Sweetpotato
Sweetpotatoes (Ipomoea batatas) are perennial dicots in the morning glory family 
(Convolvulaceae) which are cropped as annuals. Sweetpotatoes should not be confused with yams which are monocots in the family Dioscoreaceae. Yams are grown as a staple in many tropical countries, but are seldom grown in the continental United States.
Origin
Sweetpotatoes probably originated in Central or South America but are now grown in many tropical, subtropical, and temperate regions.
Plant Characteristics
Sweetpotato plants produce primary fibrous roots, pencil roots and storage roots. Storage roots are the only part eaten in the United States, but in parts of Asia the leaves are cooked like spinach and eaten as a green vegetable. Storage roots are attached to the stem by a stalk of thinner root which is usually initiated at the stem node just below the soil line. Skin color of storage roots ranges from white to brown to red-orange. Flesh color of storage roots can be red-orange, orange, yellow or white. The flesh can be either soft or firm. In the southern states, commercial types are soft-fleshed, developing a moist, sugary consistency during cooking as starches are converted into maltose and dextrins.
Cultivars
Because sweetpotatoes are vegetatively propagated and because uniformity in appearance of roots is important, at any one time only a few cultivars dominate the industry, and these cultivars tend to change slowly. Growers are now evaluating a number of new cultivars to decide which will replace the 'Jewel' cultivar that has been the industry standard for almost 20 years. Jewel has excellent eating quality, deep orange flesh, red-orange skin, good shape, and sprouts readily, making it easy to propagate.
Jewel does not do as well in Louisiana as it does in North Carolina, however, and is susceptible to mutations and flooding damage. Growers are looking for cultivars that not only have the eating quality and appearance of 'Jewel' but have a high yield, early harvest, and a high percentage of No.1 roots. Additional requirements are easy propagation and resistance or tolerance for nematodes, pox, cracking, mutations and flooding. Needless to say, no one cultivar meets all these criteria, and growers will need to select the cultivar that best matches their requirements.
'Beauregard', for example, is a very good cultivar for Louisiana, but it does not do as well in North Carolina. The following material summarizes strong and weak points of several of the newer cultivars, and also suggests ways cultural practices developed for Jewel should be modified.
Beauregard has the following advantages: pox resistance; high quality (at least in Louisiana); attractive appearance which is similar enough to Jewel that the two could be packed together; reduced need for N application, and is harvest ready in 90 rather than 120 days. Disadvantages are: lower sprout production so presprouting is required; and susceptibility to nematodes. Roots are more elongated than Jewel and should be spaced more closely together (6-inch vs. 9-inch in-row spacing). Beauregard is harder to grow in North Carolina than in Louisiana.
Hernandez has the following advantages: good pox resistance and better nematode resistance than Beauregard; uniform, attractive dark-orange storage roots with brilliant orange flesh. Disadvantages are: slow and erratic sprouting, so presprouting is required; a tendency in wet soil to develop raised bumps called 'water blisters' around the lenticels (gas exchange areas of the periderm); lower yield and later harvest than Beauregard, and inadequate root size unless planted early. Culture, yield, and days to harvest are similar to those for Jewel, except that in-row spacings should be 9 to 12 inches, compared to 9 inches for Jewel.
Goldstar has the following advantages: prolific sprouting, even earlier harvest than 'Beauregard, and skin similar enough to Jewel that the two can be packed together. Disadvantages are: a tendency to develop water blisters in wet soils; and inadequate root size unless planted early (before mid-to-late-June). Though not necessarily a disadvantage, leaves are light green even at high N levels.
LA87-59, which Louisiana may be releasing soon as 'Darby', has the following advantages: high yields; harvest one to two weeks earlier than Beauregard; red skin; and a less elongated root shape than Beauregard. The main disadvantage is a less attractive, lighter orange flesh color than Jewel.
Per capita consumption in pounds.
| 1949 | 1989 | 1992 | |
|---|---|---|---|
| Fresh sweetpotato | 13.9 lb | 4.1 lb | 4.3 lb |
Nutrition
One baked sweetpotato weighing 114g has 160 calories, 185 percent RDA of Vitamin A and 28 percent RDA of Vitamin C.
Integrated Pest Management
Life cycles and monitoring and control practices for some of the common insect pests in the southern states are described in Integrated Pest Management. Some of the important diseases of vegetables in the South and their control are described in Disease Management. The general principles of insect and disease IPM programs are also described in their respective chapters. Cultivar resistances to the more common insects and diseases in the South are listed below, as it may be useful to select cultivars with multiple resistances.
Nematodes. In 1988, root knot nematodes were found in 45 percent of sweetpotato fields in North Carolina, causing a 2 percent loss statewide. Infested fields have patches of plants with poor growth and color. Fibrous feeder roots of infested plants are often galled and reduced. Storage roots are cracked and sometimes have lesions. Some orange-fleshed sweetpotato cultivars resist root knot nematode damage but there is no known resistance to golden nematodes.
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Last Modified: Friday, September 29, 2006 9:15 AM