Tuber Quality Standards

All seed potato classes are subject to the same tuber standards–there is only one quality grade for Canada Seed Potatoes. The total allowable disease and defects permitted in a graded seed potato lot are set out in section 48.1, subsections (2) – (10) of the Seeds Regulations. The following is a summary of the shipping point tolerances:

Disease or Defect

Tolerence Level (%)

Soft rot or wet breakdowns
Dry Rot
Scab or Rhizoctonia – light
Scab or Rhizoctonia – moderate
Stem-end discolouration due to top-killing, frost, heat, or drought with penetration from 6 – 13 mm
Tubers malformed or externally damaged
Total number of tubers affected by disease and defects, not including slight scab and rhizoctonia and stem-end discolouration
Soft rot or wet breakdowns

In addition there should be no more than the following levels of foreign varieties: not more then 0.05% in Elite III, not more than 0.10% in Elite IV, and not more than 0.20% in the Foundation and 0.50% in the Certified classes of seed.