• Energy Research

AbstractMiscanthus (Miscanthus Andersson) is a perennial grass that is attracting growing interest from the biomaterial industry. Our aim was to compare miscanthus genotypes varying in stem solidness, a measure of degree to which pith fills cavity between the outer walls of the stem, and analyze whether this trait influences the mechanical properties of polypropylene composites reinforced with miscanthus particles. Six contrasting genotypes were chosen from a Miscanthus sinensis population to determine morphological variables, stem solidness, and mechanical properties of polypropylene composites including 30% of milled miscanthus particles of two sizes of 100 < × < 200 μm and 200 < × < 300 μm. Although aboveground biomass of miscanthus was closely related to the aboveground volume of the plant, namely stand volume, a few genotypes showed contrasting aboveground biomass production for similar stand volumes. This generated contrasting ratio between aboveground biomass and stand volume, namely plant‐specific weights, for similar plant volumes. A principal component analysis showed that fully pith‐filled stems, namely solid stems, were explained by a large stand volume and plant‐specific weights as well as small stem cross‐sections. Genotypes showing partially filled stems were taller with larger stem cross‐sections but smaller plant‐specific weights. They revealed high lignin and p‐coumaric acid contents. Compared to neat‐polypropylene, Young's modulus increased significantly by 139% and 134% and tensile strength by 39% and 36% for genotypes with partially filled stems compared to genotypes with fully pith‐filled stems, respectively. This difference in reinforcing capacity was similar to that of two particle sizes (139% and 134% for Young's modulus, 41% and 34% for tensile strength, respectively). A good tensile strength was obtained with large cross‐stem section, plant height and lignin and p‐coumaric acid contents. It decreased with plant‐specific weight, hemicellulose and ferulic acid contents. Wider morphological variations in other progenies or Miscanthus species should be explored further using the techniques reported here.

The hypothesis made is that thermal resistance of sorghum and miscanthus stem pieces taken at well-defined positions of the stem is simply related to their biochemical composition. For miscanthus, two different genotypes and two internode levels were selected. For each region, the stem was divided into three radial layers. For sorghum, two different genotypes were selected and the stem was divided into the same three radial layers. The results show that the thermal analysis is only sensitive to very large variations of compositions. But aside of such large composition differences, it is impossible to correlate thermal effects to biochemical composition even on very small size, well-identified pieces of plant materials. The interplay between sugar-based components, lignin and minerals is totally blurring the thermal response. Extreme care must be exercised when willing to explain why a given plant material has a thermal behaviour different of another plant material.

Abstract Breeding miscanthus for biomass production and composition is essential for targeting high-yielding genotypes suited to different end-uses. Our objective was to understand the genetic determinism of these traits in M. sinensis, according to different plant ages and environmental conditions. A diploid population was established in two locations according to a staggered-start design, which made the “year” effect partitioned into “age” and “growing season” effects. An integrated genetic map of 2,602 SNP markers distributed across 19 LGs, was aligned with the M. sinensis reference genome and spanned 2,770 cM. The QTL mapping was based on Best Linear Unbiased Predictions estimated across three climatic conditions and at least three ages in both locations. 260 and 283 QTL were related to biomass production and composition traits, respectively. In each location, 40%-60% were related to biomass production traits and stable across different climatic conditions and ages, and 30% to biomass composition traits. Ten to fifteen% were stable for both trait types across locations. Twelve QTL clusters were established based on either biomass production or composition traits, and validated by high genetic correlations between the traits. Sixty-two putative M. sinensis genes, related to the cell-wall, were evidenced in the QTL clusters of biomass composition traits, and orthologous to those of sorghum and maize. Twelve of them were differentially expressed and belonged to gene families related to the cell-wall biosynthesis identified in other miscanthus studies. These stable QTL constitute new insights into Marker-Assisted Selection breeding while offering a joint improvement of biomass production or composition traits.

To grow the bioenergy crop Miscanthus x giganteus on wider climate range requires enlarged genetic variability. Our objective was to identify key traits favouring the production of above-ground yield in a cropping environment of Miscanthus at two harvest dates. Canopy height, panicle height, shoot number, stem diameter and above-ground yield of twenty-one clones were studied and compared with emergence earliness and growth traits at autumn and winter harvests in Northern France, during the second and third crop years. Crop age, clone, harvest date, and corresponding double interactions were significant for all traits. Species and ploidy explained clone sum of square effects (92%, 78%, 80% and 89% for canopy height, panicle height, shoot diameter and yield, respectively) and clone x age and clone x harvest date interactions for yield (94% and 77%, respectively). Plant height and shoot number were higher in the third year than in the second, whatever the harvest date. The above-ground development between the two years was higher in winter harvest than in autumn, mostly for M. sinensis. Higher above-ground development and yields were observed for M. x giganteus and M. floridulus than M. sinensis and M. sacchariflorus as well as for triploid and tetraploid M. sinensis and M. sacchariflorus than diploids. Plant height, stem diameter, lateness at panicle emergence or flowering and growth rate were the main traits positively related to yield, in contrast to shoots number and growth duration. This would help to early identify high-yielding clones and breed new inter-specific hybrids. (C) 2010 Elsevier Ltd. All rights reserved.

Abstract Traits for biomass production and composition make Miscanthus a promising bioenergy crop for different bioconversion routes. They need to be considered in miscanthus breeding programs as they are subjected to genetic and genetic x environment factors. The objective was to estimate the genetic parameters of an M. sinensis population grown during four years in two French locations. In each location, the experiment was established according to a staggered-start design in order to decompose the year effect into age and climate effects. Linear Mixed Models were used to estimate genetic variance, genotype x age, genotype x climate interaction variances and residual variances. Individual plant broad-sense heritability means ranged from 0.42 to 0.62 for biomass production traits, and were more heritable than biomass composition traits with means ranging from 0.26 to 0.47. Heritability increased through time for most of the biomass production and composition traits. Low genetic variance along with large genotype x age and genotype x climate interaction variances tended to decrease the heritability of biomass production traits for young plant ages. Most of the production traits showed large interaction variances for age and climate in both locations, while biomass composition traits highlighted large interaction variances due to climate in Orléans. The genetic and phenotypic correlations between biomass production and composition traits were moderate and positive, while hemicelluloses were negatively correlated with all traits. Efficient genetic progress is achievable for miscanthus breeding when plants get older. The joint improvement of biomass production and composition traits would help provide a better response of miscanthus to selection.

Belowground materials from two miscanthus species were ground into fragments for preparing polyethylene composites. Both species show a lot of similarities in terms of polysaccharides, lignin and cell wall-linked p-coumaric and ferulic acids contents. The structures of polysaccharides and of lignins are markedly different in the miscanthus belowground and aboveground biomass. The non-cellulosic fraction of the samples comprises a high level of xylose, with the arabinose to xylose ratio about twice as high as that observed for analogous stem samples, suggesting that belowground arabinoxylans are more substituted than stem ones. The mechanical properties of the belowground miscanthus-polyethylene composites correlate with several of their compositional traits, with similar trends as for plant stem-polyethylene composites with positive correlations for lignin and p-coumaric acid contents and negative correlations for most non-cellulosic sugars.