Seedling mortality of metal hyperaccumulator plants resulting from dampingoff by Pythium spp.

Seedling mortality of Alyssum serpyllifolium sap. lusitanicum and A. murale , both nickel hyperaccumulators, was reduced by increasing concentrations o f metal within plant tissues when inoculated with the fungi Pythium mamilla tum or P. ultimum, both of which cause damping-off disease of seedlings. Py thium mamillatum, isolated from nickel-rich serpentine soil, was more toler ant of nickel than P. ultimum, isolated from low-metal control soil, and wa s more pathogenic than P. ultimum towards seedlings containing high concent rations of metal. These results support the hypothesis that metal hyperaccu mulation by plants is closely linked to increased protection against diseas e.