Symptomless endophytic colonization of maize by Fusarium moniliforme

Fusarium moniliforme Sheldon is a nonobligate parasite of maize that produces several mycotoxins. This fungus causes systemic infections of maize kernels, which then serve as dissemination vehicles and inoculum sources. Infected plants may or may not show disease symptoms. Symptomless infection was studied in maize plants and was compared with plants that eventually showed symptoms of seedling disease. Three isolates of F. moniliforme, a hygromycin-resistant mutant of two of these isolates, and Fusarium fujikuroi were used to infect surface and internally sterilized maize kernels, and symptomatic and symptomless infections were observed for 8 weeks. The results indicated that in symptomless infected plants, hyphae were intercellular only and distributed throughout the plant, whereas in plants showing disease symptoms, the fungus was both intercellular and intracellular. Symptomless plants remained symptomless throughout the observation period, and at the ultrastructural level there was no evidence of an antagonistic relationship. This indicates that the symptomless state persists beyond the seedling stage and could contribute, without visual signs, to the total mycotoxin contaminants of maize both before and during kernel development.