|YOON, SANGWOONG - University Of California|
|AUCAR, SHEYLA - University Of California|
|Hernlem, Bradley - Brad|
|BLUMWALD, EDWARDO - University Of California|
Submitted to: BioEnergy Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/14/2016
Publication Date: 10/20/2016
Citation: Yoon, S., Aucar, S., Hernlem, B.J., Edme, S.J., Sarath, G., Blumwald, E., Tobias, C.M. 2016. Generation of octoploid switchgrass by seedling treatment with mitotic inhibitors. BioEnergy Research. doi: 10.1007/s12155-016-9795-2.
Interpretive Summary: Switchgrass is a native tallgrass prairie species that produces large quantities of biomass and requires few inputs. These attributes make it attractive as a forage, for conservation planting, and as a feedstock for biofuel and bioenergy production. This species' wide geographical distribution has led to differentiation of local populations with respect to habitat preference, genome size, and chromosome number. In order to take advantage of breeding opportunities between closely related populations that have different chromosome numbers, breeders must use artificial means such as treatment with chemicals to double the chromosome number after making crosses. Potential side effects of such treatments are changes in growth rate, fertility, seedling vigor, and other traits. This report documents the results of treating high-yielding bioenergy switchgrass variety ‘Liberty’ with chemical doubling agents. The resultant population contained many individuals with a balanced doubled number of chromosomes and unique traits that can be introduced into other locally adapted switchgrass populations through the creation of novel hybrids.
Technical Abstract: Switchgrass (Panicum virgatum L.) exists as multiple cytotypes with octaploid and tetraploid populations occupying distinct, overlapping ranges. These cytotypes tend to show differences in adaptation, yield potential, and other characters, but the specific role of whole genome duplication is not clear and 8x and 4x switchgrass populations are reproductively isolated with limited genetic exchange. To create new opportunities for population improvement and to study the effects of whole genome duplication on switchgrass, seedling treatment of the tetraploid cultivar 'Liberty' with microtubule inhibitors was used to generate an octaploid population. Resulting octaploids, tetraploids and cytochimeras were resolved by intercrossing octaploid sectors to produce a population of 20 octaploid families. Fertility of octaploid sectors was significantly reduced relative to tetraploid sectors and caryopsis size significantly increased. Cell size was significantly increased which resulted in quantitative changes to leaf anatomy. During seedling and early vegetative growth stages no differences in vigor or tillering ability were seen. This technique resulted in efficient genome doubling and was simple to perform. However, aneuploids were also identified with both larger and smaller than expected genome sizes.