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United States Department of Agriculture

Agricultural Research Service

Research Project: ENHANCED INSECT RESISTANCE AND CROP MANAGEMENT FOR REDUCTION OF MYCOTOXINS IN MIDWEST CORN

Location: Crop Bioprotection Research

2010 Annual Report


1a.Objectives (from AD-416)
Make publicly available a predictive computer program for mycotoxin levels in Midwest corn and adapt as necessary for a wider range of human food use corn varieties. Use molecular biological approaches to discover, introduce, and evaluate new insect resistance genes (producing bioactive proteins and secondary metabolites), alone and in combination. Use molecular biological approaches to discover, introduce, and evaluate plant-derived selectable markers for transgenic plant production.


1b.Approach (from AD-416)
As part of the process of making the program publicly available, feedback on the present state of the program will be sought and utilized as appropriate. An electronic module to assist in making control decisions will be developed and incorporated. The program will be tested for utility in food grade corn by comparing actual field collected data with predicted levels and correcting as necessary empirically. Genes identified in the prior project that are potentially useful in combination will be examined in model systems and further evaluated. New genes of potential use will be identified through functional targeting of cDNA, array-based technology. Molecular evolution of genes coding for resistance proteins will be utilized to further optimize efficacy against insects, while at the same time minimizing vertebrate effects. Gene product efficacy will be examined in model systems and in regenerated corn. Plant-derived genes involved in toxin resistance will be the ultimate focus of the investigation, although genes from other sources will initially be examined if appropriate plant-derived gene sequence information is not yet sufficient for cloning. Efficacy of target gene products as selectable markers and against insects, alone and in combination with insect-active genes, will be investigated.


3.Progress Report
As part of the process to discover new plant-derived insect resistance compounds, several avenues were explored: --Known chemicals from crop plants were tested against insects. Chemicals from soybean and switchgrass were newly identified as promoting insect resistance. --Transgenic and bred plants expressing different potential insect defensive proteins and chemicals were assayed for insect resistance. There was some evidence that the progeny of one plant series that expressed a protein transgenically had enhanced insect resistance compared to non-transformed plants. --Switchgrass lines with varying lignin levels were evaluated for insect resistance. Some low lignin lines still retained insect resistance. As part of the process to discover improved corn inbreds to use for transformation experiments to determine new effective genes for insect resistance, several inbreds of diverse backgrounds were assayed for their ability to form callus and regenerate plants. As part of the process to determine new effective genes for insect resistance, a method was developed to more rapidly separate kernel embryos to be used for plant transformation. As part of the identification process for insect active compounds in palm, further chemical analysis determined tentative identity of major components. As part of the process to identify useful selectable markers for plant genetic transformation, a gene was introduced into corn and then tissue was evaluated for resistance to a herbicidal compound.


4.Accomplishments
1. Corn genes turned off when insect resistance was reduced are identified. Insect damage and associated ear-mold toxins cause hundreds of millions of dollars in losses each year. Corn seedlings are typically more resistant to insect pests than older plants. Using comparative gene array technology, Crop Bioprotection Research Unit scientists at the National Center for Agricultural Utilization Research Center in Peoria, IL, and cooperators at Western Illinois University, Macomb, IL, found the expression of several putative insect resistance genes was reduced as the corn plant grew and became more insect susceptible. Keeping these resistance genes turned on can potentially enhance insect resistance of corn, thereby reducing ear mold toxins, improving the health of animals and people, and increasing the exportability of U.S. corn.

2. Potential insect resistance gene combination introduced into corn enhances insect and disease resistance. Insect damage and associated ear-mold toxins cause hundreds of millions of dollars in losses each year. Scientists in the Crop Bioprotection Research Unit at the National Center for Agricultural Utilization Research in Peoria, IL, introduced gene-coding into corn for enzymes that attack different parts of an insect. The result was an enhanced resistance to caterpillars and a mycotoxin-producting fungus in plants that contained the genes compared to plants that did not have the genes. Use of these genes in appropriate corn tissues can potentially enhance insect resistance of corn, thereby reducing ear mold toxins, improving the health of animals and people, and increasing the exportability of U.S. corn.

3. New predictive computer program developed for mycotoxins in Midwest popcorn. Insect damage and associated ear-mold toxins cause hundreds of millions of dollars in losses each year. The research county area utilized is the largest popcorn growing area in the Midwest. Scientists in the Crop Bioprotection Research Unit at the National Center for Agricultural Utilization Research in Peoria, IL, did extensive data collecting of weather, pest, and mycotoxin levels from commercial fields which allowed them to develop a predictive program that significantly correlated actual vs. predicted values over a 5-year period. Use of this program in appropriate areas can allow farmers to apply controls at appropriate times and alert buyers to times when mycotoxin monitoring may be needed. These strategies would thereby reduce ear mold toxins in popcorn, improving the health of animals and people, and increasing the exportability of U.S. corn.

4. Insecticidal properties of several fungal chemicals identified. Insect damage and associated ear-mold toxins cause hundreds of millions of dollars in losses each year. Chemicals made by fungi were isolated and assayed against insects in a joint project with scientists in the Crop Bioprotection Research Unit at the National Center for Agricultural Utilization Research, Peoria, IL, and the University of Iowa, funded by NSF. Several chemicals were identified as being toxic to insects. Following appropriate toxicity testing, use of these chemicals for insect control or cloning of relevant biosynthetic genes and introduction into in appropriate corn tissues can potentially reduce insect damage of corn, thereby reducing ear mold toxins, improving the health of animals and people, and increasing the exportability of U.S. corn.


5.Significant Activities that Support Special Target Populations
A predictive computer program used as part of an ear mold toxin (mycotoxin) management program with representative farmers from a 200 farmer organization again provided useful predictions of fumonisin for corn (including popcorn) in 2009, predicting values close to those actually encountered. Evaluation of the predictive program indicated a significant association between actual vs. predicted fumonisin levels in both field corn and popcorn from 2005-2009. Average actual vs. predicted levels of aflatoxin in all fields examined through 2005-2009 were also similar. The password accessible website with this program was revised to incorporate updates. Once made widely available, this computer program should allow farmers to more economically produce larger amounts of healthier, high-quality corn with reduced levels of mycotoxins. This higher quality product should help the farmers increase sales and help livestock productivity of farmers using corn for on-farm animal feed.


Review Publications
Dowd, P.F., Johnson, E.T. 2009. Field incidence of mycotoxins in commercial popcorn and petential environmental influences. Mycotoxin Research. 26(1):15-22.

Johnson, E.T., Berhow, M.A., Dowd, P.F. 2010. Constitutive Expression of the Maize Genes B1 and C1 in Transgenic Hi II Maize Results in Differential Tissue Pigmentation and Generates Resistance to Helicoverpa zea. Journal of Agricultural and Food Chemistry. 58(4):2403-2409.

Dowd, P.F., Johnson, E.T., Pinkerton, T.S. 2010. Identification and properties of insect resistance-associated maize anionic peroxidases. Phytochemistry. 71(11-12):1289-1297. DOI: 10.1016/j.phytochem.2010.05.001

Last Modified: 9/20/2014
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