Banana (Musa sp.).

Cultivated bananas are vegetatively propagating herbs, which are difficult to breed because of widespread male and female sterility. As a complementary gene transfer method in banana, the described Agrobacterium protocol relies on highly regenerable embryogenic cell cultures. Embryogenic cells are infected and co-cultivated in the presence of acetosyringone with Agrobacterium tumefaciens harboring a binary plasmid vector to obtain a mixed population of transformed and untransformed plant cells. Transformed plant cells are promoted to grow for 2 to 3 mo on a cell colony induction medium containing the antibiotics geneticin or hygromycin as selective agents, while agrobacteria are counterselected by timentin. The whole procedure, including plant regeneration, takes approx 6 mo and results in an average frequency of 25 to 50 independent transgenic plants per plate, which equals 50 mg of embryogenic cells. This method has been applied to a wide range of cultivars and to generate large populations of transgenic colonies and plants for tagging genes and promoters in banana.