Switchgrass Selfing Confirmed by SSR Markers.

Switchgrass is an allogamous, self-incompatible species currently being bred for biomass as a biofuel feedstock. Genotypic recurrent restricted selection for general combining ability has been used to improve switchgrass yield. This method capitalizes on additive gene effects but neglects non-additive genes.  Inbreeding and hybridization have greatly improved the yield of major crops, such as maize (Zea mays), sorghum (Sorghum bicolor) and rice (Oryza sativa).  Hybridizing inbreds may have the potential to improve yield in switchgrass. The objective of this study was to investigate seed yield of selfing lowland switchgrass plants by bagging, and confirm selfed progeny by SSR markers. In 2008, 33 S₁ Alamo and 33 S₁ Kanlow switchgrass plants were bagged using two bag types: paper Lawson bags, and microfiber bags. In 2009 the same plants were bagged with larger cotton muslin bags. In 2010 the plants were bagged with all three bag types. Seeds were collected and counted. In 2008 harvest, a total of 304 Alamo seeds were collected from which 100 progenies were grown and a total of 321 Kanlow seeds from which 91 progenies were grown. From the 2009 plants a total of 498 Alamo seeds were harvested from which 123 progenies were grown and a total of 1231 Kanlow seeds from which 267 progenies were grown. In 2010 a total of 301 Alamo seeds from which 26 progenies were grown and 263 Kanlow seeds from which 17 progenies were grown. Cultivar was significant in 2009 (α=0.05) seed yields.  There was a significant difference between the seed yields of all three years (α=0.001). Bag cultivar interaction was significant in 2008 (α=0.05) and bag type was significant in 2010 (α=0.1). DNA was extracted from the respective parents and the seedlings of the 2008 plants. Six SSR primer pairs were used to confirm selfed progeny identity by determining if all progeny alleles matched its maternal parent. Of the 2008 Kanlow offspring 23 were inbreds (25.3%) and of the Alamo 33 were inbreds (33%). Of the 2009 Alamo plants 24 (23.07%) were inbred and 133 (82.1%) Kanlow plants were inbred. SSR marker analysis of 2010 progeny plants is in progress