Molecular Marker Analysis of Progeny Origins in Sibling-Mating and Crossing Populations of Inbred Lowland Switchgrass.

Switchgrass (Panicum virgatum L.) is a C4 perennial grass which has been used for soil and water conservation and as 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 genetic origins of progeny from S1, S2 and S3 inbred parents of two conditionally self-compatible genotypes grown in sibling-mating and crossing plots. Inbred progeny of two conditionally self-compatible switchgrass plants ‘NL94 LYE 16’x13’ (NL94) and ‘SL93 7x15’ (SL93) were established in 6 sibling-mating and 4 crossing plots at the Agronomy Research Station, Oklahoma State University in 2013. Seeds of selected plants in each plot were harvested separately for genotyping to determine parental origins. Progeny origins were determined using 6 or 10 simple sequence repeat (SSR) markers. In sibling-mating plots, a high preference for sibling-mating was observed in S1 parents of both genotypes while at more advanced inbreeding levels few sibling-mated seed were identified. In an S1 crossing plot the NL94 and SL93 parents set a high percentage of hybrid seed averaging 73% and 94%, respectively in 2014 and 2015. In two of the S3 crossing plots NL94 parents set 100% hybrid seed. In these same S3 crossing populations, SL93 parents set only 4% and 19% hybrid seed. Information from this study gives insight into how multiple generations of inbreeding effect seed origin and yield, and will help breeders assess the viability of producing switchgrass hybrids using inbred lines grown from seed under field conditions.