Abiotic stress and transgenics: Implications for reproductive success and crop-to-wild gene flow in Brassicas

Various abiotic and biotic stressors affect crop and weed plant performance in agroecosystems Ozone (O-3) tolerance in plants is partly regulated by the genotype and phenotypical properties, and it vanes greatly in related species of wild and crop backgrounds Thus, a continuous increase in atmospheric O-3 concentration could change population dynamics of sexually compatible crop and weed species, and consequently affect crop-to-wild gene flow in the future One way to build resistance against a biotic stressor, in this case insect-mediated herbivory, in crop plants is transgene-mediated insecticidal toxin production In this study we aimed to describe how the physiological and phenological responses in a crop Brassica and its weedy relatives functioned to affect their comparative O-3 tolerance Furthermore, we studied how harbouring a transgene affects these responses in B napus and B rapa x transgenic B napus BC2F2 backcross hybrid plants to reveal any within-plant trade-offs among toxin production, growth and O-3 tolerance We found a higher number of O-3 symptoms but more effective compensatory assimilate allocation directed to reproduction for wild B rapa compared to crop B napus under elevated O-3 This result suggested that the invasion-orientated strategy of producing a high number of seeds when vegetative growth is limited might improve the performance of weedy species under elevated O-3 The probabilities for crop-to-wild transgene flow could be increased through higher seed production in hybrids under elevated O-3, but the germination of hybrid seeds in particular was hampered by O-3 The presence of transgenes did not perturb fecundity, within-plant biomass allocation or O-3 tolerance of B napus