Location: Peanut Research
2011 Annual Report
2. Determine characteristics of soil populations important for invasion of peanut seeds by aflatoxigenic fungi and evaluate the competitiveness of nontoxigenic biocontrol strains of A. flavus.
3. Determine the chemical barriers of peanut to fungal challenge, particularly challenge by A. flavus. Investigate the basis for greater resistance to A. flavus invasion and aflatoxin contamination possessed by certain peanut genotypes for possible exploitation in breeding programs.
4. Conduct the necessary laboratory and field trials required by the EPA to extend the use of Aflaguard to other crops susceptible to aflatoxin, such as corn.
Native fungal populations in 20 different soils will be quantified and species will be identified either directly on the dilution plates or by subculturing to Czapek agar slants. Peanut seeds will be aseptically wounded and inoculated with 7.0 mg of soil paste using a small spatula. Forty seeds will be inoculated with each soil and incubated 14 d at 37 C. Twenty-four uninoculated wounded seeds will serve as controls in each experiment. A. flavus and A. parasiticus sporulating on seeds will be identified by subculturing to Czapek agar slants. In a related series of experiments, nontoxigenic biocontrol strains (conidial-color mutant A. parasiticus NRRL 21369 and a nitrate-nonutilizing mutant of A. flavus NRRL 21882) will be added to soils at different concentrations to examine their interactions with native aflatoxin-producing populations. Aflatoxin analyses of individual seeds will be performed by extracting overnight in methanol and quantifying with high performance liquid chromatography.
A series of experiments will be conducted to.
Evaluation of eight non-toxigenic strains of A. flavus for biological control of aflatoxin was completed and the data were analyzed statistically. The laboratory assay involved the co-inoculation of viable, artificially wounded peanut seeds with mixtures of non-toxigenic and aflatoxin-producing strains. Eight non-toxigenic strains (including the strain present in Afla-Guard®) that differed genetically in their inability to produce aflatoxin were paired with eight genetically different aflatoxin-producing strains in all combinations. Five of the eight non-toxigenic strains were superior to the Afla-Guard® strain in reducing aflatoxin in peanuts.
The dynamics of phytoalexin synthesis in seeds from different peanut genotypes were investigated. Disease-resistant cultivars demonstrated a faster defensive response to fungal invasion and a higher production of stilbenoid phytoalexins compared to susceptible peanut cultivars. In addition, the first systematic study on the biological activity of all known peanut stilbenoids and their analogs was completed. New stilbenoids were discovered and examined for biological activity. These compounds possessed significantly higher activity against fungal pathogens than other major peanut stilbenoids. Furthermore, the new stilbenoids showed strong antioxidant, anticancer and anti-inflammatory properties in a panel of human cell lines. Lower hydrophobicity of stilbenoids was associated with higher biological activity in numerous fungal and human-cell assays. The position of hydroxy and prenyl groups on the carbon skeleton of stilbenoids had a significant effect on their biological activity.
Molecular markers are being developed to aid in the breeding of peanuts for disease resistance. A phytoene desaturase gene is being tested as a selectable marker for herbicide resistance in peanut in the development of a method for genetic transformation. Molecular markers for Valencia peanut also are being developed in collaboration with the University of New Mexico to be used in their breeding program. In addition, molecular markers are being developed for Cercospora species that infect soybeans and peanuts.
This bridged project replaces #6604-42000-008-00D through review of the National Program.
Arias, R.S., Blanco, C.A., Portilla, M., Snodgrass, G.L., Scheffler, B.E. 2011. First microsatellites from Spodoptera frugiperda (Lepidoptera: Noctuidae) and their potential use for population genetics. Annals of the Entomological Society of America. 104(3):576-587.
Arias, R.S., Ray, J.D., Mengistu, A., Scheffler, B.E. 2011. Discriminating microsatellites from Macrophomina phaseolina and their potential association to biological functions. Plant Pathology. 60(4):709-718 DOI:10.1111/j.1365-3059.2010.02421.x.
Arias, R.S., Stetina, S.R., Scheffler, B.E. 2011. Comparison of whole-genome amplifications for microsatellite genotyping of Rotylenchulus reniformis. Electronic Journal of Biotechnology. DOI:10.2225/vol14-issue3-fulltext-13.
Arias, R.S., Techen, N., Rinehart, T.A., Olsen, R.T., Kirkbride, J.H., Scheffler, B.E. 2010. Development of simple sequence repeat markers for Chionanthus retusus (Oleaceae) and effective discrimination of closely related taxa. HortScience. 46(1):23-29.
Blanco, C., Portilla, M., Jurat-Fuentes, J., Sanchez, J.F., Viteri, D., Vega-Aquin, P., Teran-Vargas, A.P., Azuara-Dominguez, A., Lopez, J., Arias De Ares, R.S., Zhu, Y., Barrera, D., Jackson, R.E. 2010. Susceptibility of Spodoptera frugiperda (Lepidoptera: noctuidae) isofamilies to Cry1Ac and Cry1F proteins of Bacillus thuringiensis. Southwestern Entomologist. 35(3):409-415.
Han, K.M., Dharmawardhana, P., Arias, R.S., Ma, C., Busov, V., Strauss, S.H. 2011. Gibberellin-associated cisgenes modify growth, stature and wood properties in Populus. Plant Biotechnology Journal. 9(2):162-178.
Sobolev, V., Khan, S.I., Tabanca, N., Wedge, D.E., Manly, S.P., Cutler, S.J., Coy, M.R., Becnel, J.J., Neff, S.A., Gloer, J.B. 2011. Biological Activity of Peanut (Arachis hypogaea) Phytoalexins and Selected Natural and Synthetic Stilbenoids. Journal of Agricultural and Food Chemistry. 59:1673-1682.
Sheppard, G.S., Berthiller, F., Dorner, J.W., Lombaert, G.A., Malone, B., Maragos, C.M., Sabino, M., Solfrizzo, M., Trucksess, M.W., Van Egmond10, H.P., Whitaker, T.B. 2010. Developments in mycotoxin analysis: an update for 2008-2009. World Mycotoxin Journal. 3(1):3-23.
Horn, B.W., Moore, G.G., Carbone, I. 2011. Sexual reproduction in aflatoxin-producing Aspergillus nomius. Mycologia 103:174-183.
Abbas, H.K., Zablotowicz, R.M., Horn, B.W., Phillips, N.A., Johnson, B.J., Jin, X., Abel, C.A. 2011. Comparison of major biocontrol strains of non-aflatoxigenic Aspergillus flavus for the reduction of aflatoxins and cyclopiazonic acid in maize. Journal of Food Additives & Contaminants. 28:198-208.
Horn, B.W., Dorner, J.W. 2011. Evaluation of different genotypes of nontoxigenic Aspergillus flavus for their ability to reduce aflatoxin contamination in peanuts. Biocontrol Science and Technology. 21(7):865-876.
Sobolev, V., Neff, S.A., Gloer, J.B., Khan, S.I., Tabanca, N., De Lucca Ii, A.J., Wedge, D.E. 2010. New pterocarpenes elicited by Aspergillus caelatus in peanut (Arachis hypogaea) seeds. Phytochemistry and Agriculture. 71:2099-2107.