No Small Potato
By Dr. Rizwana Rahim
There is nothing ‘small’ or humble about potato.
If it were, the UN would not have called it the ‘food of the future’ or hailed 2008 as the ‘International Year of the Potato’.
Agreed that as part of the vernacular, ‘meat-and-potatoes’ bring to mind something fundamental, basic and simple – nothing ‘gourmet’.
A popular-science British weekly, New Scientist, in its 2 August 2008 issue has an interesting article, “Let them Eat Spuds” that covers from its history as staple food and its nutritious value to attempts to develop genetically-modified varieties, resistant to disease and other advantages.
First grown some 8,000 years ago, around Lake Titicaca at the border of Bolivia and Peru high up in the Andes, potato (Solanum tuberosum) was fairly successful. The Spanish brought it to Europe in 1536 but its use was minimal for the next 200 years, though some farmers did grow it in small quantities. When their value as a crop was recognized in the mid-1700s by the Prussia and later by other countries, the farmers were encouraged to grow it. French nutritionist, Antoine-Augustin Parmentier (some French potato dishes still bear his name) and Austrian empress Maria Theresa were among the early potato promoters. It received further push as an alternative to bread from her daughter, Marie Antoinette (of ‘let-them-eat-cake’ fame), a French queen, who used to wear potato flowers to give this crop a further push as an alternative to bread.
China is now the world’s biggest potato-producing country, followed by India where its annual yields are twice of the United States’. Since grain crops form the major source of food in the world and potatoes can be grown in the fallow period between the grain-seasons, there has been an increased interest in potato. Recent food shortages around the world further point to this crop as a relief. Besides being a faster crop to grow even under less than optimal climatic and other conditions, it takes less land area and water than any major crop.
Potatoes also have a higher nutritious value: more complex carbohydrates, better quality protein than several grains, and several vitamins and essential trace elements not found in rice and other staples. Baked potatoes (with skin; 100 g) compared with equal amounts of rice and pasta showed that potatoes have 5x more fiber and 20x more sugars (complex) and 15x more potassium than rice -- in addition to significantly more calcium, magnesium, phosphorus, copper than rice. Rice has no Vitamin C, but a medium-sized boiled potato (with skin) provides half of Vitamin C that an adult needs daily. Although potato and rice have comparable amounts of niacin (B3) and pantothenic acid (B5), pyridoxin (B6) in potatoes is at least 3x times higher.
Over time, potato became popular in Europe (because it could easily be a third harvest between the two regular grain-planting seasons), but then in 1845, the crop was destroyed by late blight (leading to the memorable ‘Irish potato famine’ during which in Ireland as well as elsewhere in Europe, hundred of thousand died. The main reason for the devastation may be that outside the Andes, most potatoes around the world belong to a single sub-species (S. tubersom tuberosum), that is highly susceptible to the blight-causing fungus (Phytophthora infestans), which originated in Mexico where it used to attack wild potatoes. It spread north, and then via American export of seeds, arrived in Belgium and spread across Europe. Early attempts to control the catastrophe were marginally helpful -- but not till the fungicides were invented in 1880s did the disease come under control. The crop yields then increased - through the Industrial Revolution, potato became an increasingly important food crop in Europe and other areas. Now a European farmer spends one-sixth of the crop-worth on fungicides annually.
P. infestans has now gotten more aggressive in Europe. First, its asexually-produced variety that arrived in Europe 1840s spread through spores, but with imports from Mexico during the 1976 drought, came the sexually reproducing variety. The presence of both varieties means that the fungus can grow resistant to fungicides faster and can attack potato strains previously resistant to this fungus. This poses a more catastrophic threat worldwide.
Genetic engineering in potato, just like in wheat, soybean and many other crops, fruits etc., is a possible answer to this threat, but unlike other crops, potato poses genetic problems more complex in other crops. Common potato has four copies of each of its genes, whereas most organisms carry only two. Although wheat, for instance, has six copies but since most of its varieties used in genetic-modifications are inbred for long, their genes are fairly identical, which makes it easier. Some classic methods of breeding and crossing the normal potatoes with the wild varieties (S. bulbocastanum, e.g.) have, for one reason or another, produced only unsatisfactory results.
Engineering a potato hybrid with only a two-copy genome has been disappointing, says Shelley Jansky of USDA Potato lab, Madison, WI. Since potatoes are propagated vegetatively by tuber, the product from harvest to harvest is very similar in taste etc., and although hybridization can produce other varieties, they are not going to be same as those the consumers have gotten used to – and this poses a problem for both the farmers and the industry.
Anton Haverkrot (Wageningen University, The Netherlands) has a 10-year project to isolate genes from several wild potato species resistant to late blight, and then put them into varieties commonly used by consumers. He uses a genetic engineering method that requires an antibiotic resistance genetic marker (calls his technique, cisgenic, different from the commonly used transgenic), and has isolated 8 such genes, the first of his modified plant is now in field trials, and it is not clear how popular this would be, if successfully brought to the market.
On the other hand, using the popular anti-biotic resistant marker and a hybrid of normal and blight-resistant wild potato, the German chemical firm, BASF, already using hybrid potatoes producing uniform starch for paper and fabrics, has already produced a resistant hybrid now in the third year of field trials, and hope to sell it in five-six years
Later, these genetically-modified hybrids will have to address criticism by the opponents of these genetic manipulations who worry about the introduction of antibiotic-resistant genes which could be taken by other bacteria to create most resistant ‘superbugs’.
This has to be taken together with another development announced last week. Major US food manufacturers, resulting from a multi-million dollar suit, have agreed to reduce the levels of acrylamide in their potato chips and French fries. Acrylamide is formed when potatoes and other starchy foods are baked or fried. Acrylamide, which has industrial uses, causes cancer in lab animals, and nerve damage in workers exposed to its high levels.
This brings the not-so-humble potato in the middle of the debate on genetic engineering and potential risk to harmful substances in popular potato food items.