Submitted to: Aflatoxin Elimination Workshop Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: October 23, 2001
Publication Date: February 13, 2002
Technical Abstract: Critical to propagation, dispersal, and survival of most plant pathogenic fungi is the production of asexual spores (i.e., conidia). The mycotoxigenic fungal endophyte of corn, Fusarium verticillioides, produces abundant, mostly single-celled conidia in distinctive long chains. Since conidia may be critical for establishing plant infections, greater understanding of their production and impact on in planta associations is of interest. We have isolated spontaneous mutants of F. verticillioides that elaborate phialides but are unable to produce conidia. Instead the phialides reinitiate limited apical, germ tube-like growth. Genetic analyses indicated a single locus, denoted as FPH1, is responsible for this phenotype. Another genetically inheritable locus, unlinked to FPH1, also was identified that controls pathogenicity toward corn seedlings. This pathogenicity locus is denoted as FLP1, and only strains possessing the functional allele produced disease symptoms. Seedling pathogenicity and infection assays using conidiating (FPH1) and nonconidiating (fph1) strains indicated that fph1 mutants were greatly attenuated in their ability to infect plants, yet some of these noninfecting mutants possessed the FLP1 pathogenicity allele and were still able to induce disease symptoms to wild-type levels. The collective results from these assays suggest that 1) endophytic infections can exist without any detriment to corn seedlings, 2) endophytic infection is not necessary for seedling disease development, and 3) the pathogenicity factor of F. verticillioides may be a phytotoxin.