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Funded Project |
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Funding Program:
IPM Enhancement Grants |
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Project Title:
Therapeutic Management of Pecan Bacterial Leaf Scorch Using Carbon Nanotubes |
Project Directors (PDs):
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Lead State: TX Lead Organization: Texas A&M AgriLife Extension Service |
| Undesignated Funding: $30,000 |
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Start Date: Mar-01-2017 End Date: Feb-28-2018 |
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Pests Involved: Xylella fastidiosa |
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Site/Commodity: Pecan |
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Area of Emphasis: Disease management |
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Summary:
The pecan industry is economically important to the U.S., which makes up 55% of the world’s total annual pecan production. Annual pecan production in the U.S. is estimated to be 264.2 million pounds with an estimated value of $517 million dollars on a utilized in-shell basis. Pecan bacterial leaf scorch (PBLS) caused by a xylem-inhabiting bacterium, Xylella fastidiosa subspecies multiplex, is an emerging issue for the U.S. and international pecan industry and is becoming a threat to the pecan production. The disease has been reported in Arizona and New Mexico, and its presence in California is being currently confirmed. PBLS is a chronic disease that debilitates the plant and can cause major yield losses in susceptible varieties. Researchers have found the bacterium is transmitted between grafting of scions and pecan rootstock in addition to insect vector-mediated or seed-borne transmission. It is an important issue because propagation of pecan plants is predominantly performed through grafting. There is no cure for bacterium-infected plants and few integrative pest management strategies have been developed for PBLS. Hot-water treatment of pecan scions and rootstock has been implemented as a standard phytosanitary treatment. However, the hot-heat treatment method is not practical since its disinfection efficacy and adverse effect on plant health still were not fully validated. Therefore, establishment of the effective remediation protocols for PBLS is imperative to ensure disease-free germplasm rootstock and prevent the spread of the disease. With current trends in globalization, it is more important than ever that breeders screen plant germplasm prior to national and international transport to restrict the spread of potentially dangerous pathogens. Our novel approach is to innovate the current heat treatment using the advanced nanotechnology. We are interested in the fact that carbon nanotube (CNT) by itself does not have antibiotic activity but is a strong microwave absorbing material which can produce intense heating due to its outstanding electrical properties. CNT that is absorbed through roots, translocated to the xylem and exposed with microwave can result in increase of thermal energy exclusively in the xylem where the bacterium is inhabiting. The spike of thermal energy in the xylem can kill X. fastidiosa but will minimize adverse impact on other plant tissue. Our preliminary study showed that the combination of the CNT and microwave treatment can effectively reduce the bacterial viability. In this project, CNT materials with different molecular structure and functional groups will be fabricated. Once optimal treatment conditions (CNT type, CNT concentration and microwave exposure) have been determined, the treatments will be further validated with X. fastidiosa subsp. multiplex-infected rootstock and scion samples and be compared with the traditional hot-water treatment. Outcomes of this proposal will advance practical knowledge of PBLS remediation method that enables more growers to successfully manage the emerging bacterial disease and to improve sustainable pecan production using safe and effective option.
Objectives: Planned Outputs: Develop carbon nanotube materials as an advanced alternative bactericide. Adopt this advanced technology for management of pecan bacterial leaf scorch. Convey research findings to growers and stake holders. Anticipated Outcomes: Optimize size, topological structure and functional groups of carbon nanotubes. Enhance the effectiveness of carbon nanotubes with incorporation of metal elements. Optimize application rates of carbon nanotube materials in the pecan propagation system. Implement the advanced technology in the pecan propagation system. Engage with pecan growers and stakeholders to develop solutions to pecan bacterial leaf scorch issues. Obtain economic returns in pecan production from adopting new technologies. Provide growers economic impact of new alternative technologies for management of pecan bacterial leaf scorch. Develop extension programs and educational materials. Use research results for regional and national policy how to regulate emerging technologies in the crop protection. |
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Final Report: |
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Outputs This project developed and demonstrated carbon nanotube (CNT) materials combined with microwave irradiation as an advanced alternative bactericidal method for pecan graftwood. CNT solution could be readily transpired into graftwood. Dissected samples of CNT-treated scion samples were examined with a dissecting microscope. The xylem tissue was appeared darkened, and aggregated CNT particles were identified along the periphery of the vessel elements in CNT-treated samples. CNT solution was prepared by diluting 0.01% by weight in water and used to treat scions. Then microwave irradiation was applied at different exposure times and iterations. To determine the best condition for temperature changes following microwave treatment, temperatures on scions were measured using a thermal couple or a thermal camera. The average temperature of scions was significantly higher in CNT-treated samples when exposed to microwave for 3-5 sec compared to water-treated samples with the same microwave exposure. CNT with 3-sec microwave irradiation produced ~60oC at which Xylella fastidiosa cannot survive but the viability of scions is not compromised. These research findings of future pecan graftwood sterilization technique were introduced to growers and stakeholders at the 2017 annual meeting of Texas Pecan Growers Association. The results were also presented at 2017 APS annual meeting at San Antonio, Texas. |
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Outcomes Importance of bacterial leaf scorch and their management in pecan industry was measured by a survey that was conducted at the 2017 annual conference organized by Texas Pecan Growers Association. Most pecan producers observed scorch symptoms in their orchards between July and November. The disease was suspected to cause reduced nut quality and yield loss. However, they were not very familiar to bacterial leaf scorch or its management options before this meeting. The development and application of a novel graftwood sterilization based on CNT and microwave will produce significant economic benefits to pecan growers. |
Report Appendices
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