Relative influence of cropping systems, injury profiles and institutional determinants on the spatio-temporal structure of bread wheat diversity in France

Abstract : In the current context of increasingclimate instabilities and new pest pressures, in situ crop diversity has been recognized as a relevant way to avoid crop failure, ensure yield inter-annual stability while reducing the use of synthetic inputs. However, before implementing any future deployment of within-crop diversity, a detailed nowledge of the main drivers affecting this diversity appears necessary. The temporal evolution of in situ genetic diversity of bread wheat has been previously shown to be spatially structured among regions in France over the period 1980-2006. Our study was carried out to identify the main drivers of this spatio-temporal structure of crop diversity at a fine spatio-temporal scale. We conducted a series of statistical analyses and expert surveys to identify the effects of three main catergories of drivers : agricultural systems, pathogen pressures and institutional determinants of the formal wheat sector. We hypothesized that this set of drivers could have a higher explanatory power of the varietal diversity - i.e. based only on the varietal denomination which allows varietal choice by drivers - the cultivation area of bread wheat, the nature and the diversity of the preceding crops, and the pressure of some pathogens - explained the spatio-temporal structure of varietal diversity more than the genetic one. We highlighted a correlation between bread wheat varietal and genetic diversity and a greater diversity of preceding crops, suggesting that more diversified agroecsystems seemed also promoted a higher within-crop diversity.