Submitted to: Natural Toxins
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/18/1997
Publication Date: N/A
Interpretive Summary: Toxins produced by ear molds that invade corn cause hundreds of millions of dollars of direct and indirect losses in the U.S. and affect the billion dollar corn export market. A naturally occurring plant protein, called peroxidase, when combined with naturally occurring plant defensive chemicals, greatly enhanced the ability of both to inhibit growth and germination of corn ear mold spores. Increasing the levels of appropriate peroxidases through conventional breeding or genetic engineering in corn should reduce contamination and toxin production by ear molds, thereby providing a safer and more marketable product both at home and abroad.
Technical Abstract: A series of stable quinones and their precursors, and enzymatic oxidation products of plant allelochemicals were tested for their effect on maize fungal pathogens, primarily Fusarium graminearum. Benzoquinone was typically significantly more toxic than hydroquinone, while 1,2 naphthoquinone was typically significantly more toxic than 1,2 dihydroxynaphthylene. Aspergillus flavus was the most resistant fungus to these compounds, while Phoma medicaginis was the most susceptible. Applying tyrosinase in conjunction with several phenolic compounds only increased the toxicity of gallic acid to Fusarium graminearum. Applying peroxidase generally increased toxicity of all compounds tested to this fungus in a dose-dependent fashion. Ferulic acid was generally the most toxic compound, both alone and when combined with peroxidase and H2O2, followed by coumaric acid. These results suggest that enzymatic oxidation of plant allelochemicals may result in the generation of products that either are directly toxic to maize pathogens or indirectly inhibitory due to their ability to tie up of nutrients.