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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

2009 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 economic 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 insect 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
Determining when to apply management tactics for toxin-producing ear molds of corn and developing corn that is more resistant to the insects that damage corn and promote establishment of the toxin-producing molds, can greatly increase the safety and exportability of U.S. corn. The previous developed computer program for predicting mycotoxins in Midwest corn was upgraded on a password entry governed, publicly accessible website. Evaluation of the predictive program indicated significant correlations for actual vs. predicted levels of a mycotoxin for field corn and popcorn from 2005-2008. Sufficient data for an additional mycotoxin (deoxynivalenol) appears to have been collected to develop a predictive module for this fungal toxin in Midwest corn. Corn genes coding for two insect skin degrading enzymes were cloned. Additional plants producing a modified peptide with activity against insects were evaluated for insect resistance. Palm and sedge extracts toxic to insects were separated into one major component and a few minor components for each extract. Fungal extracts and pure compounds were evaluated for insect toxicity. Additional corn plants that produce an enzyme that potentially makes new insect resistance chemical(s) were evaluated for corn earworm resistance. Insect resistance genes of corn that turn on during plant growth were identified through array analysis. The correct gene coding for an enzyme that is involved in a "switch" that turns on some insect and disease resistance genes was identified through expression studies. Corn plants that produced a novel protein with multifunctional activity were evaluated for insect and herbicide resistance. Switchgrass lines with varying lignin levels (an insect resistance mechanism) were evaluated for fall armyworm feeding. This progress will lead toward more effective means of reducing levels of mold toxins in corn, thereby resulting in a more marketable crop for farmers, a more acceptible crop for buyers, and a safer crop for humans and animals.


4.Accomplishments
1. CORN GENE INVOLVED IN INSECT AND FUNGAL RESISTANCE "SWITCH" IDENTIFIED. Insect damage and associated ear-mold toxins cause hundreds of millions of dollars in losses each year. Candidates of corn genes were cloned, expressed in bacteria, and evaluated for the resulting enzyme's ability to synthesize a specific compound that serves as a "switch" to turn on some insect and disease resistance pathways in corn. The enzyme coded by only one gene was able to do the specific synthesis, indicating it is the "switch" gene. Use of this gene can potentially enhance both disease and insect resistance of corn, thereby increasing reduction of ear mold toxins, improvement of health in animals and people, and increased exportability of U.S. corn.

2. PLANT GENE INTRODUCED INTO CORN ENHANCES INSECT RESISTANCE. Insect damage and associated ear-mold toxins cause hundreds of millions of dollars in losses each year. A corn gene that turns on pigment production was modified to be expressed in all tissues. Lines producing the pigment had enhanced insect resistance. Use of this gene in appropriate corn tissues can potentially enhance insect resistance of corn, thereby increase reduction of ear mold toxins, improve health in animals and people, and increase 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 2008 and predicted 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 2005-2008. Actual vs. predicted levels of aflatoxin in all fields combined through the same period were also associated. 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.


6.Technology Transfer

Number of Invention Disclosures Submitted2
Number of Web Sites Managed1

Review Publications
Dowd, P.F., Johnson, E.T., Pinkerton, T.S., Hughes, S.R. 2008. Genetically modified plants containing plant-derived genes for broad spectrum insect control to reduce mycotoxins. In: Wolf, T.V. and Koch, T.J.P., editors. Bioactive Proteins. Hauppauge, NY: Nova Science Publishers. p. 127-150.

Johnson, E.T., Dowd, P.F., Pinkerton, T.S. 2008. Altering plant secondary metabolism to achieve broad spectrum insect control and reduce mycotoxins. In: Wolf, T. and Koch, J., editors. Genetically Modified Plants: New Research Trends. Hauppauge, NY: Nova Science Publishers. p. 151-172.

Dowd, P.F., Johnson, E.T. 2009. Differential resistance of switchgrass Panicum virgatum L. lines to fall armyworms Spodoptera frugiperda (J. E. Smith). Genetic Resources and Crop Evolution. 56:1077-1089. DOI: 10.1007/s10722-009-9430-6

Last Modified: 10/1/2014
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