Potato Review

PLAN AHEAD FOR INCREASE IN HOME-SAVED SEED CROP HEALTH | PLANT CLINIC Supporting healthy plants and crops, increasing sustainable f ood production and protecting the environment. www.potatoreview.com POTATO REVIEW NOVEMBER 2021 51 SEED R ESTRICTIONS on seed trade between the UK land EU mean many UK growers are contemplating using home- saved seed potatoes or relying on new supply chains for the first time. Although European imports were still allowed into the country under a six-month grace period offered by the UK government, as no agreement on resuming exports to the EU had been reached when this unilateral agreement ended at the beginning of July, it was not renewed. Since then, it has not been possible for British potato growers to import or export potato seed to or from the European Union, including major seed producing countries like The Netherlands, Belgium, and France. Previously around 10,000 tonnes of seed potatoes were imported to England from the EU each year, with three times that amount being exported, mostly from Scotland. While many English ware growers will be able to obtain the seed they need from Scottish or English seed suppliers, for some European varieties, particularly in the processing sector, it may not be possible to obtain sufficient volume of Brexit seed challenges Changing import legislation means more care is needed as growers look at alternative supply routes. Adrian Fox and Brian Carter offer some advice. the varieties their customers require. FERA Science’s Principal Plant Virologist, Adrian Fox, and Bacteriologist, Brian Carter, stressed that when using home- saved seed, it is important that only clean crops that are free from virus and blackleg are used and now is the ideal period for testing to identify fields which may be suitable to use for home-saved seed. Possibly the biggest issue for growers using home-saved seed is the transmission of aphid-borne viruses, and Potato Virus Y (PVY) in particular, although for some varieties Potato Virus A (PVA) and Potato Virus V (PVV) may also be a concern. “PVY has the potential to significantly reduce yields, and may result in cracked unsaleable tubers, or tubers displaying surface damage due to PVYNTN,” said Adrian. “PVY has the potential to affect all varieties, but may affect some more than others, while some varieties are more likely to show visible symptoms. It is also important to remember that our work indicates that it isn’t just the peach potato aphid (Myzus persicae) which acts as a vector for the virus, but that there is the potential for other species, such as the willow-carrot aphid (Cavariella aegopodii) to spread virus diseases. “Aphid monitoring earlier this year showed that while overall virus pressure may have been slightly less than in recent years, there were some hot spots around the country.” To test for the presence of PVY in a field, growers should take a sample of individual tubers from 120 plants across the field. Each plant should be representative of the crop overall, and each tuber should be representative of those on the plant that is being sampled (so not the largest or smallest). The ideal time for sampling is between defoliation of the crop and harvesting, “PVY has the potential to affect all varieties, but may affect some more than others, while some varieties are more likely to show visible symptoms.” ➜