Control of root-knot nematodes with biomasses from Medicago sativa and their bioactive saponins.

Soil amendments with dry top and root material from alfalfa (Medicago sativa) were evaluated for their nematicidal effect on the root-knot nematode Meloidogyne incognita on tomato either in potting mixes or in field conditions. All amendments in potting mixes suppressed root and soil population densities of rootknot nematodes compared to nontreated and chemical controls. Amendment suppressiveness on M. incognita differed between top and root material and among rates. In field conditions, soil amendments with 20 or 40 t ha-1 of a pelleted M. sativa meal increased tomato crop yield and reduced soil population densities and root galling of M. incognita. As saponins were hypothesized to be at least partly responsible for the nematicidal activity of Medicago materials, biomolecular aspects of plant-nematode interaction were preliminarily investigated on M. incognita juveniles treated with saponins from M. sativa.