Submitted to: Asian-Pacific International Society on Toxinology Congress
Publication Type: Proceedings
Publication Acceptance Date: 10/29/2008
Publication Date: 12/6/2008
Citation: Shier, W.T., Abbas, H.K. 2008. Identifying the Most Important Factors Promoting Aflatoxin and Fumonisin Contamination in Maize (Corn): Effects of Temperature and Bt-Status. Asian-Pacific International Society on Toxinology Congress. 1:148. Interpretive Summary:
Technical Abstract: 1. Background Maize (corn, Zea mays L.) is grown worldwide in both industrialized and developing countries. Maize is unusually susceptible to mycotoxin contamination, with aflatoxin being the most important mycotoxin. Our research program seeks to identify what pre-harvest factors are most important in promoting mycotoxin contamination to facilitate predicting when contamination will occur and how to prevent it. Factors promoting mycotoxin contamination are believed to be various types of plant stressors including heat, low nutrients, drought, crowding and insect predation. It is widely believed that the most important factor is high (>20oC) nighttime temperatures during the kernel-filling period. 2. Material and methods Mycotoxin levels were measured post-harvest by ELISA and HPLC in maize harvested from sample plots and correlated with regional weather data (daily high and low temperatures, precipitation and 30-year averages) provided by the US National Climate Data Center. 3. Results In 1998 the southern US experienced an unusually hot, dry summer, which favored aflatoxin production in crops, and it was followed by several summers of moderate, more nearly typical weather. In Mississippi aflatoxin levels in harvested maize kernels averaged 4,340 ppb in 1998 vs 6.2 ppb in 1999; fumonisin levels averaged 11.2 ppm in 1998 vs 2.5 ppm in 1999. In Arkansas aflatoxin levels averaged 205 ppb in 1998 vs 15.5 ppb in 1999 and 5.1 ppb in 2001; fumonisin levels averaged 46.3 ppm in 1998 vs 2.7 ppm in 1999 and 48.3 ppm in 2001. High mycotoxin production in 1998 correlated with heat stress measured as days with Tmin>20oC or total DD20 [i.e., S(Tmin + Tmax)/2 -20] during the kernel filling period. In Arkansas in 2002, 2004 and 2005 (summers with nearly typical weather) maize planted early (which typically exposes plants to more Tmin>20oC days during the kernel-filling period) yielded kernels with lower aflatoxin levels than maize planted later, suggesting that during moderate heat stress a factor(s) other than heat stress is most important for promoting aflatoxin contamination. Comparison of Bt vs non-Bt genotype has given variable results; kernels from Bt genotypes contained less aflatoxin in some studies, less fumonisin in other studies and no significant differences in other studies. 4. Conclusions Severe heat stress appears to be a major factor in promoting aflatoxin and fumonisin contamination of maize, but during moderate heat stress other factor(s) may predominate.