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Giant miscanthus (Miscanthus x giganteus; Mxg) is a key candidate energy crop for use in biomass to liquid fuel production. It is a naturally seed sterile triploid lacking genetic variation, the basis for selection. Therefore, induced mutation techniques are particularly important in Mxg. The objective of this research was to induce variation in Freedom, an elite cultivar, through in vitro chemical mutagenesis. A previously-optimized in vitro propagation protocol for Freedom was used following the in vitro mutagenesis procedure. Immature inflorescence explants (2-3 mm) and calli (2-3 mm 3) were treated with five mutagenic dose treatments [0.01%, 0.1%, 0.5%, 1%, and 3% (v/v) of ethyl methanesulfonate (EMS) for 90 min] along with 2% (v/v) dimethyl sulfoxide (DMSO) as a carrier agent to determine the optimum mutagen dosage. The dose at which 50% of the calli/explants recovered (RP 50) after the mutagen treatment was used as the optimum EMS dose. Calli and explants of Mxg were treated with RP 50 , 2 x RP 50 , and 3 x RP 50 EMS dosages, and subsequent regenerants that arose from explants/calli were transferred to soil. Inter simple sequence repeat (ISSR) markers were used to identify variants in the regenerated plants. Results showed variability among regenerants originating from EMS mutagenic treatments. Putative mutants of Mxg may be useful for bioenergy research and functional genomics.

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Miscanthus × giganteus (giant miscanthus; Mxg) is a seed-sterile, perennial bioenergy crop with the potential to produce liquid fuel from lignocellulosic biomass. A new cultivar, Freedom, is being commercially grown in the USA on increasing acreage. To determine this genotype's regeneration responses in tissue culture, three explant sources were screened on media proven successful for other genotypes. Four callus induction media contained 13.6-22.6 μM 2,4-dichlorophenoxyacetic acid (2,4-D) alone or with 0.44-4.4 μM 6-benzyladenine (BA). Callus induction percentages for all explants ranged from 93 to 97%. Media yielding the greatest percentages of explants producing regenerable calli for shoot apices (from in vitro and greenhouse plant sources) were media containing either 13.6 μM 2,4-D plus 0.44 μM BA or 22.6 μM 2,4-D plus 0.44 μM BA. After culture on a regeneration medium containing 22 μM BA plus 1.3 μM naphthaleneacetic acid (NAA), 3.59-3.74 regenerants were obtained per explant. Immature inflorescence explants (from field-maintained plants) gave up to 77% regenerable calli and 6.99 regenerants per explant. Direct regenerants (shoots) arose from immature inflorescence explants on a medium containing 9.0 μM 2,4-D. Intact plants could be generated within 16-18 wk after culture initiation. Extensive visual assessments, and molecular assessments via inter-simple sequence repeat (ISSR) PCR analysis using 21 different primers, did not reveal distinguishable somaclonal variation among regenerants or when compared to rhizome-propagated transplants under field conditions. We believe that this is the first extensive in vitro and ex vitro analysis on a commercially grown Mxg genotype.