REPRODUCTIVE FITNESS AND PATHOGENICITY OF 8 RADOPHOLUS-SIMILIS ISOLATES ON BANANA PLANTS (MUSA AAA CV POYO)

Eight isolates of Radopholus similis were compared for their reproduct ive fitness and pathogenicity on banana (Musa AAA cv. Poyo) under cont rolled conditions in a climatic chamber. Five isolates were originally collected from African countries (Uganda, Cameroon, Nigeria, Ivory Co ast, and Guinea) and the 3 others from Guadeloupe, Queensland, and Sri Lanka. The African isolates,and particularly the one collected in Uga nda, had the highest reproductive fitness. Strong negative correlation s were observed between nematode numbers in roots 6 and 8 weeks after inoculation and fresh root and shoot weights 12 weeks after inoculatio n. These results suggest that differences in pathogenicity on banana a mong R. similis isolates are a direct consequence of differences in re productive fitness on banana tissue, and consequently that the relativ e virulence is roughly similar for all isolates considered. This study increases our knowledge of the biological intraspecific diversity of R. similis throughout the world and strengthens the hypothesis that th e high pathogenicity among African populations of R. similis due mainl y to better reproductive fitness, which could explain greater field da mage generally observed in these regions.