|Jaime Garcia, Ramon|
Submitted to: Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/15/2005
Publication Date: 6/1/2006
Citation: Jaime Garcia, R., Cotty, P.J. 2006. Spatial distribution of Aspergillus flavus and its toxigenic strains on commercial cottonseed from South Texas and its relationship to aflatoxin contamination. Plant Pathology. 55:358-366. Interpretive Summary: Aflatoxins are toxic chemicals produced by several fungi. Regulatory limitations on the quantity of aflatoxins permitted in foods and feeds exist throughout most of the world. Cottonseed with aflatoxin content of 20 ppb or higher may not enter the profitable dairy market. In order to establish area-wide measures to limit contamination, we need to determine the distribution of aflatoxin contamination in the area, as well as the factors influencing contamination. Communities of aflatoxin-producing fungi differ by region. The most common aflatoxin-producing species, Aspergillus flavus, can be divided into two strains. The S strain produces high levels of aflatoxins, while the L strain produces on average less aflatoxin. We studied the structure of A. flavus communities associated with South Texas cottonseed during 1999 through 2001. When the crops that had increased A. flavus and increased percentages of the A. flavus were the S strain, there was more aflatoxin in the crop. Areas with more S strain had greater vulnerability to aflatoxin contamination. The results suggest that procedures to reduce the incidence of the S strain will result in reduced aflatoxin contamination. This research will benefit researchers and crop growers.
Technical Abstract: The structures of Aspergillus flavus communities associated with South Texas cottonseed were determined by analyzing samples from 178 truckloads of commercial cottonseed from 35 gins extending from Fort Bend County on the north to the Rio Grande Valley in the South. Samples were taken at the Valley Co-op Oil Mill in Harlingen, TX from September 1999 through October 2001. Most gins were sampled several times during the season on a weekly basis. The quantity of A. flavus (CFU) on the cottonseed and the percent of the A. flavus composed of the S strain (Percent S) were both correlated with aflatoxin contamination of South Texas cottonseed. CFU differed between both regions and seasons, while percent S only differed between regions. Comparison of maps of both CFU and Percent S revealed that CFU has a higher variation across years while Percent S has higher spatial variation. The Rio Grande Valley had significantly lower CFU and S strain than the Coastal Bend and Upper Coast regions. Cottonseed produced in 1999 had significantly more A. flavus than that produced in either 2000 or 2001. Geographic variation in S strain incidence contributed to the spatial variation in contamination independent of influences of rain and temperature. Environmental variation across seasons affect aflatoxin content through influences on the magnitude of the overall A. flavus community on the crop.