FOREIGN GENE DELIVERY INTO MONOCOTYLEDONOUS SPECIES

Monocotyledonous plants are generally more recalcitrant to genetic tra nsformation than dicotyledonous species. The absence of reliable Agrob acterium-mediated transformation methods and the difficulties associat ed with the culture of monocotyledonous tissues in vitro are mainly re sponsible for this situation. Until recently, the genetic transformati on of monocotyledons was essentially performed by direct transfer of D NA into regenerable protoplasts or intact cells cultured in vitro, via polyethylene glycol treatment, electroporation or particle bombardmen t. Since 1990 the use of particle gun technology has revolutionized th e genetic engineering of monocotyledonous species, allowing transforma tion to be more independent of the in vitro culture requirements. Toda y, at least one genotype of each major monocotyledonous crop species, including cereals, can be genetically transformed.