ABSTRACT
Transgenic plant production today seems a far cry from the mid-1980s, when recalcitrance to in vitro manipulation in the major cereal and legume crops appeared to be the major limitation to the advancement of agricultural biotechnology. These days, no species should be considered a priori to fall outside the range of those amenable to transformation. The term recalcitrant species has largely disappeared from our vocabulary in recent years. Experience has taught that, given sufficient effort, any plant species can be transformed. Maize is a case in point. Because maize was seemingly nontransformable by virtue of its resistance to Agrobacterium infection (1) and its relatively recalcitrant to in vitro manipulation (2), not until the invention of a novel deoxyribonucleic acid (DNA) delivery means (3), the development of a new selectable marker system (4), the cloning of monocot expression elements (5), and major advances in tissue culture (6) did reliable transgenic maize production become a reality (7,8).
