Okada, Miki , Lanzatella-Craig, Christina , Tobias, Christian .
Genetic diversity in tetraploid and octoploid cultivars of switchgrass (Panicum virgatum) as assesses by EST-derived microsatellite markers.
Switchgrass is widely viewed as a promising biofuel crop for production of lignocellulosic ethanol. Switchgrass is a self-incompatible, perennial species, native to the tallgrass prairie in North America. It has a wide geographical distribution, and lowland and upland ecotypes are recognized within the species. Lowland and upland ecotypes are predominantly tetraploid and octoploid, respectively. Switchgrass cultivars include both ecotypes and display variation in agronomic traits, including biomass and adaptation to latitudinal environmental gradients. Switchgrass cultivars have been derived from native stands and are expected to be genetically diverse populations, but genetic diversity within and between cultivars have not been quantified. The objectives of our study were to determine the level of genetic variation within and among cultivars using EST-derived microsatellite markers and whether these markers can be used to differentiate and identify the cultivars. We screened 40 individuals from a total of twelve cultivars, six each from tetraploid and octoploid cytotypes using 25 primer pairs. Only the loci that amplified alleles from one of the genomes, thus displaying diploid segregation in tetraploids, were used in the study. Based on a preliminary analysis with eight cultivars and seven loci, the number of alleles detected across loci ranged from seven to 51. Within tetraploid cultivars, gene diversity varied from 0.46 to 0.73, and FST among cultivars was 0.282. Average Shannon diversity index within cultivars was higher in octoploids (2.64) than in tetraploids (1.85). In contrast, an FST analog based on Shannon diversity index was greater among tetraploids (0.350) than octoploids (0.235). Population assignment using STRUCTURE successfully differentiated the cultivars and assigned the individuals to respective cultivars with the exception of two cultivars, one of which was derived from the other. The number of loci required to assign an unknown individual to the correct cultivar will be explored.
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1 - U.S. Department of Agriculture - ARS, Western Regional Research Center, 800 Buchanan Street, Albany, CA, 94710, USA
Presentation Type: Oral Paper:Papers for BSA Sections
Location: Cottonwood C/Snowbird Center
Date: Monday, July 27th, 2009
Time: 11:00 AM