The cultivation of genetically modified (GM) Bt maize (Zea mays L.) events MON810 and Bt11 is permitted in Uruguay. Local regulations specify that 10% of the crop should be a non-GM cultivar as refuge area for biodiversity, and the distance from other non-GM maize crops should be more than 250 m in order to avoid crosspollination. However, the degree of cross-fertilization between maize crops in Uruguay is unknown. The level of adventitious presence of GM material in non-GM crops is a relevant issue for organic farming, in situ conservation of genetic resources and seed production. In the research reported here, the occurrence and frequency of cross-fertilization between commercial GM and non-GM maize crops in Uruguay was assessed. The methodology comprised field sampling and detection using DAS-ELISA and PCR. Five field-pair cases where GM maize crops were grown near non-GM maize crops were identified. These cases had the potential to cross-fertilize considering the distance between crops and the similarity of the sowing dates. Adventitious presence of GM material in the offspring of non-GM crops was found in three of the five cases. Adventitious presence of event MON810 or Bt11 in non-GM maize, which were distinguished using specific primers, matched the events in the putative sources of transgenic pollen. Percentages of transgenic seedlings in the offspring of the non-GM crops were estimated as 0.56%, 0.83% and 0.13% for three sampling sites with distances of respectively 40, 100 and 330 m from the GM crops. This is a first indication that adventitious presence of transgenes in non-GM maize crops will occur in Uruguay if isolation by distance and/or time is not provided. These findings contribute to the evaluation of the applicability of the "regulated coexistence policy" in Uruguay.

This research analysed the response of onion (Allium cepa) and A. fistulosum against Fusarium oxysporum f. sp. cepae (Foc) isolates and the associated changes in peroxidase, β-1,3-glucanase and chitinase activities. The response of A. cepa and A. fistulosum at different stages of seedling development were also evaluated. Several seedling tests were performed, and disease symptoms were evaluated 12-14 days after inoculation. Allium fistulosum behaved as more resistant than A. cepa cultivars by exposition to the most aggressive Foc isolates at sowing date. Increased levels of peroxidase and glucanase activities were found in the A. cepa and A. fistulosum seedlings exposed to the pathogen, and were positively correlated with disease symptoms. For chitinase activity, this correlation was found only for A. cepa. Two peroxidase isoforms were found to be specific for A. fistulosum roots after inoculation and could be involved in resistance. The inoculation at 7, 14 and 42 days after sowing showed that both host species were resistant to Foc, proving that onion susceptibility decreased promptly after germination. However, an increase in peroxidase and glucanase activities in 7-and 14-day-old inoculated seedling was detected only for A. cepa, suggesting an earlier acquisition of resistance in A. fistulosum.