Equivalent field generations
The number of field generations used to produce the final product of the seed schemes from the Netherlands, Canada, Scotland and Western Australia varies and are shown in Table 1.
The final fifth generation of Western Australian certified seed is produced at least two years earlier than the end product of seed schemes from Canada and the Netherlands and three years earlier than the Scottish scheme.
The Netherlands seed scheme end product is Class C certified seed, which is produced at generation seven (G7), two field generations later than Western Australia’s end product of G5 certified seed.
Western Australian G5 certified seed is equivalent to the Netherlands Class E seed. The Netherlands has an alternative pathway for production of seed potatoes where Class SE seed is produced prior to Class E. This means that potato seed from the Netherlands may be three field generations later than Western Australian G5 certified seed.
The Canadian scheme’s end product is generation 7 certified seed; two field generations older than Western Australia’s seed scheme final product. Western Australian G5 certified seed is equivalent to the Elite 4 seed in the Canadian seed scheme.
The Scottish scheme produces Basic E seed at generation 7 which is used to produce generation 8 ‘Certified Seed’ outside Scotland. That is, three generations after Western Australian G5 certified seed. Western Australian G5 certified seed is equivalent to Basic S seed in the Scottish seed scheme.
Generation | Seed scheme | |||
---|---|---|---|---|
Western Australia 2015 | Netherlands* 2005 | Scotland 2017 | Canada 2017 | |
Source | Minitubers | Mother plant/tissue culture | Pre-basic tissue culture | Nuclear seed |
1 | G1 certified seed | 1st year clone | Pre-basic 1 | G1 pre-elite |
2 | G2 certified seed | 2nd year clone | Pre-basic 2 | G2 elite 1 |
3 | G3 certified seed | 3rd year clone: Class S pre-basic seed | Pre-basic 3 | G3 elite 2 |
4 | G4 certified seed | Class SE basic seed | Pre-basic 4 | G4 elite 3 |
5 | G5 certified seed | Class E basic seed | Basic S | G5 elite 4 |
6 | — | Class A certified seed | Basic SE | G6 foundation |
7 | — | Class C certified seed | Basic E | G7 certified seed |
8 | — | — | Certified seed, | — |
* Fast-track multiplication. An alternative multiplication can be used which takes an additional year. |
Western Australian G5 certified seed is equivalent to:
-
Class SE or Class E (the Netherlands, depending upon multiplication pathway used), or
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Basic S (Scotland), or
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Elite 4 (Canada).
Disease and disorder tolerances
Western Australian certified seed must have similar disease and disorder tolerances to other schemes for it to be of equivalent quality. Tables 2 and 3 compare disease and disorder tolerances.
Field inspections
Field disease tolerances for the seed classes equivalent to Western Australian G5 certified seed are compared (Table 2). The indicated maximum disease tolerance levels for Western Australian G5 certified seed are those at the second inspection for crops with a disease tolerance rating of 2. This rating is used as it is assumed the seed will be used for further multiplication.
The Western Australian specification for total virus tolerance is 0.1%, which is the same as the Netherlands Class E seed. The Scottish Basic S has a higher 0.2% tolerance while Canadian Elite 4 seed allows 0.3% virus.
All schemes have low tolerance for mixtures; the Netherlands has 0% and 0.1% for Canada.
Disorder | Seed potato scheme | |||
Western Australia G5 certified seed (Rating 2 at second inspection) 2015 | Netherlands Class E 2005 | Scotland Basic S 2017 | Canada G5 Elite 4 2017 | |
Virus (total) | 0.10%* | 0.10% | 0.2% | 0.30% |
Mixtures | 0.01% | 0% | 0.1% | 0.10% |
* Nil tolerance for PVY, crops with PVY are relegated to Rating 3. |
Tuber inspections
Tuber inspection tolerances for seed leaving the seed schemes are compared in Table 3. Western Australia and Canada assess defects by tuber count, while the Netherlands and Scotland assess defects by tuber weight.
The tuber disorders assessed within each scheme do not correspond exactly, however the tuber disorder tolerances for Western Australian certified seed are similar to those for the Canadian and the Netherlands schemes. Most differences vary by only 1–2%.
Disorder (Tuber inspection) | Seed scheme | |||
— | Western Australia* G5 certified seed 2015 | Netherlands** Class E 2005 | Scotland** Basic E 2017 | Canada* All classes 2017 |
Virus using ELISA | — | 1% | — | — |
Rots: | — | — | 0.2% | — |
| 0.25% | 0.0% |
| 0.1% |
| 2% | 0.5% | — | 1% |
Surface diseases | 2% | — | 1.5% | 10% |
Total diseases | 2% | — | — | — |
Other defects/damage | 2% {+2% minor defects}*** | 1.0% | 3.0% | 2% |
Total defects | 4% | — | 4.7% | — |
Soil | 'practically free' | 1.0% | 0.5% | — |
* % by count ** % by weight, Scottish tolerances are for seed potatoes exported outside the European Union *** Minor = damage where tubers have no more than two feeding holes per tuber, not more than 3mm deep, containing no soil and damaged skin has healed. |
Rotation
All these seed potato schemes require a rotation, or period free from potatoes and related crops, in order to reduce the risk of volunteer plants and pest and disease carry-over. Local conditions such as the freezing of soil may also reduce carry-over making comparisons difficult. However, Canada requires seed potato fields to be free of potatoes for two years before replanting, Western Australia requires three years free of potatoes for G5 certified seed and Scotland requires five years for Basic S and older generation seed.
Conclusion
The final product of Western Australian certified seed is produced at generation 5, which is two years earlier than the final certified seed product allowed by Canada, at least two years earlier than the final certified seed product allowed by the Netherlands and three years earlier than the certified seed produced from Scottish seed.
Disease and disorder tolerances of Western Australian certified seed are comparable to the other schemes; total virus tolerance is 0.1% for Western Australian crops with rating 2 which is the same as the Netherlands Class E seed.
Tuber disorder tolerances for Western Australian certified seed are similar to those for the Canadian and Netherlands schemes.
The Western Australian certified seed potato scheme rotation required for generation 5 certified seed is three years, which is a year longer than the Canadian requirement and two years shorter than the Scottish requirement.