BIOCONTROL OF AFLATOXIN IN CORN BY INOCULATION WITH NON-TOXIGENIC ASPERGILLUS FLAVUS ISOLATES

Authors: Abbas, Hamed; Zablotowicz, Robert; Bruns, Herbert

Submitted to: Biocontrol Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2005
Publication Date: 2/27/2006
Citation: Abbas, H.K., Zablotowicz, R.M., Bruns, H.A. 2006. Biocontrol of aflatoxin in corn by inoculation with non-toxigenic aspergillus flavus isolates. Biocontrol Science and Technology. Vol. 16: 437-449.

Interpretive Summary: Contamination of corn by aflatoxin (a toxic compound produced by fungi [molds]) is a significant threat to food and feed quality and is a serious limitation to corn production in the southern USA. Thus development of methods to control the fungus that produces this toxin is an important challenge. Scientists at Stoneville, MS identified two fungal strains that don't produce these toxins and conducted four years of field trials to assess the efficacy of this biological control approach. In years with high levels of natural toxin contamination, treatment of soil with these biocontrol fungi reduced corn aflatoxin contamination by 60 to 85%. When soil was treated with mixtures of the biocontrol fungi and toxin producing Aspergillus, corn had 65 to 94% less aflatoxin compared to corn treated with the toxin producing fungus strain alone. These biocontrol fungal (non-toxigenis strains of the fungus called Aspergillus flavus) have potential to reduce aflatoxin contamination of corn grown in the southern USA which will make our food and feed supply safer.

Technical Abstract: The ability of two non-aflatoxigenic Aspergillus flavus Link isolates (CT3 and K49) to reduce aflatoxin contamination of corn was assessed in a four-year field study (2001 to 2004). Soil was treated with six wheat inoculant treatments: toxigenic isolate F3W4; two non-aflatoxigenic isolates (CT3 & K49); two mixtures of CT3 or K49 with F3W4; and an autoclaved wheat control, applied at 20 kg ha-1. In 2001 inoculation with the toxigenic isolate increased corn grain aflatoxin levels by 167% compared to the non-inoculated control, while CT3 & K49 inoculation reduced aflatoxin levels in corn grain by 86% & 60%, respectively. In 2002 the non-toxigenic CT3 & K49 reduced aflatoxin levels by 61% and 76% compared to non-inoculated controls, respectively. In 2001 mixtures of toxigenic and non-toxigenic isolates had little effect on aflatoxin levels, but in 2002 inoculation with mixtures of K49 and CT3 reduced aflatoxin levels 68 and 37% compared to non-inoculated controls, respectively. In 2003 and 2004, a low level of natural aflatoxin contamination was observed (8 ng/g). However, inoculation with mixtures of K49 + F3W4 and CT3 + F3W4, reduced levels of aflatoxin 65 to 94% compared to the toxigenic strain alone. Compared to the non-sclerotia producing CT3, strain K49 produces large sclerotia, has more rapid in vitro radial growth, and a greater ability to colonize corn when artificially inoculated, perhaps indicating greater ecological competence. Results indicate that non-toxigenic, indigenous A. flavus isolates, such as strain K49, have potential use for biocontrol of aflatoxin contamination in southern USA corn