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HORT410 - Vegetable Crops
Potatoes - Notes
Common name: white potato, or Irish potato.
Latin name: Solanum tuberosum L.
Family: nightshade family or Solanaceae [Solanaceae Images].
Autotetraploid (2n = 48).
Dicotyledon.
Annual.
Closely related species grown as vegetables: tomato, pepper, eggplant.
Harvested organ; tuber--the enlarged end of a stolon, or underground stem--with tan to purple skin. The flesh of the tuber is usually white or light yellow, although in some Andean varieties it is purple.
The tuber has external buds, or "eyes" that can sprout into new plants. These eyes, rather than the seeds of the fruit, are planted to grow a new crop.
Tubers are rich in carbohydrates, protein, calcium, niacin and vitamin C.
Tubers are cooked fresh and can also be frozen or dried. They are processed into flour, starch, and alcohol and are used as fodder, especially in Europe. Potatoes are the fourth largest world crop, surpassed only by wheat, rice, and corn.
Origin: Peruvian Andes; cultivated in Peru and Bolivia; along with maize, was a staple of the Inca diet.
Introduced into Europe by 16th-century Spanish explorers.
Because the potato is a nightshade, it was slow to be accepted as a food by Europeans; not grown as a food crop in England and Ireland until mid-18th century.
Soon became a major food staple, particularly in Ireland (today the vegetable is often called the "Irish" potato, to distinguish it from the unrelated sweetpotato).
A potato blight caused the crop to fail during the period 1845 - 1847. About 1 million people died in Ireland and an equal number emigrated to N. America. Immigrants had already brought the potato to N. America; was first grown in volume in New Hampshire in the early 1700's.
Potato history (TAMU).
A cool season crop; temperatures averaging 16 to 18 C are optimum.
Typically grown from small, eyed tubers (or cut portions of larger tubers [seed pieces]), planted in rows 34 to 36 inches apart, with seed pieces 9 to 11 inches apart in the row, at a depth of 10 to 15 cm. Seed pieces are typically 1.5 to 2 oz.
Use of certified seed pieces reduces tuber-borne diseases.
Potatoes have a relatively wide pH tolerance. Soil pH's as low as 5.0 to 5.2 can be tolerated; such acidic pHs can be beneficial in controlling common scab. However, low soil pH reduces the availability of P and increases availability of toxic elements such as Mn and Al. Use of scab resistant varieties at a soil pH of 6.5 is recommended to increase P availability and minimize Mn and Al toxicity.
When the plant tops emerge, additional soil (hilling) is used to protect the tubers from insects and exposure to the sun. Sunlight causes a potato to turn green and produce poisonous glycoalkaloids, such as solanine [glycoalkaloid levels of newly released cultivars must be less than 20 mg per 100 g fresh weight to be considered non-poisonous].
Cultivation is used to begin the hilling process, to control weeds and increase soil aeration. The last cultivation is usually completed before blooming has started.
Potatoes mature in 90 to 130 days, depending on cultivar and production region. Various methods are used to kill the vines prior to harvesting the tubers; mechanical methods, application of chemicals, and use of propane burners.
Almost all commercially grown potatoes are now machine harvested.
Following harvest potatoes are held at 15 to 18 C and a high relative humidity (90 - 95%) for 10 - 14 days. After this curing period, temperatures are lowered to 3 to 5 C to prevent sprouting.
Tubers can be stored for up to 8 months at temperatures slightly above freezing, but at temperatures below 5 C, some of the potato starch turns to sugar, reducing cooking quality. Before processing potatoes are therefore often moved to a holding area at temperatures high enough to convert the sugars back to starch.
Chemicals applied to stored tubers or growing plants can delay sprouting, because sprouting greatly reduces the food value of potatoes. Maleic hydrazide is commonly used as a sprouting inhibitor.
Major disease of potato in the Midwest:
Major insect pests of potato in the Midwest:
Minor pests of potato in the Midwest:
(see: ID-56: Midwest Vegetable Production Guide for Commercial Growers 2003 - Potato (PURDUE) [pdf] for information on potato varieties, spacing, fertilizing, vine-killing, chemical sprout control, and specific potato disease, weed and insect control recommendations for the Midwest)
The Irish potato is thought to be derived by artificial selection for long-day adapted varieties of Solanum tuberosum subsp. andigena, a tetraploid derived from Solanum phureja and Solanum stenotomum (Douches and Jastrzebski, 1993). Chromosome numbers, distributions and origins of the major Solanum species are summarized below (derived from: Douches and Jastrzebski, 1993)
Species; 2n; Distribution; Origin
1. Solanum tuberosum subsp. tuberosum (long-day adapted); 2n = 48; Cosmopolitan; By artificial selection in Europe, N. America, and Chile from introduced clones of group 2 (initially a few genotypes of andigena were introduced to
Spain and were selected to tuberize under long days (day neutrality)).
2. Solanum tuberosum subsp. andigena (short-day adapted); 2n = 48; Venezuela to N. Argentina, also sporadically in Central America and Mexico; From groups 4 and 5 by spontaneous doubling of the chromosome number.
3. Solanum chaucha ; 2n = 36; Central Peru to N. Bolivia; By hybridization between groups 2 & 4, or 2 & 5.
4. Solanum phureja; 2n = 24; Venezuela to N. Bolivia; By selection for short tuber dormancy from group 5.
5. Solanum stenotomum; 2n = 24; S. Peru to N. Bolivia; By natural hybridization between wild species followed by natural selection.
6. S. x juzepczukii; 2n = 36; Central Peru to S. Bolivia; From crosses of S. acaule with groups 4 or 5.
7. S. x curtilobum; 2n = 60; Central Peru to S. Bolivia; Crosses of S. x juzepczukii with group 2.
Solanum demissum is a dwarf wild potato found in Central Mexico at about 3000 m. Solanum demissum has been used in modern breeding and is found in the ancestry of many modern varieties of potato (Phillips and Rix, 1993).
Note that the basic chromosome number in Solanum is x = 12, and the genus contains species that constitute a polyploid series ranging from 2x (2n = 24), to 5x (2n = 60) (Douches and Jastrzebski, 1993). Generally the even-numbered ploidy levels are sexually fertile, and the odd numbered polyploids are male sterile (Douches and Jastrzebski, 1993). The cultivated potato (group 1) functions as an autotetraploid (2n = 4x = 48) with 4 sets of similar chromosomes (Douches and Jastrzebski, 1993). The genetics of the tetraploid potato is complicated by the pairing of 4 sets of chromosomes during meiosis, which has important consequences for the transmission of genes to progeny (Douches and Jastrzebski, 1993).
Sources of information:
Mahr, S., Wyman, J., Radcliffe, E., Hoy, C., Ragsdale, D. Potatoes. In "Vegetable Insect Management With Emphasis on the Midwest", (ed. R. Foster, B. Flood), Meister Publishing Co., Willoughby, Ohio, pp. 63-76 (1995).
Nonnecke, I.L. "Vegetable Production", Van Nostrand Reinhold, NY (1989).
Lorenz, O.A. Potato. In "The Software Toolworks Multimedia Encyclopedia", Version 1.5, Grolier, Inc. (1992).
Phillips, R., Rix, M. "The Random House Book of Vegetables", Random House, NY (1993).
Douches, D.S., Jastrzebski, K. Potato, Solanum tuberosum L. In "Genetic Improvement of Vegetable Crops", (ed. G. Kalloo, B.O. Bergh), Pergamon Press, Oxford, U.K., pp. 605-644 (1993).
Midwest Vegetable Production Guide for Commercial Growers, ID-56, eds. R. Foster, D. Egel, E. Maynard, R. Weinzierl, H. Taber, L.W. Jett, B. Hutchinson, Purdue University Cooperative Extension Service, 2003.
Jadhav, S.J., Kadam, S.S. Potato. In "Handbook of Vegetable Science and Technology: Production, Composition, Storage, and Processing", (ed. D.K. Salunkhe, S.S. Kadam), Marcel Dekker, Inc., NY, pp. 11-69 (1998).
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