MICROCOSM EXPERIMENTS ON THE DEVELOPMENT OF DIFFERENT PLANT-PARASITICNEMATODE FAUNA IN 2 SOILS FROM THE SOUDANESE-SAHELIAN ZONE OF WEST-AFRICA

To test the hypothesis that the structure of plant parasitic nematode communities is affected by soil characteristics, experiments were cond ucted in a greenhouse with two soils with different physical and chemi cal characteristics and land management histories (fallow and a cultiv ated field) from adjacent plots. The cultivated soil was more sandy an d had lower organic matter and nutrient contents than the fallow soil. Four nematode assemblages of Scutellonema cavenessi, Helicotylenchus dihystera and Tylenchorhynchus gladiolatus were inoculated in the soil s. The pot experiment was conducted on millet during 2 months. Multipl ication rates of H. dihystera were not significantly different in the two soils. T. gladiolatus had a lower multiplication rate in the fine- textured soil. S. cavenessi seemed to reproduce better in the coarse-t extured soil when inoculated in low density with H. dihystera. The pre sence of plant parasitic nematodes in the cultivated soil caused a sig nificant decrease of millet biomass, whereas plants in the follow soil were less sensitive to nematode damage and were only affected when th e soil was inoculated with T. gladiolatus alone. This experiment did n ot explain the distribution of plant parasitic species observed in the field. However. parameters other than the presence of a favourable ho st plant and micro-climatic conditions were found to induce difference s in the reproductive rates of several species of plant parasitic nema todes.