Tuber inspections for seed potatoes

f A passed tuber inspection is peace of mind for yourself and the consignee to know the particular line meets the specifications set out by the certified seed scheme.

Seed that has experienced stressful conditions, is likely to be prematurelyaged.

BY JULIAN ACKLEY POTATO SEED GROWER

In the autumn 2021 edition of WA Grower, we delved into what was involved in starting to grow seed potatoes. Now that the crop has grown and we have passed our field inspections, the next step is getting the tubers themselves to pass certification. For this edition, we look at tuber inspections, what they are and what you will need to do to pass one.

What is a tuber inspection?

Tuber inspections are part of the certified seed scheme where an Authorised Tuber Inspector will assess a seed line to ensure it is compliant with the requirements set out within the certified seed scheme rules. A passed tuber inspection is peace of mind for yourself and the consignee to know the particular line meets the specifications set out by the certified seed scheme, it may also be useful when the consignee disputes the quality of your seed line. When do I require a tuber inspection?

A tuber inspection is required for any seed line that is being exported outside of Western Australia. If a seed line has a black label and is leaving your property, this can also trigger the requirement for a tuber inspection, additionally a consignee may request a tuber inspection. Before the tuber inspection

If you are going to require a tuber inspection, you should be in contact with your inspector well in advance of requiring the inspection to ensure your consignment is not held up waiting for tuber inspection. Before requesting a tuber inspection, the Form 404 seed works summary must have been submitted, and you have received your labels.

Secondly, a 402 TADS Form must be prefilled and provided with your application for inspection. Before the inspector arrives, the consignment should be graded and packed ready for delivery, you will need to provide access to the consignment due to be inspected. If the consignment has been treated with fungicide or pesticide, advise the inspector in advance of the inspection commencing.

Can I do my own inspection?

For export, only a DPIRD Certification Officer can currently conduct the tuber inspection. For domestic an Authorised Tuber Inspector (ATI) can inspect their own seed for domestic sale, but an ATI cannot inspect a third party’s seed line. ATI Training is available through DPIRD, and courses are run annually. If you have not completed an ATI course or the consignee requests an independent inspection, then you will require a DPIRD Certification Officer to perform the inspection. How is the inspection done? The inspector will dig into each container and remove a random sample. A single sample for inspection is 100 tubers, the minimum quantity of tubers an inspector may take for any inspection is 300 tubers, unless the total consignment is less than 300 tubers, in which case the entire consignment would be inspected. 0.25 per cent soft rot, then combined they would be 2.25 per cent for this type of defect, causing the line to fail the inspection. Minor defects

A combined total of 2 per cent minor defects is allowed, these include simple things like mechanical damage, foreign varieties, excessive soil adhesion, insect damage and black scurf (see Table 2). Additionally, this includes undersize or oversize where the consignee has specified the size range. The inspector will also cut open several tubers in this part of the inspection looking for defects like hollow heart and stem end browning. TABLE 1. MAJOR DEFECTS. Defect 1. Soft rot (Erwinia carotovora) 2. Dry rot (Fusarium sp., Phoma sp.) Total allowable defects The total allowable defects for major and minor defects combined is 4 per cent; this number may seem unreasonably low to any potato grower; however, it is comparable to most other certified seed schemes around the world.

ATI Training is available through DPIRD, and courses are runannually.

Grading is critically important

It is unlikely that you could continuously achieve below 4 per cent defects without having first graded each seed line. Good staff training and supervision can go a long way to getting the line ready on the first pass, however if you have a line with significant defect load, it may be necessary to grade your seed more than once.

Max tolerance (%)

0.25

For larger consignments, the quantity of samples is 100 tubers per 5 tonnes of consignment with a minimum of 300 tubers, and up to 1200 tubers maximum for consignments 60 tonnes or more.

3. Pink rot (Phytophthora erythroseptica) 4. Eelworm (Meloidogyne spp.) 5. Powdery scab (Spongospora subterranean), Common scab (Streptomyces scabies) together @ < 1% of tubers > 5 lesions per tuber

Total of faults 1–5

0.25

Once the inspector has collected the samples, the inspector will then assess each tuber systematically looking for defects.

Defects

Major defects A combined total of 2 per cent major defects is allowed, this includes defects such as soft rots, eel worm and scab (see Table 1). In the case of scab, any amount of powdery scab on a tuber is counted as a defect, however common scab is not considered a defect unless the tuber has at least 5 lesions or more than 5 per cent of the tuber surface covered. Some soft rots have 0.25 per cent allowable where scab and eelworm have higher allowable defects at 2 per cent, however, the total combined allowable defect within this group is only 2 per cent. This means if you had 2 per cent powdery scab, and TABLE 2. MINOR DEFECTS.

Defect

6. Insect, bird and rodent damage 7. Potato tuber moth (Phthorimaea operculella) 8. Malformed, growth cracks, root constriction 9. Mechanical damage — shatter, splitting, cuts, cracks, bruise (damage > 3mm deep) 10. Foreign cultivars 11. Oversize

12. Undersize 13. Miscellaneous (e.g. sunburn, sprouting, shrivelling) 14. Soil adhesion 15. Stem end browning (cut 5% of inspected tubers for internal defects) 16. Hollow heart

17. Black heart 18. Black scurf (Rhizoctonia solani)

Total of faults 6–18

Max tolerance (%)

f GOOD grading practices are critical to passing a tuber inspection.

In a line where it is impossible to reduce a specific defect below the allowable standard, then this should be communicated with the consignee and a written agreement from the consignee may allow the seed to pass inspection as red label or be accepted with a failed inspection. What if I am growing as a 3rd party? The grower will still need to obtain the labels for the seed and pass all relevant certified seed protocols in their own name. If the seed is only sold domestically a tuber inspection is not required.

In the situation where a grower is sending the seed to a third party to be graded and packed for export, an on farm post-harvest tuber inspection is still required, despite that it will likely be failed. A tuber inspection Being prepared for tuber inspections in advance is the key. is still done to determine the likely pack out of the consignment. This is necessary to ensure supply chain integrity and tracking. The certification body requires a clear understanding of how much seed is leaving the property for packing, and what percentage of that is likely to qualify for export. An additional tuber inspection may still need to be done by the exporter after it is graded and packed. What to do if you failed the inspection

Should you fail your first inspection, you can get the seed inspected a second time, however this will incur another set of inspection fees. In this case you will need to regrade the consignment to bring it up to standard and/or contact the consignee and discuss the fault causing the line to fail the inspection. Achieving the impossible

Passing a tuber inspection is a daunting consideration, even for an experienced seed grower. Being prepared for the inspection in advance is key. Contact your local inspector and talk about your consignee’s requirements and obtain any required forms you don’t have. Before grading, check the line to see what defects are most common and instruct your grading staff accordingly. Ensure you understand each type of defect and check your own consignments before an inspection is due to take place. Finally, the window of time for tuber inspections is often very small, keeping in contact with your inspection officer well ahead of time is the most important factor for having your consignment ready before it is due to be collected.

MORE INFORMATION For more information on the West Australian Seed Scheme please refer to the certified scheme rules found online at

www.agric.wa.gov.au/plant-biosecurity/ potato-seed-certification

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