Fusarium verticillioides Migration in Attached and Detached Sweet Corn Ears

Abstract

Mycotoxins harmful to humans and other animals are produced in kernels of sweet corn (Zea mays L.) during colonization by the fungus Fusarium verticillioides (Sacc.) Nirenberg. Experimentation is limited under field conditions, due to the seasonality of the organisms, to once each year in temperate climates and under greenhouse conditions by the number of plants that can be grown. The objective of this study was to examine grocer ears (pistillate inflorescence) from retail stores as an alternative source for experimental material to use in bioassays to study this important food safety problem. Fusarium verticillioides migration was compared in sweet corn ears from a local grocery store and from greenhouse and field plants. Ears were inoculated with a F. verticillioides transformant tagged with a selection gene encoding resistance to hygromycin, a fungicidal antibiotic, and with a reporter gene encoding for ß-glucuronidase, an enzyme detectable by histochemical staining. Screening kernels for both genes ensures unequivocal identification of the source of subsequent mycelia. Fusarium verticillioides colonized sweet corn ears towards the ear apex and base from the inoculation site regardless of ear source, incubation protocol, or attachment of the ear to the plant or to the shuck (spathe) and silks (styles) to the ear. Thus, ears from retail grocers can serve as experimental material for analyzing sweet corn and F. verticillioides interactions throughout the year.