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Plant Quarantine Programs Managed by APHIS-PPQ

Plant Germplasm Quarantine Program (PGQP)
Permit Holder: Dr. Joseph Foster
Email: Joseph.A.Foster@aphis.usda.gov

The quarantine programs for the various crops processed by PGQP are listed below with a short description of how each functions.

Bamboo Clones and Seed 
Contact: Dr. Clarissa Maroon-Lango
Email: Clarissa.J.Maroon-Lango@aphis.usda.gov

Clonal bamboo is usually imported as clumps that include stems with a few to several nodes or sometimes as plantlets in tissue culture. The quarantine for clonal bamboo if healthy is one year during which the plants are inspected during growth and tested twice for viruses, phytoplasmas, and undescribed pathogens. Tests include leaf dip assay via electron microscopy, ELISA serology, and PCR. Infected clones are discarded. Introductions that test negative for pathogens are released from quarantine and distributed as whole plants to importers.

Alternatively, bamboo may be imported into the U.S. as seed. Bamboo seed is treated to control bacteria and fungi, germinated in seed trays, and eventually potted. These seedlings are also observed for disease symptoms and insect pests, and tested for viruses, phytoplasmas, and undescribed pathogens by ELISA serology and PCR. Apparently symptom-free plants that test negative for the various pathogens are released from quarantine for distribution as whole plants.

Cassava Clones (Manihot
Contact: Dr. Jorge Abad
Email: Jorge.A.Abad@aphis.usda.gov

Cassava plants for propagation are usually imported as tissue cultures but may arrive as bare-rooted plants. During growth, the plants are tested for pathogens by mechanical transmission to sensitive indicator plants, grafting to a sensitive cassava cultivar, ELISA serology, and PCR. Infected cassava is subjected to meristem tip culture and heat therapy, and then the resulting plants are retested to ensure elimination of the pathogen(s). This therapy treatment usually adds one year to the quarantine period. Cassava accessions are shipped to each recipient in the form of 3-4 in vitro plantlets per clone.

Grass Clones and Seeds
Contact: Dr. Clarissa Maroon-Lango
Email:Clarissa.J.Maroon-Lango@aphis.usda.gov

Grass clones may arrive as whole plants, rhizomes, sprigs, stools, canes/stems, or plantlets in tissue culture from all countries. The growing plants are inspected for fungal or bacterial pathogens and tested twice in a year for many exotic viruses and phytoplasmas. Pathogen tests include mechanical transmission to sensitive herbaceous indicator plants, leaf dip assay via electron microscopy, ELISA serology, and PCR. Infected germplasm may either be destroyed with the approval of the importer or entered intothe therapy program for pathogen elimination by heat treatment and tissue culture. Grass clones released from quarantine are usually shipped to the importer as whole plants.

Seeds of certain grasses are prohibited in commercial quantities from certain countries but can be imported through quarantine. The seeds are sown in spring, the growing plants are inspected for pests, and the seed of these plants are harvested and shipped to the recipient. If pests are found, the seed lot is destroyed.

Pome Fruit Clones [Apples (Malus), Pears (Pyrus), Quinces (Cydonia, Chaenomeles)]
Contact: Dr. Margarita Bateman
Email: Margarita.F.Bateman@aphis.usda.gov

Pome fruits are usually imported as dormant budwood, but could arrive as bare-rooted plants. Selected buds are propagated on the appropriate domestically purchased seedling rootstocks. Growing plants are inspected for pests and tested for viruses, viroids, and phytoplasmas by PCR and molecular hybridization. Dormant budwood is used to test for viruses by double budding the introduction and a sensitive indicator variety on a domestic seedling rootstock. Provisional or early releases within 1-2 years of importation are possible if the tested clone is negative in tests for common latent viruses, phytoplasmas and viroids. Importers must obtain a permit from APHIS-PPQ to grow provisionally released pome fruits. Additional testing for fruit markers, bark disorders, and poorly characterized pathogens involves budding the tested clone on sensitive indicator trees in the orchard and observing the leaves, fruit and bark of these trees for 3 growing seasons. Thus, the quarantine period for healthy pome introductions is 4-5 years. Infected introductions are grown in tissue culture and exposed to heat treatments and meristem tip culture to eliminate the detected pathogen(s), thus adding years to the quarantine period. Pome fruits are distributed as budwood from the tested clone.

Potato Clones and Seed (Solanum)
Contact: Dr. Jorge Abad
Email: Jorge.A.Abad@aphis.usda.gov

Potato clones are usually imported as plantlets in tissue culture but may arrive as cleaned tubers. During growth from September to May, the potato clones are tested for many viruses, phytoplasmas, bacteria and potato spindle tuber viroid by mechanical transmissions to sensitive indicator plants, ELISA serology, leaf dip assay by electron microscopy, molecular hybridization, and PCR. Suspicious symptoms in the imported plant may be investigated by grafting healthy potato plants with the introduction. Potatoes that are free of pathogens may be released in spring, 9 months after arrival. Infected potatoes are exposed to chemotherapy and thermotherapy in tissue culture, meristem tips are grown, and then the resulting plants are retested to determine the success of the therapy. The therapy process may add a year or more to the quarantine period. Vegetatively propagated potatoes from the tested clones are distributed to each recipient as 3-4 in vitro plantlets per clone.

Samples from each potato seed lot are germinated and grown in a quarantine greenhouse from September to May. Each sample is inspected during growth and tested for viruses by mechanical transmission tests to sensitive indicator plants and for potato spindle tuber viroid by molecular hybridization. Seed lots with samples testing negative for pathogens are distributed to recipients in the spring without the seeds removed for testing purposes. Infected seed lots are destroyed.

Rice Seeds (Oryza)
Contact: Dr. Clarissa Maroon-Lango
Email: Clarissa.J.Maroon-Lango@aphis.usda.gov

Quarantine regulations are designed to prevent the importation of several exotic seed-borne fungal and bacterial rice pathogens and control the introduction of certain rice species (Oryza longistaminata, O. punctata, and O. rufipogon), which are listed on the Federal Noxious Weed list. Upon entry in spring, the rice seeds are inspected and treated with hot water (56C, 15 min) by an APHIS-PPQ inspector at the Beltsville Plant Inspection Station. Dried and repackaged seed, which serves as the parental seed, is released to the crop manager. For each accession, at least 30 apparently healthy seeds are dehulled and surface sterilized in a 30% solution of commercial bleach (6.25% sodium hypochlorite) for 2 hours. Ater rinsing in sterile deionized water, seed is grown in tissue culture medium (PDA + 0.5X MS) for 2-3 weeks. Seeds contaminated with fungal or bacterial growth are discarded. Plants from microbe-free cultures are transplanted into pots in the greenhouse. These plants are inspected visually during growth and at least once as seed heads ripen for fungal or bacterial pathogens. Seeds free of pests are released in the fall or early winter and shipped to the importer.

Small Fruit Clones (Ribes)
Contact: Dr. Joseph Foster
Email: Joseph.A.Foster@aphis.usda.gov

Currants and gooseberries are usually imported as cuttings but may also arrive as bare-rooted plants. Gooseberry cuttings are usually grafted onto domestic jostaberry plants to establish them and promote vigorous growth before rooting cuttings. Growing plants are tested for pathogens by mechanical transmission to sensitive herbaceous plants and PCR. Dormant buds are budded onto sensitive currant indicator plants to test for graft-transmissible pathogens. Introductions that test negative can be released within 2-3 years. Infected introductions are exposed to therapy procedures involving treatment of tissue cultured plants and then the resulting plants are retested to confirm that the pathogen has been eliminated. Currants and gooseberries are distributed as bare-rooted plants.

Stone Fruit Clones and Seeds (Prunus)
Contact: Dr. Margarita Bateman
Email: Margarita.F.Bateman@aphis.usda.gov

Stone fruits, which include fruiting and ornamental almonds, apricots, cherries, nectarines, peaches, plums and prunes, are usually imported as dormant budwood but may arrive as cuttings for rooting or bare-rooted plants. Selected buds are propagated on the appropriate domestically purchased seedling rootstocks. Growing plants are inspected during growth and tested for viruses, viroids, bacteria, and phytoplasmas by mechanical transmission tests to sensitive herbaceous indicators, ELISA serology, and PCR. Dormant budwood is used to detect viruses by budding sensitive indicators or by double budding the introduction and indicator on a domestic seedling rootstock. Provisional or early release of clones that test negative in the intial testing is possible 1-2 years after arrival. Importers must obtain a permit from APHIS-PPQ to grow provisionally released stone fruits. Final release of the tested clone occurs after all tests for pathogens are negative, usually within 2-3 years of importation. Infected clones are exposed to heat treatments in tissue culture, meristem tips are grown, and then the resulting plants are retested to determine if therapy was successful. Stone fruit clones are usually distributed as dormant budwood.

Stone fruit seeds are germinated in the fall and winter and then grown in the greenhouse in spring. Growing seedlings are tested individually for plum pox virus by ELISA and PCR, and for potyviruses and ilarviruses by PCR. Buds from dormant budwood from each seedling are budded on GF 305 peach seedlings to check for various pathogens. Seedlings that test negative are released and sent to the importer as whole plants.

Sugarcane and Related Grass Clones (Saccharum)
Contact: Dr. Clarissa Maroon-Lango
Email: Clarissa.J.Maroon-Lango@aphis.usda.gov

Sugarcane is usually exchanged as cane setts and occasionally as plantlets in tissue culture. Setts should reach PGQP by March (southern hemisphere origins) or August (northern hemisphere origins). Growing plants are observed for symptoms during each of two growing cycles and tested for bacteria, viruses and phytoplasmas by mechanical transmission to sensitive herbaceous plants, serology, culturing attempts, and PCR. Additional tests are conducted after cutting back and then at shipping. The released setts will be taken from mature plants of the tested clones that were grown from long, hot-water treated cane pieces. Distributed setts are subjected to a long hot water treatment prior to shipping. The quarantine period for healthy sugarcane clones imported for propagation is usually about 18 months. Infected clones are entered into the tissue culture program for pathogen elimination, and then the resulting plants are retested to determine if therapy was successful. Therapy prolongs the quarantine period for infected sugarcane.

Sweet Potatoes Clones (Ipomoea)
Contact: Dr. Jorge Abad
Email: Jorge.A.Abad@aphis.usda.gov

Sweet potato clones are usually imported as plantlets in tissue culture but may occasionally arrive as cleaned roots or cuttings. Plants are grown from May through August in quarantine greenhouses. Growing plants are inspected for pests and are tested for viruses and phytoplasmas by grafting stem pieces to Ipomoea setosa and by PCR. Clones that test negative may be released 9 months after arrival. Infected sweet potatoes are subjected to meristem tip culture and heat therapy, and then the resulting plants are retested to verify that the therapy procedure eliminated the detected pathogen(s). This therapy treatment usually adds one year to the quarantine period. Sweet potatoes are released and then shipped to recipients as 3-4 in vitro plantlets per clone.

Woody Ornamentals
Contact: Dr. Joseph Foster
Email: Joseph.A.Foster@aphis.usda.gov

During the last five years, various prohibited woody ornamentals, including chestnuts, elms, maples, mulberries, barberries, and a rose have been imported by PGQP. Woody ornamentals are usually imported as bare-rooted plants but may arrive as cuttings which require grafting or rooting. The inspection and testing requirements vary with each genus. Barberries only require inspection during growth for evidence of black stem rust of wheat. Other genera, such as elms and maples, involve inspections during growth and pathogen tests for viruses, viroids, and phytoplasmas. Plants testing negative for pathogens are released and shipped to the importer as whole plants.



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