1a.Objectives (from AD-416)
Characterize influences of agrichemicals, including glyphosate and copper, on communities of aflatoxin-producing fungi and evaluate the potential for improved aflatoxin management through altered use of agrichemicals and improved biocontrol with chemical resistant atoxigenic strains. Improve understanding of the genetic relationships among aflatoxin-producing and closely related fungi with varying sensitivity to agrichemicals.
1b.Approach (from AD-416)
Collections of Aspergillus flavus from agricultural environments in Arizona and Texas will be screened for sensitivity to agrichemicals. Relationships between chemical sensitivity and chemical exposure will be assessed. Genetic relationships among sensitive and resistant fungi will be assessed and barriers to gene flow among resistant and sensitive isolates evaluated. Competitiveness of resistant and sensitive fungi will be compared and attempts will be made to select atoxigenic strains with improved resistance to agrichemicals as elite biocontrol strains.
Research activities are carried out in close proximity to Agricultural Research Service (ARS) laboratories in Tucson, Arizona. Initial screening of Aspergillus (A.) flavus (a producer of the potent carcinogen, aflatoxin) fungal isolates from Texas and Arizona for sensitivity to a common herbicide failed to detect significant differences in sensitivity. Isolates with varying sensitivity to boron containing compounds continued to be detected. Variation in sensitivity of A. flavus isolates to several antibiotics was investigated. Zeocin was found to have the most consistent influence on A. flavus isolates. There was considerable variation among isolates in sensitivity to zeocin with S strain isolates less sensitive than L strain isolates. The value of zeocin as a selectable marker for genetic analysis of A. flavus is currently being evaluated. It is anticipated that a zeocin-based transformation system will be of value in dissecting competitive differences among A. flavus isolates and in identifying characteristics of value in elite atoxigenic biocontrol agents. Research progress was monitored through weekly meetings with the principal investigator and through periodic discussions with the student involved in the studies.