JEREMY SCHMUTZ & JANE GRIMWOOD
Genetically, switchgrass plants typically either have four (“tetraploid,” or 4x) or eight (“octoploid,” or 8x) copies of each chromosome. Along with researchers at the Univer- sity of Texas (UT) at Austin and the U.S. Department of Energy (DOE) Joint Genome Institute (JGI), the HGSC helped sequence and assemble the reference genomes for both tetraploid switchgrass 1 and and analyze the genomes of octoploid switchgrass. 2 . While the genomes were sequenced, UT Austin led the establishment of switchgrass community research gardens where a diverse set of plants collected from across its natural range grow. Tetraploid switchgrass pop- ulations grow best in their local climate but produce much less biomass when grown in climates different from home. In contrast, biomass production of octoploid switchgrass decreased far less dramatically when grown outside their climate of origin. Maps representing the collection location of the plants in the gardens revealed large areas where the distribution of tetraploid and octoploid switchgrass do not overlap, suggesting they adapted to different niches. The results suggest that tetraploid switchgrass is a specialist that has consistently high productivity in its ‘home’ climate but is much less successful in different climates. In contrast, octoploid switchgrass is a generalist with more tolerance to climate variations and can maintain high productivity and fitness in a wider variety of climates. Digging into the switchgrass genomes uncovered some interesting information about octoploid switchgrass that may help explain its generalist nature. Researchers found unique combinations of genetic variation in octoploid switchgrass that likely allowed for the expansion of switch- grass’ ecological niche, representing a valuable breeding resource. It may be possible to combine the agricultural benefits of the generalist strategy of octoploids with strong locally adapted trade-offs of tetraploids to buffer the increased variability and unpredictable nature of future climates. Optimizing switchgrass to grow efficiently in diverse environments is a key component of ensuring its success as a biofuel feedstock.
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Above, Research Associate LaTonya Moore, and below, Library Construction & Sequencing Lead Melissa Williams help to prepare the reference genome for switchgrass
RESEARCH REPORT
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