Molecular Marker Analysis of Progeny Origins in Sibling-Mating and Crossing in Lowland Switchgrass [Panicum Virgatum L.].

Switchgrass (Panicum virgatum L.) is a C4 perennial grass which has been used for soil and water conservation and forage for decades. In recent years it has been targeted for development as a bioenergy crop.   However, breeding methods for developing economically viable hybrid cultivars are not available to improve switchgrass.  Accordingly, the objective of this study was to assess the viability of generating inbred lines through self-pollination, and crossing them under field conditions for hybrid cultivar production.  The seed yields of 6 sibling-mating and 4 crossing plots established in 2013 were measured, and progeny of selected plants were genotyped to determine parental origins in 2014 and 2015.  Total seed yields were measured for whole plots with the exception of selected plants, from which 341 progeny were germinated and genotyped using SSR markers.  We found significant differences in seed yield between plots containing S1 and S3 inbred progeny, and between crossing and sibling-mating plots. The combined average seed yield for 2014 and 2015 was 37.5 kg/ha for the S1 crossing plot, while the S3 crossing plots averaged 18.7 kg/ha, and the average seed yield for sibling-mating plots were 51.2 kg/ha, 21.7 kg/ha, and 13.6 kg/ha for S1, S2, and S3 plots respectively.  We also found differences in the parental origins of progeny between inbreeding level and plot type.  In 2014 for all sibling-mating plots 17.3%, 82.7%, and 0% of progeny were identified as selfed, sibling-mating, and crossed progeny respectively.  In crossing plots the percentages were 20.4%, 5.3%, and 74.3% for S3 plots, and 0%, 11.5%, and 88.5% for the S1 plot.  Information from this study gives insight in how multiple generations of inbreeding effect seed origin and yield, and will help breeders assess the viability of producing hybrids using inbred lines grown from seed under field conditions.