Candidate Bioenergy Crop Research Articles

Exploring the role of plant lysin motif receptor-like kinases in regulating plant-microbe interactions in the bioenergy crop Populus

For plants, distinguishing between mutualistic and pathogenic microbes is a matter of survival. All microbes contain microbe-associated molecular patterns (MAMPs) that are perceived by plant pattern recognition receptors (PRRs). Lysin motif receptor-like kinases (LysM-RLKs) are PRRs attuned for binding and triggering a response to specific MAMPs, including chitin oligomers (COs) in fungi, lipo-chitooligosaccharides (LCOs), which are produced by mycorrhizal fungi and nitrogen-fixing rhizobial bacteria, and peptidoglycan in bacteria. The identification and characterization of LysM-RLKs in candidate bioenergy crops including Populus are limited compared to other model plant species, thus inhibiting our ability to both understand and engineer microbe-mediated gains in plant productivity. As such, we performed a sequence analysis of LysM-RLKs in the Populus genome and predicted their function based on phylogenetic analysis with known LysM-RLKs. Then, using predictive models, molecular dynamics simulations, and comparative structural analysis with previously characterized CO and LCO plant receptors, we identified probable ligand-binding sites in Populus LysM-RLKs. Using several machine learning models, we predicted remarkably consistent binding affinity rankings of Populus proteins to CO. In addition, we used a modified Random Walk with Restart network-topology based approach to identify a subset of Populus LysM-RLKs that are functionally related and propose a corresponding signal transduction cascade. Our findings provide the first look into the role of LysM-RLKs in Populus-microbe interactions and establish a crucial jumping-off point for future research efforts to understand specificity and redundancy in microbial perception mechanisms.

Agroecosystem model simulations reveal spatial variability in relative productivity in biomass sorghum and maize in Iowa, USA

AbstractBiomass sorghum (Sorghum bicolor L. Moench) is an annual C4 grass that has emerged as a candidate bioenergy crop but has not been widely grown in the United States. Corn (Zea mays L.), another annual C4 grass, has been produced on a large scale in the United States for biofuels. Iowa leads the nation in both corn and ethanol production. The high productivity of corn in Iowa creates the research question: could biomass sorghum be as or more productive than corn in the state in terms of bioenergy? Efforts to use crop models to fill the gaps left by field experimentation on biomass sorghum have also been limited thus far. To address our research question, we collected biophysical data on biomass sorghum grown in Iowa for two growing seasons, used them to develop a biomass sorghum module in an agroecosystem model (Agro‐IBIS), and predict the potential performance of biomass sorghum across Iowa compared to maize. Despite dry conditions in 2019 and 2020, average biomass sorghum yields were 17.20 Mg ha−1. By comparison, average corn aboveground biomass was higher in 2020 (22.02 Mg ha−1). Soil cores indicated average belowground biomass of 1.46 Mg ha−1, with roots concentrated near the surface (73% of biomass above 50 cm in a 1 m core). When biomass sorghum model parameters were calibrated with measured values, model output was in close agreement with measured biomass (slope = 0.932, R2 = 0.91) and evapotranspiration (slope = 0.757, R2 = 0.64). Subsequent regional simulations revealed a notable latitudinal gradient in biomass sorghum yield, with a strong linear relationship between yield and seasonal growing degree‐days (R2 = 0.89). When these yields were compared to simulated corn aboveground biomass yields, only 3.4% of the state had biomass sorghum yields that were significantly higher than corn. This number was reduced to 0.3% when comparing the crops in terms of energy ethanol yield. Thus, we conclude biomass sorghum must be improved to be competitive with corn as an annual biofuel crop in Iowa. This study provides a baseline against which to compare advancements in sorghum breeding for biomass and stress tolerance in Iowa.

An Improved Leaf Protoplast System for Highly Efficient Transient Expression in Switchgrass (Panicum virgatum L.).

As a robust perennial C4-type monocot plant and a native species to North America, switchgrass (Panicum virgatum) has been evaluated and designated as a strong candidate bioenergy crop by the U.S. DOE. Although genetic modifications of switchgrass have been used to successfully reduce the recalcitrance of switchgrass biomass for biofuel production, the generation of transgenic switchgrass is still a slow and laborious process. A transient protoplast system can provide an excellent platform to accelerate the selection of genes-of-interest for tailoring switchgrass biomass. However, partially due to the lack of the complete genomic information, the attempts to optimize the transient protoplast system for switchgrass remain scarce. In this chapter, we provide an improved protocol for switchgrass protoplast isolation, increased transformation efficiency using CsCl gradient ultracentrifugation-derived plasmid DNA and extended application of the transient switchgrass protoplast system to analyze protein expression using western blot.

Hybrid Napier grass (Pennisetum purpureum Schumach × P. americanum (L.) Leeke cv. Pakchong1) and Giant reed (Arundo donax L.) as candidate species in temperate European paludiculture: Growth and gas exchange responses to suboptimal temperatures

Hybrid Napier grass (Pennisetum purpureum × P. americanum cv. Pakchong1) and Giant reed (Arundo donax) are candidate bio-energy crops in temperate European paludiculture, due to their high growth and biomass production rates, ease of harvesting and resistance to temporary flooding. We conducted a growth chamber experiment with the two species in two different temperature regimes (15 °C and 20 °C of daytime growth temperature, respectively), to investigate whether the two species were capable of acclimating to typical growth season temperatures of temperate Europe, which are sub-optimal for the two species. After a 7-week period of growing in the climatized chambers, measurements of photosynthetic responses to light and CO2 were conducted. Surprisingly, the C4 species hybrid Napier grass was the most productive species in both temperature regimes and had the highest photosynthetic rates, but it was also more sensitive and responded with stronger differences to the temperatures than the C3 species Giant reed. Giant reed exhibited a more stable physiology (for example with quantum yield, dark respiration rate, maximum electron transport rate and maximum carboxylation rate of Rubisco), but had lower photosynthesis and produced less biomass than hybrid Napier grass. In contrast, hybrid Napier grass had a stable allocation to biomass fractions under both temperature regimes, while Giant reed responded to 15 °C with lower leaf allocation and higher root allocation. Both species showed individual limitations to suboptimal temperatures, but grew comparably well, especially at 20 °C. We showed that both hybrid Napier grass and Giant reed are potential paludiculture candidate species even in cooler climates, and prolonged outdoor trials are needed to verify our results under field conditions.

Transcriptome Analysis of the Heritable Salt Tolerance of Prairie Cordgrass (Spartina pectinata Link)

The salt-tolerant capability of the candidate bioenergy crop prairie cordgrass greatly surpasses that of previously characterized prairie grass species and most other plants. To understand the mechanism of inherited salt tolerance, we compared phenotypic and genetic qualities in half-sib families of prairie cordgrass after salt treatment. Each family was treated with a 400 mM NaCl solution or a water control and then measured for various health phenotypes. Phenotypes associated with salt tolerance were shown to be moderately heritable between parent and offspring. RNA-seq analysis revealed differential regulation in unique pathways including metabolism, signaling, photosynthesis, and the circadian rhythm. The studies herein suggest that alternative regulation of the photosynthetic pathway could confer increased salt resistance in halophytes and can be monitored phenotypically or genetically in breeding programs. The improvement of salt-tolerant traits in prairie cordgrass would increase its potential to be grown as a bioenergy crop on lands that are not suitable for the growth of food crops.

Legacies in Switchgrass Resistance to and Recovery from Drought Suggest That Good Years Can Sustain Plants Through Bad Years

The warm-season perennial switchgrass (Panicum virgatum) is a candidate bioenergy crop. To be successful, switchgrass production must be maintained on low-quality landscapes with minimal inputs while facing future climates that are expected to be more extreme and more variable. We propose that antecedent rainfall constrains how plants respond to drought, as well as subsequently recover from drought. To test this idea, we examined how six switchgrass genotypes responded to a 1-year severe drought and then recovered under normal rainfall in the following year. These plants had previously grown for 3 years under a range of dry to wet rainfall levels in a shallow-soil common garden with no fertilizer. Plants previously exposed to drought produced less biomass, and basal area after the severe drought was relieved compared to previously well-watered plants. In addition, there were legacy effects caused by plant size: plants that were larger pre-drought were more likely to survive the severe drought, and plants that were larger during the severe drought recovered more biomass, basal area, and tillers post-drought. Although genotypes differed somewhat in their responses, the size constraint was consistent across genotypes. These findings suggest that we can establish more drought-resilient switchgrass stands by, for example, planning for initial irrigation or planting during a wet year to allow plants to grow larger prior to experiencing drought. Additional studies are needed to understand whether these rainfall and size legacies persist or are transient.

Long-term studies on switchgrass grown on a marginal area in Greece under different varieties and nitrogen fertilization rates

Switchgrass (Panicum virgatum L.) is a perennial grass that has been selected as a candidate bioenergy crop for USA in the early 80s, while the research in Europe started a decade later. A long-term study on switchgrass had been carried out (1998–2015) on a marginal area in Greece comparing five varieties (having lowland or upland ecotype) at increasing nitrogen fertilization rates (0, 75 and 150kgNha−1). Due to the successful establishment of the plantation quite satisfactory yields were recorded even at the establishment year (8.9MgDMha−1) and the ceiling yields were recorded in the 2nd year and came up to 20MgDMha−1. The under study lowland varieties (Alamo, Kanlow and Pangburn) were more productive compared to the upland varieties (Blackwell and CIR) with mean dry yields 12.37 and 11.39 Mgha−1, respectively and showed higher resistance to lodging. Among the five under study varieties, Alamo was the best performing giving an average yield of 12.7MgDMha−1, averaged over all treatments and years, while CIR was the least performing producing a corresponding average yield of 10.8MgDMha−1. From the fourth growing season and onwards significantly higher yields were recorded under increasing N fertilization up to 150kgNha−1 with an average yield of 13.9MgDMha−1 (150kgN/ha) over all varieties and years. The corresponding yields for the other two tested nitrogen rates (0 and 75kgN/ha) were 10.31 and 11.69MgDMha−1, respectively.

The biomethane, silage and biomass yield obtainable from three accessions of Cynara cardunculus

In the light of the possible contribution of bioenergy to reducing the dependence on fossil fuel imports and to controlling greenhouse gas emission, a present priority is to develop crops which can be raised using minimal production inputs. The potential of the cardoon (Cynara cardunculus) has been investigated here by assessing the outcome of anaerobically digesting two cultivated forms and one wild one. Fermentation lab tests were performed on ensiled biomass, as in the real scale conditions, and they were aimed at measuring the biomethane production per unit of feedstock. The cultivated forms (‘Altilis 41’ and ‘Bianco avorio’) produced, respectively, 19.1 and 16.8t dry matter (DM) per hectare per year, from which, respectively 4074 and 4162Nm3 of biomethane was generated; the wild cardoon accession was less productive both in terms of biomass accumulation (11.8t DM per hectare per year) and estimated biomethane yield (2867Nm3). The yield of biomethane ranged from ∼200 (‘Altilis 41’) to 245 (‘Bianco avorio’ and wild cardoon) Nm3 per t DM, a level sufficiently high to justify considering C. cardunculus as a promising candidate bioenergy crop in the Mediterranean environment.

Four‐year decline in radioactive cesium transfer to perennial Gramineae candidate bioenergy crops in a field polluted by radioactive fallout from the Fukushima Daiichi Nuclear Power Plant in 2011

AbstractThe accident caused at the Tokyo Electric Power Company's Fukushima Daiichi Nuclear Power Plant by the Great East Japan Earthquake of 11 March 2011 resulted in radioactive fallout over a wide area of eastern Japan. Production of bioenergy crops and their conversion to energy may be one way to resume agricultural production at an early date and to put renewable energy to practical use. We examined yearly changes in radioactive cesium concentrations in the harvested parts of six perennial Gramineae candidate bioenergy crops and the distribution of the cesium in plant organs and rhizosphere soil layers under no‐till conditions in an experimental field 112 km from the nuclear power plant. Average radioactivity of the sum of cesium‐134 and cesium‐137 in the harvested parts (foliage) of the six bioenergy crops on the day of harvest declined considerably from 193.3 Bq kg−1 in 2011 to 31.6% of the 2011 level in 2012, 28.8% in 2013 and 28.7% in 2014. Radioactivity was higher in the underground plant parts (subterranean stem and root) than in the aboveground parts (foliage and stubble). In 2014, radioactivity in the untilled rhizosphere soil was higher in the shallow layer (0–5 cm from the soil surface) than in the deeper layers, indicating that rainfall and perennial bioenergy crop cultivation for more than 3 years had a limited effect on the soil distribution of the fallout. These results provide unique and specific information on radioactive cesium transfer to bioenergy crops and could help in the planning of feedstock supplies in radiation‐polluted areas.

Predicting Biofuel Invasiveness: A Relative Comparison to Crops and Weeds

AbstractConcern raised against using highly competitive, exotic, large-statured, perennial grasses with fast growth rates as bioenergy crops has led to calls for risk assessment before widespread cultivation. Weed risk assessments (WRAs) are decision support tools commonly used throughout the world to determine the invasion risk of new plant taxa—primarily used as a pre-entry screen. Here, we compare the common Australian (A-WRA) and newer U.S. (US-WRA) models to evaluate the invasion risk of 16 candidate bioenergy crops and to compare their WRA scores to 14 important agronomic crops and 10 invasive species with an agronomic origin. Of the 40 species assessed, the A-WRA and US-WRA ranked 34 and 28 species, respectively, as high risk, including the major crops alfalfa, rice, canola, and barley. Surprisingly, in several cases, both models failed to effectively parse weeds from crops. For example, cereal rye received scores above (US-WRA) or comparable to (A-WRA) kudzu, a widespread damaging invader of the Southeastern United States introduced as forage. Our results indicate that these models are unable to accurately address broad, intraspecific variation and that species introduced for agronomic purposes pose special limitations to WRAs. This further supports other calls for postborder evaluation (e.g., field testing) following WRA screening. We should be cautious of the role of WRAs in setting policy, as illustrated by this relative evaluation of novel crops.

Contrasting allelic distribution of CO/Hd1 homologues in Miscanthus sinensis from the East Asian mainland and the Japanese archipelago.

The genus Miscanthus is a perennial C4 grass native to eastern Asia and is a promising candidate bioenergy crop for cool temperate areas. Flowering time is a crucial factor governing regional and seasonal adaptation; in addition, it is also a key target trait for extending the vegetative phase to improve biomass potential. Homologues of CONSTANS (CO)/Heading date 1(Hd1) were cloned from Miscanthus sinensis and named MsiHd1. Sequences of MsiHd1 homologues were compared among 24 wild M. sinensis accessions from Japan, 14 from China, and three from South Korea. Two to five MsiHd1 alleles in each accession were identified, suggesting that MsiHd1 consists of at least three loci in the Miscanthus genome. Verifying the open reading frame in MsiHd1, they were classified as putative functional alleles without mutations or non-functional alleles caused by indels. The Neighbor-Joining tree indicated that one of the multiple MsiHd1 loci is a pseudogene locus without any functional alleles. The pseudogene locus was named MsiHd1b, and the other loci were considered to be part of the MsiHd1a multi-locus family. Interestingly, in most Japanese accessions 50% or more of the MsiHd1a alleles were non-functional, whereas accessions from the East Asian mainland harboured only functional alleles. Five novel miniature inverted transposable elements (MITEs) (MsiMITE1-MsiMITE5) were observed in MsiHd1a/b. MsiMITE1, detected in exon 1 of MsiHd1a, was only observed in Japanese accessions and its revertant alleles derived from retransposition were predominantly in Chinese accessions. These differences in MsiHd1a show that the dependency on functional MsiHd1a alleles is different between accessions from the East Asian mainland and Japan.

Response of Naturalized and Ornamental Biotypes ofMiscanthus sinensisto Soil-Moisture and Shade Stress

A recent trend in bioenergy-feedstock development includes the use of large-statured perennial grasses whose rapid growth and biomass-accumulation rates in low-fertility conditions make them highly desirable; however, these species tend to have much in common with many invasive plant species. Miscanthus sinensis (Chinese Silvergrass), an extremely popular ornamental grass and candidate bioenergy crop, has naturalized in over half of US states, yet little is known about its environmental-stress tolerance, which is a characteristic important for bioenergy development and invasiveness. Previous studies of Chinese Silvergrass have suggested that the species' enhanced tolerance to shade and drought conditions may be contributing to its invasion success in the US. To test this hypothesis, we conducted a greenhouse study to compare shade and soil-moisture stress tolerance among phenotypically diverse ornamental cultivars and naturalized biotypes of Chinese Silvergrass. We found enhanced plant growth and vigor in naturalized biotypes compared to ornamental biotypes across light levels from 5% to 100% of full sun. We also found that both the naturalized and the ornamental cultivars were not significantly affected by soil-moisture stress, and thus exhibited significant drought tolerance. Greater vigor and performance of naturalized biotypes in low light conditions compared to ornamental biotypes suggest that naturalized biotypes have enhanced shade tolerance, possibly due to hybridization. Our results provide direction for additional evaluations and weed-risk assessments of Chinese Silvergrass that will be critical in preventing future invasions and guide breeding for horticulture and bioenergy.

Reducing the negative human-health impacts of bioenergy crop emissions through region-specific crop selection

An expected global increase in bioenergy-crop cultivation as an alternative to fossil fuels will have consequences on both global climate and local air quality through changes in biogenic emissions of volatile organic compounds (VOCs). While greenhouse gas emissions may be reduced through the substitution of next-generation bioenergy crops such as eucalyptus, giant reed, and switchgrass for fossil fuels, the choice of species has important ramifications for human health, potentially reducing the benefits of conversion due to increases in ozone (O3) and fine particulate matter (PM2.5) levels as a result of large changes in biogenic emissions. Using the Community Earth System Model we simulate the conversion of marginal and underutilized croplands worldwide to bioenergy crops under varying future anthropogenic emissions scenarios. A conservative global replacement using high VOC-emitting crop profiles leads to modeled population-weighted O3 increases of 5–27 ppb in India, 1–9 ppb in China, and 1–6 ppb in the United States, with peak PM2.5 increases of up to 2 μg m−3. We present a metric for the regional evaluation of candidate bioenergy crops, as well as results for the application of this metric to four representative emissions profiles using four replacement scales (10–100% maximum estimated available land). Finally, we assess the total health and climate impacts of biogenic emissions, finding that the negative consequences of using high-emitting crops could exceed 50% of the positive benefits of reduced fossil fuel emissions in value.

Evapotranspiration partitioning and water use efficiency of switchgrass and biomass sorghum managed for biofuel

Switchgrass (Panicum virgatum L.) and biomass sorghum (Sorghum bicolor L. Moench) are two candidate bioenergy crops for the US Southern Great Plains region. In this water-limited region, there is a need to partition evapotranspiration (ET) and to determine the water use efficiency (WUE) of these potential feedstocks. Both crops were grown in a field plot experiment at Stillwater, OK. Soil water content measurements were made by neutron probe every two weeks to a depth of 2.0m in 0.2-m intervals over the course of three growing seasons. Growing season ET was estimated as the difference between growing season precipitation and change in root zone soil water storage. Evapotranspiration was partitioned by measuring canopy interception using interception trays and estimating soil evaporation using the FAO-56 dual crop coefficient method. Transpiration was calculated as ET minus soil evaporation and canopy interception. Transpiration was the largest component of ET; however, soil evaporation and canopy interception accounted for 28% of growing season ET for switchgrass and 42% for biomass sorghum. Although the non-productive losses were greater from biomass sorghum, WUE values of 9–49kgha−1mm−1 based on ET and 22–83kgha−1mm−1 based on transpiration were observed for biomass sorghum, which were greater than the WUE values of switchgrass, 8–21kgha−1mm−1 based on ET and 12–28kgha−1mm−1 based on transpiration. These results demonstrate that biomass sorghum is a candidate feedstock with potential to achieve greater WUE than switchgrass at this location; however, other factors such as economics and ecosystem services should also be considered.

Power requirements and field performance in harvesting energycane and sugarcane

Energycane is emerging as a candidate bioenergy crop, and it resembles sugarcane in stature and cultivation practices. Preliminary trials indicated that sugarcane billet harvesters have insufficient power to harvest energycane. This study quantified the power requirements of selected harvester components and field performance of harvesters for sugarcane and energycane. The elevator pour rate for energycane was lower (43.3 Mg h−1, wet weight) than for sugarcane (132.7 Mg h−1, wet weight). At the observed pour rates, power consumption of the basecutter, elevator, and the entire harvester was comparable for energycane and sugarcane. However, the power requirements of the chopper were 1.65 times higher for energycane than for sugarcane. Greater stem damage and higher stubble heights were observed for energycane compared to sugarcane. Overflowing of the elevator was observed for energycane because of lower bulk density of the biomass (billets and trash, 143.8 kg m−3) compared to sugarcane (predominantly billets, 349.4 kg m−3). The field capacity of the harvester for energycane (0.32 ha h−1) was lower than for sugarcane (0.61 ha h−1), and the harvesting cost for energycane (5.91 $ Mg−1) was considerably higher than for sugarcane (1.87 $ Mg−1). Design modifications to the existing sugarcane harvester models would be needed to adapt them to harvest energycane.

Stem bending force and hydraulic system pressure sensing for predicting napiergrass yield during harvesting

Napiergrass, which resembles sugarcane in stature and cultivation practices, is emerging as a candidate bioenergy crop. However, limited studies investigating harvesting and yield sensing of napiergrass are available. This study investigated stem-bending force, and the hydraulic pressures of basecutter, chopper and elevator drives in a John Deere 3522 sugarcane billet harvester as indicators of napiergrass yield. The coefficients of determination (R2) between napiergrass yield and hydraulic pressures were 0.73, 0.88 and 0.81, respectively for the basecutter, chopper and elevator drives. The highest correlation (R2=0.92) was found between stem-bending force and napiergrass yield. The yield prediction errors were 4.9% and 8.6% for the calibration and validation plots with the stem-bending force yield sensor. Cross-validation, in which each harvested row was treated as a data point, showed that the average yield prediction errors were 10.9% and 11.8% for the calibration and validation data sets. Yield maps were also generated employing the stem-bending yield sensor. In addition, it was expected that the stem-bending yield sensor could be utilized to control harvester operation such as travel speed. Further studies would be needed to extend the stem-bending concept to other thick stemmed crops.

Influence of soil texture and crop management on the productivity of miscanthus (Miscanthus × giganteus Greef et Deu.) in the Mediterranean

AbstractBiomass productivity is the main favorable trait of candidate bioenergy crops. Miscanthus × giganteus is a promising species, due to its high‐yield potential and positive traits including low nutrient requirements and potential for C sequestration in soils. However, miscanthus productivity appears to be mostly related to water availability in the soil. This is important, particularly in Mediterranean regions where the risk of summer droughts is high. To date, there have been no studies on miscanthus responses under different soil conditions, while only a few have investigated the role of different crop managements, such as irrigation and nitrogen fertilization, in the Mediterranean. Therefore, the effects of contrasting soil textures (i.e. silty‐clay‐loam vs. sandy‐loam) and alternative agricultural intensification regimes (i.e. rainfed vs. irrigated and 0, 50, 100 kg ha−1 nitrogen fertilization), on miscanthus productivity were evaluated at three different harvest times for two consecutive years. Our results confirmed the importance of water availability in determining satisfactory yields in Mediterranean environments, and how soil and site characteristics strongly affect biomass production. We found that the aboveground dry yields varied between 5 Mg ha−1 up to 29 Mg ha−1. Conversely, nitrogen fertilization played only a minor role on crop productivity, and high fertilization levels were relatively inefficient. Finally, a marked decrease, of up to −40%, in the aboveground yield occurred when the harvest time was delayed from autumn to winter. Overall, our results highlighted the importance of determining crop responses on a site‐by‐site basis, and that decisions on the optimal harvest time should be driven by the biomass end use and other long‐term considerations, such as yield stability and the maintenance of soil fertility.

Adult activity and oviposition of corn rootworms, Diabrotica spp. (Coleoptera: Chrysomelidae), in Miscanthus, corn and switchgrass

The ability of the biomass crop Miscanthus (Miscanthus × giganteus Greef and Deuter ex Hodkinson and Renvoize) to support larval development for both United States and European populations of the western corn rootworm, Diabrotica virgifera virgifera LeConte, suggests an avenue for interactions with corn (Zea mays L.). To provide context to survival of D. v. virgifera on Miscanthus, adult activity and oviposition of Diabrotica spp. were monitored in central Illinois in 2010–2011 in Miscanthus, corn and switchgrass (Panicum virgatum L.). For D. v. virgifera, vial traps within corn plots captured 3–10 times as many adults as in Miscanthus or switchgrass, while soil samples showed females laid approximately 10 times as many eggs in corn as in the perennial grasses. Adult southern corn rootworms, Diabrotica undecimpunctata howardi Barber, were the most abundant species in 2010 and clearly preferred switchgrass as an adult habitat, with vial traps in switchgrass capturing 5–10 times as many D. u. howardi as those in corn or Miscanthus. Based on the small production areas for Miscanthus and switchgrass (and low use of both by D. v. virgifera), it seems likely that there are no current impacts of these perennial grasses on pest status of Diabrotica spp. in corn or other crops. However, adaptations by Diabrotica spp. to pest management practices suggest they could be a source for interactions between biomass and food or feed crops. Early-season soil samples did not recover eggs of D. u. howardi, but their use of switchgrass as an adult habitat suggests additional research in areas where switchgrass may be grown near peanuts, alfalfa or other hosts may be needed. Also, investigation of other candidate bioenergy crops known to support Diabrotica spp. larval development is needed to better understand the possible effects of a changing agricultural landscape on corn rootworms.

Bamboo: an overlooked biomass resource?

Bamboo is the common term applied to a broad group (1250 species) of large woody grasses, ranging from 10 cm to 40 m in height. Already in everyday use by about 2.5 billion people, mostly for fiber and food within Asia, bamboo may have potential as a bioenergy or fiber crop for niche markets, although some reports of its high productivity seem to be exaggerated. Literature on bamboo productivity is scarce, with most reports coming from various parts of Asia. There is little evidence overall that bamboo is significantly more productive than many other candidate bioenergy crops, but it shares a number of desirable fuel characteristics with certain other bioenergy feedstocks, such as low ash content and alkali index. Its heating value is lower than many woody biomass feedstocks but higher than most agricultural residues, grasses and straws. Although non-fuel applications of bamboo biomass may be actually more profitable than energy recovery, there may also be potential for co-production of bioenergy together with other bamboo processing. A significant drawback is the difficulty of selective breeding, given the lack of knowledge of flowering physiology. Further research is also required on propagation techniques, establishment and stand management, and mechanized harvesting needs to be developed.