Seed classification and limited generation

1. All seed potatoes must be limited to seven years of reproduction in the field. Seed lots may be reproduced beyond this limit with prior approval of the state seed department providing the seed lot has been winter tested and eligible for recertification. 2. Prenuclear seed stocks must originate from tissue-culture derived plantlets, minitubers, microtubers, or pathogen-tested stem cuttings. Experimental breeding selections shall originate from pathogen-tested material. The first year of reproduction of these stocks will be regarded as nuclear seed stock. The certified designation will be granted to lots meeting the minimum standards outlined in section 74-04-01-08 and by approval of the commissioner. Subsequent generations will be regarded as: a. FY1 (first field year) is the progeny of nuclear seed. b. FY2 (second field year) is the progeny of FY1. c. FY3 (third field year) is the progeny of FY2. d. FY4 (fourth field year) is the progeny of FY3. e. FY5 (fifth field year) is the progeny of FY4. f. FY6 (sixth field year) is the progeny of FY5. g. Certified class (seventh field year) is the progeny of FY6. 3. Prenuclear seed stocks intended to be grown in the greenhouse as minitubers, microtubers, or stem cuttings must be laboratory-tested, be demonstrated to be free of the following pathogens, and meet the following standards: a. Clavibacter michiganensis subsp. sepedonicus (ring rot). b. Erwinia carotovora (blackleg and soft rot). c. Potato virus A. d. Potato virus M. e. Potato virus X. f. Potato virus Y. g. Potato leafroll virus. h. Potato spindle tuber viroid. i. Potato mop top virus. j. All micropropagation production must be approved by a certification agency. k. Good records must be maintained on all tests and submitted with the application for field inspection. l. A minimum of one percent of the plantlets must have been tested for the above pathogens using the most reliable testing techniques. 4. Basic seed must originate from sources described above and developed in seed plots and have met specific field inspection and winter test standards established by the state seed department. Seed stocks will be grown a limited number of field years. Experimental cultivars under evaluation by the state seed department in cooperation with universities or industry will meet program requirements of and will be maintained under guidelines and standards established by the state seed department. Seed stocks will be grown a limited number of field years. 5. Foundation class seed must be seed meeting standards for recertification. a. Foundation seed will be produced on farms found to be free of bacterial ring rot for three years. All seed stocks must be replaced on a farm in which bacterial ring rot has been found. b. Excessive blackleg symptoms will be cause for rejection as foundation stock. 6. The certified class must meet the minimum field tolerances described in section 74-04-01-08. The classification serves as a quality standard for commercial planting purposes only and must meet all the requirements and responsibilities of this chapter. The certified class designation may be applied to any field year under the criteria set forth in section 74-04-01-07.8. 7. Field year designations increase with years of field reproduction from the original seed source. Field year five (FY5) will be the final generation of seed eligible for recertification. The certified seed class is not eligible for recertification. If seed availability is low for a specific potato variety, seed lots with more advanced generation numbers may be eligible for recertification providing the seed lot has passed a winter test and prior approval of the state seed department has been obtained. 8. Except for varietal mixtures, seed lots may be downgraded and placed in the certified class and sold by their field year designation as certified seed providing they meet the specifications for that class. Disease tolerances for each field year of seed are outlined in the section on field inspection standards.