1. Department of Plant and Microbial Biology; University of California; Berkeley CA 94720-3102
2. Département Génétique et Ecologie Evolutives Laboratoire Ecologie, Systématique et Evolution, CNRS-UPS-AgroParisTech; Université de Paris-Sud; 91405 Orsay France
3. Department of Microbiology and Immunology; Montana State University; Bozeman MT 59717
4. INRA, UMR BGPI; Campus International de Baillarguet; 34398 Montpellier France