Rice is considered the main food for most of the population, soybeans, as the legume with the highest protein value, and corn, as the cereal with the highest world production, are vegetables of great importance for consumption. Working with these species in fields of biotechnology, at the genomic or molecular level, requires obtaining the DNA macromolecule with certain quality parameters. Likewise, if the application of any of the variants of the PCR is required, for purposes such as the identification of species or the identification of transgenic components, in any of the products that contain rice, corn or soybeans, it is necessary to establish the bases for their application. Therefore, this thesis work contemplated the evaluation, in terms of purity and concentration, of DNA extraction methodologies from foliar and grain samples of the aforementioned plants. DNA extraction carried out using the PureLinkTM Kit, the CTAB method and the modified lysis buffer method, together with the molecular PCR technique, allowed us to identify the presence of the wx, lectin and zein genes, which in turn are distinctive characteristics of each species. Statistically significant differences highlighted the usefulness of one method over another based on the type or variant of the plant sample. This research allowed to demonstrate the functionality of the different methodologies in the detection of genetic modifications, gene identification or the authentication of the rice, soybean and corn plant species; plants of great value for the panamanian food and economy.