Submitted to: Multicrop Aflatoxin and Fumonisin Elimination and Fungal Genomics Workshop-The Peanut Foundation
Publication Type: Proceedings
Publication Acceptance Date: 10/27/2004
Publication Date: 5/1/2005
Citation: Dowd, P.F., Berhow, M.A., Boston, R.S., Duvick, J.P., Johnson, E.T., Lagrimini, L.M., White, D.G. 2005. Insect management for reduction of mycotoxins FY 2004 report. In: Proceedings of the 2004 Multicrop Aflatoxin/Fumonisin Elimination and Fungal Genomics Workshop, October 16-28, 2004, Sacramento, California. p. 98.
Technical Abstract: Plant Resistance A chitinase-like gene from Arabidopsis, potentially producing a protein homologous to one previously identified with activity against insects, was introduced into maize. Insect bioassays and histochemical assays for enzyme activity of regenerated maize tissue indicated mortality levels were significantly positively correlated with histochemical ratings for enzyme activity for two series of plants tested. Further confirmatory assays and introduction of related gene forms are planned. Petunia flower assays (as a model system) coupled with individual assays of purified chemicals, suggested type and structural positioning of anthocyanin sidechain moieties influence activity against insects. Gene knock out assays with petunia, and silk specific transformation of maize are planned to better explore the potential of modifying anthocyanin to increase insect resistance. A peroxidase gene cloned from maize was identified by stable tissue expression assays as one that produces an isozyme previously identified with several types of disease resistance and may potentially contribute to insect resistance. A transformed line of Arabidopsis that continuously expresses a regulatory gene that turns on multiple defensive pathways, including anthocyanin biosynthesis, had significantly enhanced resistance to fall armyworms, but seed production was significantly decreased compared to wild type plants. This information suggests targeting fewer, more potent resistance genes may be preferable to continuous induction of multiple defensive genes. Hybrid plant seed has been produced from tobacco plants identified as expressing tobacco anionic peroxidase or maize RIP homozygously (both insect resistance genes) in order to determine if the gene combination will be compatible (additive, synergistic, or antagonistic). Some compounds involved in caterpillar silk resistance in the maize inbred Tex6 are close to being identified. Field studies Results from 2003 indicated Bt corn had significantly less fumonisin than nonBt versions in the presence of European corn borer populations in excess of about 30% with limited damage by corn earworms. Values for fumonisins obtained from corn field samples in commercial fields were close to values predicted by the predictive computer program (mostly 0.5 to 1.5 ppm). Low or no aflatoxin was predicted by the computer program, and only very low levels were found in a single sample in two fields. For 2004, only low levels of fumonisin were predicted (and no aflatoxin). Field samples from 2004 have had very little symptomatic mold (mycotoxin analysis pending). Corn rootworm beetles were very common in some fields, which was unusual for this area, but did not appear to contribute to mold problems. A commercial company has shown interest in making the predictive computer program commercially available. Publications Dowd, P.F. Validation of a mycotoxin predicting computer program for U.S. Midwest grown maize in commercial fields. Mycopathologia. 2004. 157(4):463. Dowd, P.F. Insect management to facilitate preharvest mycotoxin management. J. Toxicol. 2003. 22(23):327-350. Dowd, P.F. Reliability of a computer program for predicting mycotoxin levels in Midwestern USA corn. XI International IUPAC Symposium on Mycotoxins and Phycotoxins. 2004. Abstract #D-31. p. 102. Dowd, P.F. Considering the importance of insect resistance in corn ears in relation to the contribution of insects to the mycotoxin problem. Proceedings, 40th Annual Illinois Corn Breeders School, March 1-2, 2004. University of Illinois, Urbana, IL. 2004. pp. 127-137. Johnson, E.T., Dowd, P.F. Management of insects involved in pre-harvest mycotoxin contamination in corn. XI International IUPAC Symposium on Mycotoxins and Phycotoxins. 2004. Abstract #C-07. p. 79. Johnson, E.T., Dowd, P.F. Methylation of an anthocyanin increases its abi