MISCANTHUS  genetic experiment © Aline Waquet

Miscanthus, a very promising plant...

Forecast studies to establish selection criteria

Until now, selection criteria used at INRA have been high yields with minimum input, good quality, and traits that keep propagation of the plant under control: sterility and compact rhizomes.

By Pascale Mollier - Maryse Brancourt-Hulmel - Hubert Boizard - Fabien Ferchaud, translated by Inge Laino
Updated on 04/19/2013
Published on 02/15/2013

Today, two species of miscanthus make up the bulk of crops in Europe: Miscanthus x giganteus in Great Britain, Germany and France, and Miscanthus sinensis in colder climates such as Denmark. Miscanthus x giganteus is a sterile triploid derived from a natural cross between two species: M. sacchariflorus and M. sinensis.

Until now, selection criteria used at INRA have been high yields with minimum input, good quality, and traits that keep propagation of the plant under control: sterility and compact rhizomes. While Miscanthus x giganteus has many of these qualities, it is nevertheless important to consider other species, notably M. sinensis, and broaden the range of cultivated varieties, as is common practice for all crop plants. Indeed, an ever-larger range of soil and climate conditions must be covered, and the risk of the sudden appearance of pests accounted for.

Miscanthus x giganteus: unmatched yields

Visit to the experimental plots of energy crops introduced as part of the European project Bioenergy chains on 10 October 2005. Miscanthus giganteus plots, a year and a half after planting. © CADOUX Stéphane
Visit to the experimental plots of energy crops introduced as part of the European project Bioenergy chains on 10 October 2005. Miscanthus giganteus plots, a year and a half after planting. © CADOUX Stéphane

It comes as no surprise that one of the most sought-after traits in choosing biomass crops is high yields. Studies have been carried out in Europe, but not in France, to compare different clones and species. Since 2007, INRA has been running trials at Estrées-Mons to compare the agronomic potential of 21 clones of three species (M. x giganteus, M. sacchariflorus and M. sinensis). Clones were grown for five years without nitrogen input or pesticides. Results confirmed that M. x giganteus is the most productive regardless of harvest date, with average yield rates of 30 tonnes/ha/year (compared with 1 tonne/ha/year for other, less productive, clones).

Key traits for the production of biomass

A multivariate analysis in principal components has shown that the key features of biomass production are: late flowering, height and diameter of stems, and rapid growth. Conversely, a long growing period and dense stems are not advantageous. The best combination is: late flowering + tall plants (thanks to rapid, short-term growth) + few and thick stems (Zubet 2011, PEL project). Biomass production is further boosted by rapid growth (Zub et al, 2011b, PEL project).

Autumn or winter harvest?

When harvested in winter, stems are richer in cellulose, hemicellulose and lignins, and poorer in soluble fractions (sugars) and ash - a make-up that is well suited for biomass production (Futurol project). A winter harvest is therefore the better choice, especially since plants left standing until the end of the vegetative cycle give nitrogen a chance to travel from the stems to rhizomes, which cuts down on, or even eliminates altogether, the need for nitrogen fertilisers (Loïc Strullu 2011 thesis, Enerbio project). This study was followed up by an experiment in the field based on a clone of Miscanthus x giganteus.  Results showed that 80% of nitrogen in the exposed part of the plant in summer comes from nitrogen stored in the rhizomes, of which half is arginine and asparagine (Guillaume Lebas 2012 thesis, Miscazote project). This goes to show how unique this system is, allowing for a very efficient use of nitrogen when harvesting takes place late in the year.

Resistance to frost

“The literature shows that few biotic stress factors, such as disease and pests, come in to play in miscanthus crops in Europe, which is why we focused on abiotic factors instead, such as nitrogen and cold,” explains Maryse Brancourt (Zub et al, 2010). “Based on an experiment in controlled conditions on five clones (one clone of M. x giganteus and four clones of M. sinensis), we found that the plant has good resistance when exposed to successive frosts (-3°C for three consecutive days). Sensitivity to frost manifested itself during more intense frosts (-8°C for two consecutive days) and in more mature plants (at the seven-leaf stage as opposed to three-leaf stage). Frosts at the time of planting should not be a major problem in France (especially northern France), while the opposite is true for Denmark, which is a Nordic country in comparison (Zub et al, 2012a).

“Furthermore, the field experiment with a Miscanthus x giganteus clone showed that the plant is able to produce biomass for as long as there is no frost, (i.e. until early December in our experiment), and that the cold has little affect on photosynthesis (Archi C4 project). This could shed light on the advantages linked to late flowering (itself correlated with the late emergence of the plant) that have been observed in our first project comparing species.”  

Controlling propagation

Miscanthus can reproduce by seeds or by vegetative reproduction, via rhizomes.

To avoid propagation via seeds, and thereby promote the integration and acceptability of miscanthus crops, sterility is an essential trait. Miscanthus x giganteus is triploid, and therefore sterile.

When it comes to vegetative reproduction, an experiment carried out on a crop in 2007 showed that plants with a compact/clumping rhizome system stay in close proximity to the domain plant, whereas a running rhizome system tends to spread out. The compact rhizome trait is therefore the more desirable one. This issue is addressed in the MISC-PIC project.

References

Zub, H.W. and Brancourt-Hulmel, M. (2010) Agronomic and physiological performances of different species of Miscanthus, a major energy crop. A review. Agronomy for Sustainable Development,30(2): p. 201-214.

Zub, H.W., Arnoult, S. and Brancourt-Hulmel, M. (2011) Key traits for biomass production identified in different Miscanthus species at two harvest dates. Biomass & Bioenergy,35(1): p. 637-651.

Zub, H.W., Rambaud, C., Béthencourt, L. and Brancourt-Hulmel, M. (2012a) Late emergency and rapid growth maximize the plant development of Miscanthus clones. Bioenergy Research, 5(4): p. 841-854.

Zub H.W., Arnoult S., Younous J., Lejeune-Hénaut I. and Brancourt-Hulmel, M. (2012b) The frost tolerance of miscanthus at the juvenile stage: differences between clones influenced by leaf-stage and acclimation. European Journal of Agronomy 36:32-40.