Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 10/23/2002
Publication Date: 10/23/2002
Citation: Williams, W.P., Windham, G.L., Buckley, P.M., Daves, C. 2002. Aflatoxin accumulation in conventional and transgenic corn hybrids infested with southwestern corn borer (Lepidoptera: Crambidae)[abstract]. Proceedings of the 2nd funal Genomics, 3rd Fumonisin Elimination Workshops. p. 109.
Technical Abstract: Aflatoxin is a potent carcinogen produced by the fungus Aspergillus flavus. Aflatoxin contamination of corn greatly diminishes its value and is a major impediment to profitable corn production in the South. Aflatoxin contamination is frequently linked with drought, high temperatures, and insect damage. Southwestern corn borer, Diatraea grandiosella, and corn earworm, Helicoverpa zea, are major insect pests in the southern United States. Both insects have been linked to high levels of aflatoxin contamination. Genetically engineered corn hybrids expressing genes from Bacillus thurgiensis that encode proteins with insecticidal properties provide farmers with new opportunities for insect control. This investigation was conducted to compare aflatoxin contamination levels for Bt and non-Bt corn hybrids following inoculation with A. flavus and infestation with southwestern corn borer. In 2000 and 2001, five pairs of commercially available conventional and transgenic Bt corn hybrids were inoculated with an A. flavus spore suspension using either an injection into the side of the ear, which wounded kernels, or weekly sprays, which did not wound kernels. An additional treatment consisted of weekly sprays with a spore suspension and infestation of developing ears with southwestern corn borer larvae. An uninfested and uninoculated control was also included. Aflatoxin contamination of Bt and non-Bt hybrids was compared following the four treatments. Larval survival and ear damage were compared in additional plots infested with southwestern corn borer. The side needle, or kernel-wounding, technique resulted in the highest levels of aflatoxin contamination in both 2000 and 2001. In 2000, differences between non-Bt and Bt hybrids were not significant. Aflatoxin contamination was significantly higher in hybrids infested with southwestern corn borer and inoculated with A. flavus than in hybrids that were only inoculated with A. flavus. The Bt hybrids exhibited less ear damage from insect feeding and lower levels of aflatoxin contamination than non-Bt hybrids. Only 0.1 southwestern corn borer larva per plant was recovered from ears of Bt hybrids 14 days after infestation with 60 southwestern corn borer larvae per plant, but 0.9 larva per plant was recovered from non-Bt hybrids. Although not artificially infested with corn earworm larvae, approximately 0.5 larva per plant was recovered from ears of both Bt and non-Bt hybrids. In areas where southwestern corn borer is a problem, Bt hybrids could play a significant role in reducing aflatoxin contamination.