Combining late blight resistance and better tuber quality with resistance to potato virus Y (PVY) to improve Maris Piper potato

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The potato crop is susceptible to many diseases and pests, notably late blight (LB) caused by Phytophthora infestans. This disease causes at least $6B in losses worldwide every year, costs £50M per year in the UK and led to the Irish potato famine in the 1840s.Potato tubers are also prone to problems. Storage in cool conditions elevates levels of reducing sugars, and after high temperature cooking such as frying or roasting, these sugars can be converted into toxic acrylamide. Potato tubers are damaged by bruising if dropped or crushed, resulting in discolouration by an enzyme reaction, leading to significant food wastage. Tubers can also be lost to tuber blight in storage.Finally, potato virus Y can result in severe yield losses or rejection of seed potato tubers, imposing an additional burden and expense on the potato industry.We cloned three very effective LB Resistance genes called Rpi-vnt1, Rpi-amr3 and Rpi-amr1 and have shown that when deployed together in GM potato, they confer complete resistance in the field to all currently circulating LB races. This should provide a durable solution to the late blight problem in the UK.We also obtained commercially deployed and validated genes from the American potato company Simplot Inc that reduce levels of the enzymes that elevate reducing sugars and that mediate the discolouration upon bruising, thus alleviating the problem. In a currently running grant, we introduced the 3 Rpi genes and the tuber quality traits, into UK-favoured variety Maris Piper (MP), using Agrobacterium, creating PiperPlus 1.0. However, all lines that we generated are susceptible to PVY, greatly impairing our capacity to bulk them up for more extensive field trials. PVY is aphid transmitted, and difficult to control, especially as insecticides used to control PVY-transmitting aphids are being increasingly restricted, and global warming means that aphids and PVY are an increasing problem for seed potato production in Scotland. Also, Scotland is still opposed to planting GM crops, meaning that seed potato production outside of Scotland will be needed.With colleagues, we cloned an extremely effective PVY resistance gene, Ry-sto. We aim in this project to combine PVY resistance with the LB resistance and tuber quality traits of PiperPlus 1.0, to create PiperPlus 2.0. We have made a DNA construct to introduce all traits together on one T-DNA via Agrobacterium and are producing transgenic Maris Piper lines using the GM method. We expect to be able to field-trial ~20 PiperPlus 2.0 candidate lines in Norwich in summer 2022, and another ~20 in summer 2023. We can easily identify lines in which Ry and all 3 Rpi genes are expressed and we will also select those plant lines with the improved tuber quality traits. The best lines from batch 1 in the Norwich trial in 2022 will be multiplied up for field trials in summer 2023 at NIAB in Cambridge, and the best lines from batch 2 in Norwich 2023 will be multiplied up for NIAB trials summer 2024, to select the best performing PiperPlus 2.0 lines that will be indistinguishable from normal Maris Piper, except that they will be LB resistant, PVY resistant and have the improved tuber quality traits. These lines will also be evaluated to verify comparable yield to that of normal Maris Piper, and to ensure that use of the GM method has not resulted in acquisition of any deleterious traits, such as elevated production of steroidal glycoalkaloids. We will also define exactly where in the potato genome the DNA that we added has inserted, and that the final selected PiperPlus 2.0 line carries a simple, single copy insertion event.The project will thus enable us to make by 2024 a commercially viable line with these added traits, and we anticipate that by 2024 changes in the regulatory framework will enable this improved line to be approved for commercial production and public consumption.