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United States Department of Agriculture

Agricultural Research Service

Research Project: ENHANCING CORN WITH RESISTANCE TO AFLATOXIN CONTAMINATION AND INSECT DAMAGE Title: Comparison of Inoculation Methods for Evaluating Maize for Resistance to Aspergillus flavus Infection and Aflatoxin Accumulation

Authors
item Williams, William
item Alpe, Michael
item Windham, Gary
item Ozkan, Seval -
item Mylroie, John

Submitted to: International Journal of Agronomy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 20, 2013
Publication Date: November 20, 2013
Citation: Williams, W.P., Alpe, M., Windham, G.L., Ozkan, S., Mylroie, J.E. 2013. Comparison of two inoculation methods for evaluating maize for resistance to Aspergillus flavus infection and aflatoxin accumulation. International Journal of Agronomy. 2013:972316. DOI:10.1155/2013/972316.

Interpretive Summary: Aflatoxin, causes cancer in humans and is toxic to livestock, pets, and wildlife. It is produced by the fungus Aspergillus flavus and is found corn, peanuts, and other crops. Growing corn hybrids with genetic resistance to aflatoxin contamination is generally considered a highly desirable way to reduce losses to aflatoxin. Developing resistant hybrids requires reliable inoculation methods to screen corn germplasm for resistance to A. flavus infection and aflatoxin accumulation. A technique using a tree marking gun to inject an A. flavus conidial suspension underneath the husks into the side of the ear was developed by USDA-ARS scientists at Mississippi State 25 years ago and is still widely used. This technique, referred to as the side-needle technique, physically wounds the ear of corn and bypasses some potential mechanisms of resistance such as good husk coverage. It is also labor intensive. In the current study a second inoculation method which involves placement of wheat kernels infected with A. flavus into plant whorls at 35 and 49 days after planting was evaluated and compared with the side-needle technique for two years. Results showed that although the side-needle technique produced higher levels of aflatoxin accumulation, the difference in A. flavus biomass produced by the two inoculation techniques was not significant. Both inoculation techniques were effective in differentiating resistant and susceptible single cross hybrids irrespective of the use of A. flavus infection or aflatoxin accumulation as a basis to define resistance. This technique will be useful in breeding corn hybrids with resistance to aflatoxin accumulation.

Technical Abstract: Aflatoxin, the most potent carcinogen found in nature, is produced by the fungus Aspergillus flavus. Aflatoxin occurs naturally in maize, Zea mays L. Growing maize hybrids with genetic resistance to aflatoxin contamination is generally considered a highly desirable way to reduce losses to aflatoxin. Developing resistant hybrids requires reliable inoculation methods to screen maize germplasm for resistance to A. flavus a infection and aflatoxin accumulation. A technique using a tree marking gun to inject an A. flavus conidial suspension underneath the husks into the side of the ear was developed by USDA-ARS scientists at Mississippi State and is widely used. This technique, referred to as the side-needle technique, physically wounds the ear and, thus, limits the expression of some potential mechanisms of resistance. It is also labor intensive. In the current investigation, a second inoculation method that involves placement of wheat kernels infected with A. flavus into plant whorls at 35 and 49 days after planting was evaluated together with the side-needle technique for two years. Results showed that although the side-needle technique produced higher levels of aflatoxin accumulation, the difference in A. flavus biomass produced by the two inoculation techniques was not significant. Both inoculation techniques were effective in differentiating resistant and susceptible single cross hybrids irrespective of the use of A. flavus infection or aflatoxin accumulation as a basis to define resistance.

Last Modified: 12/19/2014
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