Submitted to: Phytoparasitica
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/26/2006
Publication Date: 6/1/2007
Citation: Windham, G.L., Williams, W.P. 2007. A comparison of inoculation techniques for inducing alfaltoxin contamination and Aspergillus flavus kernel infection on corn hybrids in the field. Phytoparasitica. 35:244-252. Interpretive Summary: Aflatoxin contamination of corn grain is a major problem for producers in the southern United States. The most desirable method for controlling aflatoxin contamination in corn is the use of resistant plants. To identify resistant plants, researchers must evaluate plants for aflatoxin resistance in the field. Infection by Aspergillus flavus, the fungus that produces aflatoxin, is sporadic from year to year so researchers must apply fungal spores to the test plants. Our study compared two new fungal inoculation methods to the standard inoculation method, the side-needle technique. Fungal spores were increased on corn cob grits, and corn silks were infested with this material. Fungal infection and aflatoxin levels were much higher in ears of a susceptible corn hybrid inoculated with the side-needle technique compared to ears infested with the corn cob grits. In another study, a modified pinbar was compared to the side-needle technique. The modified pinbar was constructed by embedding four small finishing nails in a wooden dowel. Ears were inoculated by dipping the modified pinbar in a fungal spore suspension and inserting the pins through the corn husks into the kernels. Ears inoculated with the modified pinbar had aflatoxin levels and fungal infection similar to ears inoculated with the side-needle technique. The modified pinbar has the potential to be a useful tool for researchers to identify aflatoxin resistant plants in the field.
Technical Abstract: Two Aspergillus flavus inoculation techniques were compared to the standard inoculation technique, the side-needle technique, on aflatoxin resistant and susceptible corn hybrids. The first study evaluated the use of A. flavus infested corn cob grits as a dry inoculum carrier. The side-needle and the dry carrier techniques produced similar levels of aflatoxin contamination in the resistant hybrid. In the susceptible hybrid, aflatoxin contamination was much higher in ears inoculated with the side-needle technique compared to the dry carrier. Aspergillus flavus kernel infection was higher in resistant and susceptible ears inoculated with the side-needle technique compared to the dry carrier. In the second study, a modified pinbar was compared to the side-needle technique. Resistant and susceptible ears inoculated with A. flavus using the modified pinbar technique had similar levels of kernel infection and aflatoxin contamination compared to ears inoculated with the side-needle technique. The modified pinbar technique has the potential of being a useful tool in evaluating corn germplasm for aflatoxin resistance.