Importance Des Interactions Entre Les Organismes Du Sol Et L'Etat Phytosanitaire Des Plantes : Une Experience De Laboratoire

We studied the effect of the earthworm, Pontoscolex corethrurus, on the phytoparasitic nematode, Radopholus similis, and on the banana. We realised a mesocosm experimentation. Each banana plant grew during 4 months in a 3- litres container filled with upper andosol, with or without earthworms and/or nematodes. 4 treatments and 12 repetitions by treatment were conducted. Leaf area of banana was measured weekly. At the end of the experiment, we measured shoot fresh and dry biomasses, roots fresh biomass and shoot nitrogen content on banana, nematode density into the roots, final population and multiplication factor. We measured mineral nitrogen and organic matter contents in the soil. Leaf areas, shoot fresh and dry biomass, roots fresh biomass, shoot nitrogen content and mineral nitrogen in the soil were higher in the presence of earthworms whereas total nitrogen soil content was lower. The nematode population did not decrease in the presence of earthworms but the percentage of roots necrosis decreased whereas the fresh shoot biomass was not affected. Our results indicate that earthworms have a strong positive influence on the development of bananas and permit it to be more resistant to the nematode attack. Those results reveal the importance of below- / aboveground interactions for plant health. Further investigations are necessary to verify those results on the field and to determine the nature of the interactions (trophic or non-trophic) between those organisms.