Table of Contents
Collins, W.W. 1993. Root vegetables: New uses for old crops. p. 533-537.
In: J. Janick and J.E. Simon (eds.), New crops. Wiley, New York.
Root Vegetables: New Uses for Old Crops
Wanda W. Collins
- DISTRIBUTION AND PRODUCTION OF MAJOR ROOT VEGETABLES
- USE OF ROOT VEGETABLES IN THE UNITED STATES
- Cassava, Yams, and Aroids
- POTENTIAL FOR INCREASED USE AND PRODUCTION OF SWEETPOTATOES
- Ethnic Markets
- Development of New Value-added Products
- Sweetpotato in Breads and Flours
- Use as Animal Feed or an Animal Feed Supplement
- POTENTIAL FOR NEW MINOR ROOT CROPS
- FUTURE PROSPECTS
- Table 1
Vegetables grown for their edible roots or tubers encompass a wide range of
starchy root crops, some of which are true botanical roots and others which are
tubers or corms. The most economically significant root crops globally include
potato (Solanum tuberosum L.), sweetpotato (also spelled sweet potato)
[Ipomoea batatas (L) Lam.], cassava (Manihot esculenta Crantz),
yams (Dioscorea spp.), and aroids [principally Colocasia
esculenta (L.) Schott var. esculenta and Xanthosoma spp.].
Although traditionally, root vegetables have been considered low status and
generally unimportant crops by consumers, governmental organizations, and
researchers, on a global scale they account for three of the seven most
important food crops in the world (FAO 1989).
Of these five majors root crops, only potato and sweetpotato are grown to any
extent in the United States, and of these two, sweetpotato has the greatest
potential for increased usage and consumption. However, there are other
starchy root vegetables grown in various areas of the world where they are of
local economic and cultural importance and which could conceivably be
considered potential new crops for domestic consumption (O'Hair 1990a, b).
Among the most promising may be some of the Andean root crops (Sperling and
King 1990). In addition, apios (Apios americana), has received
attention as a potential new crop. Apios is unique among the root and tuber
crops mentioned in that it fixes nitrogen and also produces edible tubers,
fleshy roots, and seeds (Putnam et al. 1991). Tubers are high in protein and
carbohydrates (Walter et al. 1986) and are preferred by some to the domestic
potato, Solanum tuberosum. The potential of apios as a new crop has
been described by Reynolds et al. (1990).
Most root vegetables are produced in developing countries. In developed
countries, 99% of root production is in potato (Rhoades and Horton 1990).
Fresh weight production of the five major root vegetables (potato, sweetpotato,
cassava, yams, and aroids) is listed in Table 1 and compared with the other
major crops which are produced at a level of 100 million tonnes globally.
Potatoes, cassava, and sweetpotato rank among the seven major, global food
crops which are produced at that level. Yams and aroids are produced at a much
lower level, but are important staple food crops on a regional level.
Sweetpotatoes and potatoes are produced in the United States (Table 1).
Cassava, yams, and aroids are long season crops requiring one to two years for
maturity which precludes their being grown in any significant amount in the
continental United States. Although some short-season types are available,
they still require six months or more for maturity. There are some
experimental results indicating that yams could be successfully produced
domestically (Marsh 1991).
There is little consumption or consumer familiarity with cassava, yams, or
aroids in the United States outside of ethnic populations. This status is not
likely to change except for increased consumption by steadily increasing ethnic
populations. They are, however, imported into the United States from the
Caribbean and Latin America and are available for consumption. Quality of
imported products is generally poor unless purchased immediately from a local
market. Once the product reaches grocery shelves, it is generally well below
fresh quality standards.
Studies in Missouri have shown that yams can be produced in that state by
starting them in a greenhouse for six weeks followed by about 22 weeks in the
field (Marsh 1988). Yield per plant was much lower than those obtained in
tropical growing areas (3.5 kg/plant as opposed to 20 to 30 kg/plant) but yams
were of good marketable quality.
Potatoes have been the most widely used root vegetable grown in the United
States; current per capita consumption is about 56.4 kg. Quality is excellent,
consumption is high, and there are a multitude of products available to the
consumer. Potatoes are used in many ways as a vegetable and as a snack food.
Even so, new types of potatoes are being introduced to the fresh market for
consumers to try. Among these are yellow potatoes and blue potatoes. The
unique characteristics of these potatoes are novelty traits which may capture a
very small portion of present markets. They do represent a potential for
specialty markets at very high prices.
Sweetpotatoes are consumed in the United States on a much smaller scale than
potatoes with the per capita consumption now about 5.8 kg. Quality is
excellent but few products are available. Normally sweetpotatoes can be
purchased fresh, canned (whole or cut), as a reconstituted patty, and in baby
food. They are most often used in pies or as a candied vegetable. Use is
seasonal revolving around Thanksgiving, Christmas, and Easter. This
seasonality has been a major problem in marketing efforts to increase
consumption. In the past, various products have been developed from
sweetpotatoes, such as chips and fries, but none have been successful.
Sweetpotato does have the potential for increased production and consumption.
Sweetpotato germplasm, like that of potato, is diverse with many types with
different flesh colors, skin colors, textural properties, and nutritional
components. There is excellent potential for the development of new products
and new types of sweetpotatoes to fit various demands of different consumer
groups. Breeding efforts in the United States have focused almost exclusively
on a single phenotype: a sweet vegetable type (luxury type) which has copper
skin, deep orange flesh (high carotene), sweetness, and moist texture (Collins
1987). The American public, through surveys, has expressed a flexibility of
choice for some attributes, but the desired marketing type has remained the
same. Although this type can still be greatly improved through breeding
efforts, it is unlikely that the demand for the luxury type of sweetpotato will
increase significantly unless new uses and products are developed.
Populations of ethnic cultural groups in the United States are substantial and
continue to increase (Marsh 1991). Opportunities exist for American growers in
the United States to produce different types of sweetpotatoes for those
markets. Unlike cassava, aroids, and yams, importation of sweetpotatoes into
the United States is prohibited by law. Hence, there is little or no supply
for potential ethnic markets because the type of sweetpotato demanded by those
markets is different from the normal phenotype which is now the major focus of
domestic commercial sweetpotato production. Preferred types are red or white
skinned, cream to white flesh, non-sweet or very slightly sweet, and dry in
texture. Consumers in these groups are more accustomed to eating sweetpotato
as a carbohydrate energy source (staple or supplemental staple type) than as a
dessert or sweet vegetable (luxury type).
Staple, supplemental staple, and luxury types of sweetpotatoes were described
by Villareal (1981) and further characterized by Collins (1987). Desired
traits for each type are very different and breeding programs must have
specific programs for developing acceptable cultivars of these types.
Some efforts do exist to meet the demands of ethnic markets. In Florida,
"boniatoes," white-fleshed, dry, firm textured sweetpotatoes, have been
produced for many years for the Hispanic market. Cultivars used in this
production have been brought into Florida from nearby Caribbean islands, such
as Cuba (O'Hair et al. 1983), and have not been improved for United States
growing conditions. A new Japanese clone recently entered the domestic market
and is being grown in California and North Carolina. This cultivar may not be
ideally suited to domestic growing conditions. There is ample opportunity for
breeders to respond to the need for new phenotypes to meet new market
opportunities. No surveys have been conducted to assess potential demand, but
it could equal as much as 25% of current production if the crop is properly
marketed. Market feasibility studies would establish the extent of the
potential market, and should they be positive, convince growers of the
profitability of producing this type of sweetpotato.
The North Carolina State University sweetpotato breeding program has a small
project underway to develop the type of sweetpotato described. The variability
in sweetpotato is great enough so that almost any type desired can be
constructed with proper breeding procedures. Several clones with different
characteristics are in various stages of testing. There are also several
research projects underway to study specific characteristics which are
important in breeding clones with the necessary traits, such as studies on the
heritability and factors affecting ß-amylase activity which lead to
non-sweet types. Non-sweetness has proved to be one of the most difficult
traits to incorporate in these clones even though non-sweet types exist in the
breeding materials. Results of preliminary tests indicate that sweetness and
the perception of sweetness is very complex and that lowering ß-amylase
activity alone may not necessarily lead to non-sweet sweetpotatoes.
The range of variability in sweetpotatoes is so great that many different
phenotypes can be made available for special product development depending on
the characteristics needed. Often it is difficult to determine, even through
trial and error, what the best characteristics are for particular products.
Value-added products such as french fries, chips, and flakes, have been
developed from sweetpotato but none has been successfully marketed for any
length of time. Much effort has been devoted to sweetpotato fries. However,
consumer comments often refer to the sweetness, texture, and oil content as
problems. The products developed, such as fries, have always been developed
from the existing single phenotype grown in the United States today and this
may be a major reason for the disappointing results with such products.
There have been efforts in the private sector to capitalize on the enormous
potential for sweetpotato products. At least one patent has been granted for
producing sweetpotato bread and flour composed of 100% sweetpotato. These
products are marketed as hypoallergenic for people who cannot tolerate grain
breads and flours. The price is quite high (approximately $12/lb. for flour
and up to $17 for a loaf of bread) as is demand. The inventor in this case has
surmounted the problems normally associated with increased amounts of
sweetpotato flour in breads. A "boniato" type sweetpotato from Florida is used
to make these products. As the process is patented, it is not available for
general production at present. Several other patents are pending for other
processes involving sweetpotato (K. Slimak pers. commun.).
Where wheat has to be imported or can be grown only with extensive inputs (such
as in developing countries), sweetpotato is a viable alternative component for
breads and flours. There are disadvantages such as reduced loaf volume and
decreased storage life (Keya and Hadziye 1990), but the reduced costs and
decreased dependability on imports may outweigh the disadvantages. The
acceptability of component breads and flours is excellent with as much as 10 to
15% content of sweetpotato flour (Sammy 1984). Some researchers have reported
using up to 25% sweetpotato flour with no adverse consumer reaction. In the
United States, where wheat is plentiful and relatively inexpensive, this
alternative use of sweetpotato does not appear to be economically justified
except as a specialty product.
Sweetpotato is used as an animal feed and supplement in developing countries
(Gohl 1981). Both vines and roots are used. Starch and protein digestibility
of raw sweetpotatoes has been cited as an obstacle to increased use for animal
feed. Trypsin inhibitor has been implicated in poor protein digestibility.
Genetic variability does exist for level of trypsin inhibitor activity and
genotypes with no measurable activity are available. In the United States,
competition with maize (Zea mays L.) is a major impediment to increased
usage of sweetpotato for animal feeds and supplements although interest is
growing in the potential use as a component in chicken feed.
Recently, much attention has been focused on minor crops which are very
important to the culture and subsistence of local farmers in many parts of the
world. Concern has been raised about the future security of the genetic
resources of these minor crops. In particular, recent attention has been
focused on the Andean root and tuber crops. In addition to potatoes, several
roots and tubers have played a significant role in the Andean culture and are
cultivated in that area. Two of these which are more well known than others
could be domestically grown. A third is lesser known but could also have some
potential for production.
Oca (Oxalis tuberosa Molina, Oxalidaceae) is probably the most well
known root vegetable other than potato in the Andean region. It is quite
unusual in appearance with a brightly colored edible tuber and a pleasant mild
flavor. Oxalic acid is a component of the tubers, but levels are generally not
higher than those found in some other popular crops (S. O'Hair pers. commun.).
Oca is commercially produced in Peru and has been commer-cialized in New
Zealand (Yamaguchi 1983). A number of clones are grown and many accessions
have been collected (S. O'Hair pers. commun.).
A second Andean root vegetable, ulluco or olluco or ullucu(s) (Ullucus
tuberosus Caldas, Bassellaceae) is also grown commercially in the Andean
regions of Peru. This is also a crop of wide genetic diversity with perhaps 50
to 70 clones being grown in the Andean region (S. O'Hair pers. commun.).
External colors of tubers can be white, yellow, green, or magenta; the plants
are frost resistant and require 140 to 150 days for tuber development
Mashua or anu (Tropaeolum tuberosum Ruiz & Pav. Family
Tropaeolaceae) is a third Andean root vegetable and is related to the
ornamental nasturtium. It is not commercially produced on the same scale as
the other two crops. Consequently, it is not as well known as the other two.
It is said to have medicinal properties and some cultivars may have pesticide
properties (S. O'Hair pers. commun.).
Each of the three Andean root vegetables can be eaten fresh or dehydrated. All
are used in the Andean region, along with potato, to make chuo, a dehydrated
and frozen product which can last several years and serves as a secure food
source when necessary. Each has the potential to be grown in certain areas of
There are several opportunities for increased production and usage of root and
tuber crops in the United States. Of the five major root crops, sweetpotato
has the greatest potential for new uses and increased production. As
sweetpotatoes cannot be imported in the United States, there is no significant
current supply for specific types of sweetpotatoes suited to ethnic cultural
preferences. Growers in North Carolina, who produce over 30% of the
sweetpotatoes in the United States, have been reluctant to begin production of
new types for ethnic markets. Market feasibility studies need to be undertaken
to determine the potential markets.
With respect to new and unknown root crops, three Andean root crops, oca,
ulluco, and mashua, offer potential for new production. However, a lack of
funds to investigate the possibilities may preclude any development.
- Collins, W.W. 1987. Improvement of nutritional and edible qualities of
sweetpotato for human consumption, p. 221-226. In: Exploration, maintenance
and utilization of sweet potato genetic resources: Report of the first sweet
potato planning conference, International Potato Center, Lima, Peru.
- FAO. 1990. 1989 production yearbook. Rome, Italy.
- Gohl, B. 1981. Tropical feeds. FAO, Rome, Italy.
- Keya, E.L. and D. Hadziyev. 1990. p. 188-196. In: R.H. Howeler (ed.). Proc.
8th Symposium of the International Society for Tropical Root Crops. Oct.
30-Nov. 5, 1988. Bangkok, Thailand, 1990.
- Marsh, D.B. 1988. Production of specialty crops for ethnic markets in the
United States. HortScience 23:628.
- Marsh, D.B. 1991. Ethnic crop production: An overview and implications for
Missouri. HortScience 26:1133-1135.
- O'Hair, S.K. 1990a. Tropical root and tuber crops. Hort. Rev. 12:157-196.
- O'Hair, S.K. 1990b. Tropical root and tuber crops, p. 424-428. In: J. Janick
and J.E. Simon (eds.). Advances in new crops. Timber Press, Portland, OR.
- O'Hair, S.K., R. McSorley, J.L. Parrado, and R.F. Matthews. 1983. The
production and qualities of Cuban sweetpotato cultivars in Florida. Proc.
Amer. Soc. Hort. Sci. Tropical Region 27:35-41.
- Reynolds, B.D., W.J. Blackmon, E. Wickremesinhe, M.H. Wells, and R.J.
Constantin. 1990. Domestication of Apios americana, p. 436-442. In:
J. Janick and J.E. Simon (eds.). Advances in new crops. Timber Press,
- Rhoades, R. and D. Horton. 1990. p. 8-19. In: R.H. Howeler (ed.). Proc. 8th
Symposium of the International Society for Tropical Root Crops. Oct. 30-Nov.
5, 1988. Bangkok, Thailand.
- Sammy, G.S. 1984. The processing potential or tropical root crops. Proc.
Caribbean Regional Workshop on Tropical Root Crops, Jamaica, April 10-16, 1983.
- Sperling, C.R. and S.R. King. 1990. Andean tuber crops: worldwide potential,
p. 428-435. In. J. Janick and J.E. Simon (eds.). Advances in new crops.
Timber Press, Portland, OR.
- Villareal, R.L. 1981. Sweet potato. Proc. First International Symposium.
Asian Vegetable Research and Development Center, Tainan, Taiwan. p. 3-16.
- Walter, W.M., E.M. Croom, G.L. Catignani, and W.C. Thresher. 1986.
Compositional study of Apios princena tubers. J. Agr. Food Chem.
- Yamaguchi, M. 1983. World vegetables: Principles, production and nutritive
values. AVI, Westport, CT.
Table 1. Production of major world food crops and root
zSource: FAO 1989 Production Yearbook (FAO 1990)
|Crop ||Global |
|Wheat ||538,056 ||55,407|
|Rice ||506,291 ||7,007|
|Maize ||470,318 ||191,197|
|Barley ||168,964 ||8,784|
|Potato ||276,740 ||16,659|
|Sweetpotato ||133,234 ||542|
|Cassava ||147,500 ||---|
|Yam ||23,459 ||---|
|Aroids ||5,814 ||3|
|Root crops total ||590,176 ||17,204|
Last update April 28, 1997