereby inhibiting plant growth. The inhibitory effect of Miscanthus seed on germination percentages was related to seed number within clusters. An extract from germinating Miscanthus seed inhibited the germination of Miscanthus seed. The extract was analysed by HPLC, which identified a complex mixture including several known allelopathic compounds including proanthocyanidins and vanillic acid. There was also evidence of root competition in soil in a controlled environment experiment. When the experiment on competition was replicated at field scale, the establishment rates were much lower and there was evidence of shoot competition. We conclude that the numbers of seed required to ensure an acceptable level of establishment in the field may be economically impractical until other agronomic techniques are included either to reduce the inhibitory effects of higher seed numbers or to reduce oversowing rates.

Preparation of cellulose nanofibers from Miscanthus x. Giganteus by ammonium persulfate oxidation

Carboxylic acid functionalized cellulose nanofibers (MxG-CNFA-CO2H) were successfully isolated from a sustainable grass hybrid Miscanthus x. Giganteus by a new two-step chemical oxidation, that involves bleach treatment and ammonium persulfate oxidation, followed by ultrasonication. The resulting MxG-CNFA-CO2Hs have ca. 1200 mmol/kg carboxylic acid surface groups, an aspect ratio of 230 (height of ca. 3.8 ± 0.8 nm and length of ca. 880 ± 300 nm) and 70% crystallinity. Interestingly, these MxG-CNFA-CO2Hs exhibit better thermal stability (as measured by thermal gravimetric analysis) and better dispersibility in DMF than corresponding cellulose nanocrystals (CNC) obtained from same biosource (MxG-CNC-CO2Hs) via acid hydrolysis. Poly(vinyl acetate):MxG-CNFA-CO2H composites show an increase in storage modulus (above Tg) with increasing filler content. Importantly, the mechanical properties of the poly(vinyl acetate):nanocellulose composites showed that the MxG-CNFA-CO2Hs exhibit significantly better reinforcement than the MxG-CNC-CO2H at the same weight percent filler content.

Enhanced production of lactate-based polyesters in Escherichia coli from a mixture of glucose and xylose by Mlc-mediated catabolite derepression

Lignocellulose-utilizing biorefinery is a promising strategy for the sustainable production of value-added products such as bio-based polymers. Simultaneous consumption of glucose and xylose in Escherichia coli was achieved by overexpression of the gene encoding Mlc, a multiple regulator of glucose and xylose uptake. This catabolite derepression gave the enhancement in the production of poly (15mol% lactate-co-3-hydroxybutyrate), up to 65% from 50% (wild-type strain) in the cellular contents, of the Mlc-overexpressing strain of E.coli on a mixture of glucose and xylose as carbon sources. Microscopic analysis indicated that the Mlc-overexpressing strain showed the enlargement of cell volume in the presence and absence of polymer production, consequently making an expanded volumetric space available for enhanced polymer accumulation. The enhanced polymer production by the catabolite derepression was also reproducible using the biomass, Miscanthus×giganteus (hybrid Miscanthus), which was cultivated in the farm of Hokkaido University.

Comparison of Miscanthus and Switchgrass Cultivars for Biomass Yield, Soil Nutrients, and Nutrient Removal in Northwest Spain

Core Ideas Miscanthus and switchgrass are often touted as biomass crop choices, but have rarely been compared side‐by‐side. Miscanthus was slower to establish than switchgrass cultivars, but out‐yielded switchgrass in the latter 3 yr of the trial. Phosphorus was the soil nutrient most likely to be drawn down to levels requiring fertilization, after N. Comparative performance tests of perennial grasses for biomass yield, quality, and soil nutrient removal are needed to guide decisions toward meeting European Union targets for renewable energy production. We compared hybrid miscanthus (Miscanthus × giganteus Greef and Deuter ex Hodkinson and Renvoize) and switchgrass (Panicum virgatum L.) cultivars Cave‐in‐Rock, (upland type), Alamo, and Kanlow (lowland types) for biomass yield and changes in soil macronutrient levels and removal rates in a humid Spanish environment. Soil and plant nutrient and C levels were measured after each annual biomass harvest for 4 yr. Plant nutrient concentrations were multiplied by biomass yield to express nutrient removal. Yield ranking (4‐yr mean) was miscanthus (17.6 Mg ha−1) &gt; Kanlow (13.3 Mg ha−1) = Alamo (13.0 Mg ha−1) &gt; Cave‐in‐Rock (7.7 Mg ha−1). Miscanthus biomass yield peaked in the third year at 27.0 Mg ha−1. The high yield of miscanthus together with its relatively low macronutrient concentrations and intermediate removal rates, indicate its advantages over switchgrass as a biomass crop choice. Alamo and Kanlow usually removed more macronutrients than Cave‐in‐Rock, suggesting a greater long‐term fertilizer requirement for the lowland types. Soil C stocks increased by a mean of 2850 kg ha−1 over 4 yr at 0‐ to 20‐cm depth. Phosphorus was the macronutrient most likely to become deficient after repeated harvests. Miscanthus and lowland switchgrass cultivars performed well in the Atlantic maritime region of Spain, therefore the choice of crop would rely on economics of establishment and long‐term stand maintenance.

Improved Feedstock Option or Invasive Risk? Comparing Establishment and Productivity of Fertile Miscanthus × giganteus to Miscanthus sinensis

The perennial grass genus Miscanthus has great promise as biomass feedstock, but there are concerns about potential invasion outside production fields. While the sterile hybrid Miscanthus × giganteus is currently one of the leading feedstock options due to its low invasive potential, fertile varieties are being developed to reduce establishment costs, and their invasive risks need to be further assessed. We performed seed addition experiments in Ohio and Iowa, USA to examine the establishment, flowering, persistence, and shoot biomass per plot of a fertile M. × giganteus biotype (‘PowerCane’) and two Miscanthus sinensis biotypes, one feral, and one ornamental. Seeds were added to small, replicated plots in each of the 2 years under two seeding densities and two competition treatments, and plots were monitored for 2–3 years. The ‘PowerCane’ biotype established better, survived better, and produced greater amounts of biomass per plot than both M. sinensis biotypes. All three biotypes flowered by the second or third year after establishment, with inflorescences more numerous in ‘PowerCane’ and the Ornamental M. sinensis biotypes. Effects of seeding density and competition on these patterns were minor in most cases. Our research suggests that ‘PowerCane’ exhibits many traits shared by both biomass crops and invasive species: multi-year persistence, high biomass potential, and fertility. We suggest that the benefits of a seeded M. × giganteus should be carefully weighed against its increased invasive risk prior to deployment across the landscape.

Microbial production of poly(lactate-co-3-hydroxybutyrate) from hybrid Miscanthus-derived sugars

P[(R)-lactate-co-(R)-3-hydroxybutyrate] [P(LA-co-3HB)] was produced in engineered Escherichia coli using lignocellulose-derived hydrolysates from Miscanthus × giganteus (hybrid Miscanthus) and rice straw. Hybrid Miscanthus-derived hydrolysate exhibited no negative effect on polymer production, LA fraction, and molecular weight of the polymer, whereas rice straw-derived hydrolysate reduced LA fraction. These results revealed that P(LA-co-3HB) was successfully produced from hybrid Miscanthus-derived sugars.

Radiation capture and conversion efficiencies of Miscanthus sacchariflorus, M.sinensis and their naturally occurring hybrid M.×giganteus.

Miscanthus is a rhizomatous C4 grass of great interest as a biofuel crop because it has the potential to produce high yields over a wide geographical area with low agricultural inputs on marginal land less suitable for food production. At the moment, a clonal interspecific hybrid Miscanthus × giganteus is the most widely cultivated and studied in Europe and the United States, but breeding programmes are developing newer more productive varieties. Here, we quantified the physiological processes relating to whole season yield in a replicated plot trial in Wales, UK. Light capture and conversion efficiency were parameterized for four carefully selected genotypes (M. sinensis, M. sacchariflorus and Miscanthus × giganteus). Differences in the canopy architecture in mature stands as measured by the extinction coefficient (k) were small (0.55–0.65). Sensitivity analysis on a mathematical model of Miscanthus was performed to quantify the accumulative intercepted photosynthetically active radiation (iPAR) in the growing season using (i) k, (ii) variation in the thermal responses of leaf expansion rate, (iii) base temperature for degree days and (iv) date start of canopy expansion. A 10% increase in k or leaf area per degree day both had a minimal effect on iPAR (3%). Decreasing base temperature from 10 to 9 °C gave an 8% increase in iPAR. If the starting date for canopy expansion was the same as shoot emergence date, then the iPAR increases by 12.5%. In M. × giganteus, the whole season above ground and total (including below ground) radiation‐use efficiency (RUE) ranged from 45% to 37% higher than the noninterspecific hybrid genotypes. The greater yields in the interspecific hybrid M. × giganteus are explained by the higher RUE and not by differences in iPAR or partitioning effects. Studying the mechanisms underlying this complex trait could have wide benefits for both fuel and food production.

Discovery of Natural Interspecific Hybrids Between Miscanthus Sacchariflorus and Miscanthus Sinensis in Southern Japan: Morphological Characterization, Genetic Structure, and Origin

Natural Miscanthus grasses are useful for improving biomass production. We found a population of putative triploid interspecific hybrids between Miscanthus sacchariflorus and Miscanthus sinensis in southern Kyushu, Japan. This study aims to investigate its morphological variation, genetic structure, and origin. Miscanthus plants were collected from 114 points, mainly beside a river along a distance of 2.8 km in the Tashiro–Fumoto area. They resembled M. sacchariflorus but showed morphology intermediate between the two species. They had a nuclear DNA content corresponding to that of a hybrid between tetraploid M. sacchariflorus and diploid M. sinensis, and had species-specific alleles from both species revealed by DNA marker analysis. This indicates that the plants are triploid hybrids between M. sacchariflorus and M. sinensis. Genotyping using simple sequence repeat markers revealed only four genotypes among the hybrid population, of which two accounted for most plants. The genotypes showed mostly discrete geographical distributions. The two major genotypes showed contrasting phenotypes in pollen viability and in frequency of awns in florets. Some seeds collected from the population germinated and the seedlings showed a wide range of nuclear DNA content from diploid to tetraploid. In this area, many M. sinensis plants also grew, but we could not find M. sacchariflorus. The hybrid Miscanthus might be selected due to its improved adaptability introduced from M. sinensis. Furthermore, genetic and phenotypic characterization suggests the polyphyletic origin and clonal propagation of this population. Such partially fertile hybrids could be interesting for the improvement of Miscanthus as a biomass crop.

Miscanthus Production in Eastern Canada as Affected by Genotypes and Nitrogen Levels

Interest in new biomass and biofuel crops has soared in the last few years due to the changing climate and the search for renewable energy options. Under eastern Canada conditions, perennial C4 grasses can produce 8-11 Mg dry matter ha-1 year-1 [1,2]. However, Miscanthus spp. seems to be more promising with dry matter production values exceeding 30 Mg ha-1 year-1 [3,4]. In this study, four genotypes of hybrid miscanthus (Miscanthus sinensis x M. sacchariflorus) were planted in Kemptville, Ontario, Canada in 2009. Genotypes “M1 Select”, “Nagara”, “Polish” and “Amuri” were established from rhizomes spaced at 75cm squares. The effect of four nitrogen rates (0, 40, 80 and 120kg N ha-1 year-1) was studied on growth and production parameters.The first summer and winter (with minimum temperatures reaching -40°C) were the most crucial for the establishment of the crop, and any plants that survived that first year have successfully established and regrew every year. Dry matter production generally increased with the level of nitrogen application and ranged between 25-50 Mg ha-1 year-1 in 2014. Genotype “Amuri” was the most productive while “M1 Select” was the least productive. Leaf area index increased with nitrogen application rate and was highest for “Nagara”. Similarly, leaf SPAD absorbance increased with nitrogen levels and was lower in “M1 Select” than the three other genotypes. Our results show the potential of miscanthus production under Canadian conditions with low nitrogen inputs.

A detailed gene expression study of the Miscanthusgenus reveals changes in the transcriptome associated with the rejuvenation of spring rhizomes

BackgroundThe Miscanthus genus of perennial C4 grasses contains promising biofuel crops for temperate climates. However, few genomic resources exist for Miscanthus, which limits understanding of its interesting biology and future genetic improvement. A comprehensive catalog of expressed sequences were generated from a variety of Miscanthus species and tissue types, with an emphasis on characterizing gene expression changes in spring compared to fall rhizomes.ResultsIllumina short read sequencing technology was used to produce transcriptome sequences from different tissues and organs during distinct developmental stages for multiple Miscanthus species, including Miscanthus sinensis, Miscanthus sacchariflorus, and their interspecific hybrid Miscanthus × giganteus. More than fifty billion base-pairs of Miscanthus transcript sequence were produced. Overall, 26,230 Sorghum gene models (i.e., ~ 96% of predicted Sorghum genes) had at least five Miscanthus reads mapped to them, suggesting that a large portion of the Miscanthus transcriptome is represented in this dataset. The Miscanthus × giganteus data was used to identify genes preferentially expressed in a single tissue, such as the spring rhizome, using Sorghum bicolor as a reference. Quantitative real-time PCR was used to verify examples of preferential expression predicted via RNA-Seq. Contiguous consensus transcript sequences were assembled for each species and annotated using InterProScan. Sequences from the assembled transcriptome were used to amplify genomic segments from a doubled haploid Miscanthus sinensis and from Miscanthus × giganteus to further disentangle the allelic and paralogous variations in genes.ConclusionsThis large expressed sequence tag collection creates a valuable resource for the study of Miscanthus biology by providing detailed gene sequence information and tissue preferred expression patterns. We have successfully generated a database of transcriptome assemblies and demonstrated its use in the study of genes of interest. Analysis of gene expression profiles revealed biological pathways that exhibit altered regulation in spring compared to fall rhizomes, which are consistent with their different physiological functions. The expression profiles of the subterranean rhizome provides a better understanding of the biological activities of the underground stem structures that are essentials for perenniality and the storage or remobilization of carbon and nutrient resources.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-14-864) contains supplementary material, which is available to authorized users.

Transcriptomic and proteomic comparison of two Miscanthus genotypes: high biomass correlates with investment in primary carbon assimilation and decreased secondary metabolism

Background and aims The plant genus Miscanthus combines high biomass production in temperate climates with low nutrient input requirements. Among the widely studied genotypes, the triploid hybrid Miscanthus x giganteus has attracted most interest because of its outstanding yields. Here, M. x giganteus was compared to its parent M. sinensis to identify traits associated with high biomass.

OOS 38: Ecological Dimensions of Biofuel Production

OOS 38: Ecological Dimensions of Biofuel Production

Miscanthus as a feedstock for fast-pyrolysis: Does agronomic treatment affect quality?

The objectives of the experiment were to assess the impact of nitrogen (N) and potassium (K) fertiliser application on the cell wall composition and fast-pyrolysis conversion quality of the commercially cultivated hybrid Miscanthus x giganteus. Five different fertiliser treatments were applied to mature Miscanthus plants which were sampled at five intervals over a growing season. The different fertiliser treatments produced significant variation in concentrations of cell wall components and ash within the biomass and affected the composition and quality of the resulting fast-pyrolysis liquids. The results indicated that application of high rates of N fertiliser had a negative effect on feedstock quality for this conversion pathway: reducing the proportion of cell wall components and increasing accumulation of ash in the harvested biomass. No exclusive effect of potassium fertiliser was observed. The low-N fertiliser treatment produced high quality, low ash–high lignin biomass most suitable as a feedstock for thermo-chemical conversion.

Phylogenetic analysis of organellar DNA sequences in the Andropogoneae: Saccharinae

To study the phylogenetics of sugarcane (Saccharum officinarum L.) and its relatives we sequenced four loci on cytoplasmic genomes (two chloroplast and two mitochondrial) and analyzed mitochondrial RFLPs generated using probes for COXI, COXII, COXIII, Cob, 18S+5S, 26S, ATPase 6, ATPase 9, and ATPase α (D'Hont et al. 1993). Approximately 650 bp of DNA in the intergenic spacer region between rbcL and atpB and approximately 150 bp from the chloroplast 16S rDNA through the intergenic spacer region tRNA(val) gene were sequenced. In the mitochondrial genome, part of the 18S rRNA gene and approximately 150 bp from the 18S gene 3' end, through an intergenic spacer region, to the 5S rRNA gene were sequenced. No polymorphisms were observed between maize, sorghum, and 'Saccharum complex' members for the mitochondrial 18S internal region or for the intergenic tRNA(val) chloroplast locus. Two polymorphisms (insertion-deletion events, indels) were observed within the 18S-5S mitochondrial locus, which separated the accessions into three groups: one containing all of the Erianthus, Eccoilopus, Imperata, Sorghum, and 1 Miscanthus species; a second containing Saccharum species, Narenga porphyrocoma, Sclerostachya fusca, and 1 presumably hybrid Miscanthus sp. from New Guinea; and a third containing maize. Eighteen accessions were sequenced for the intergenic region between rbcL and atpB, which was the most polymorphic of the regions studied and contained 52 site mutations and 52 indels, across all taxa. Within the Saccharum complex, at most 7 site mutations and 16 indels were informative. The maternal lineage of Erianthus/Eccoilopus was nearly as divergent from the remaining Saccharum complex members as it was from sorghum, in agreement with a previous study. Sequences from the rbcL-atpB spacer were aligned with GENBANK sequences for wheat, rice, barley, and maize, which were used as outgroups in phylogenetic analyses. To determine whether limited intra-complex variability was caused by under sampling of taxa, we used seven restriction enzymes to digest the PCR-amplified rbcL-atpB spacer of an additional 36 accessions within the Saccharum complex. This analysis revealed ten restriction sites (none informative) and eight length variants (four informative). The small amount of variation present in the organellar DNAs of this polyploid complex suggests that either the complex is very young or that rates of evolution between the Saccharum complex and outgroup taxa are different. Other phylogenetic information will be required to resolve systematic relationships within the complex. Finally, no variation was observed in commercial sugarcane varieties, implying a world-wide cytoplasmic monoculture for this crop.