Aflatoxin accumulation in corn (Zea may L.) influenced by cultural production practices in the U.S. Mid-South

Authors: WILLIAMS, J - Mississippi State University; HENRY, W - Mississippi State University; Smith, Jesse; BUEHRING, N - Mississippi State University; BOYKIN, D - Retired ARS Employee

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/9/2020
Publication Date: 1/25/2021
Publication URL: https://handle.nal.usda.gov/10113/7709369
Citation: Williams, J.J., Henry, W.B., Smith, J.S., Buehring, N.W., Boykin, D.L. 2021. Aflatoxin accumulation in corn (Zea may L.) influenced by cultural production practices in the U.S. Mid-South. Crop Science. 61:729-738. https://doi.org/10.1002/csc2.20330.
DOI: https://doi.org/10.1002/csc2.20330

Interpretive Summary: Aspergillus flavus is a pathogen of corn that infests developing corn ears. Aspergillus flavus produces toxic compounds called aflatoxins that can contaminate corn grain prior to harvest. Aflatoxin contaminated corn grain poses health threats to consumers and economic threats to farmers. Corn is more susceptible to A. flavus during periods of stress caused by heat, drought, and insect damage. Farming practices intended to manage aflatoxin contamination in corn grain typically aim to reduce aflatoxin by reducing these sources of plant stress. The present study tested the effect of three cultural practices (selection of hybrid type, planting date, and irrigation level) on aflatoxin contamination in corn with and without artificial inoculation in two locations and in two years. Hybrid types consisted of conventional short season, conventional full season, and transgenic drought tolerant full season hybrids. There was an early planting date in March and a late planting date in April, and plots received either high or low levels of irrigation. Under natural contamination (no artificial inoculation), all hybrid types accumulated low levels of aflatoxin across all combinations of planting date and irrigation level. Under artificial inoculation, aflatoxin levels were much higher, but varying irrigation had no impact on aflatoxin. Planting date and hybrid type interacted to affect aflatoxin levels. The lowest levels of aflatoxin were observed in the full season hybrids planted in April, but there was no significant difference between the conventional full season hybrids and the drought tolerant full season hybrids.

Technical Abstract: Maize (Zea mays L.) is more susceptible to Aspergillus flavus infestation and the subsequent accumulation of aflatoxin during periods of biotic (e.g., insect damage) and abiotic stress (e.g., heat and drought). Cultural management of aflatoxin in pre-harvest maize grain is typically focused on reducing these sources of stress on the developing crop. The present study tested the effect of three cultural practices - season-long irrigation thresholds (full irrigation at -50 cbar versus limited irrigation at -125 cbar), planting date (late March versus late April), and hybrid selection (conventional short-season (CSS), drought-tolerant full-season (DTFS), or conventional full-season (CFS)) - on aflatoxin contamination in corn with and without artificial inoculation in two locations and in two years. The hypotheses were that full irrigation and DTFS hybrids would reduce aflatoxin by reducing drought stress, and that early planting and CSS hybrids would reduce aflatoxin by shifting the grain-filling period earlier in the season when conditions are typically less stressful. Under natural infestation, all hybrid types accumulated low levels of aflatoxin across planting date and irrigation treatment combinations. Under artificial infestation, there was no significant effect due to irrigation, and planting date and hybrid type interacted to affect aflatoxin levels. Counter to the original hypothesis, the lowest levels of aflatoxin in inoculated samples were observed in full season hybrids planted in April, but there was no significant difference between the DTFS and the CFS hybrid types.