Three isolates of root-lesion nematodes, originally collected on coffee trees in Guatemala, were studied for their penetration dynamics on hypocotyledonar stages of C. arabica seedlings. Roots were stained with acid fuschine, 24, 48 and 96 hours after the inoculation of 300 nematodes/plant. Stained nematodes were directly counted in situ. Pathogenicity of each isolate was also studied on 3 months coffee seedlings. Nematode population densities in roots, stem height and fresh root and shoot weights were measured, 50, 100 and 150 days after the inoculation of 200 nematodes/plant. Penetration dynamics, reproductive fitness and amount of damages varied the same way among the three isolates. Negative correlations were observed between nematode numbers in roots 5 0 and 100 days after inoculation and fresh shoot and root weights 150 days after inoculation. These results suggested that pathogenicity of Pratylenchus spp. isolates on coffee is highly related to their reproductive fitness. According to another study, reproductive barriers were observed between the two isolates showing the lowest and highest degrees of pathogenicity, respectively, although they presented very similar morphological and biological characteristics (closely related to descriptions of P. coffeae sensu lato). Reproductive barriers were also observed between the two isolates with highest and intermediate degrees of pathogenicity, respectively. However, degree of reproductive isolation among these isolates must be specified. (Texte intégral)