2009 Annual Report
1a.Objectives (from AD-416)
Extend development of atoxigenic strain technology and characterization of the epidemiology of cottonseed contamination. Improve atoxigenic strain formulations and recommendations for on-farm use of atoxigenic strains. Identify factors influencing over-wintering of atoxigenic strains and agronomic practices that optimize atoxigenic strain performance including sporulation, dispersal, crop colonization, and over-wintering. Increase understanding of the biology and epidemiology of the highly toxigenic S strain.
1b.Approach (from AD-416)
Models will be developed that predict aflatoxin contamination of cotton and S strain incidence in agricultural fields from environmental and agronomic parameters. To identify factors favoring S strain development in commercial fields, communities will be monitored in several regions with varying initial incidences of the S strain. Factors identified as favoring the S strain will be tested in vitro. Incidence, distribution, and behavior of S strain sclerotia will be evaluated in commercial fields to assess roles and S strain life cycles. Dynamics of fungal community compositions as related to atoxigenic strains and the S strain will be monitored during diverse crop rotations in Arizona, including production of winter and spring produce prior to cotton or corn. Sorghum grain will be incorporated into advanced formulations and evaluated in commercial fields as a potential less expensive, more efficacious alternative to wheat.
Aflatoxin management programs based on atoxigenic strains seek both long-term and area-wide reductions to the average aflatoxin producing ability of fungal communities in order to achieve additive and multiple season benefits and to obtain influences on rotation crops. We have noticed differences among farms and regions in over-wintering of the atoxigenic Aspergillus flavus biocontrol strain, AF36, between seasons. However, there is little information on how agronomic practices and crop rotations influence the longer term survival of the atoxigenic strain (over-wintering). To determine the impacts of rotation crop, cultivation type, and soil type on over-wintering of both atoxigenic strains and the highly toxigenic strain S, six fields treated with the AF36 biocontrol agent have been monitored at several times starting after harvest of the treated cotton crop. Preliminary data shows a high variation in the effectiveness of the treatments with displacement of inhabitant toxigenic A. flavus in the soil by the applied atoxigenic AF36 immediately after harvest by over 90% in some fields and as low as 40% in other fields. Analysis of overwintering data for the AF36 biocontrol is underway. In the case of the highly toxigenic strain S, data show that there is a drop in the percentage of strain S in the soil in winter, and an increase by spring. Additional fields will be monitored during 2010 in order to get insight into variables that dictate both S strain and AF36 overwintering. Research progress was monitored through routine teleconferencing, meetings, emails, and reports.