Potato

The potato is a herbaceous perennial usually grown as an annual, 0.6–1 m tall with erect, softly hairy, green stems. Its leaves are pinnately compound, with about 3–4 pairs of ovate leaflets and a larger terminal leaflet, the margins entire or slightly wavy. The inflorescence is a branched cyme at the top, bearing bisexual, bilaterally symmetrical flowers with five fused petals forming a wheel- to star-shaped corolla in white, pink or purple, and five stamens whose yellow anthers form a cone. The fruit is a round green berry up to about 2–4 cm across containing many small seeds; it is inedible because of its glycoalkaloids. The harvested part is the tuber — actually a swollen underground stem (stolon) rich in starch, with skin coloured yellow, brown, red or purple and white or yellow flesh; its surface bears “eyes” that are dormant buds. It is grown mainly from sprouted seed tubers.

According to Plants of the World Online (Kew POWO), the native range of the potato is W. & S. South America to NW. Venezuela — a tuberous geophyte of the subtropics. It was domesticated once in the Andes around Lake Titicaca (southern Peru and extreme north-western Bolivia) about 7,000–10,000 years ago from ancestors in the Solanum brevicaule complex; genomic work (PNAS, 2017) supports a single origin in southern Peru. The Spanish brought the potato to Europe around the 1570s, after which it spread worldwide and became a staple in many countries. Today it is grown in temperate and subtropical regions across the globe, with major producers including China, India, Russia, Ukraine, the USA and Germany; world output reached about 360 million tonnes (2020), with China alone accounting for more than 22%. In Vietnam potatoes can be grown only in cool highlands such as Da Lat (Lam Dong) and in some winter crops in the north.

Chemically, the main component of the tuber is starch (amylose and amylopectin), about 15–20% of fresh weight and most of the dry weight; when cooked and then cooled, part of it converts to resistant starch (RS3), which benefits gut bacteria and lowers the glycaemic response. The tuber also contains the storage protein patatin (a glycoprotein making up much of the soluble protein and the major potato allergen, Sol t 1), together with protease inhibitors. A characteristic group and a key safety issue are the glycoalkaloids: mainly α-solanine and α-chaconine (over 95% of total glycoalkaloids), sharing the aglycone solanidine and concentrated in sprouts, skin and green tissue. Tubers normally contain about 20–100 mg/kg fresh, the recommended safety limit being 20 mg/100 g (200 mg/kg) fresh; the peel holds 3–10 times more than the flesh, and light triggers both chlorophyll (greening) and glycoalkaloid accumulation. The tuber also supplies potassium (about 400 mg/100 g), vitamin C (declining with storage and cooking), vitamin B6, fibre, the phenolic acids chlorogenic and caffeic acid, and flavonoids; yellow-fleshed types contain carotenoids (lutein, zeaxanthin) and red/purple types anthocyanins.

Potato is a staple food and vegetable: tubers are boiled, steamed, roasted, mashed, fried (French fries), made into salads, soups and cakes, or processed industrially into starch, chips, snacks, purée and alcohol. In Vietnam potatoes are grown mainly around Da Lat and used in stir-fries, fried dishes and soups. In research the potato is a major genetic model: its genome was sequenced and published (Potato Genome Sequencing Consortium, Nature, 2011), accelerating breeding for disease resistance and improved nutritional value, and work in PNAS (2017) clarified its domestication history. Nutritionally and medically, the protein patatin and potato peptides are studied for antioxidant activity and for allergy; resistant starch helps stabilise blood glucose; and anthocyanins and phenolic acids in coloured cultivars show antioxidant activity. The potato has also been central to history — the Great Irish Famine (1845–1849) caused by late blight showed the importance of cultivar diversity.

As food, potato is healthy when used properly, but two issues matter. The first is glycoalkaloids: α-solanine and α-chaconine accumulate when tubers are exposed to light (greening), sprout, are bruised or are stored warm; they cause gastrointestinal toxicity (nausea, vomiting, diarrhoea) and neurological effects at sufficient doses, and cooking does NOT destroy them. Store potatoes in a dark, cool (about 7–10 °C, avoiding the fridge because it raises sugars), airy place; peeling thickly and removing sprouts reduces glycoalkaloids by 30–80%, and green or bitter tubers should be discarded. The second is acrylamide: frying or baking above 120 °C makes asparagine react with reducing sugars to form acrylamide (a suspected carcinogen), so fry at moderate temperatures, avoid deep browning, and soak or rinse before frying. People with diabetes should note the high glycaemic index of boiled or mashed potato and favour cooking methods that create resistant starch (cook then cool). On conservation, the potato is Not Evaluated (NE) on the IUCN Red List and is not listed in the CITES appendices; field and genebank germplasm is very rich (over 5,000 varieties; more than 4,000 accessions at CIP), so it is not threatened. Priorities are conserving Andean landrace diversity and disease-resistant, climate-adapted varieties.