Explaining the decrease in the genetic diversity of wheat in France over the 20th century

Recent studies indicate that crop diversity in agricultural fields may ensure pest control and yield stability in the face of environmental changes. However, few studies have evaluated crop diversity in the field, especially at the within-species level. Applying a new indicator, HT*, the authors followed the evolution of bread wheat genetic diversity on French agricultural landscapes during the 20th century. The HT* indicator revealed increasing genetic homogenization overall. This trend was due to the disappearance of diversity within varieties, to the spatial homogenization occurring in the last period of the 20th century with the different ‘départements’(French administrative territories) progressively cultivating the same varieties and to their increasing genetic similarities. This result calls into question the effects of plant breeding, seed system organization and seed regulation on wheat genetic diversity, especially in the context of current environmental changes.