S. 2010. Comparison of rhizosphere impacts of two wheat genotypes differing in phosphorus utilization efficiency. Can. J. Plant Sci. 90: 311Á317. Exploitation of high phosphorus (P) use efficiency genotypes of crops and understanding their rhizosphere P activation mechanisms is essential to development of beneficial management practices for sustainable agricultural production. A pot experiment was carried out to investigate the differences in changes of pH, phosphatase activity, and water-soluble P in the rhizosphere soil and crop growth and P content of two constrasting wheat genotypes (P-efficient, Xiaoyan54, and P-inefficient, Jing411) in a calcareous soil supplied with three rates (0, 50, and 100 mg kg(1 soil, which are coded as P 0 , P 50 and P 100 , respectively) of fertilizer P. Results showed that root biomass, root/shoot ratio and efficiency index of Xiaoyan54 were significantly higher than those of Jing411 at the same P level. In addition, the roots of Xiaoyan 54 absorbed significantly more P than the roots of Jing 411, except for the P 50 . The dry weight of shoot biomass was similar between the two wheat genotypes. Wheat biomass and P content in shoot, root and the total for both genotypes increased for P supplied treatments, compared with those without P supply. The rhizosphere acidification capacity of Xiaoyan54 was greater than Jing411 without P addition. However, Xiaoyan54 acidified rhizosphere soil at a larger distance than Jing411 at high P fertilization. The phosphatase activity did not differ between the two genotypes, regardless of the location in the rhizosphere. Soil applied with high P decreased the phosphatase activity for the root surface soil only. Water-soluble P concentration in rhizosphere and the bulk soil were similar for Xiaoyan54 and Jing411, and increased as increasing P levels. Xiaoyan54's large root biomass and strong acidification ability might be the main mechanisms contributing to high P uptake under P-deficient conditions.Key words: Phosphatase activity, acidification, wheat, genotype, root biomass Yan, H., Liu, W., Liu, X., Li, G. et Zhang, S. 2010. Comparaison de l'impact de la rhizosphe`re de deux ge´notypes du bleú tilisant diffe´remment le phosphore. Can. J. Plant Sci. 90: 311Á317. Il est essentiel d'utiliser des cultures qui exploitent tre`s efficacement le phosphore (P) et de comprendre les me´canismes qui activent le P dans la rhizosphe`re si l'on veut adopter des pratiques agronomiques propices a`une production agricole durable. Les auteurs ont effectue´une expe´rience en pots afin de pre´ciser les e´carts entre deux ge´notypes de ble´contrastants (le ge´notype P-efficace Xiaoyan54 et le ge´notype Pinefficace Jing411) eu e´gard a`la variation du pH, a`l'activite´de la phosphatase et a`la concentration de P hydrosoluble dans le sol de la rhizosphe`re, ainsi qu'au niveau de la croissance des plantes et de leur teneur en P. L'expe´rience s'est de´roule´e sur un sol calcaire qu'on a bonifie´avec de l'engrais P a`trois concentrations (0, 50 et 100 mg de P par kg de s...