Fusarium verticilliodes dissemination among maize ears of field-grown plants

Authors: Yates, Ida; SPARKS, DARRELL - HORTICULTURE/UGA, ATHENS

Submitted to: Crop Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/7/2007
Publication Date: 2/1/2008
Citation: Yates, I.E., Sparks, D. 2008. Fusarium verticilliodes dissemination among maize ears of field-grown plants. Crop Protection Journal. 27:606-613.

Interpretive Summary: A fungus, Fusarium verticillioides, grows on corn kernels. The corn kernel/fungus interaction may result in disease and/or toxin synthesis in the kernels. Diseases may reduce crop production and toxins can cause harmful effects on humans and animals. The migration of the fungus among corn plants in the field is unknown. The purpose of theses studies was to examine the frequency of the fungus in kernels inoculated and non-inoculated ears on field grown plants. The fungus used for inoculations carried two foreign genes that can be detected in the laboratory. Ears were inoculated by injecting the fungus mid-length of the ear through the shuck or at the top of the ear through the silks at two stages of development, green silks versus brown silks. Kernels from inoculated ears tested positive for the foreign genes. In contrast, kernels from non-inoculated ears on plants growing next to plants with inoculated ears were not positive for the genes. Thus, F. verticillioides was not spread from plant to plant under field conditions existing in Georgia during the growing seasons of 2001, 2002, and 2003.

Technical Abstract: The consequences of Fusarium verticillioides colonization of kernels of corn, Zea mays L., may be plant disease and/or mycotoxin production. Plant disease results in reduced crop production and mycotoxins cause harmful, and often fatal, effects on humans and animals. The fungus grows as an endophyte within the corn plant without producing toxins or causing disease until external factors, such as pests or other plant stress conditions intervene. Understanding the dynamics between the corn plant and F. verticillioides during this metamorphic relationship is essential to developing strategies that prevent diseases and eliminate mycotoxins from our food chain. The purpose of the current research was to analyze the field dissemination of F. verticillioides from ears inoculated with F. verticillioides RRC PATg, a transformant with a selection gene, hph, for hygromycin resistance (hygr) and a reporter gene, gusA, coding for ß-glucuronidase (GUS). Corn ears were inoculated through either the shuck or the silk channel at two stages of development, green silks versus brown silks. Kernels from inoculated ears tested 67% positive for hph and of these 96% tested positive gusA. No kernels tested positive for hph and gusA from non-inoculated ears on plants adjacent to inoculated plants. Thus, F. verticillioides was not disseminated from plant to plant under field conditions existing in Georgia during the growing seasons of 2001, 2002, and 2003.