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ARS Home » Southeast Area » Fort Pierce, Florida » U.S. Horticultural Research Laboratory » Subtropical Plant Pathology Research » Research » Publications at this Location » Publication #161061
Title: POPULATION DYNAMICS OF ASPERGILLUS FLAVUS IN THE AIR OF AN INTENSIVELY CULTIVATED REGION OF SOUTHWEST ARIZONA

Author
item BOCK, CLIVE - USDA, ARS
item MACKEY, B. - USDA
item COTTY, P. J. - USDA

Submitted to: Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/24/2004
Publication Date: 8/1/2004
Citation: Bock, C., Mackey, B., Cotty, P. 2004. Population dynamics of aspergillus flavus in the air of an intensively cultivated region of southwest arizona. Plant Pathology. 53:422-433.

Interpretive Summary:

Technical Abstract: Air borne propagules of A. flavus were quantified to investigate population dynamics of A. flavus in a region of southwest Arizona prone to epidemics of aflatoxin contamination of cottonseed. Air was sampled continuously from May 1997 to March 1999 at two sites using Burkard cyclone samplers. One sampler was initially at the center of 65 ha of cotton treated with an atoxigenic strain of A. flavus to manage aflatoxin contamination of cottonseed. The second sampler was 0.6 km from the treated field. Total fungal colony forming units (CFUs) sampled ranged from 17 to 667 per m3 and from 9 to 1277 per m3, at the untreated and treated sites, respectively. Counts of A. flavus ranged from 0 to 406 per m3 and 0 to 416 per m3. A. flavus comprised 1 to 46% and 1 to 51% of the total cultured fungi at the treated and untreated sites, respectively. Peaks in total fungal and A. flavus CFUs coincided with boll maturation and cotton harvest (day 251-321). Autoregression analysis suggested that there was no difference in total fungal CFUs between treated and untreated sites, but the analysis showed the quantity of A. flavus decreased at the treated site, likely due to changes in cropping making the conditions less conducive to growth and reproduction of A. flavus in the surrounding fields. The incidence of the S strain of A. flavus was highest between May and August. The L strain accounted for up to 100% of the A. flavus sampled in the other months, and autoregression analysis showed that the L strain accounted for a greater overall proportion of the A. flavus population at the treated site compared to the untreated site. Autoregression analysis also showed the vegetative compatibility group of the applied strain was a greater proportion of the L-strain A. flavus at the treated site (5-75%) than at the untreated site (0-65%), although this decreased with time. The quantity of A. flavus sampled at both the treated and untreated sites was correlated with air and soil temperature. Large quantities of A. flavus occurred in the soil (up to 34,474 CFUs per g) of cotton fields and on cotton plant parts and debris (up to 272,461 CFUs per g) adjacent to the cyclone samplers. A. flavus is a major constituent of the airborne mycoflora associated with cotton fields in southwest Arizona when temperature is conducive to fungal growth. Although application of atoxigenic A. flavus altered the proportion of A. flavus strains and VCGs in the aerial mycoflora, the total quantity of A. flavus remained similar to that in untreated fields. Dispersal of A. flavus between fields suggests atoxigenic fungi will be most effective in area-wide management programs.