Chromosome doubling of the bioenergy crop, Miscanthus×giganteus

Abstract

The perennial grass, Miscanthus  giganteus is a sterile triploid, which due to its growth rate and biomass accumulation has significant economic potential as a new bioenergy crop. The sterility associated with the triploid genome of this accession requires laborintensive vegetative, instead of seed propagation for potential commercial production. Chromosome doubling was used to produce hexaploid plants in an effort to restore fertility to M  giganteus. Tissue culture derived calli from immature inflorescences were treated with the antimitotic agents, colchicine and oryzalin in liquid and solid media. Calli survival rate decreased with increasing concentrations and durations of colchicine or oryzalin treatments and ranged from 0% to 100%. Nuclear DNA content, as determined by flow cytometry, indicated that the frequency of chromosome-doubled calli varied between compounds and concentrations with the greatest proportion of callus doubling observed using 2-day treatments of 15 lM oryzalin (78%) or 939 lM colchicine (67%). Liquid media treatments were more effective than solid gels for chromosome doubling. Although oryzalin was effective at chromosome doubling, it inhibited callus growth and plant regeneration frequency. Seven hexaploid plants with doubled DNA content were generated, which displayed increased stomata size (30.0 AE 0.2 lm) compared with regenerated triploid M.  giganteus plants (24.3 AE 1.0 lm). Following clonal replication these plants will be evaluated for growth rate, biomass accumulation, and pollen viability. Successful chromosome doubling and plant regeneration of M.  giganteus suggests that ploidy manipulation of this plant and its parental species (Miscanthus sinensis and Miscanthus sacchariflorus) could be a means to access genetic variability for the improvement of Miscanthus as a biofuel/bioenergy crop.

Production of Autopolyploid Lowland Switchgrass Lines Through In Vitro Chromosome Doubling

“…The generation of autooctoploid plant lines through chromosome doubling has been used to create novel germplasms in many breeding programs [19][20][21][22][23][24][25]41]. The development of autopolyploid plants has also been used to overcome the cross incompatibility barrier between different ploidy levels [42][43][44].…”

“…Chromosome doubling can be induced by treating the plant tissue with heat or cold shock [26,27], or by treating with antimitotic agents like NO gas [28], colchicine [24,29], oryzalin [24,30], and trifluralin [31]. Because antimitotic chemical treatment is relatively easy to perform and the results are reproducible, it is the most frequently used method for inducing chromosome doubling in many plant species [24,32].…”

“…Because antimitotic chemical treatment is relatively easy to perform and the results are reproducible, it is the most frequently used method for inducing chromosome doubling in many plant species [24,32]. However, the antimitotic chemical concentration and the treatment duration needs to be systematically evaluated in order to develop efficient and effective chromosome doubling methods in a given plant species [24,32]. In this report, we developed an efficient chromosome doubling system to regenerate octoploid switchgrass lines from somatic embryogenic (SE) calli treated with the antimitotic chemical colchicine.…”

“…Autooctoploid lowland ecotypes could be generated through chromosome doubling, and would then be cross-compatible with the natural octoploid upland switchgrass ecotypes. Presently, there have been no reports about generating autooctoploid switchgrass lines through chromosome doubling, though such kind of breeding efforts have been frequently used in many other plant species [19][20][21][22][23][24][25].…”

Miscanthus: a case study for the utilization of natural genetic variation

“…Chromosome doubling has been used to generate artificial polyploids in Miscanthus and has potential to introduce new genetic diversity into breeding programmes especially for M. £ giganteus types by manipulating the ploidy of the parental species, restoring fertility or disrupting the self-incompatibility system Głowacka et al, 2009Głowacka et al, , 2010aYu et al, 2009). Another stimulus for artificial polyploid formation has been the desire to generate novel sterile genotypes that lower the risk of invasiveness following introduction as a crop (Petersen et al, 2003;Barney and Ditomaso 2008;Jørgensen, 2011).…”