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Mutation Research 544 (2003) 223–233

Genetically modified crops: environmental and human health concerns
João Lúcio Azevedo∗ , Welington Luiz Araujo
Departamento de Genética, Escola Superior de Agricultura, Luiz de Queiroz, Universidade de São Paulo,
P.O. Box 83, 13400-970 Piracicaba, São Paulo, Brazil
Received 5 May 2003; received in revised form 30 June 2003; accepted 1 July 2003

About 10,000 years ago subsistence farmers started to domesticate plants and it was only much later, after the discovery of the fundaments of genetics, those organisms were submitted to rational genetic improvement mainly by selecting of traits of interest. Breeders used appropriate gene combinations to produce new animal races, plant varieties and hybrids, as well as improved microorganisms such as yeasts. After the introduction of recombinant DNA techniques, the transfer of DNA between species belonging to different genera, families or kingdoms became possible. The release of transgenic plants has aroused debates about several aspects of the environmental and human risks that could result from the introduction of genetically modified crops. Less effort has been dedicated to evaluate the impact of transgenic plants on their associated microorganisms, some of which (e.g. nitrogen-fixing bacteria, mycorrhizal fungi and endophytic microbiota) are extremely important for the survival of the plant. Investigations have been made regarding the horizontal transfer of genetic material between transgenic plants and microorganisms and on the disturbance of useful symbiotic associations between plants and endophytic, epiphytic and rhizosphere communities. In most cases the results do no show any adverse effect of transgenic plants on autochthonous plant-associated microorganisms. Results from our laboratory show small changes caused by genetically modified endophytic bacteria on the indigenous endophytic population of the sweet orange Citrus sinensis. In tests using appropriated fungal strains preliminary results using extracts from transgenic plants indicate that these plants do not affect haploidization, mitotic crossing-over, mutation rate or chromosomal alterations.
© 2003 Elsevier B.V. All rights reserved.
Keywords: Transgenic plants; Plant-associated microorganisms; Nitrogen-fixing bacteria; Mycorrhizae; Endophytic microorganisms;
Rhizosphere microbiota

1. Introduction
Humans started to cultivate and domesticate plants for their subsistence about 8000 b.c. and by around
6000–7000 b.c. domestication of crops such as wheat, beans, lentils and peas started in the near East. At
∗ Corresponding author. Tel.: +55-19-34294251; fax: +55-19-34336706.
E-mail address: jazevedo@esalq.usp.br (J.L. Azevedo).

about the same time, agriculture began in the new world with domestication of beans and gourds (e.g. pumpkins) among others. Maize started to be domesticated around 5000 b.c. and sugarcane and soybean about 1000 b.c.—pineapple, rubber and palm oil being domesticated only relatively recently. Domestication led to genetic modification in such a way that wild plants became cultivated plants, many of which were no longer able to survive in the wild [1]. Genetic diversity was also reduced, but from a human

1383-5742/$ – see front matter © 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.mrrev.2003.07.002 224

J.L. Azevedo, W.L. Araujo / Mutation Research 544 (2003) 223–233

point of view, over the past 10,000 years improvements in agricultural techniques have meant that the same area which fed one person now feeds more than
For millennia, farmers used empirical, albeit efficient, processes to select appropriated species, varieties and cultivars, and it was only with the rediscovery of Mendel’s laws at the beginning of the 20th century and the application of genetic principles to plant, animal and microbial breeding by professional breeders that qualitative and quantitative advances were more easily and rapidly achieved. The development of