Breeding Cold-hardy Energy Grasses

Perennial grasses have considerable potential as bioenergy crops.  However, high-yielding, subtropical/tropical perennial grasses like conventional sugarcane (Saccharum officinarum) and energy canes (mostly Saccharum spontaneum hybrids), lack adequate cold hardness to be grown as dedicated energy crops throughout most of the temperate US.  Miscanthus (Miscanthus spp.) are promising bioenergy crops that can be grown in temperate regions.  However, there has been limited breeding and development efforts to improve and domesticate these crops. The original Miscanthus ×giganteus was a natural occurring, highly infertile allotriploid (2n = 3x = 57) hybrid between a tetraploid M. sacchariflorus (2n = 4x = 76) and a diploid Miscanthus sinensis (2n = 2x = 38).  This clone has high biomass yields, but limited genetic diversity.  Allohexaploids of M. ×giganteus were developed through oryzalin-mediated chromosome doubling to restore fertility.  These fertile hybrids were crossed with diploid M. spp. to develop new fertile allotetraploid breeding lines and advanced to F₂ populations.  Improved allotetraploids were then crossed with selected diploids.  Embryo culture was used to produce new triploid hybrids with broader genetic diversity.  These initial breeding efforts have also shown considerable improvement in biomass yield and should provide improved bioenergy feedstocks for temperate regions.