SUMMARY

Fusarium oxysporum f.sp. lycopersici (FOL) induces wilting in tomato plants (Lycopersicon esculentum). This disease causes large losses and it increases when prac-tices include monoculture or limited crop rotation. Un-der these conditions, large quantities of tomato plant residues decompose in the field and may affect growth of tomato and FOL and their interactions. Here we show that undecomposed tomato residues are phytotox-ic in laboratory and greenhouse bioassays and that leaves are more phytotoxic than roots. During decom-position, phytotoxicity of leaves and roots decreases un-der aerobic conditions, but increases under anaerobic conditions. On the contrary, FOL radial growth and hy-phal density are increased by undecomposed leaves and roots, but decreased with aerobically decomposed plant material. Tomato wilting caused by FOL increased when the soil was amended with undecomposed leaves. Our study shows that, under controlled conditions, un-decomposed tomato residues affect the growth of toma-to (autotoxic effect) and FOL (substrate effect), by causing an increase in incidence of the disease