Biolistic transformation of elite genotypes of switchgrass (Panicum virgatum)

Abstract

Transformation of elite switchgrass (Panicum virgatum L.) genotypes would facilitate the characterization of genes related to cell wall recalcitrance to saccharification. However, transformation of explants from switchgrass plants has remained difficult. Therefore, the objective was to develop a biolistic transformation protocol for elite genotypes. Three switchgrass genotypes (ST1, ST2, and AL2) were previously selected for tissue culture responsiveness. One genotype, SA37, was selected for further use due to its improved formation of callus amenable to transformation. Various media sets were compared and the Somleva et al. (2002) media provided cultures with >96% embryogenic callus and high regenerablility. Data on transient gene expression and stable transformation were used to optimize biolisitic parameters, and test novel switchgrass (PvUbi) promoters in switchgrass and rice. SA37 and ST2 produced transgenic plants at a frequency of >1%. It is now possible to engineer elite switchgrass genotypes at a frequency commonly reported for maize.