Assessing effects of transgenic crops on soil microbial communities.

Deleterious effects of transgenic plants on soils represent an often expressed concern, which has catalyzed numerous studies in the recent past. In this literature review, studies addressing this question have been compiled. A total of 60 studies has been found, and their findings as well as their analytical approaches are summarized. These studies analyzed the effects of seven different types of genetically engineered traits, i.e., herbicide tolerance, insect resistance, virus resistance, proteinase inhibitors, antimicrobial activity, environmental application, and biomolecule production. Sixteen genetically engineered plant species were investigated in these studies including corn, canola, soybean, cotton, potato, tobacco, alfalfa, wheat, rice, tomato, papaya, aubergine, and silver birch. Many of these plants and traits have not been commercialized and represent experimental model systems. Effects on soil microbial characteristics have been described in various studies, indicating the sensitivity and feasibility of the analytical approaches applied. However, classification of the observed effects into acceptable and unacceptable ones has not been possible so far. Establishment of validated indicators for adverse effects represents a scientific challenge for the near future, and will assist risk assessment and regulation of transgenic plants commercially released to the field.