Tolerance and Metabolism of Furanocoumarins by the Phytopathogenic Fungus Gibberella Pulicaris (fusarium Sambucinum)

Sixty-two strains of Gibberella pulicaris (anamorph: Fusarium sambucinum) from diseased plants and from soil were tested for tolerance of the furanocoumarin xanthotoxin in vitro. Twenty-one (88%) of the plant-derived strains and two (5%) of the soil-derived strains were highly tolerant ofxanthotoxin. Sixteen selected strains were tested further against 16 furanocoumarins or furanocoumarin precursors. All plant-derived strains tested were highly tolerant of and, in most cases, able to completely metabolize all 16 compounds. Most soil-derived strains tested were tolerant of furanocoumarin precursors but sensitive to certain furanocoumarins. Linear compounds methoxylated at C-8 appeared more toxic than both those unsubstituted and those with longer-chain ethers. Tolerance of angelicin, xanthotoxin, pimpinellin and isopimpinellin correlated in large part with their metabolism. All strains that were highly virulent on Pastinaca sativa root were tolerant of xanthotoxin, which is corroboration that xanthotoxin is a phytoalexin in P. sativa.