of spring wheat (Triticum aestivum L.) by coexistent Bacillus species. Can. J . Microbiol. 34: 925-929.Seven bacterial strains belonging to the genus Bacillus were isolated from rhizosphere soil of spring wheat (Triticum aestivum L.) cv. Katepwa. The plants from which the microorganisms were isolated were collected from a field that had been continuously cropped with spring wheat for the past 27 years. Cultivar Katepwa had been grown for the last 5 years whereas the closely related cv. Neepawa had been cultivated for the 12 previous years. When tested as single strain inoculum in a sterilized sand and Turface (montmorillonite clay) mix. six of seven isolates promoted root growth of cv. Katepwa spring wheat (p < 0.05), but none promoted that of cv. Necpawa or of the more distant genetic relative cv. HY320. Shoot height was also increased in CV. Katepwa @ < 0. I), but shoot weight of all three cultivars was unaffected by inoculation.Consequently, the roor to shoot weight ratio of cv. Katepwa was also greater because of bacterization. These results indicate that beneficial bacteria may be isolated by employing a natural plant cultivar enrichment technique. CHANWAY, C. P., NELSON, L. M., et HOLL, F. B. 1988. Cultivar-specific growth promotion of spring wheat (Triticum aestivum L.) by coexistent Bacillus species. Can. J . Microbiol. 34 : 925-929. Sept souches bactkriennes appartenant au genre Bacillus ont ete isolees du sol de la rhizosphere de plants de ble de mars (Tr~trcum aestivum L.) cv. Katepwa. Ces bacteries sont ete isolees a partir de plants recoltes dans un champ qui avait Cte reserve exclusivement a la culture du ble de mars depuis les 27 dernieres annees. Le cv. Katepwa y avait ete cultive pendant les derniers 5 ans alors que le cultivar trks apparente Neepawa y avait ete cultive pendant les 12 annees precedentes. Chacune des souches isolees a Cte inoculee separiment dans un mklange sterilisC de sable et Turface (argile de montmorillonite).La croissance des racines du cv. Katepwa a ete favoriske par six des sept souches de Bacillus ( p < 0.05), mais aucune souche n'a favorise la croissance chez le cv. Neepawa ou le cv. HY320 dont la parente genktique est plus lointaine. La hauteur des tiges est aussi favorisee cher le cv. Kaiepwa @ < 0. I), mais l'inoculation n'a pas fait varier le poids des tiges chez aucun des lrois cultivars. En consequence le rapport de poids racine : tige du cv. Katepwa etait encore plus grand a cause de la colonisation bactirienne. Ccs resultats nlontrent hien que des bacteries utiles peuvent Etre isolees en employant une technique naturelle d'enrichissement du cultivar d'une plante.[Traduit par la revue]