Instability of transgenes in in vitro-maintained banana plants

In vitro stability of the transgene was studied in the Brazilian 'Maca' banana {Musa spp. AAB group) transformed with the magainin2 and ahas genes by the biolistic method. The presence of the transgenes in sixty independent transgenic plantlets was confirmed by PCR and Southern analyses. Recovered plants were maintained in black polyethylene bags containing soil in a glasshouse for 2 years. After this period, the plantlets were re-established in vitro and maintained on modified MS medium for 2 years. Six transgenic lines were then randomly selected and analyzed by PCR. All plantlets from two lines showed the presence of the transgene, but 17 to 100% of plantlets from the other four lines lacked the foreign genes. Instability of exogenous genes in transgenic banana during extended in vitro cultivation is discussed.