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Funded Project |
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Funding Program:
Regional IPM Grants (S-RIPM) |
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Project Title:
Novel Approaches to Integrated Management of Armillaria Root Rot of Peach |
Project Directors (PDs):
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Lead State: SC Lead Organization: Clemson University |
| Research Funding: $150,000 |
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Start Date: Aug-01-2005 End Date: Jul-31-2008 |
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Summary:
Regional stakeholder groups and the Georgia/South Carolina crop profile for peach, a part of the national Pest Management Strategic Plan website, affirm that Armillaria root rot is a serious threat to peach production as a primary cause of premature orchard decline and mortality in the Southeastern United States. Both institutions recognize that there are currently neither practical nor effective means for managing Armillaria root rot, mandating the need for an integrated management program in the Southeast. The overall goal of this project is to evaluate novel applications of cultural, chemical, and transgenic technologies as management options to be implemented within the existing framework of a pre- and post-plant management program for Armillaria root rot currently being developed at our institution. Specific objectives are to: 1) improve orchard sustainability on Armillaria infested sites through a combination of raised-bed planting, root collar excavation, and mycorrhizal root-dips; 2) determine the potential for reduced risk fungicides used in combination with systemic injection technology to prevent root collar colonization of Armillaria; 3) propagate and characterize transgenic plum lines expressing Gastrodia anti-fungal protein (GAFP) for the development of Armillaria resistant rootstocks. This proposal addresses both future directions and focus directions for IPM programming of the IPM roadmap for the National Intergrated Pest Management Program since results from this project provide an environmentally sound means (cultural and biological) of improving the sustainability of stone fruit production without relying on hazardous and costly agricultural fumigants.
Objectives: 1. Improve orchard sustainability on Armillaria infested sites through a combination of raisedbed planting, root collar excavation, and mycorrhizal root-dips 2. Determine the potential for reduced risk fungicides used in combination with systemic injection technology to prevent root collar colonization of Armillaria 3. Propagate and characterize transgenic plum lines expressing Gastrodia anti-fungal protein (GAFP) for the development of Armillaria resistant rootstocks. |
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Final Report: |
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Results From report submitted bt the PI to USDA CRIS report system PROGRESS: 2005/08 TO 2008/07 OUTPUTS: We initiated four research programs to find management strategies for ARR control. Two of them, the root collar excavation and the use of Trichoderma, are long-term field experiments that are still ongoing and results are expected within the next 2 growing seasons. Two other programs, including the development and characterization of transgenic plum lines and targeted chemical treatment of trees via trunk injections, were short term projects and research results were obtained. The Gastrodia anti-fungal protein (GAFP) is a monocot mannose-binding lectin isolated from the Asiatic orchid Gastrodia elata. This lectin has provided increased disease resistance in transgenic tobacco against root diseases from different phylogenetic lineages, but its potential to confer disease resistance in tree species is not known. Agrobacterium tumefaciens mediated transformation yielded three GAFP-1 expressing plum lines (Prunus domestica var. Stanley) designated 4J, 4I, and 5D. These lines possessed one, two, and four copies of the GAFP-1 gene, respectively, as demonstrated by southern analysis. Lines 4J and 4I were not phenotypically different from the non-transformed control line, but line 5D showed significant divergence with regard to its leaf morphology and growth habit. Compared to the inoculated control line, lines 4J and 4I exhibited increased tolerance to Phytophthora root rot (PRR), caused by P. cinnamomi. When inoculated with the root-knot nematode, Meloidogyne incognita, the 4J and 4I lines showed a significantly lesser degree of galling than the inoculated control line. Nematode reproduction in these lines, as measured by eggs produced per gram root tissue, was not significantly different from the control line (P = 0.05). The 5D line did not demonstrate increased tolerance to either pathogen. Intravascular trunk infusion of propiconazole has been associated with beneficial effects on Armillaria root rot control in Prunus sp. but its basipetal movement has not been verified. Propiconazole, a sterol demethylation inhibitor fungicide, was more effective in inhibiting mycelial growth of Armillaria tabescens isolates in vitro (average EC50 value of 0.6 ppm) compared to fungicides from five other chemical classes (EC50 values ranging from 4.6 to >1000 ppm). The fungicide was infused into the vascular system of peach trees in the spring, summer, and fall of 2005 and 2006. Propiconazole concentration was determined using gas chromatography mass spectrometry in trunk sections above and below the infusion site and in primary roots. Over two experimental years, spring and fall infusions resulted in consistent propiconazole accumulations in primary peach roots. Spring infusions yielded propiconazole concentrations of 1.7 ppm in 2005 and 5.6 ppm in 2006, whereas the highest accumulations were detected following fall infusions with 9.2 ppm in 2005 and 6.7 ppm in 2006. Propiconazole was also consistently detected in trunk sections collected from above and below the infusion site. PARTICIPANTS: Dr. Ralph Scorza at the USDA station in Kearneysville conducted the plum transformation for us Dr. Achour Amiri is a postdoctoral scientist in my lab and conducted the injection study TARGET AUDIENCES: The entire stone fruit industry will benefit from this project. For example, Armillaria root rot is a major problem for SC and GA peach growers, MI and IL cherry growers. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period. IMPACT: 2005/08 TO 2008/07 The results of this study suggest that the expression of GAFP-1 in the roots of a woody plant may confer some resistance to PRR and root-knot nematode disease. This is a significant finding because rootstocks resistant to PRR are commercially not available. This genetically engineered rootstock may be the first of a line of rootstocks with resistance to ARR as well. Long term field trials will be necessary to confirm this hypothesis. Management of the disease in existing orchards is a second priority of our research. The basipetal movement of propiconazole in peach trees and its inhibitory activity against A. tabescens in vitro suggest that propiconazole infusion could be useful for targeted Armillaria root rot management. In other words, injecting propiconazole into healthy trees neighboring diseased trees may be a solution to limit the spread of the disease. This approach does not require large amounts of chemicals and is therefore environmentally much friendlier than fumigation or chemical drenches. It cannot be mechanized, however, and therefore will require some manual labor. In the future, we believe that an integrated approach of infusion, biological control, cultural method and rootstock selection will be a solution for ARR management. PUBLICATIONS (not previously reported): 2005/08 TO 2008/07 1. Amiri, A., Bussey, K. E., Riley, M. B., Schnabel, G. 2008. Propiconazole inhibits Armillaria tabescens in vitro and translocates into peach roots following trunk infusion. Plant Dis. 92:1293-1298. 2. Nagel, A.K., Schnabel, G., Petri, C. and Scorza, R. 2008. Generation and characterization of transgenic plum lines expressing the Gastrodia antifungal protein. HortScience 43:1514-1521. |
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Outcomes N/A |
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Impacts From report submitted bt the PI to USDA CRIS report system The results of this study suggest that the expression of GAFP-1 in the roots of a woody plant may confer some resistance to PRR and root-knot nematode disease. This is a significant finding because rootstocks resistant to PRR are commercially not available. This genetically engineered rootstock may be the first of a line of rootstocks with resistance to ARR as well. Long term field trials will be necessary to confirm this hypothesis. Management of the disease in existing orchards is a second priority of our research. The basipetal movement of propiconazole in peach trees and its inhibitory activity against A. tabescens in vitro suggest that propiconazole infusion could be useful for targeted Armillaria root rot management. In other words, injecting propiconazole into healthy trees neighboring diseased trees may be a solution to limit the spread of the disease. This approach does not require large amounts of chemicals and is therefore environmentally much friendlier than fumigation or chemical drenches. It cannot be mechanized, however, and therefore will require some manual labor. In the future, we believe that an integrated approach of infusion, biological control, cultural method and rootstock selection will be a solution for ARR management. |
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