Progress 11/26/02 to 05/17/07
Outputs
Progress Report Objectives (from AD-416) Objective 1: Assess the potential of microbes to control soil-borne plant pathogenic fungi and determine biological, environmental and ecological factors affecting performance of these microbes. Objective 2: Characterize biological, ecological and genetic relationships among and within pathogenic, saprophytic and biocontrol soil-borne microorganisms. Objective 3. Elucidate mechanisms of action of biocontrol agents used against soil-borne plant pathogens, and, where previous work identified a general mechanism of action, identify the specific underlying basis of the mechanism. Work will include, but is not limited to, the nature of resistance to Fusarium wilt in tomato induced by Fusarium oxysporum strain CS-20. Approach (from AD-416) For objective 1, the approach will include studies on inoculum density relationships between biocontrol agents and pathogens, tests on tomato cultivars with different combinations of resistance genes, effect of environmental parameters on biocontrol performance, efficacy against pathogens other than Fusarium, studies on mechanisms of action of biocontrol agents, field testing, production, formulation and delivery of biocontrol agents, and integration into the production system. For objective 2, genetic relationships among pathogenic, saprophytic and bicontrol Fusaria will be determined, and markers for biocontrol ability will be identified. Biological and ecological interactions among these groups will be determined. For objective 3, the relationship of resistance induced by F. oxysporum CS-20 to systemic acquired resistance and the location of resistance in the plant will be determined. Significant Activities that Support Special Target Populations The goal of this project is to provide alternative disease management tools for use against soilborne plant pathogenic fungi, particularly Fusarium oxysporum. Two ABC transporter genes from pathogenic and biocontrol strains of Fusarium oxysporum were cloned and sequenced. We determined that pathogenic and biocontrol strains each had two copies of each gene and that sequences from pathogenic and biocontrol strains were highly homologous. Work in progress will determine if sequence differences are biologically significant. Accomplishments Discovery of activation of systemic plant defense in response to the presence of a biocontrol Fusarium The biocontrol fungus Fusarium oxysporum strain CS-20 was previously shown to reduce incidence of Fusarium wilt of tomato through an uncharacterized host-mediated response. Since phenolic compounds are involved in the defense response of tomato to pathogens and other stressors, this work was undertaken to determine if biocontrol strains induced changes in phenolic compounds in leaves and roots of tomato seedlings in the presence and absence of pathogenic F. oxysporum f. sp. lycopersici. There were significant qualitative and quantitative differences between the two sampling times (24 or 72 h). Compared to the control treatment, strain CS-20 significantly altered (usually increasing) the ferulic, caffeic, and vanillic acid contents, and concentrations one unidentified phenolic compounds recovered from leaves and roots. Further, the amount of pathogen present did not significantly affect the plant phenolic response to the presence of strain CS-20. This work demonstrates that tomato responds systemically within 24 h to the presence of the biocontrol strain CS-20 by alterations in secondary metabolism that are typical of resistance responses in tomato. This work is directly related to Component I, Preplant Soil Fumigation Alternatives, of the action plan for National Program Area 308, Alternatives to Methyl Bromide.
Impacts
(N/A)
Publications
- Fravel, D.R., Moravec, B.C., Bailey, B.A. 2007. Identification and regulation of genes from a biocontrol strain of fusarium oxysporum. Phytopathology. 155:526-530.
- Panina, Y., Fravel, D.R., Shcherbakova, L.A., Baker, C.J. 2007. Biocontrol and plant pathogenic fusarium oxysporum-induced changes in phenolic compounds in tomato leaves and roots. Journal of Phytopathology. 155:475- 481.
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Progress 10/01/05 to 09/30/06
Outputs
Progress Report 1. What major problem or issue is being resolved and how are you resolving it (summarize project aims and objectives)? How serious is the problem? Why does it matter? As regulated by an international treaty and by the U.S. Clean Air Act, the use of the soil fumigant methyl bromide is being phased out due to its role in ozone depletion. Alternatives to methyl bromide are needed for control of soil-borne plant pests. Methyl bromide is a broad- spectrum biocide that kills many different kinds of pests. The largest single use of methyl bromide in the United States is for fumigation of soil prior to planting tomatoes in Florida. While the immediate solution to replacing methyl bromide for tomato production is likely to be a combination of chemicals, other alternatives need to be developed since more and more chemicals are being withdrawn from the market. One approach is biological control - the use of beneficial microbes to mitigate the effects of
plant pathogenic microbes. Fusarium wilt is one of the most important soil-borne problems faced by tomato growers and this disease is expected to increase when methyl bromide is no longer available. I am resolving the problem by discovering and developing beneficial Fusarium oxysporum for control of Fusarium wilt. Fusarium wilt is one of the top three pest problems faced by Florida tomato growers and is expected to increase when methyl bromide is no longer available. Race 3 of the pathogen has increased even while methyl bromide is in use. In general, soil-borne diseases are limiting factors in the production of many crops and account for 10 - 20% yield losses annually. Losses in individual fields can be as high as 100%. Management of soil-borne pathogens is necessary for a secure and stable supply of food and fiber, as well as for maintaining agricultural exports. This work directly relates to National Program 308 Methyl Bromide Alternatives under the component Preplant Soil
Fumigation Alternatives and STP code 2.2.1.3, Plant Disease and Nematode Control. Objectives of the project include: 1) Assess the potential of microbes to control soil-borne plant pathogenic fungi and determine biological, environmental and ecological factors affecting performance of these microbes, 2) Characterize biological, ecological and genetic relationships among and within pathogenic, saprophytic and biocontrol soil-borne microorganisms, and 3) Elucidate mechanisms of biocontrol. 2. List by year the currently approved milestones (indicators of research progress) Objective 1 - New biocontrol agents 1a. Inoculum density 1b. Different cultivars 1c. Environmental parameters 1d. Other Pathogens 1e. Mechanisms 1f. Field testing 1g. Production, formulation, delivery 1h. Production system Objective 2 - Biological, ecological and genetic relationships 2a. Genetic relationships 2b. Biological and ecological relationships Objective 3 - Mechanisms of action 3a. Relationship to SAR 3b.
Location of resistance 3c. Protein profiles and assays 3d. Histology 4a List the single most significant research accomplishment during FY 2006. Previous research in this project found that Fusarium oxysporum strain CS- 20 reduced the incidence of Fusarium wilt, caused by F. oxysporum, in tomato and other plants. Further, split-root and other tests demonstrated that the main mechanisms of control is resistance in the plant induced by strain CS-20. In FY 06, research was conducted to identify specific chemical changes induced by strain CS-20. Phenolic compounds are known to be involved induced resistance in many plants. Four phenolic compounds (vanillic, caffeic and ferulic acids, and an unknown) produced by tomato roots in response to F. oxysporum strain CS- 20 (biocontrol strain), but not plant pathogenic F. oxysporum were found. Experiments are in progress to establish the role of these in induced resistance of tomato to Fusarium wilt. Fundamental knowledge of induced resistance
in plants will contribute to development of novel disease management strategies. This research is related to NP308, Component 1. 4b List other significant research accomplishment(s), if any. The soil-inhabiting fungus Fusarium oxysporum occurs as plantpathogenic, plant-beneficial (biocontrol) and saprophytic strains. Pathogenic, biocontrol, and saprophytic F. oxysporum strains all look exactly the same. Currently the only way to distinguish the three forms is to expose plants to the fungus and observe the plants reaction. The differences in behavior of the fungus could be due to differences in the presence or absence of genes, or in the way these genes are turned on and off (gene regulation). In FY 06, three genes were identified that appear different between biocontrol and plant pathogenic F. oxysporum. All three have the same number of copies of each of the three genes in both types of F. oxysporum, but two (an ABC transporter and an amidohydrolase super family gene) are
regulated differently in the two types of F. oxysporum. Research is in progress to determine the role of these genes in biocontrol. Understanding specifically what traits confer biocontrol ability or pathogenicity will contribute to development of new disease management strategies. This research is related to NP308, Component 1. 5. Describe the major accomplishments to date and their predicted or actual impact. We have determined that four species of Trichoderma are not good candidates for combining with the soil fumigant metam sodium. We have determined compatibility of the biocontrol fungus F. oxysporum CS-20 with fungicides used on tomato. This information is needed to integrate biocontrol into the production system. We have found genes in strain CS- 20 activated by a fungicide and the phytoalexin tomatine. We identified three genes that are regulated differently in CS-20 and plant pathogenic F. oxysporum, and have indications of sequence differences between the two. We have
identified three known phenolics and one unknown phenolic produced by plant roots in response to CS-20, but not the pathogen. This research is related to NP308, Component 1. 6. What science and/or technologies have been transferred and to whom? When is the science and/or technology likely to become available to the end- user (industry, farmer, other scientists)? What are the constraints, if known, to the adoption and durability of the technology products? With an interested party from industry, CS-20 could be commercialized in 5 10 years for management of Fusarium wilt on tomato and other crops. Research on induced resistance and on traits associated with biocontrol ability is longer termed and is aimed at development of new disease management strategies with wider application.
Impacts
(N/A)
Publications
- Cavigelli, M.A., Lengnick, L.L., Buyer, J.S., Fravel, D.R., Handoo, Z.A., McCarty, G.W., Millner, P.D., Sikora, L.J., Wright, S.E., Vinyard, B.T., Rabenhorst, M. 2005. Landscape level variation in soil resources and microbial properties in a no-till corn field. Applied Soil Ecology. 29:99- 123.
- Fravel, D.R. 2005. Commercialization and implementation of biological control. Annu. Rev. Phytopathol. doi: 10.1146/annurev.phyto.43.032904. 092924.
- Fravel, D. R., Deahl, K. L., and Stommel, J. R. 2005. Compatibility of the biocontrol fungus Fusarium oxysporum strain CS-20 with selected fungicides. Biological Control. 34:165-169 .
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Progress 10/01/04 to 09/30/05
Outputs
1. What major problem or issue is being resolved and how are you resolving it (summarize project aims and objectives)? How serious is the problem? What does it matter? As regulated by an international treaty and by the US Clean Air Act, the use of the soil fumigant methyl bromide is being phased out due to its role in ozone depletion. Alternatives to methyl bromide are needed for control of soil-borne plant pests. Methyl bromide is a broad-spectrum biocide that kills many different kinds of pests. The largest single use of methyl bromide in the United States is for fumigation of soil prior to planting tomatoes in Florida. While the immediate solution to replacing methyl bromide for tomato production is likely to be a combination of chemicals, other alternatives need to be developed since more and more chemicals are being withdrawn from the market. One approach is biological control - the use of beneficial microbes to mitigate the effects of plant pathogenic
microbes. Fusarium wilt is one of the most important soil-borne problems faced by tomato growers and this disease is expected to increase when methyl bromide is no longer available. I am resolving the problem by discovering and developing beneficial Fusarium oxysporum for control of Fusarium wilt. This work directly relates to Nationa l Program 308 "Methyl Bromide Alternatives" under the component "Preplant Soil Fumigation Alternatives" and STP code 2.2.1.3, Plant Disease and Nematode Control. MES MES Race 3 of the Fusarium wilt pathogen has increased even while methyl bromide is in use. In general, soil-borne diseases are limiting factors in the production of many crops and account for 10 - 20% yield losses annually. Losses in individual fields can be as high as 100%. Management of soil-borne pathogens is necessary for a secure and stable supply of food and fiber, as well as for maintaining agricultural exports. Objectives of the project include: 1) Assess the potential of
microbes to control soil-borne plant pathogenic fungi and determine biological, environmental and ecological factors affecting performance of these microbes, 2) Characterize biological, ecological and genetic relationships among and within pathogenic, saprophytic and biocontrol soil-borne microorganisms, and 3) Elucidate mechanisms of biocontrol. 2. List the milestones (indicators of progress) from your Project Plan. Objective 1 - New biocontrol agents 1a. Inoculum density 1b. Different cultivars 1c. Environmental parameters 1d. Other Pathogens 1e. Mechanisms 1f. Field testing 1g. Production, formulation, delivery 1h. Production system Objective 2 - Biological, ecological and genetic relationships 2a. Genetic relationships 2b. Biological and ecological relationships Objective 3 - Mechanisms of action 3a. Relationship to SAR 3b. Location of resistance 3c. Protein profiles and assays 3d. Histology 3a List the milestones that were scheduled to be addressed in FY 2005. For each
milestone, indicate the status: fully met, substantially met, or not met. If not met, why. 1. The three milestones to be addressed (milestones1c, 1d and 1e) were the effects of environmental parameters on new biocontrol agents, the effects of new biocontrol agents on pathogens other than the tomato Fusarium wilt pathogen, and mechanisms of action of new biocontrol agents. I am continuing to focus on milestones 1a and 1b (early stages of screening for new biocontrol agents), since screening thus far has not identified any agent which consistently provides better control than the one I had already identified. Milestone Substantially Met 2. Emphasis has shifted to differences in gene regulation between biocontrol and pathogenic Fusarium strains. Milestone Substantially Met 3. We were to conduct protein assays on tomato roots to determine which proteins are involved in the resistance induced by the biocontrol agent CS-20. We had difficulty in obtaining sufficient protein form roots
for the assays and have thus taken a different approach using over and under- producers of jasmonate and ethylene. Milestone Substantially Met 3b List the milestones that you expect to address over the next 3 years (FY 2006, 2007, and 2008). What do you expect to accomplish, year by year, over the next 3 years under each milestone? Year 3 (FY 2006) Objective 1: Continue development of strains of F. oxysporum with demonstrated potential for control of Fusarium wilt on tomato. Continue investigations of the effects of environmental parameters on the performance of these strains; test these stains for biocontrol of Fusarium wilt of other crops and test the strains against other soil- borne pathogens. Objective 2: Study regulation of genes we identified in CS-20 that are turned on or off by toxins. Objective 3: Determine if there are differences in phenolics or active oxygen species among plants treated with i) nothing, ii) CS-20, iii) the Fusarium wilt pathogen, or iv) both CS-20
and the pathogen. Year 4 (FY 2007) Objective 1: Depending on the outcome of all previous tests, continue development of any strains that continue to be promising for biocontrol of Fusarium wilt. Objective 2: Continue studies to find genetic differences among groups of Fusaria; initiate studies to study regulation of genes of known function that are different among the groups to determine their role in biocontrol; initiate studies to determine the role of genes of unknown function in biocontrol. Objective 3: Measure jasmonate in treated and non-treated plants. Year 5 (FY 2008) This will be a new project which is expected to continue identifying genes associated with biocontrol ability, understanding genetic differences and differences in gene regulation between biocontrol and plant pathogenic Fusaria. 4a What was the single most significant accomplishment this past year? We identified genes in F. oxysporum strain CS-20 turned on and off by a fungicide (thiram) and by a compound
produced in some plants in response to infection that is toxic to many fungi. Preliminary evidence indicates that regulation of these genes may differ between pathogenic and beneficial Fusaria. 5. Describe the major accomplishments over the life of the project, including their predicted or actual impact. We have determined that four species of Trichoderma are not good candidates for combining with the soil fumigant metam sodium. We have determined compatibility of the biocontrol fungus F. oxysporum CS-20 with fungicides used on tomato. This information is needed to integrate biocontrol into the production system. We have found genes in strain CS- 20 activated by a fungicide and the phytoalexin tomatine. This information will be used to dissect differences in gene expression and regulation between pathogenic and biocontrol F. oxysporum. These accomplishments relate to National Program 308 "Methyl Bromide Alternatives" under the component "Preplant Soil Fumigation Alternatives" and
STP code 2.2.1.3, Plant Disease and Nematode Control. 6. What science and/or technologies have been transferred and to whom? When is the science and/or technology likely to become available to the end- user (industry, farmer, other scientists)? What are the constraints, if known, to the adoption and durability of the technology products? The biocontrol strain F. oxysporum CS-20 has been transferred to other researchers and to industry. Most researchers had success with CS-20. One researcher and industry did not. The failures are now attributed to incompatible interactions with fungicides used in those production systems. Thus, part of how soon the technology is available to the end user becomes what constraints the end user is willing to accept. If the end user is willing to accept this incompatibility with fungicides, with an industry partner, strain CS-20 could be ready for registration with EPA in about three years. Alternatively, it may be possible to alter the formulation
or delivery of CS-20 to increase its compatibility with fungicides. This will take additional research. The newer biocontrol agents being developed are likely ten to fifteen years from registration with EPA.
Impacts
(N/A)
Publications
- Cavigelli, M.A., Lengnick, L.L., Buyer, J.S., Fravel, D.R., Handoo, Z.A., McCarty, G.W., Millner, P.D., Sikora, L.J., Wright, S.E., Vinyard, B.T., Rabenhorst, M. 2005. Landscape level variation in soil resources and microbial properties in a no-till corn field. Applied Soil Ecology. 29:99- 123.
- Fravel, D.R. 2005. Commercialization and implementation of biological control. Annu. Rev. Phytopathol. doi: 10.1146/annurev.phyto.43.032904. 092924.
- Fravel, D. R., Deahl, K. L., and Stommel, J. R. 2005. Compatibility of the biocontrol fungus Fusarium oxysporum strain CS-20 with selected fungicides. Biological Control. 34:165-169 .
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Progress 10/01/03 to 09/30/04
Outputs
1. What major problem or issue is being resolved and how are you resolving it (summarize project aims and objectives)? How serious is the problem? What does it matter? As regulated by an international treaty and by the US Clean Air Act, the use of the soil fumigant methyl bromide is being phased out due to its role in ozone depletion. Alternatives to methyl bromide are needed for control of soil-borne plant pests. Methyl bromide is a broad-spectrum biocide that kills many different kinds of pests. The largest single use of methyl bromide in the United States is for fumigation of soil prior to planting tomatoes in Florida. While the immediate solution to replacing methyl bromide for tomato production is likely to be a combination of chemicals, other alternatives need to be developed since more and more chemicals are being withdrawn from the market. One approach is biological control - the use of beneficial microbes to mitigate the effects of plant pathogenic
microbes. Fusarium wilt is one of the most important soil-borne problems faced by tomato growers and this disease is expected to increase when methyl bromide is no longer available. I am resolving the problem by discovering and developing beneficial Fusarium oxysporum for control of Fusarium wilt. Fusarium wilt is one of the top three pest problems faced by Florida tomato growers and is expected to increase when methyl bromide is no longer available. Race 3 of the pathogen has increased even while methyl bromide is in use. In general, soil-borne diseases are limiting factors in the production of many crops and account for 10 - 20% yield losses annually. Losses in individual fields can be as high as 100%. Management of soil-borne pathogens is necessary for a secure and stable supply of food and fiber, as well as for maintaining agricultural exports. This work directly relates to National Program 308 -Methyl Bromide Alternatives- under the component "Preplant Soil Fumigation
Alternatives" and STP code 2.2.1.3, Plant Disease and Nematode Control. Objectives of the CRIS include: 1) Assess the potential of microbes to control soil-borne plant pathogenic fungi and determine biological, environmental and ecological factors affecting performance of these microbes, 2) Characterize biological, ecological and genetic relationships among and within pathogenic, saprophytic and biocontrol soil-borne microorganisms, and 3) Elucidate mechanisms of biocontrol. 2. List the milestones (indicators of progress) from your Project Plan. FY 03 Inoculum density relationships determined for new biocontrol agents. Begin studies on genetic relationships among biocontrol agents. Determine relationship of resistance induce by CS-20 to systemic acquired resistance. Determine location of this resistance. FY 04 Determine the effectiveness of new biocontrol agents on different tomato cultivars. Initiate studies on the effects of environmental parameters on biocontrol performance.
Initiate studies on proteins associated with induced resistance. FY 05 Conclude studies on the effects of environmental parameters on biocontrol performance. Assess the ability of new biocontrol agents to control other pathogens. Initiate studies on mechanisms of new biocontrol agents. Conclude studies on genetic relationships among biocontrol agents. Initiate studies on biological and ecological relationships among Fusaria. Continue protein studies. FY 06 Conclude mechanism studies on new biocontrol agents. Depending on results of tests in previous years, initiate field testing, production, formulation, delivery and integration into production system studies with new biocontrol agents. Continue studies on biological and ecological relationships among Fusaria. Conclude protein studies. Initiate studies to document physical interactions between biocontrol agent and pathogen on and in roots. FY 07 If initiate in the previous year, conclude field testing, production, formulation,
delivery and integration into production system studies with new biocontrol agents. Conclude studies on biological and ecological relationships among Fusaria. Conclude documentation of physical interactions between biocontrol agent and pathogen on and in roots. 3. Milestones: FY 04 milestones: Determine the effectiveness of new biocontrol agents on different tomato cultivars. Initiate studies on the effects of environmental parameters on biocontrol performance. Initiate studies on proteins associated with induced resistance. Milestones were substantially met or are in progress, although a different approach is being used for the protein studies because we had difficulty in obtaining sufficient protein form roots for the assays. Instead, we have obtained transgenic tomato seed for over and under- producers of jasmonate and ethylene. We have confirmed in greenhouse tests that the parent material of these transgenic seeds is susceptible to our isolates of the Fusarium wilt
pathogen. We are now conducting tests to determine if the transgenic plants are altered in their ability to be induced by CS-20. This should point to pathways involved in biocontrol by CS-20. We are trying to obtain additional seed for tomatoes over or under-producing other proteins known to be involved in plant defense responses. B. List the milestones (from the list in question #2) that you expect to address over the next 3 years (FY 2005, 2006 and 2007). What do you expect to accomplish, year by year, over the next 3 years under each milestone? FY 05 Continue development of strains of F. oxysporum with demonstrated potential for control of Fusarium wilt on tomato. Continue investigations of the effects of environmental parameters on the performance of these strains; test these stains for biocontrol of Fusarium wilt of other crops and test the strains against other soil- borne pathogens. Extend differential display studies of biocontrol, pathogenic and saprophytic Fusaria to
include more strains and more primers. Sequence regions that appear to be consistently different among the groups. Initiate studies on root colonization by CS-20 and the pathogen. Continue studies with over and under-producers of plant defense proteins. FY 06 Initiate studies on mechanisms of action of new biocontrol agents that still appear promising after the ecological studies in year 3. Depending on the outcome of all previous tests, if any strains appear to have commercial potential, initiate studies on production, formulation and delivery, as well as small-scale field testing. Continue studies to find genetic differences among groups of Fusaria; initiate studies to study regulation of genes of known function that are different among the groups to determine their role in biocontrol; initiate studies to determine the role of genes of unknown function in biocontrol. Finish root colonization studies. Finish work with over and under-producers of plant defense proteins. FY 07
If isolates appear to have true commercial potential, continue field testing; finish studies on production, formulation and delivery; and determine compatibility of biocontrol strains with fungicides used on tomato. Finish genetic studies; finish studies on gene function in biocontrol. Document physical interaction between the biocontrol agent and pathogen on and in the root. 4. What were the most significant accomplishments this past year? We tested the compatibility of the biocontrol fungus F. oxysporum CS-20 with all fungicides labeled for use on tomato. Tests were conducted in vitro and on tomato plants growing in field soil. In plate tests, thiram, bravo and quadric were most toxic to CS-20. When fungicides were applied to seeds, soil or plants as directed on the labels, all eight fungicides tested reduced biocontrol significantly. The seed fungicide thiram resulted in the greatest reduction in biocontrol. Thus, Cs-20 cannot be used with thiram-treated seed and use of other
fungicides must be limited. B. Other significant accomplishment(s), if any. Strains of Talaromyces species were isolated in a survey of soil samples from ten countries and sixteen states in the United States. T. flavus was the most common species isolated (35 strains), followed by T. trachyspermus (5 strains), T. wortmannii (3 strains) and T. ucrainicus (3 strains). Variation in ascospore size, colony characters, internal transcribed spacer rDNA (ITS) partial ss-tubulin and partial glyceraldehyde-3-phosphate dehydrogenase (GDP) gene sequences were studied in a collection of 20 Talaromyces flavus strains. Seventeen strains had identical ITS sequences. Three strains, all from the US, formed a second group and were among the five strains with the longest ascospores. ss-tubulin sequences were more divergent; T. flavus strains grouped into two divergent clusters, each with two sub-clusters. The GDP tree was the most resolved, with the majority of the strains having unique sequences. The
three strains that grouped separately in the ITS analysis, also grouped together in the ss-tubulin and GDP analyses, but had different sister strains; this group did not meet the criteria to be recognized as a distinct phylogenetic species. Phylograms for the three sequence data sets revealed no correlation between groupings and geographic origin. C. Significant activities that support special target populations. None. D. Progress Report None. 5. Describe the major accomplishments over the life of the project, including their predicted or actual impact. We have determined that four species of Trichoderma are not good candidates for combining with the soil fumigant metam sodium. We have determined compatibility of the biocontrol fungus F. oxysporum CS-20 with fungicides used on tomato. This information is needed to integrate biocontrol into the production system. We have determined the genetic relatedness of strains of the biocontrol fungus Talaromyces from 10 countries and 16
states in the US. This information is needed to determine the degree of similarity of strains released for biocontrol to native strains. 6. What science and/or technologies have been transferred and to whom? When is the science and/or technology likely to become available to the end- user (industry, farmer, other scientists)? What are the constraints, if known, to the adoption and durability of the technology products? The biocontrol strain F. oxysporum CS-20 has been transferred to other researchers and to industry. Most researchers had success with CS-20. One researcher and industry did not. The failures are now attributed to incompatible interactions with fungicides used in those production systems. Thus, part of how soon the technology is available to the end user becomes what constraints the end user is willing to accept. If the end user is willing to accept this incompatibility with fungicides, with an industry partner, strain CS-20 could be ready for registration with EPA
in about three years. Alternatively, it may be possible to alter the formulation or delivery of CS-20 to increase its compatibility with fungicides. This will take additional research. The newer biocontrol agents being developed are likely five to ten tears from registration with EPA. 7. List your most important publications in the popular press and presentations to organizations and articles written about your work. Gave presentation on research in the Vegetable Laboratory to the Minister of Agriculture of Kazakhstan, members of his delegation and representatives of the World Bank, July 14, 2004.
Impacts
(N/A)
Publications
- Fravel, D. R. Lewis, J. A. 2004. Effect of label and sublabel rates of metam sodium in combination with Trichoderma hamatum, T. harzianum, T. virens, and T. viride on survival and growth of Rhizoctonia solani. Phytoparasitica 32:111-118.
- Bao, J., Fravel, D. R., Lazarovits, G., Chellemi, D., van Berkum, P., and O'Neill, N. 2004. Biocontrol genotypes of Fusarium oxysporum from tomato fields in Florida. Phytoparasitica 32:9-20.
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Progress 10/01/02 to 09/30/03
Outputs
1. What major problem or issue is being resolved and how are you resolving it? As regulated by an international treaty and by the US Clean Air Act, the use of the soil fumigant methyl bromide is being phased out due to its role in ozone depletion. Alternatives to methyl bromide are needed for control of soil-borne plant pests. Methyl bromide is a broad-spectrum biocide that kills many different kinds of pests. The largest single use of methyl bromide in the United States is for fumigation of soil prior to planting tomatoes in Florida. While the immediate solution to replacing methyl bromide for tomato production is likely to be a combination of chemicals, other alternatives need to be developed since more and more chemicals are being withdrawn from the market. One approach is biological control - the use of beneficial microbes to mitigate the effects of plant pathogenic microbes. Fusarium wilt is one of the most important soil-borne problems faced by
tomato growers and this disease is expected to increase when methyl bromide is no longer available. Research at the Beltsville ARS Vegetable Lab is resolving the problem by discovery and development of beneficial Fusarium oxysporum for control of Fusarium wilt. 2. How serious is the problem? Why does it matter? Fusarium wilt is one of the top three pest problems faced by Florida tomato growers and is expected to increase when methyl bromide is no longer available. Race 3 of the pathogen has increased even while methyl bromide is in use. In general, soil-borne diseases are limiting factors in the production of many crops and account for 10-20% yield losses annually. Losses in individual fields can be as high as 100%. Management of soil-borne pathogens is necessary for a secure and stable supply of food and fiber, as well as for maintaining Agricultural exports. 3. How does it relate to the National Program(s) and National Program Component(s) to which it has been assigned? This
work directly relates to National Program 308 "Methyl Bromide Alternatives" under the component "Preplant Soil Fumigation Alternatives" and STP code 2.2.1.3, Plant Disease and Nematode Control. 4. What were the most significant accomplishments this past year? A. Combining biocontrol agents with reduced rates of fumigants may provide control of soil-borne diseases with fewer deleterious environmental effects than current treatments. In the Vegetable Laboratory, four species of Trichoderma were tested in combination with sublabel rates of the soil fumigant metam sodium for reduction of soil populations of the plant pathogen Rhizoctonia solani. The addition of biocontrol fungi significantly reduced viability of R. solani, but did not kill the pathogen as well as the fumigant alone. Unless control can be improved through formulation of Trichoderma or timing of its application, combining Trichoderma with sublabel metam sodium does not appear feasible for disease control. B. Other
significant accomplishment(s), if any None. C. Significant accomplishments/activities that support special target populations None. D. Progress report Combining biocontrol fungi with reduced rates of soil fumigants. Isolates of Trichoderma virens, T. hammatum, T. harzianum and T. viride were selected for their ability to kill the plant pathogen Rhizoctonia solani. To mimic their natural soil habitats, we used R. solani in beet seeds and Trichoderma on wheat bran. Under these conditions, species of Trichoderma were more sensitive to metam sodium than was R. solani. While the combination of biocontrol fungi plus metam sodium was more effective than metam sodium alone, the combination was found not feasible for grower use unless control can be improved through formulation Trichoderma or timing of its application. 5. Describe the major accomplishments over the life of the project, including their predicted or actual impact. This new project builds on a project that identified beneficial
fungi for the control of several soil-borne plant pathogenic fungi and the mechanisms of their control. The new project focuses more specifically on biocontrol of Fusarium wilt, since Fusarium wilt of tomato is expected to increase as methyl bromide is phased out. In particular, the new work seeks to understand the relationship between pathogenic and biocontrol strains of Fusarium, as well as the nature of the plant resistance induced by biocontrol strains of Fusarium. 6. What do you expect to accomplish, year by year, over the next 3 years? FY 2004 - CRIS Objective 2a (Genetic relationships and markers) Experiments will be conducted to determine if the ABC transporter in Fusarium oxysporum is inducible and how it is regulated. CRIS Objective 3c (Mechanisms of biocontrol) We will determine whether pathogenesis related proteins are produced in response to F. oxysporum strain CS-20, a biocontrol strain that induces resistance to the Fusarium wilt pathogen in tomato. If these are
produced, the determination of the quantity, timing and cellular site of production will be ascertained. FY 2005 - CRIS Objectives 1 and 1c (Potential of microbes for biocontrol) We will identify microbes with biocontrol potential and determine ecological parameters affecting control ability. FY 2006 - Objective 2b (Biological and ecological interactions) Important documentation of the spatial and temporal interactions of biocontrol and pathogenic strains of F. oxysporum on and in tomato roots will be made. CRIS Objective 1a, 1b and 1d (Inoculum density relationships, effect of host cultivar, and other pathogens) We will determine the amount of inoculum of the biocontrol agent needed to achieve control compared to the amount of pathogen present, and if the biocontrol agent works on different hosts, and against different pathogens.
Impacts
(N/A)
Publications
- Deahl, K. L., Fravel, D. R. Occurrence of leaf blight on petunia caused by Phytophthora infestans in Maryland. Plant Disease. 2003. v. 87 p. 1004.
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