ARS | Publication request: Evaluation of maize inbred lines for resistance to Aspergillus and Fusarium ear rot and mycotoxin accumulation

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 6, 2009
Publication Date: N/A

Interpretive Summary: Fungi contaminate corn. Some of these fungi are especially problematic because they grow on the corn ear and contaminate the grain. Although fungal contamination of grain is bad, toxic byproducts produced by the fungi are worse. Toxins from these fungi contaminate corn grain worldwide and pose a threat to both human food safety and animal feed ingredients. Ideally, we would like to identify corn plants that are not affected by the various fungi and do not accumulate toxin in the grain. To this end, a select group of inbred corn lines was evaluated in field trials for mycotoxin accumulation in grain and ear rot caused by Aspergillus flavus and Fusarium verticillioides. Our goal was to identify lines resistant to both fungi. Inbred lines were inoculated with the fungi and after harvest ears were rated for rot and toxins. Several of the inbred lines in our study exhibited resistance to both of the fungi we applied. Inbred line Mp317 has previously demonstrated low levels of F. verticillioides kernel infection and also had low levels of aflatoxin contamination. F. verticillioides and A. flavus ear rot measured in (cm2) was significantly correlated to toxin production for both fumonisin and aflatoxin, indicating that inbreds exhibiting aflatoxin resistance may also be good sources of fusarium resistance. Our method of measuring ear rot may also be used to rapidly screen lines for A. flavus resistance and subsequent aflatoxin accumulation in preliminary evaluations. In summary, it appears that lines resistant to fungus may also be resistant to other fungi and ear rot may be useful to rapidly screen varieties in the field.

Technical Abstract: Mycotoxin contamination in corn grain is a worldwide threat to both human food safety and animal feed ingredients. A select group of inbred corn lines was evaluated in field trials for mycotoxin accumulation in grain and ear rot caused by Aspergillus flavus and Fusarium verticillioides. Our goal was to identify lines resistant to both fungi. In separate tests, 20 inbred lines were inoculated with either A. flavus or F. verticillioides. After harvest, ears were rated for rot and levels of aflatoxin or fumonisin contamination were quantified. Aflatoxin resistant inbred line Mp717 had the lowest levels of fumonisin contamination. Inbred line Mp317 has previously demonstrated F. verticillioides kernel infection had low levels of aflatoxin contamination. F. verticillioides and A. flavus ear rot measured in (cm2) was significantly correlated to toxin production for both fumonisin (p = 0.0002; r = 0.74) and aflatoxin (p = 0.004; r = 0.61), respectively, indicating that inbreds exhibiting aflatoxin resistance may also be good sources of fusarium resistance. Our method of quantifying ear rot may also be used to rapidly screen lines for A. flavus resistance and subsequent aflatoxin accumulation in preliminary evaluations.