The following HTML text is provided to enhance online
readability. Many aspects of typography translate only awkwardly to HTML.
Please use the page image
as the authoritative form to ensure accuracy.
Environmental Effects of Transgenic Plants: The Scope and Adequacy of Regulation
Finding 7.3: With few exceptions, the environmental risks that might accompany future novel plants cannot be predicted. Therefore, they should be evaluated on a case-by-case basis.
Finding 7.4: In the future many crops can be expected to include multiple transgenes.
Potential Environmental Impacts of Novel Traits
The Animal and Plant Health Inspection Service (APHIS) appropriately refrains from speculation on environmental risks associated with crops that may or may not reach the stage of commercialization. Full and fair discussion of such risks presupposes information that cannot be known until a functional phenotype has been developed and grown in limited field trials. However, a brief discussion of the general issues associated with some new crops currently being developed will help frame the context in which environmental risks from commercialization of the next generation of transgenic crops may be discussed.
Tolerance to Abiotic Stresses
Abiotic stresses significantly limit crop production worldwide. Cumulatively, these factors are estimated to be responsible for an average 70% reduction in agricultural production (Bresson 1999). Drought stress not only causes a reduction in the average yield for crops but also causes yield instability through high interannual variation in yield. Globally, about 35% of arable land can be classified as arid or semiarid. Of the remainder, approximately 25% consists of drought-sensitive soils. Even in nonarid regions where soils are nutrient-rich, drought stress occurs regularly for a short period or at moderate levels. Furthermore, it has been predicted that in the coming years rainfall patterns will shift and become more variable due to increased global temperatures. Thus, improved stress tolerance may improve agricultural production.
Research to create crop plants that are transformed to tolerate abiotic stresses, such as heat, drought, cold, salinity, and aluminum toxicity, is ongoing. Current research efforts in drought tolerance include the isolation of crop plant mutants to understand the molecular basis for salt responses (Borsani et al. 2001), studies on the transduction network for signaling guard cell responses and their subsequent control of carbon dioxide intake and water loss (Schroeder et al. 2001), and genetic activation and suppression screens that influence interrelationships among multiple signaling systems that control stress-adaptive responses in plants (Hasegawa et al. 2000). The actual development and field testing of novel crop plant varieties is likely to be 5 to 10 years in the future owing to the