Potato Review

20 POTATO REVIEW MARCH/APRIL 2022 HISTORY OF VIRUS-TESTING J OHN Marshall, my father, was not from a farming background, his father owned a haberdashery in Falkirk. John wanted to return to his past family roots and studied agriculture first in Glasgow then Edinburgh. He excelled, achieving two gold medals. Following a job as an economic advisor, he took up a tenancy on a farm near Auchterarder before purchasing Dalreoch near Dunning in Perthshire just before the outbreak of WW2. The Government was much quicker to respond with plans to produce food than during WW1 when, towards the end, there were rocketing prices. Potatoes promoted by Potato Pete were at the forefront of the dig for victory campaign. We had been importing more than 60% of our food and with German u boats prowling UK waters, torpedoing the grain convoys from the US was a constant threat. Britain desperately needed home-grown food. At this time, he would produce his high-grade seed, SS Grade, on strenuously- rogued fields on a farm at Milton of Craigie near Pitlochry, which was free from aphids and far away from other crops. He would bring the seed, all Majestic, to the lower farm at Dalreoch, multiplying up on a The story of virus tested seed potatoes John M Marshall describes post war farming and the transformation of the potato industry. commercial scale for other seed growers. After the war, one hot day, he was exhausted with rogueing and needing a break but wanting to finish when a gentleman in a raincoat and a fedora, whom he called “a townie” leaned over the gate and shouted “pull the good ones out”. Rather than shout back, he approached him for a discussion. It turned out to be Dr McIntosh, Head Scientist at the Department of Agriculture East Craigs. He explained what he had in mind: The introduction of another grade virus tested seed initially from one visually healthy clone. The Department had already tackled the variety mix, wart disease and severe viruses such as Y and Leafroll could be easily seen by the eye but the low-level mild infections of virus x were elusive. The build-up, once in the commercial crops, was adversely affecting yields. Parish’s first freezer! In 1950 he built a laboratory greenhouse at Dalreoch at his own expense to grow tobacco plants and, encouraged by Dr McIntosh, joined the Virus Tested Clonal Production Scheme. Leaf samples were taken from the selected healthy clone, in the first year around 10 plants. These were initially pulped using a pestle and mortar to extract the juice. This technique was tiresome and was soon replaced by placing them in a deep freeze. My mother boasted that this was the first in the parish! The deep freeze soon filled up with potato leaves and not her abundant garden produce as she had hoped. The leaves were removed from the small bags and placed on cheese gauges whilst they defrosted. The whole family was involved - my brother, sister and myself each having a specific task. It was easy to squeeze the potato juice on to the two-leafed Burly tobacco plants which had been transferred at the two- leaf stage into rows of terracotta pots. To ensure uptake of the potato sap, the tobacco was gently rubbed with an abrasive carborundum dust. The marker plants grew rapidly and afterwards would indicate whether there was a low-level virus infection in the potato clone. If there was any mottling, the plot was dug out. As the generations moved forward one to five years, so the tobacco testing declined but visual inspection by the department of the growing crop stepped up. VT story PMB publication cover. John Marshall (Father).