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United States Department of Agriculture

Agricultural Research Service

Research Project: AFLATOXIN CONTROL IN PISTACHIOS, ALMONDS, AND FIGS: BIOCONTROL USING ATOXIGENIC STRAINS Project Number: 6435-42000-022-01
Project Type: Specific Cooperative Agreement

Start Date: Sep 19, 2007
End Date: Jul 31, 2012

Objective:
For pistachios: Apply the atoxigenic strain AF36 in commercial pistachio orchards. Complete the survival studies for atoxigenic strains previously applied in research orchards. Identify spatial patterns associated with aflatoxin contamination in pistachio orchards using processor library samples. Determine the incidence of AF36 among A. flavus isolates obtained from commercial pistachio orchards in 2006. For almonds: Determine the incidence of atoxigenic strains among A. flavus isolates naturally occurring in almond orchards at various locations. Initiate studies on biocontrol of aflatoxin-producing fungi in a drip-irrigated almond orchard using the AF36 strain of A. flavus. Determine establishment/survival of AF36 in an almond orchard and displacement of toxigenic A. flavus and/or A. parasiticus. Provide data from the biocontrol for an application to be submitted to the EPA to obtain an experimental use permit (EUP) to treat major acreage of almond orchards in “aflatoxin-hot” areas to reduce aflatoxins (no-cost objective). For figs: Follow the survival and spread of atoxigenic A. flavus strains previously applied in a research fig orchard. Prepare for application of AF36 in commercial fig orchards.

Approach:
For pistachios: Continue research on biocontrol of aflatoxin-producing fungi using atoxigenic A. flavus strains: (1) apply the atoxigenic strain AF36 (currently working with EPA in order to apply AF36 in commercial pistachio orchards); (2) determine the survival of the atoxigenic strains, including the atoxigenic strain AF36 previously applied as a wheat formulation in two research pistachio orchards; (3) use the results from the aflatoxin analyses of “library” samples to identify spatial patterns of aflatoxin contamination in California. Library samples, which consist of 20 pounds of nuts taken at the processing plant as nuts are being unloaded, represent a valuable research tool because it is easy to collect numerous nut samples from many commercial orchards representing extensive acreage. The resulting information will assist in deciding which commercial orchards would be best for applying AF36; (4) determine the incidence of AF36 naturally occurring in commercial pistachio orchards with a history of high aflatoxin contamination. For almonds: The density of A. flavus and A. parasiticus and the ratio of toxigenic to atoxigenic strains will be determined in almond orchards and specifically the incidence of the AF36 atoxigenic strain of A. flavus. AF36 will be applied in experimental plots to obtain data on its survival, displacement of the toxigenic strains, and reduction of aflatoxin contamination in almonds. Data of survival of the atoxigenic strain(s) and the displacement of toxigenic A. flavus and/or A. parasiticus will be used to expand the application of registering AF36 from pistachios to include almonds. For figs: Continue research on biocontrol of aflatoxin-producing fungi using the atoxigenic Aspergillus flavus strain AF36. AF36 has been applied in a fig orchard in California, resulting in AF36 becoming the dominant A. flavus strain where it was applied. The survival and spread of the previously applied atoxigenic strain AF36 (no AF36 will be applied in 2007) will be measured in order to determine how many years after treatment AF36 will still be the dominant strain and the extent that AF36 will move outside the treated areas. All results will be statistically analyzed and summarized in preparation for applying AF36 large scale in commercial fig orchards.

Last Modified: 10/24/2014
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