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United States Department of Agriculture

Agricultural Research Service

Research Project: Chemical Approaches to Eliminate Fungal Contamination and Mycotoxin Production in Plant Products

Location: Foodborne Toxin Detection and Prevention Research

2011 Annual Report

1a. Objectives (from AD-416)
The overarching goal of this project is to develop methods to improve the safety of our food with regard to contamination by microbial toxins, mainly mycotoxins. In this regard, the project has a series of interconnected objectives. These objectives and their interrelationships are described as follows: Objective 1: Develop detection methods for Volatile Organic Compounds (VOCs) to pinpoint food contaminants. Develop methods for identifying specific, "signature," volatile organic compounds (VOCs) as telltale indicators of microbial, mycotoxin contamination or insect infestation. This VOC detection will be applied to Objective 2. Objective 2: Develop methods for real-time detection of pathogen or insect contamination and toxins. Telltale VOCs will be used as real-time "signals" for detecting the presence of pathogens, mycotoxin-producing fungi or insects in crops or crop products, in post harvest storage or processing environments. This detectability will permit optimization of any intervention measures that are needed; which will be developed in Objective 3. Objective 3: Develop intervention technologies using plant VOCs / natural products as tools for the control of pathogens and insects. Specifically target the genetic control mechanisms through the use of chemosensitization and formulation development. Objective 4: Investigate the biochemical and genetic regulation of toxin production within fungal communities, with special emphasis on communication. Investigate the factors controlling aflatoxin catabolism and identification of the catabolic products.

1b. Approach (from AD-416)
Identify the natural constituents responsible for resistance of certain varieties of tree nuts to growth of aflatoxigenic strains of aspergillus. Isolate and identify novel metabolites in sclerotia of Aspergillus and develop analytical methods for such compounds in order to assess exposure levels of tree nut orchards to the fungus. Identify genes involved in triggering mycotoxin biosynthesis using high-through put bioassays. Assays involve use of deletion mutants, gene knockouts and complementation analysis. Discover natural compounds that disrupt functionality of gene targets identified. Develop biosensors for detecting toxic fungi in pre- and post harvest environments. Replacing 5325-42000-035-00D (1/11).

3. Progress Report
This report documents progress for the parent Project 5325-42000-037-00D CHEMICAL APPROACHES TO ELIMINATE FUNGAL CONTAMINATION AND MYCOTOXIN PRODUCTION IN PLANT PRODUCTS which started February 2011 and includes continuation of some research from Project 5325-42000-035-00D MOLECULAR AND GENETIC APPROACHES TO SUPPRESSING FUNGAL PATHOGENS AND MYCOTOXIN CONTAMINATION. This new project is organized into four objectives, as follows: 1) develop detection methodologies based on profiling volatile organic chemicals (VOCs) to identify and monitor food contaminants; 2)develop technologies and instrumentation to detect pathogens, insects, or toxins based on the activities described in the first objective; 3)identify and develop natural products to inhibit pathogens and insects directly or through chemosensitization; 4)identify factors from other microorganisms that either promote mycotoxin production or degrade mycotoxins. As of the writing of this report, this project has only a few months of research progress to report. Despite this short period of time, substantial findings have already been made, some even published. These include development of an apparatus to collect plant volatiles on a large scale basis. Some of the volatiles associated with fungal infection and aflatoxin contamination of almond have already been identified. A variety of new, safe, natural compounds have been identified that significantly synergize commercial antifungal agents. And, several fungi have been identified that have enzymatic capability of breaking down aflatoxin.

4. Accomplishments
1. Improving the efficacy of commercial fungicides with natural products. Human fungal diseases are very difficult to treat and the fungi causing these diseases are often resistant to the antifungal drugs currently available. ARS scientists at Albany, California, are looking for new methods to improve antifungal drugs. A number of safe, natural phenolic compounds were identified that synergize the activity of antifungal drugs against yeast pathogens, such as Candida sp. and Cryptococcus neoformans, two yeast pathogens that are commonly associated with mortality of humans suffering from immunodeficiency diseases. These compounds will be tested on drug resistant strains of these yeast pathogens being identified by Portuguese collaborators. This may have significant impact on the chemotherapy of patients suffering from these diseases.

2. Discovery of new target to control fungal pathogens. Fungi that infect crops are a major problem in agriculture. ARS scientists at Albany, California, are looking for new targets in fungi to improve the ability to kill them with antifungal agents. A new target for control of agricultural fungal pathogens has been identified. This target involves use of compounds that disrupt the mitochondrial respiratory complex. By disrupting this complex, we found the ability to create a vast synergism using antifungal agents. This finding could greatly impact use of agricultural fungicides, reducing dosages and costs, and concomitantly reduce the environmental hazards associated with their use.

3. Degradation of aflatoxin by microbes. Aflatoxin is a potent carcinogen that can contaminate food. ARS scientists at Albany, California, and Russian collaborators are trying to find ways to decontaminate aflatoxin contaminated products. Several culturable fungi have been identified that can completely degrade aflatoxin, when added to the culture media. The potential exists for identifying the aflatoxin degrading enzymes. Development of aflatoxin degrading technology could have some industrial application which would have a major impact on food safety and economic value of food commodities germane to the problem of aflatoxin contamination.

4. Finding the best volatile blend for the navel orangeworm (NOW). NOW feeding damage allows fungal infection of almonds. Control of this insect might be possible by using traps that have chemicals that serve as a lure. Some of these chemicals exist in almond orchards; they only need to be identified. Several candidate blends, based on volatile analyses are currently undergoing intensive field trapping studies for female NOW attractancy efficacy by ARS scientists in Albany, CA. There are combinations of such compounds that show great promise as an effective lure of NOW. These lures will be a significant tool for controlling NOW, the major insect pest of almonds and pistachios.

Review Publications
Beck, J.J., Higbee, B.S., Gee, W.S., Dragull, K.D. 2011. Ambient orchard volatiles from California almonds. Phytochemistry Letters. 4(2):199-202.

Beck, J.J., Mahoney, N.E., Cook, D., Gee, W.S. 2011. Volatile analysis of ground almonds contaminated with naturally occurring fungi. Journal of Agricultural and Food Chemistry. 59(11):6180-6187.

Faria, N.C., Kim, J.H., Goncalves, L., Martins, M., Chan, K.L., Campbell, B.C. 2011. Enhanced activity of antifungal drugs using natural phenolics against yeast strains of Candida and Cryptococcus. Letters in Applied Microbiology. 52:506-513.

Chang, P.-K., Scharfenstein, L.L., Luo, M., Mahoney, N.E., Molyneux, R.J., Yu, J., Brown, R.L., Campbell, B.C. 2011. Loss of msnA, a putative stress regulatory gene, in Aspergillus parasiticus and Aspergillus flavus increased production of conidia, aflatoxins and kojic acid. Toxins. 3:82-104.

Knight, A.L., Light, D.M., Trimble, R.M. 2011. Identifying (E)-4,8-dimethyl-1,3,7-nonatriene plus acetic acid as a new lure for male and female codling moth (Lepidoptera: Tortricidae). Environmental Entomology. 40(2):420-430.

Kim, J.H., Chan, K.L., Mahoney, N.E., Campbell, B.C. 2011. Antifungal activity of redox-active benzaldehydes that target cellular antioxidation. Annals of Clinical Microbiology and Antimicrobials. 10:23.DOI:10.1186/1476-0711-10-23.

Last Modified: 06/27/2017
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