2013 Annual Report
Over the next 5 years our research will focus on the following objectives:
Objective 1: Determine the environmental fate of non-toxigenic strains of Aspergillus (A.) flavus using molecular tools. Sub-Objective 1a. Compare DNA sequence information from current biocontrol strains with indigenous strains to identify unique molecular markers. Sub-Objective 1b. Monitor the post-release spatial and temporal distribution of A. flavus biocontrol strains in corn fields.
Objective 2: Determine the mechanisms of biocontrol efficacy with non-toxigenic Aspergillus flavus strains.
Objective 3: Optimize a water dispersible formulation and application procedure for the use of non-toxigenic strains of Aspergillus flavus for biocontrol of mycotoxins in corn. Sub-Objective 3a. Develop and evaluate water dispersible granular (WDG) formulation of non-toxigenic Aspergillus flavus strains. Sub-Objective 3b. Evaluate the Accu-Flo™ spray nozzle for aerial application of biological materials. Sub-Objective 3c. Determine the effect of timing of the application of K49 and Afla-Guard® as a WDG formulation. Sub-Objective 3d. Compare the effect of a combined inoculum of K49 and Afla-Guard® to these inoculants used separately.
Objective 1: HiSEQ Illumina-based sequencing was performed on 2 commercially available and 1 experimental biocontrol strain and is being compared to a native toxin-producing strain. Subsequently, the sequence data was mapped to a published sequence and a de novo assembly has been performed on each strain. Additional sequencing has been performed on 150 Mississippi-native strains to evaluate indigenous diversity. The second season of the four-year study has been planted on a private farm and biocontrol strains have been applied. Soil samples were collected and Aseprgillus (A.) flavus strains were isolated as a reference for the A. flavus population prior to introduction of biocontrol strains.
Objective 2: An assay was developed for the in vitro study of competition by measuring fungal growth and aflatoxin production.
Objective 3: Fungal spores of both strains K49 and Afla-Guard were mass produced as a Water Dispersible Granule (WDG) formulation in 2013. Research on biological methods for controlling aflatoxin in corn is progressing with difficulties such as weather effects, lands, and lack of equipment availability in 2013. Field studies in several locations for optimizing WDG formulation for improvement of delivery of both non-toxigenic Aspergillus flavus K49 and Alfa-Guard strains is in its second season. These studies included rate of application; time of application; and mixed vs sole application of both strains of WDG formulation. Some applications were missed as indicated above. The WDG formulation of both strains was provided to ARS scientist (collaborator) to perform preliminary evaluation of droplet characteristics in 2012 and 2013 in order to determine useful data that could be used for adjusting droplet size in field aerial application of WDG by plane. Accu-Flo® nozzles obtained for correct droplet size range had needles too small to pass the formulation. Alternative nozzles with larger openings have been ordered and pattern tests will be conducted using these new nozzles. A filtration scheme may also be considered as long as liquid pressure drop is not too large.
Abbas, H.K., Mascagni, Jr., H.J., Bruns, H.A., Shierd, W.T., Damanne, K.E. 2012. Effect of planting density, irrigation regimes, and maize hybrids with varying ear size on yield, and aflatoxin and fumonisin contamination levels. American Journal of Plant Sciences. 3:1341-1354.
Kebede, H.A., Abbas, H.K., Fisher, D.K., Bellaloui, N. 2012. Relationship between aflatoxoin contamination and physiological responses of corn plants under drought and heat stress. Toxins. 4:1385-1403.
Manning, B. B., Abbas, H. K. 2012. nThe effect of Fusarium mycotoxins deoxynivalenol, Fumonisin, and Moniliformin from contaminated moldy grains on aquaculture fish. Toxin Reviews. 31:1-5.
Willcox, M., Davis, G., Warburton, M.L., Windham, G.L., Abbas, H.K., Betran, J., Holland, J.B., Williams, W.P. 2013. Confirming quantitative trait loci for aflatoxin resistance from Mp313E in different genetic backgrounds. Molecular Breeding. 32(1):15-26.
Bellaloui, N., Mengistu, A., Fisher, D.K., Zobiole, L.H., Abbas, H.K. 2012. Irrigation management: effects of soybean diseases on seed composition in genotypes differing in their disease resistance under irrigated and nonirrigated conditions. Nova Hedwigia. 1:1-42.
Koger III, C.H., Zablotowicz, R.M., Patterson, M.R., Walker, T.W., Weaver, M.A., Street, J.E. 2013. Effect of Winter Flooding on Weeds, Soybean Yield, Straw Degradation, and Soil Microbiol Activity. American Journal of Plant Sciences. 4:10-18.
Manning, B.B., Abbas, H.K., Wise, D.J., Greenway, T. 2013. The effect of feeding diets containing deoxynivalenol contaminated corn on channel catfish (Ictalurus punctatus) challenged with Edwardsiella ictaluri. Aquaculture Research, 1-5; doi:10.1111/are.12123.
Herath, B., Jacob, M., Wilson, A., Abbas, H.K., Nanayakkara, D. 2012. New secondary metabolites from bioactive extracts of the fungus Armillaria tabescens. Journal of Natural Products. 27(17):1562-1568.
Abbas, H.K., Bellaloui, N., Zablotowicz, R.M., Bruns, H.A., Gillen, A.M. 2012. Corn-soybean rotation systems in the Mississippi Delta, implications on mycotoxin contamination and soil populations of Aspergillus flavus. International Journal of Agronomy. 2012, Article ID 935463, 7 pages doi:10.1155/2012/935463.