Effect of endomycorrhizas and nematodes on the growth of seedlings of Dicorynia guianensis Amshoff, a tree species of the tropical rain forest in French Guiana

Seedlings of Dicorynia guianensis Amshoff, an economically important timber tree species of the primary tropical rain forest of French Guiana, were grown in pots containing a disinfected soil inoculated or not with forest soil, mycorrhizal roots of D guianensis or nematodes. Plant growth parameters and root endomycorrhizal colonization were measured after 200 days. The results are inconclusive about the role of nematodes but clearly show that D guianensis is dependent on endomycorrhizal symbiosis for its development: the top dry weights of the seedlings inoculated with soil or roots (with 87-84% endomycorrhizal roots) are 77 and 54% higher, respectively, than that of the uninoculated seedlings (with no mycorrhizas observed). In relation with previous observations in the forest, these results support the hypothesis that endomycorrhizas play a major role in the regeneration of D guianensis.