Miscanthus - Industrial Crops: Breeding for BioEnergy and Bioproducts - page 44

Introduction

Global climate change and energy security have accelerated the interest in produc-
tion and increased availability of alternative energy sources. Considerable research
has been accomplished in developing maize ( Zea mays ) grain as ethanol for fuel
consumption in the USA [ 1 ]. However, large energy and economic inputs are
required to maintain the high productivity of maize [ 2 ]. Lignocellulosic biomass
is an important feedstock source for biorefineries as biofuel production, is able to
mitigate greenhouse gas emissions [ 3 - 5 ], and reduces dependency on fossil oil [ 6 ,
7 ]. The second generation of bioenergy crops has targeted nonedible plants species
[ 8 - 10 ] owing to their advantages in response to land utilization and avoiding
conflict with food security [ 11 - 13 ] and to establish an efficient production system
at low cost. All these factors if well combined are believed to contribute in the
scaling up of biofuel production. Currently, increase of bioenergy is the main
priority to meet predicted energy demand [ 14 , 15 ]. However, feedstock supply is
still limited because of the few number of suitable energy crops and their low
productivity due to inadequate management system and poor performance under
various environmental stresses [ 16 ].
The genus Miscanthus is among the promising candidate lignocellulosic energy
crops [ 16 - 18 ]. It is a rhizomatous and perennial warm-season C 4 grass species.
Miscanthus spp. is native to East Asian tropical and subtropical regions and is
endemic in high-latitude areas up to 45 N, where the climate is cool [ 19 , 20 ]. In
recent years, the genus has received considerable attention as a potential bioenergy
crop in Europe and the USA [ 21 , 22 ]. To date, Miscanthus is considered with
reference to the single clone, Miscanthus

giganteus , a sterile interspecific hybrid
between M. sinensis and M. sacchariflorus (originally collected from Japan)
(Fig. 3.1 ). Field trials showed that M.

giganteus is easy to grow and resistant to
diseases. Very few insect and other invertebrate pests have been found to infest
M. giganteus [ 23 ], and, to date, no report of yield reduction has been cited. It has

high biomass production even under low temperature, which is an efficient phys-
iological function for carbon fixation [ 24 ]. Genetic uniformity, however, has
increased M.

giganteus vulnerability to diseases, pests, and environmental
stresses [ 25 ]. Furthermore, M. giganteus sterility prevents development of new

varieties of M. giganteus has been attempted by

restoring fertility through polyploidization [ 26 - 28 ]. A genetic transformation sys-
tem has been successfully established in Miscanthus [ 29 ]. Efforts at artificial
crossing between M. sinensis and M. sacchariflorus have also been documented
[ 30 , 31 ]. Recently, Nishiwaki et al. [ 32 ] investigated sympatric populations of
M. sinensis and M. sacchariflorus to locate natural hybrids between M. sinensis
and M. sacchariflorus . Three natural hybrids were successfully identified and
subsequently verified by morphological analysis and sequencing of ribosomal
DNA internal transcribed spacer regions [ 33 ].

giganteus [ 25 ]. Improving M.