1. University of Bordeaux, UMR 1202 BIOGECO, F‐33405 Talence, France
2. INRA, UMR 1202 BIOGECO, 69 route d'Arcachon, 33612 Cestas, France
3. Division of Biological Sciences, The University of Montana, Missoula, MT 59812, USA
4. INRA, UMR 547 PIAF, F‐63100 Clermont‐Ferrand, France