GENETIC-ANALYSIS OF FUMONISIN PRODUCTION AND VIRULENCE OF GIBBERELLA-FUJIKUROI MATING POPULATION A (FUSARIUM-MONILIFORME) ON MAIZE (ZEA-MAYS) SEEDLINGS

The phytopathogenic fungus Gibberella fujikuroi mating population A (a namorph, Fusarium moniliforme) produces fumonisins, which are toxic to a wide range of plant and animal species. Previous studies of field s trains have identified a genetic locus, designated fum1, that can dete rmine whether fumonisins are produced. To test the relationship betwee n fumonisin production and virulence on maize seedlings, a cross betwe en a fum1(+) held strain that had a high degree of virulence and a fum 1(-) field strain that had a low degree of virulence was made, and asc ospore progeny were scored for these traits. Although a range of virul ence levels was recovered among the progeny, high levels of virulence were associated with production of fumonisins, and highly virulent, fu monisin-nonproducing progeny were not obtained. A survey of field stra ins did identify a rare fumonisin-nonproducing strain that was quite h igh in virulence. Also, the addition of purified fumonisin B-1 to viru lence assays did hot replicate all of the seedling blight symptoms obt ained with autoclaved culture material containing fumonisin. These res ults support the hypothesis that fumonisin plays a role in virulence b ut also indicate that fumonisin production is not necessary or suffici ent for virulence on maize seedlings.