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United States Department of Agriculture

Agricultural Research Service

Title: Comparison of Two Inoculation Methods for Evaluating Corn for Resistance to Aflatoxin Contamination

Authors
item Buckley, Paul
item Williams, William
item Windham, Gary

Submitted to: Mississippi Agricultural and Forestry Experiment Station Research Report
Publication Type: Experiment Station
Publication Acceptance Date: August 1, 2006
Publication Date: April 1, 2006
Citation: Buckley, P.M., Williams, W.P., Windham, G.L. 2006. Comparison of two inoculation methods for evaluating corn for resistance to aflatoxin contamination. Mississippi Agricultural and Forestry Experiment Station Bulletin 1148. 6 pp.

Interpretive Summary: Aflatoxin, produced by the fungus Aspergillus flavus, is a naturally occurring toxin in corn and the most potent carcinogen found in nature. Aflatoxin contamination is a major obstacle to profitable corn production in the southern United States. Growing aflatoxin resistant hybrids is generally considered the best strategy for reducing or eliminating aflatoxin contamination; however, hybrids with adequate levels of resistance are not currently available commercially. The development of corn hybrids with resistance to aflatoxin accumulation depends on successfully differentiating among corn genotypes with varying degrees of resistance and susceptibility to aflatoxin contamination. Numerous methods have been used to inoculate developing ears of corn with an A. flavus spore suspension to improve the chances of correctly identifying resistant genotypes. For almost 20 years, the side-needle technique has been the primary method of inoculation at Mississippi State. With this method, a tree-marking gun is fitted with a 14-gage needle; the needle is inserted under the husks; and a suspension of A. flavus conidia is injected over the kernels. This method is time consuming and causes physical injury to the ear. In this investigation, an alternate method of inoculation was compared with the side-needle inoculation. The husks and silks of developing ears were sprayed weekly for five weeks with a spore suspension using a backpack sprayer. Although the spray inoculation resulted in lower levels of aflatoxin accumulation than the side-needle technique, both methods differentiated between resistant and susceptible genotypes. Because the multiple-spray method of inoculation does not wound the ear, it can be used to evaluate the effects of resistance-related traits in husks and silks that would not be apparent with the side-needle technique. This method of inoculation can also be used when evaluating the benefits of insect resistance in reducing aflatoxin contamination. The availability of this technique should hasten the development and marketing of corn hybrids with resistance to aflatoxin contamination.

Technical Abstract: Aflatoxin, produced by the fungus Aspergillus flavus, is a naturally occurring toxin in corn, Zea mays L., and the most potent carcinogen found in nature. Plant resistance is generally considered the best strategy for reducing or eliminating aflatoxin contamination. The development of corn hybrids with resistance to aflatoxin accumulation depends on successfully differentiating among corn genotypes with varying degrees of resistance and susceptibility to fungal infection and aflatoxin accumulation. Numerous methods have been used to inoculate developing ears of corn with an A. flavus spore suspension to improve the chances of correctly identifying resistant genotypes. For almost 20 years, the side-needle technique has been the primary method of inoculation at Mississippi State. With this method, a tree-marking gun is fitted with a 14-gage needle; the needle is inserted under the husks; and a suspension of A. flavus conidia is injected over the kernels. This method is time consuming and causes physical injury to the ear. In this investigation, an alternate method of inoculation was compared with the side-needle inoculation. The husks and silks of developing ears were sprayed weekly for five weeks with a spore suspension using a backpack sprayer. Although the spray inoculation resulted in lower levels of aflatoxin accumulation than the side-needle technique, both methods differentiated between resistant and susceptible genotypes in most environments. Because the multiple-spray method of inoculation does not wound the ear, it can be used to evaluate the effects of resistance-related traits in husks and silks that would not be apparent with the side-needle technique. This method of inoculation can also be used when evaluating the benefits of insect resistance in reducing aflatoxin contamination.

Last Modified: 4/23/2014
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