Fitness and maternal effects in hybrids formed between transgenic oilseed rape (Brassica napus L.) and wild brown mustard [B. juncea (L.) Czern et Coss.] in the field.

BACKGROUND Gene flow between crops and weedy relatives depends on the survivorship and reproduction of early-generation hybrids in a field environment. The primary aim of this study was to compare the fitness of transgenic crop x wild hybrids with their parental types and a non-transgenic crop type in the field under enhanced temperature and humidity. RESULTS Transgenic insect-resistant oilseed rape (Brassica napus L.), wild brown mustard [B. juncea (L.) Czern et Coss.], their hybrids and non-transgenic B. napus were grown in such a way as to mimic field conditions after harvest under which volunteer plants might appear in agricultural settings. Factor analysis revealed that vegetative growth characteristics explained most of the observed differences among plant types. Wild brown mustard had the highest fitness during its entire life history. Hybrids had intermediate composite fitness and lowest reproductive fitness. The hybrid and the wild weed shared similar vegetative growth characteristics and seed dormancy in their respective progenies. CONCLUSION These data indicate that there might be enhanced persistence of the transgene in warmer climates. The absence of fitness cost of the transgenes might allow transgenes to persist in ecosystems. These data will contribute to risk assessments of transgene persistence and weed management against the backdrop of global climate change.