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ARS Home » Southeast Area » Stoneville, Mississippi » Crop Production Systems Research » Research » Publications at this Location » Publication #188311
Title: Mycotoxin occurrence and Aspergillus flavus soil propagules in a corn and cotton glyphosate-resistant cropping systems

Author
item Reddy, Krishna
item Abbas, Hamed
item Zablotowicz, Robert
item Abel, Craig
item Koger Iii, Clifford

Submitted to: Journal of Food Additives & Contaminants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/5/2007
Publication Date: 10/4/2007
Citation: Reddy, K.N., Abbas, H.K., Zablotowicz, R.M., Abel, C.A., Koger III, C.H. 2007. Mycotoxin occurrence and Aspergillus flavus soil propagules in a corn and cotton glyphosate-resistant cropping systems. Journal of Food Additives & Contaminants, 24(12):1367-1373.

Interpretive Summary: Corn and cotton seed are frequently contaminated with aflatoxins and fumonisins produced by toxigenic fungi, making them unfit for human and animal consumption. Mycotoxin contamination is influenced by level of infestation by toxigenic fungi and environmental factors that stress crop plants. Scientists at Southern Weed Science Research Unit, Crop Genetics and Production Research Unit, and Southern Insect Management Research Unit, Stoneville, MS have examined the effects simple agronomic practices such as crop rotation and selection glyphosate-resistant cultivars on Aspergillus flavus populations in soil and aflatoxin and fumonisin in corn and cotton seed in a 6-yr field study conducted during 2000-2005 at Stoneville, MS. There were four rotation systems (continuous cotton, continuous corn, cotton-corn, and corn-cotton) for each glyphosate-resistant (GR) and non-GR cultivars. A. flavus populations in surface 5-cm soil sampled before planting (March/April), mid-season (June), and after harvest (September) ranged from 1.4 to 5.8 log (10) cfu/g soil with no clear trend among eight rotation systems in 2002, 2003, 2004, and 2005. In cotton seed, aflatoxin and fumonisin levels were ('4 ppb and non-detectable, respectively) similar regardless of rotation and glyphosate. In corn grain, aflatoxin was above the regulatory level ('20 ppb) only in GR cultivar in 2004 and 2005. Fumonisin was higher in non-GR cultivar (4 ppm) regardless of rotation in 2004. These results indicate the potential for increased aflatoxin levels (1 of 4 years) in corn. There was no evidence that rotation of corn with cotton had any affect on reducing inoculum potential in soil and there was no consistent effect of glyphosate on propagule density of A. flavus.

Technical Abstract: The effects of cotton-corn rotation and glyphosate use on levels of soil-borne Aspergillus flavus and aflatoxin and fumonisin in corn and cotton seed were determined during 2002-2005 in a 6-yr field study conducted from 2000 through 2005 at Stoneville, MS. There were four rotation systems (continuous cotton, continuous corn, cotton-corn, and corn-cotton) for each glyphosate-resistant (GR) and non-GR cultivars arranged in a randomized complete block design with four replications. A standard glyphosate-based program for the GR cultivars and a nonglyphosate herbicide-based program for the non-GR cultivars were used for weed control. A. flavus populations in surface (5-cm depth) soil sampled before planting (March/April), mid-season (June), and after harvest (September) ranged from 1.4 to 5.8 log (10) cfu/g soil with no clear trend among eight rotation systems in 2002, 2003, 2004, and 2005, although populations of A. flavus were significantly greater in plots with GR cultivars compared to non-GR cultivars on several sampling dates. In cotton seed, aflatoxin and fumonisin levels were ('4 ppb and non-detectable, respectively) similar regardless of rotation and glyphosate. In corn grain, aflatoxin was above the regulatory level ('20 ppb) only in GR cultivar in 2004 and 2005. Fumonisin was higher in non-GR cultivar (4 ppm) regardless of rotation in 2004; however, in 2002, 2003, and 2005, aflatoxin and fumonisin levels were similar regardless of rotation and glyphosate. These results indicate the potential for increased aflatoxin and fumonisin levels (1 of 4 years) in corn, however, climatic conditions encountered during this study did not allow for complete infection by the mycotoxin-producing fungi.