Progress 10/01/12 to 09/30/13
Outputs
Progress Report 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. 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. This serves as a final report for project 6435-42000-022-03S. Research activities carried out in Agricultural Research Service (ARS) laboratories on the campus of the University of Arizona, Tucson, AZ, and on commercial agricultural fields. Application of the strain AF36 of Aspergillus (A.) flavus, which does not produce the potent carcinogen aflatoxin (atoxigenic), has been successful in commercial cotton fields in Arizona. Previous observations of commercial applications of the AF36 biocontrol product in Arizona indicate that application to fields can benefit subsequent crops in treated areas and that applications might have beneficial influences for several years. However, factors that influence this atoxigenic strain's persistence are not well documented. Determining influences of cropping practices and rotation on persistence of AF36 in desert production areas of Arizona is one of the objectives of the present project. Data from the 2012 season on community structure of A. flavus, including total population, percentage of the highly toxigenic strain S and percentage of the applied atoxigenic strain AF36 confirm results from previous seasons. Quantities of A. flavus in soil of fields treated with the AF36 biocontrol were highest immediately after harvest the treated cotton crop, declining significantly after four months, once winter crops were planted. The percentage of the applied AF36 biocontrol decreased significantly following an exponential decay model and the percentage of the highly toxigenic S strain of the fungus increased. The time required for the population of A. flavus to reach equilibrium (strain S > 75% and AF36 < 10%) differed with area and field. In both areas, soils of treated fields had A. flavus populations containing over 60% AF36 one year after application. Results suggest that A. flavus communities are significantly affected by winter and summer crops. Agronomic practices might be optimized to maximize long-term displacement of aflatoxin producers by atoxigenic biocontrol agents. In a joint effort between the University of Arizona, ARS, and the Arizona Cotton Research & Protection Council, soil samples throughout several areas where there has been a history of AF36 use were collected during 2009, 2010 and 2011 to establish area-wide and long-term influences applications. Data is being analyzed to describe both temporal and spatial influences on long-term efficacy. Percentage of the applied biocontrol in the soil of treated fields one year after application was not significantly different from the percentage occurring in the crop. However, this percentage decreased significantly after two years. Thus, biocontrol applications might be beneficial to the next crop, but generally only applications should be made at least every other year. The goal of understanding agronomic influences retention of atoxigenic strains will be incorporated into future projects to develop general rules for predicting how strains behave in cropping systems, as well as, recommendations for encouraging fungal communities with reduced aflatoxin-producing potential.
Impacts
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Publications
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Progress 10/01/11 to 09/30/12
Outputs
Progress Report 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. 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. Research activities for the current project are carried out in Agricultural Research Service (ARS) laboratories on the campus of the University of Arizona, Tucson, AZ, and on commercial agricultural fields. Application of the strain AF36 of Aspergillus (A.) flavus, which does not produce the potent carcinogen aflatoxin (atoxigenic), has been successful in commercial cotton fields in Arizona. Previous observations of commercial applications of the AF36 biocontrol product in Arizona indicate that application to fields can benefit subsequent crops in treated areas and that applications might have beneficial influences for several years. However, factors that influence this atoxigenic strain's persistence are not well documented. Determining influences of cropping practices and rotation on persistence of AF36 in desert production areas of Arizona is one of the objectives of the present project. Quantities of A. flavus in fields treated with the AF36 biocontrol were highest immediately after harvest, declining significantly after four months, once winter crops were planted. The biocontrol further declined thereafter and maintaining low levels until new applications were done. Time after the application of the biocontrol significantly affected the population structure of A. flavus in applied fields. The percentage of the applied AF36 biocontrol decreased significantly after 15 months, while the percentage of the highly toxigenic S strain of the fungus significantly increased in the same period. The population structure of the fungus in applied fields is differentially affected in different areas. The biocontrol population decreased faster in the Yuma, AZ, area with levels below 35% after one year from application compared to levels over 55% in the Mohawk, AZ, area. These two areas differ in several characteristics including soil type and chemistry, and crop rotations. Effects of practices on the proportion of the A. flavus community composed of AF36 are not clear. Results suggest that A. flavus communities are significantly affected by winter and summer crops. Analysis of fungal communities in soils of treated fields suggest agronomic practices influence both the quantity and quality of A. flavus resident in fields and that practices might be optimized to maximize long- term displacement of aflatoxin producers by atoxigenic biocontrol agents. A component of understanding long-term influences of applications includes completion of a second joint effort between the University of Arizona, ARS, and the Arizona Cotton Research & Protection Council. Soil samples throughout several areas where there has been a history of AF36 use were collected during 2009, 2010 and 2011 to establish the extent of area wide and long-term influences of the AF36 applications in cotton. Data is being analyzed to describe both temporal and spatial influences on long-term efficacy. Geostatistics and geographic information systems (GIS) are being employed to provide quantitative basis for treatment decisions by the Arizona cotton industry. Data from 2011 confirm results from previous years suggesting that long-term influences of the biocontrol applications are dependent upon field, region, and cropping system. Percentage of the applied biocontrol in the soil of treated fields one year after application was not significantly different from the percentage occurring in the crop. However, this percentage decreased significantly after two years. This indicates that biocontrol applications might be beneficial to subsequent crops, but only to the next year�s crop, and applications are required at least every other year. The goal of understanding agronomic influences on fungal community composition and retention of atoxigenic strains will be incorporated into future projects with the goal of developing general rules for predicting how strains will behave in cropping systems and cropping recommendations for encouraging fungal communities with reduced aflatoxin-producing potential.
Impacts
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Publications
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Progress 10/01/10 to 09/30/11
Outputs
Progress Report 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. 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. The research activities of the present project are carried out mostly in Agricultural Research Service (ARS) laboratories at the University of Arizona in Tucson and in commercial agricultural fields. The application of atoxigenic strains of Aspergillus (A.) flavus (which does not produce the potent carcinogen, aflatoxin) has been successful in commercial cotton fields in Arizona. Previous observations of commercial applications of the AF36 biocontrol product in Arizona indicate that application of fields can benefit subsequent crops in treated fields and that applications might have beneficial influences for several years. Factors that influence atoxigenic strain persistence are not well documented. Quantities of A. flavus in fields treated with the AF36 biocontrol were highest immediately after harvest, declining significantly once winter crops were planted. Time lapsed since application of the biocontrol significantly affected the population structure of A. flavus in applied fields. The percentage of the applied AF36 biocontrol decreased significantly after 15 month, while the percentage of the highly toxigenic S strain significantly increased in the same period. Analysis of fungal communities in soils of treated fields suggest, agronomic practices influence both the quantity and quality of A. flavus resident in fields and that practices might be optimized to maximize long-term displacement of aflatoxin producers by atoxigenic biocontrols. Geostatistics and geographic information systems (GIS) are being employed to provide quantitative basis for treatment decisions by the Arizona cotton industry. Data suggest that long term influences of the biocontrol applications are dependent upon field, region, and cropping system. The percentage of the applied biocontrol in the soil of treated fields after one year from application is not significantly different from the percentage occurring in the crop; however, it decreased significantly after two years. The goal of understanding agronomic influences on fungal community composition and retention of atoxigenic strains will be incorporated into future projects with the goal of developing general rules for predicting how strains will behave in cropping systems and cropping recommendations for encouraging fungal communities with reduced aflatoxin-producing potential. Progress is monitored through weekly meetings, performing experiments together, through consultations during analysis of results, presentations at professional meetings and shared trips to research fields.
Impacts
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Publications
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Progress 10/01/09 to 09/30/10
Outputs
Progress Report 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. 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. Many of the research activities are carried out in Agricultural Research Service (ARS) laboratories in Tucson, Arizona. Previous observations of commercial fields applied with the AF36 biocontrol product in Arizona indicate that application of this atoxigenic strain of Aspergillus (A.) flavus which does not produce the potent carcinogen, aflatoxin, to fields can benefit subsequent crops in treated fields and that applications have beneficial influences for several years. However, factors that influence this atoxigenic strain's persistence are not well documented. Determining influences of cropping practices and rotation on persistence of AF36 in desert production areas of Arizona is one of the objectives of the present project. Quantities of A. flavus in fields treated with the AF36 biocontrol were highest immediately after harvest, declining significantly once winter crops were planted. Effects of practices on the proportion of the A. flavus community composed of AF36 are not clear. Initial results suggest that A. flavus communities are significantly affected by spring and summer crops. Analysis of fungal communities in soils of treated fields suggest agronomic practices influence both the quantity and quality of A. flavus resident in fields and that practices might be optimized to maximize long-term displacement of aflatoxin producers by atoxigenic biocontrols. A component of understanding long- term influences of applications includes completion of a joint effort with Arizona Cotton Research & Protection Council. Soil samples throughout several areas where there has been a history of AF36 use were collected during 2009. Incidence of AF36 is being analyzed to establish the extent of area wide and long-term influences of the AF36 applications in cotton in regions where AF36 continues to be used and in regions where use has been discontinued (i.e., the Mohave Valley). Data is being analyzed to describe both temporal and spatial influences on long-term efficacy. Geostatistics and geographic information systems (GIS) will be employed and emphasis will be on providing a quantitative basis for treatment decisions by the Arizona cotton industry. Data to date suggest that long term influences of the biocontrol applications are dependent upon field, region, and cropping system. The goal of understanding agronomic influences on fungal community composition and retention of atoxigenic strains will be incorporated into future projects with the goal of developing general rules for predicting how strains will behave in cropping systems and cropping recommendations for encouraging fungal communities with reduced aflatoxin-producing potential. Research progress was monitored through weekly meetings with investigators, presentations at professional meetings, and trips to research fields.
Impacts
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Publications
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Progress 10/01/08 to 09/30/09
Outputs
Progress Report 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. 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. Significant Activities that Support Special Target Populations 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.
Impacts
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