Influence of soil organic matter and ion concentration on some Senegalese plant-parasitic nematodes

To determine the effect of different physicochemical soil parameters on pla nt-parasitic nematodes, organic matter, KNO3 and NaCl salts were added to s terilised sand or sandy soil. The five most frequently observed species in Senegal were inoculated on millet together or as individual species. The sp ecies were Helicotylenchus dihystera, Pratylenchus pseudopratensis, Tylench orhynchus gladiolatus, Scutellonema cavenessi and Criconemella curvata. Sho ot and root weights were measured at the end of the experiment. Organic mat ter had no effect on shoot growth but reduced root growth when present in a high proportion whereas KNO3 improved both shoot and root growth. Individu al populations of H. dihystera increased root growth. The reproductive inde x of species such as S. cavenessi and C. curvata was not affected by the su bstrate whereas that of H. dihystera, T. gladiolatus and P. pseudopratensis was affected. The addition of KNO3 and NaCl had no influence on the reprod uctive index of T. gladiolatus, but reduced that of H. dihystera. These eff ects disappeared when nematodes were inoculated together. These experiments show that soil characteristics, as well as the soil solution influence nem atode reproduction, but the response could be different if the species is p resent as a population or in a community. Results show that modifying the s oil solution can influence nematode interactions, but this may not necessar ily lead to reduction in their pathogenicity as plant susceptibility may in crease in the changed environment. (C) 2000 Editions scientifiques et medic ales Elsevier SAS.