Location: Biological Control of Pests Research2017 Annual Report
The overall objective of this project is the improved biological control of aflatoxin in corn through a more complete ecological understanding of the pathogen and the agroecosystem through applied investigation of biocontrol agent delivery systems. Over the next 5 years, our research will focus on the following objectives: Objective 1: Enhance shelf life, survival growth, germination, and host colonization of biocontrol agents for aflatoxin management through formulation improvements. Objective 2: Refine aerial, foliar and seed treatment application strategies of biocontrol agents for aflatoxin management. Objective 3: Develop and implement molecular markers for post-release tracking of foliar and seed treatment biocontrol applications. Objective 4: Determine population size, chemotype and mating type frequency in soil-borne Aspergillus (A.) flavus populations and subsequent infections in corn to improve predictions of aflatoxin risk and enhance biocontrol measures. Sub-Objective 4a.Correlation of aflatoxin contamination of corn with the population distribution of A. flavus in soil. Sub-Objective 4b. Correlating A. flavus mating type with corn infection. Objective 5: Apply novel formulation and application technology to other pathogen biocontrol systems.
Biological control technology is an effective method for reducing aflatoxin contamination in corn; however, present formulation and application strategies are still rudimentary and fundamental gaps remain in our knowledge of the population structure of Aspergillus (A.) flavus. Improved application technology will be developed aimed at increasing adoption of biocontrol measures by increasing efficacy and convenience of the application systems. Although previous efforts using a water dispersible formulation did not meet industry standards, they provided avenues for further research using bioplastic as a vector for application of biocontrol agents. Corn starch-based bioplastics are naturally-derived, biodegradable, recyclable, inexpensive, and provide nutrition favoring fungal growth after application. Bioplastics are easily prepared by heating commercial bioplastic for 2-3 hours at 80-90°C and applying (i.e., aerial, foliar, and seed treatment) after cooling. Bioplastic vectors promise to provide effective, efficient delivery of biocontrol agents. We also plan to develop and implement molecular markers for post-release monitoring of biological control agents. The resulting data will enable optimizing delivery tools to meet industry standards. Knowledge of local A. flavus population size, chemotype and mating type frequency will also lead to a better understanding of aflatoxin risk and permit more sound decisions of when fields warrant application of commercial biocontrol products. Domestic and international industrial companies have already inquired and invested in the development of this technology for control of various agricultural pests beyond just A. flavus. Optimization of these techniques during the next five years will improve the efficiency and practicality of biocontrol agents used in agriculture.
This project has been certified and began in March 2017. A copious amount of non-toxigenic strains of Aspergiullus (A.) flavus (strains K49 and Afla-Guard) spores were produced. Preliminary laboratory evaluations of spores, including viability, germination, concentration and quality control, were conducted to determine purity of the spores. Preliminary studies for corn seed treatments and sprayable formulation of non-toxigenic A. flavus formulated in starch-based material (bioplastic) were conducted in the field. These experiments are proceeding in spite of difficult weather conditions and limited availability of field equipment and personnel needed to accomplish the goals of this objective. Some of the research in this project plan is being conducted in collaboration with scientists nationally and internationally. Locations have been identified for corn soil survey and isolation of A. flavus from corn. Contacts with local famers have been made to facilitate acquisition of aflatoxin-contaminated corn.
1. Reductions of Aflatoxin in the Field. ARS Scientiest at Stoneville, Mississippi, conducted peliminary field evaluations using Aspergiullus flavus (Strain K49) to determine the efficacy under field conditions to control aflatoxin in pre-harvest corn. Planting the fully-protected seed resulted in an average of 84.0% reduction in aflatoxin levels. The application of the biocontrol agent has been utilized to optimize the application method using sprayable, granule application, and/or seed treatment techniques of a corn-starch based formulation, called “bioplastic”. Results from the present study opened the potential for a novel technical approach for reducing the risk of aflatoxin contamination in corn by using a reduced dose of inoculum (spores) of biocontrol isolates. The results from this study will provide useful information to the public and private sector research units including ARS, academia, and industrial grain producers.
2. Loop-mediated amplification primer development. ARS researchers at Stoneville, Mississippi, have investigated the population diversity of Aspergiullus flavus in agricultural soils and in aflatoxin-contaminated grain. Traditional methods involve DNA extraction, which can be expensive and time-consuming from soil, but the new methods reduce the extraction steps and allow amplification and analysis of DNA more directly from samples. This method will facilitate the analysis of a greater number of samples and a more complete understanding of this pathogen.
Guo, B., Ji, X., Ni, X., Fountain, J.C., Li, H., Abbas, H.K., Lee, D., Scully, B.T. 2017. Evaluation of maize inbred lines for resistance to pre-harvest aflatoxin and fumonisin contamination in the field. The Crop Journal. 5:259-264. doi:10.1016/j.cj.2016.10.005.
Accinelli, C., Abbas, H.K., Little, N., Kotowicz, J.K., Mencarelli, M., Shier, T.W. 2016. A liquid bioplastic formulation for film coating of agronomic seeds. Crop Protection. 89:123-128.
Weaver, M.A., Abbas, H.K., Brewer, M.J., Prueter, L.S., Little, N. 2017. Integration of biological control and transgenic insect protection for mitigation of mycotoxins in corn. Crop Protection Journal. 98:108-115.
Weaver, M.A., Abbas, H.K., Jin, X., Elliott, R.B. 2016. Efficacy of water dispersible formulations of biocontrol strains of Aspergillus flavus for aflatoxin management in corn. Food Additives & Contaminants. 33:346-351.
Weaver, M.A., Boyette, C.D., Hoagland, R.E. 2016. Rapid kudzu eradication and switchgrass establishment though herbicide, bioherbicide and integrated programs. Biocontrol Science and Technology. 26:640-650.
Abbas, H.K., Shier, W.T., Plasencia, J., Weaver, M.A., Bellaloui, N., Kotowicz, J.K., Accinelli, C., Torre-Hernandez, M., Zablotowicz, R.M. 2016. Mycotoxin contamination in corn smut (Ustilago maydis) galls in the field and in the commercial food products. Food Research International. 71:57-63.