Abstract
Switchgrass (Panicum virgatum L.) is a naturally allogamous species. Recent studies indicated conditional self-compatibility exists in the species and can be used to produce inbreds for the exploitation of heterosis in biomass production. However, efficient and reliable bagging methods are unavailable for development of inbreeding. This study was designed to determine the efficacy of a polyester bagging method in blocking extraneous pollen such that switchgrass may self more efficiently. In this experiment four northern lowland (NL) inbreds, four NL non-inbreds, two southern lowland (SL) non-inbreds and 16 upland-lowland (interecotypic) F1 hybrids were self-pollinated by enclosing their inflorescences in polyester bags in the field; bags were also placed on 14 F1 interecotypic hybrid plants potted in a greenhouse. The reliability of the bags was determined using eight to ten simple sequence repeat (SSR) markers that distinguished the genetic parentage of the pollen. Contaminants were identified in two groups: outcrossing contaminants (OCs) and physical contaminants (PCs) based on the amplified alleles of their progeny and their seed parents. Of 39 polyester bags field tested in 2012, 35 bags showed 100 % selfed progeny, four showed PCs; no OCs were identified. Similarly, of 61 bags tested in 2013 in two field plots, 50 bags produced 100 % selfed progeny, while four bags produced OCs, five produced PCs and the other two produced both OCs and PCs. No contaminants were identified from the progeny of 18 bags used in the greenhouse, suggesting that high wind speed, physical damage or handling errors may have resulted in the contaminations of bagged progeny in the field. The result of this experiment establishes the increased reliability of the polyester bagging method over previously tested methods for selfing switchgrass under field and greenhouse conditions. Additionally, the S1, S2 and S3 inbreds produced in this study will contribute to developing completely or near completely homozygous inbred lines in the future.