Corn-Soybean Rotation Systems in the Mississippi Delta: Implications on Mycotoxin Contamination and Soil Populations ofAspergillus flavus

Abstract

The effect of corn-soybean rotation on mycotoxin contamination in corn (Zea maysL.) and soybean (Glycine maxL. Merrill.) grains has not been fully evaluated. Therefore, this research investigated the effect of corn-soybean rotation on aflatoxin and fumonisin contamination in respective grains. The results showed that aflatoxin levels in soybean averaged 2.3,<0.5, 0.6, and 6.8 ng/g in 2005, 2006, 2007, and 2008, while corn aflatoxin levels were 16.7, 37.1, 2.4, and 54.8 ng/g, respectively.Aspergillus flavuscolonization was significantly greater (P≤0.05) in corn (log 1.9, 2.9, and 4.0 cfu/g) compared to soybean (<1.3, 2.6, and 2.7 cfu/g) in 2005, 2007, and 2008, respectively. AflatoxigenicA. flavusisolates were more frequent in corn than in soybean in all four years. Higher fumonisin levels were found in corn (0.2 to 3.6 μg/g) than in soybean (<0.2 μg/g). Rotating soybean with corn reduces the potential for aflatoxin contamination in corn by reducingA. flavuspropagules in soil and grain and reducing aflatoxigenicA. flavuscolonization. These results demonstrated that soybean grain is less susceptible to aflatoxin contamination compared to corn due to a lower level of colonization byA. flavuswith a greater occurrence of non-aflatoxigenic isolates.