Somatic Hybridization in the Moss Physcomitrella patens Using PEG-Induced Protoplast Fusion

INTRODUCTION As an alternative to sexual crossing, protoplasts from two strains of moss (Physcomitrella patens) can be hybridized using polyethylene glycol (PEG). Although the efficiency is low, it requires no sophisticated apparatus. Hybrids are readily obtained using complementary auxotrophic mutants or strains with transgenic antibiotic resistance markers. It is now routine to obtain hybrids using transgenic strains that are hygromycin- or G418-resistant by selecting hybrids on medium containing both antibiotics.