FIGURE 1.

Methods to genetically engineer crops. (A) Conventional engineering requires Gram-negative bacterium Agrobacterium tumefaciens, selection for cells carrying the engineered traits (normally antibiotics), and regenerating fertile plants from cells on medium containing combinations of hormones to help make roots and shoots. Under the best of conditions this could take 4.5 mo. (B) A new method also utilizes Agrobacterium but expresses developmental genes and the transgene, where the transgenic plant grows in cell culture without using the hormone regime. This method requires ∼3 mo. (C) The most promising method uses Agrobacterium expressing developmental genes and the transgene from soil-grown plants. This method takes ∼2 mo and does not require any tissue culture (16).