Synthetic polyploid production of Miscanthus sacchariflorus,Miscanthus sinensis, and Miscanthus x giganteus

Abstract Plants from the genus Miscanthus are potential renewable sources of lignocellulosic biomass for energy production. A potential strategy for Miscanthus crop improvement involves interspecific manipulation of ploidy levels to generate superior germplasm and to circumvent reproductive barriers for the introduction of new genetic variation into core germplasm. Synthetic autotetraploid lines of M iscanthus sacchariflorus and M iscanthus sinensis , and autoallohexaploid M iscanthus x giganteus were produced in tissue culture from oryzalin treatments to seed‐ and immature inflorescence‐derived callus lines. This is the first report of the genome doubling of diploid M . sacchariflorus . Genome doubling of diploid M . sinensis , M . sacchariflorus, and triploid M . x giganteus to generate tetraploid and hexaploid lines was confirmed by stomata size, nuclear DNA content, and chromosome counts. A putative pentaploid line was also identified among the M . x giganteus synthetic polyploid lines by nuclear DNA content and chromosome counts. Comparisons of phenotypic performance of synthetic polyploid lines with their diploid and triploid progenitors in the greenhouse found species‐specific differences in plant tiller number, height, and flowering time among the doubled lines. Stem diameter tended to increase after polyploidization but there were no significant improvements in biomass traits. Under field conditions, M . x giganteus synthetic hexaploid lines showed greater phenotypic variation, in terms of plant height, stem diameter, and tiller number, than their progenitor lines. Production of synthetic autopolyploid lines displaying significant phenotypic variation suggests that ploidy manipulation can introduce useful genetic diversity in the limited M iscanthus germplasm currently available in the United States. The role of polyploidization in the evolution and breeding of the genus M iscanthus is discussed.