Aims: To determine the biodiversity of rhizobial strains nodulating Cicer arietinum L. in representative soils from various areas of Morocco. Methods and Results: Symbiotic traits, utilization of 49 carbohydrate sources, resistance to antibiotics and heavy metals, tolerance to salinity, to extreme temperatures and pH were studied as phenotypic markers. In addition, restriction fragment length polymorphism (RFLP) of PCR-amplified 16S rDNAs were compared with those of reference strains. Numerical analysis of the phenotypic characteristics showed that the 48 strains studied fell into three distinct groups. RFLP analysis of 16S rRNA genes revealed an additional heterogeneity and four ribotypes were identified.

Phenotypic characteristics of fifty-six rhizobia strains isolated from root nodules of two chickpea (Cicer arietinum L.) cultivars, growing in soils collected from different areas of Morocco, were studied. Tolerance to salinity, high temperatures, acid and alkaline pHs, heavy metals and to antibiotics as well as symbiotic and cultural characteristics allowed the description of a wide physiological diversity among tested isolates. Numerical analysis of the phenotypic characteristics showed that, below the boundary level of 82% average similarity, isolates fell into at least five distinct groups. A number of potential isolates have been identified for inoculation trials. They were effective and able to grow at pH ranging from 5 to 8, tolerated salt concentration (1-1.5%) and grew at a maximum temperature between 30 and 35 o C. biodiversity / Cicer arietinum / phenotypic characterization / Rhizobium Résumé-Caractérisation phénotypique des rhizobia isolés du pois chiche (Cicer arietinum) cultivé sur les sols marocains. Cinquante six souches de rhizobium nodulant deux cultivars de pois chiche (Cicer arietinum L.) et isolées de différentes régions du Maroc, ont été caractérisées sur le plan phénotypique. L'analyse de leur tolérance à la salinité, aux températures élevées, aux pH acides et alcalins, aux antibiotiques, aux métaux lourds ainsi que leurs caractéristiques symbiotiques et culturales ont permis de mettre en évidence une large diversité physiologique au sein de ces populations de rhizobium nodulant le pois chiche. L'analyse numérique de ces caractéristiques phénotypiques a montré qu'à un niveau de 82 % de similarité, ces souches bactériennes se sont réparties en cinq groupes distincts. Des souches intéressantes pour les essais d'inoculation ont été identifiées. Elles sont efficientes et capables de tolérer des pHs allant de 5 à 8, des concentrations en NaCl de 1 à 1,5 % et des températures maximales comprises entre 30 à 35 o C. biodiversité / caractérisation phénotypique / pois chiche / Rhizobium Communicated by Jean-Jacques Drevon (Montpellier, France)