This study is a product of the ANR Bakery research project. From a panel of 40 bakers, a selection of 4 types of sourdough, differentiated by the microbial diversity of the yeast and bacteria populations, was selected.The 4 bakers chosen on the specificity of their sourdoughs initiated 6 chef sourdoughs, during 3 weeks, in their work environment and with their practices, using 6 flours from a mixture of modern varieties and a mixture of varieties from ancient wheat populations, each cultivated in 3 different terroirs.The aim was to observe the effect of these factors (bakery, flour, terroir) on the characteristics of the leavens produced.From these master yeasts, all-point yeasts were prepared for the implementation of bread-making trials with a reference diagram using the flours of the study. The impact of these sourdoughs during bread-making and on the breads was characterised by observation of the properties of the dough and by measurements of acidity, gas production and the dosage of chemical components on the breads.Wheat and baking practices influence the activity of the yeast and the characteristics of the breads.