title: Phenotypic drift inBradyrhizobium japonicum populations after introduction into soils as established by numerical analysis.
abstract: The degree of phenotypic variation of the bacterial strains USDA 125-Sp, USDA 138 and USDA 138-SmBradyrhizobium japonicum a long time after introduction was studied in three experimental fields. A total of 54 phenotypic characters were analyzed by constructing a dendrogram based on an hierarchic classification. Strong similarities (92.6, 94 and 95%) were found between the isolates introduced into soil 8, 10 and 13 years ago and between their respectiveB. japonicum parental clones. The dendrogrammic analysis detected a small amount of phenotypic drift, however, between soil isolates and parental clones belonging to the same serogroup (selective effects were found to have generated 0 to 3.9% variation for the USDA 125-Sp inoculum introduced 8 years ago, and 3.2-3.5% after 10 and 13 years, respectively, for the USDA 138 and USDA 138-Sm bacterial inocula) and within the serogroup 125 soil isolates (2.7%). We found a similar evolution of serogroup 125 isolates when compared with parental clones conserved on slant agar at 4°C. When a drift was observed, the isolates from soil presented a lower activity for several enzymes and lower diversity compared with the parental clones.
authors.affiliation: Laboratoire d'Ecologie Microbienne CNRS URA 697, Université Claude Bernard Lyon I, 43, Bd du 11 Novembre 1918, 69 622, Villeurbanne Cedex, France.
authors.forename: B
authors.initials: B
authors.lastname: Brunel
authors.forename: J M
authors.initials: JM
authors.lastname: Boeufgras
authors.forename: D
authors.initials: D
authors.lastname: Bernillon
authors.forename: R
authors.initials: R
authors.lastname: Bardin