Potato Review

52 POTATO REVIEW NOVEMBER 2021 SEED and Adrian stresses that it is important to representatively sample across the whole field as not every plant may have PVY, and not every tuber from infected plants contains the virus. Another concern for growers when identifying possible crops from which to save seed is blackleg, and Fera’s soft rot sampling service can be used to assess the risk of rots, and if necessary, identify the causal bacteria such as Dickeya. Brian said: “We take 100 tubers and split them into five sub-samples, which prevents a very high bacterial load in a single tuber affecting the overall result. I’m not aware of any other provider who does this subdivision of samples. After two days incubation with a suitable media, we provide an indication of the level of soft rot-causing bacteria on the tubers.” Where higher levels of rot are found, a further test using DNA-analysis can be used to identify the most common bacteria present, including Dickeya and Pectobacteria. The results can then be used to identify which crops may be suitable for use as home-saved seed, or in the case of ware crops, can inform the best storage and marketing regime to minimise the risk of blackleg disease development after “When you test (for soft rot), it is partly about what you are trying to achieve with the crop, and so to identify potential seed stocks, testing at harvest would be extremely useful.” harvest. Blackleg testing is also sometimes performed by seed suppliers as an added level of reassurance for susceptible varieties. This soft rot testing can be performed at any stage of the crop’s development, but again it is important that a representative sample is submitted. “The test is accurate for the point in time at which it is carried out,” Brian said. “When you test, it is partly about what you are trying to achieve with the crop, and so to identify potential seed stocks, testing at harvest would be extremely useful.” With the predicted rise in home-saved seed for the 2022 season, Adrian Fox stresses the importance of protecting the potato industry with adequate testing of seed stocks. “Not only will testing ensure that the cleanest possible crops are utilised for the coming season, maximising yield and profit potential for ware growers, but they will also increase the number of stocks which may be suitable for future replanting if a political solution to the current restrictions on UK-EU trade in seed potatoes is not found. When viewed in such a light, the added security provided by testing represents a sound investment for the whole supply chain.”