ANNEX VSupplementary provisions
ANNEX V Quantification of the degree of resistance of potato varieties and protocol for resistant testing, as referred to in Article 8(3) 1. Degree of resistance The relative susceptibility of a given potato variety is attributed in accordance with the scores indicated in the table and the formula set out in point 2.16. Score 9 corresponds to the highest level of resistance. Standard scoring notation in relation to relative susceptibility of potato varieties for the specified pests Relative susceptibility (%) (RS) Score ≤ 1 9 1 < RS ≤ 3 8 3 < RS ≤ 5 7 5 < RS ≤ 10 6 10 < RS ≤ 15 5 15 < RS ≤ 25 4 25 < RS ≤ 50 3 50 < RS ≤ 100 2 > 100 1 2. Protocol for resistance testing 2.1. The test shall be performed in a quarantine facility, either in open space, glasshouses or climate chambers. 2.2. The test shall be performed in pots each containing at least one litre of soil or other suitable substrate. 2.3. The soil temperature in the test containers throughout the duration of the test shall not exceed 25 °C and adequate watering shall be provided. 2.4. When planting the test or control variety one potato eye plug of each test or control variety shall be used. 2.5. The potato variety ‘Désirée’ shall be used as a standard susceptible control variety in every test. Additional fully susceptible control varieties of local relevance may be added as internal controls. 2.6. The following standard populations of the specified pest shall be used in resistance tests against Globodera rostochiensis pathotypes Ro1, Ro5 and Globodera pallida pathotypes Pa1 and Pa3: Ro1: population Ecosse Ro5: population Harmerz Pa1: population Scottish Pa3: population Chavornay Other populations of local relevance may be added. For these populations, records of how their pathotype was determined shall be available. New virulent populations may be added, taking into account where such populations may not yet be stable and pathotypes not yet established. 2.7. The identity of the standard population used shall be checked using appropriate methods. It is recommended that at least two resistant varieties or two differential standard clones of known resistance capacity are used in the test experiments. 2.8. The inoculum of specified pest (Pi) shall consist in total of five infective eggs and juveniles per ml of soil. The specified pest may be inoculated as cysts, or combined as eggs and juveniles in a suspension. 2.9. The viability of the content of cysts of the specified pest used as the inoculum source shall be at least 70 %. It is recommended that the cysts are 6 to 24 months old and are kept for at least four months at 4 °C immediately prior to use. 2.10. There shall be at least four replicates (pots) per combination of population of the specified pest and potato variety tested. 2.11. The duration of the test shall be at least three months and the maturity of developing females shall be checked before completing the experiment. 2.12. Cysts of the specified pest from the four replicates shall be extracted and counted separately for each pot. 2.13. The final population (Pf) on the standard susceptible control variety at the end of the resistance test shall be determined by counting all cysts from all replicates and the eggs and juveniles from at least four replicates. 2.14. A multiplication rate of at least 20 × (Pf/Pi) on the standard susceptible control variety shall be achieved. 2.15. The coefficient of variation (CV) on the standard susceptible control variety shall not exceed 35 %. Other statistical tests may be applied at a later stage if there is evidence that those tests will increase the precision of the test results. 2.16. The relative susceptibility of the tested potato variety to the standard susceptible control variety shall be determined and expressed as a percentage according to the formula: Pf test variety /Pf standard susceptible control variety × 100 %. 2.17. If a tested potato variety has a relative susceptibility of 3 % or more, cyst counts will suffice. In cases where the relative susceptibility is less than 3 %, eggs and juveniles shall be counted in addition to cyst counts. 2.18. Where the results of tests in the first year indicate that a variety is fully susceptible to a pathotype (when the score is < 3), there is no requirement to repeat these tests in the second year. 2.19. If the tested variety is not fully susceptible to a pathotype (when the score is ≥ 3), the results of the tests shall be confirmed by at least one other trial performed in another year. The arithmetic mean of the relative susceptibility in the two years shall be used to derive the score in accordance with the table set out in point 1.