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Seed Grading and Marketing | |
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| | Return to the Guide to Commercial Potato Production on the Canadian Prairies
Make every effort to prevent bruising.
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Seed potatoes should be sized to meet the market requirements. The standard method of sizing seed potatoes is based on weight. Tubers can also be graded by dimension. When sizing by dimension, screen sizes appropriate for each variety must be used.
All seed potato classes are subject to the same tuber standards (i.e. there is only one quality grade for Canada Seed Potatoes). The quality standards provide a tolerance for symptoms of disease, damaged tubers and varietal mixtures that could affect the quality of the seed. Tolerance for disease and defect in the graded stock is defined by the tuber standards [sections 48.1 (2) to (10)] in the seed potato regulation,
Seed potato grade tolerance
 | Tolerance (% by count) |
| Disease or Defect | At shipping | A destination |
| Soft rot or wet breakdown | 0.10% | 0.50% |
| Dry rot, including late blight | 1.00% | 1.00% |
| Scab or Rhizoctonia light | 10.00% | 10.00% |
| Scab or Rhizoctonia medium | 5.00% | 5.00% |
| Stem-end discoloration due: to vine killing, frost, heat, or drought with a penetration from 6 -13 millimetres | 4.00% | 4.00% |
| Tubers malformed or externally damaged. | 2.0% | 3.00% |
In addition, the tolerance for foreign varieties is as follows:
- Elite 3 or Elite 4 classes of seed - none
- Foundation class of seed - 0.05%
- Certified class of seed - 0.10%
In any lot of graded seed potatoes, at least 98% of the tubers shall be firm and well shaped.
Growers are encouraged to take samples of the graded stock regularly during the grading operation to ensure the grade requirements are being met. Where problems are identified, appropriate adjustments should be made at the grading line. These may include adding additional staff or reducing the speed of the conveyers.
Seed potatoes may be packed or shipped in a variety of container sizes, including the normal jute bag and bulk containers. Bagged seed potatoes must be labelled with an official tag that identifies the variety, class and certification number of the seed lot being shipped. The following tag colors identify the respective seed classes:
- Orange tags identify the Elite Classes of seed
- White tags identify the Foundation Class of seed
- Blue tags identify the Certified Class of seed
In the case of bulk loads, the regulations require loads to be accompanied by a bulk-movement certificate. Growers are responsible for the safe storage and correct use of official labels and to ensure the seed is correctly labelled.
Written by D. Lidgett |
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For more information about the content of this document, contact Shelley Barkley.
This information published to the web on February 2, 2005.
Last Reviewed/Revised on September 24, 2008.
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