EFFECT OF RECOMBINANT DEFENSIN (pdf1.2) ON BENEFICIAL MICROORGANISMS ASSOCIATED WITH GENETICALLY MODIFIED COMMON BEANS

Abstract

Genetically modified organisms have as a requirement for their release into the environment at the experimental stage an assessment of the possible risks that could be caused to the environment, to biological diversity, and to plant, animal and aquaculture health, in accordance with the biosafety law of genetically modified organisms in Mexico. Common bean (Phaseolus vulgaris L.) modified with the Arabidopsis thaliana defensin gene (pdf1.2) has the characteristic of conferring broad-spectrum tolerance/resistance to plant pathogenic fungi of beans. The interactions between five common bean homozygous lines cv. Flor de Mayo Anita modified with the defensin gene (FMA-pdf1.2), with the antagonistic Trichoderma harzianum, the symbiotic association with Rhizobium tropici and the Rhizophagus intraradices mycorrhizae association were analyzed. Sterile soil was inoculated with those microorganisms and their density and infection or colonization in bean roots were evaluated. T. harzianum showed a larger number of colony-forming units (CFU) in non-modified plants than in those that expressed defensin; however, CFU values in the modified plants were within the range reported by other authors for this type of symbiotic relationships. On the other hand, even though R. tropici develops at inter and intracellular spaces, where the defensin protein is expressed, the number of nodules exceeded that of unmodified control plants. Finally, the R. intraradices percentage of infection was inconsistent, being low in both FMA-pdf1.2 and unmodified plants; therefore, the effect of defensin was not clear. The above suggests that the presence of defensin does not represent a risk factor against microorganisms that do not invade the intra and intercellular space of the modified plants, or against microorganisms not included in the spectrum of action of pdf1.2.