Sponsoring Institution
Agricultural Research Service/USDA
Status
ACTIVE
Funding Source
USDA INHOUSE
Reporting Frequency
Annual
Project Director
VACANT
Accession Number
424246
Project Number
2036-21000-010-06T
Dates
2011-10-01 - 2015-09-30
Recipient Organization
AGRICULTURAL RESEARCH SERVICE
RIVERSIDE,CA 92507
Keywords
citrus
cryopreservation
cryotherapy
disease
pathogen
Research Effort
Applied (100%)
Basic (0%)
Developmental (0%)
Classification Parameters
| Knowledge Area | Subject of Investigation | Field of Science | Percent |
|---|
| 202 - Plant Genetic Resources |
910 - Grapefruit |
1080 - Genetics (excludes breeding) |
25% |
| 202 - Plant Genetic Resources |
920 - Orange |
1080 - Genetics (excludes breeding) |
25% |
| 202 - Plant Genetic Resources |
930 - Lemon |
1080 - Genetics (excludes breeding) |
25% |
| 202 - Plant Genetic Resources |
999 - Citrus, general/other |
1080 - Genetics (excludes breeding) |
25% |
Goals / Objectives
There are currently two methods available for therapy of Citrus: thermotherapy and shoot tip grafting (STG). Thermotherapy does not eliminate viroids, and is inefficient at eliminating HLB and Citrus tatterleaf virus (CTlV). Although STG has been shown to eliminate all graft transmissible pathogens, pathogens such as viroids and Citrus Tatterleaf virus are still difficult. However, the major drawback to STG is the requirement for a high level of expertise since the technique is mastered only after many months of practice and it requires a very steady hand. A relatively new technology, cryotherapy, has been successfully implemented in potato, sweet potato, grapevine, raspberry, and Prunus to eliminate pathogens that have been challenging when using traditional methods. Recently HLB was shown to be eliminated from Citrus by cryotherapy. In cryotherapy, cells containing pathogens do not survive the exposure to liquid nitrogen, thus eliminating the pathogen. In cryotherapy, a meristem with up to three leaf primodia (about 1 mm long) are excised, in contrast to the meristem with a single leaf primordium (about 0.1 mm long) excised in traditional STD. Use of larger shoot tips increases the survival rate and makes the procedures more reproducible.
Methods (unparsed)
A cryotherapy protocol will be developed by the Volk lab and then applied to tissue infected with stock virus isolates obtained from the USDA-ARS Citrus Repository. Experimental variables will include shoot tip size, antibiotic treatments, and liquid nitrogen exposure. Recovering shoots will be micrografted to Carrizo seedlings and then tested for the presence of pathogens. Validation of method to eliminate exotic pathogens will be done.
Methods
A cryotherapy protocol will be developed by the Volk lab and then applied to tissue infected with stock virus isolates obtained from the USDA-ARS Citrus Repository. Experimental variables will include shoot tip size, antibiotic treatments, and liquid nitrogen exposure. Recovering shoots will be micrografted to Carrizo seedlings and then tested for the presence of pathogens. Validation of method to eliminate exotic pathogens will be done.
Project Timeline Tracking
Outputs
This project is related to objective 1 and 2 (identification of priority genetic resources of citrus and characterization of the genotypes of citrus, respectively) of the parent project. The primary goal of this project is to develop cryotherapy as a practical, reliable method of eliminating graft transmissible pathogens from Citrus and citrus relatives without inducing juvenility. Permits have been obtained to ship pathogen infected citrus material from Riverside, California, and from the Exotic Disease Quarantine Laboratory, Beltsville, Maryland, to the USDA ARS Plant Germplasm Preservation Research Unit, Ft. Collins, Colorado. Initial research has been directed to elimination of viroids and Citrus tatterleaf virus in the recovered plants. We have demonstrated the efficient elimination of viroids and Citrus tatter leaf virus, the most difficult graft transmissible pathogens to eliminated by use of conventional shoot tip grafting and thermotherapy.