IF YOU CAN'T TUNE A PIANO, MAYBE YOU CAN TUNA CACTUS
SCIENTIFIC NAME: Opuntia species
FAMILY: Cactaceae
INTRODUCTION
Cactaceae (cactus) is a family of tropical and sub-tropical plants which has generally been ignored by many horticulturalists. Edible cactus may be put into three groups: the tunas, the pitayas, and the pereskias. The tunas are the most important as a food source. There are probably 100 species, mostly of the genus Opuntia, which bear edible fruit.
Opuntia spp. prefer dry soils where few other plants can thrive. Their fruits, consumed fresh, and the tender, young joints, cooked as a green table vegetable, are enjoyed by indigenous peoples. Moreover, spineless joints, and those burned to remove spines, are considered good forage for livestock. They are also used as medicinal plants, and for other purposes. Tunas have a high potential for horticultural development, especially in areas where drought is a limiting factor for production of more common fruits or forage.
ORIGIN AND BOTANY
All species of Opuntia are native to the Americas from Canada to South America; however, the greatest number are indigenous to the desert zones of northwestern Mexico and the southwestern United States. Some species of Opuntia were taken by Spanish explorers to the Mediterranean from there to India, South Africa, and Australia.
Plants are succulent with jointed, branching stems. The joints are either flat or cylindrical, bearing small, mostly-subulate, deciduous leaves. Areoles bear spines and tufts of glochids. Flowers are sessile and usually bear spines. The fruit are globose to obovoid and often spiny. The edible portion of the fruit is made up of a number of funicels intermixed with juicy papillary hairs.
CULTIVATION
The tuna (Opuntia ficus-indica) and possibly a few other allied species are grown commercially in Mexico, Italy, Sicily, and the southwestern United States. Propagation is often by vegetative means such as slips, joints, or shoots, particularly of selected cultivars, but it can be grown from seeds.
Fruiting of vegetatively propagated plants begins after 2 or 3 years and reaches full production around 7 years. A mature plant can produce around 150 fruits. Plantations are usually made on dry slopes of hills as the plants do not thrive where there is much moisture, or in heavy clay soils. Joints, cut or broken from the plant, are used instead of seeds, and are planted at a distance of 6 to 8 feet in furrows from 6 to 15 feet apart.
UTILIZATION
Uses as fruit. Sour fruit, produced by some species of prickly pear, are called 'xoconoxtles', whereas the sweet fruit produced by other species are called 'tunas'. In California, the fruit is harvested in late spring and late summer by laborers wearing special leather clothing for protection against the minute spicules and spines that remain in the fruit. A stick, at the tip of which is attached a tin can with opening upward, is used for harvesting. The fruit are cut from the plant with the sharp edge and fall inside the can.
Due to its high nutritive value, tuna forms an important dietary staple in many regions. Bailey, 1916, reported however, that prickly pears did not get the same attention as other fruit crops by horticulturists, although they were much more widely used and of far more economic importance than many plants which have an established place in the literature. The fruits of Opuntia have been used by Mexicans and Indians of New Mexico, Arizona, California, and Utah under the common Spanish name of tunas.
Great quantities are dried for use in the winter. Fresh, unripe fruit is often boiled in water until it becomes like applesauce. When allowed to ferment a little, it becomes stimulating and nutritious. An alcoholic drink is usually made from the fruit where it is grown extensively. The juice of highly-colored types is sometimes used to color confectionery.
During their season, tunas are the principal food of people in parts of Mexico. 'Queso de tuna' (tuna cheese) consists of the dried fruit pressed into large cakes; this is widely sold in the market in Mexico. 'Miel de tuna' (tuna honey) is a syrup prepared from the fruit. 'Melcocha' is a thick paste made by boiling down the juice. 'Colonche' is the boiled, fermented juice. 'Nochote' or 'nochocle' is a fermented beverage prepared from the juice of the fruit. 'Tejuino' is also a beverage prepared from the juice. Jams and jellies are also made with a flavor somewhat like that of guava jelly. Among some of the Indians in California, the seeds were an important food. These were stored until winter when they were ground and used to prepare a kind of 'atole' (seed meal).
The fruit is rich in sugar, small amounts of vitamin C, thiamin, riboflavin, and niacin. It is fairly rich in calcium and potassium. Lysine, tryptophan, and methionine are also present in small quantities. Fruits contain about 90% water, 6% glucose, 2.7% starch and dextrine, 1% protein, and 0.3% ash in the edible part of tuna. It has been ascertained that some of the best varieties are capable of producing as much as 18,000 pounds of fruit to the acre in lean, sandy, or rocky soil, ill-suited for growing ordinary crops. When it is considered that this is equal to 2,500 pounds of sugar, as well as other valuable food constituents, it may be readily seen that the nutritional value is considerable. Three kg of dried biomass with a protein content of around 45% has been obtained from the juice of 100 kg of tuna fruit.
An important advantage in the culture of these plants is the regularity of the yearly crop. They begin bearing in about two to three years after planting and continue bearing for many years. In Mexico, 8 metric tons per hectare of fruit can be expected within the fourth year of planting.
Uses as a vegetable. The tender, young joints are often cooked as a vegetable. 'Nopalitos' are the tender, young pads of prickly pear eaten as a vegetable in Mexico and the southwestern United States where there are large populations of people of Mexican heritage. The pads are traditionally prepared during the Lenten season as a cooked green vegetable, particularly during Holy Week, and as a marinated vegetable throughout the year. Some Indians roast joints of opuntia in hot ashes. When cooked, the outer skin with the thorns is easily removed, leaving a slimy, sweet, succulent dish.
Uses as forage. In drought periods, when grasses have been overgrazed or have become senescent, the tuna plant remains succulent and green. Spines are destroyed with a gasoline torch by passing a flame over the surface of the plant. The dry spines burn easily especially if they are abundant and close. Other methods of making the spines harmless are soaking in water, steaming, or washing with soda, although species which are spineless are more valuable for use as forage.
Opuntia spp. are fairly palatable, and when fed in liberal amounts can replace drinking water; however, the nutritive value is not sufficient to maintain weight in animals receiving only cactus. Sheep are known to survive up to eight months on a diet consisting entirely of opuntia. Preferably, the feed should be supplemented with other, less succulent, dry feed, such as 1-2 kg of straw or dry grass and 0.5 kg of cottonseed daily.
Uses as a medicinal plant. Young joints are applied as poultices to reduce inflammation and acute rheumatism. When baked, they have been used for chronic ulcers, gout, and recent wounds. The juice and gummy exudation have been used to relieve cases of kidney stones. A mucilaginous decoction of the joint is commonly used as a demulcent drink to treat pneumonia and other lung infections. It is also claimed that the cut joints are discutient, and the juice has endermal and emollient, hydrating, and decongestive action. In some countries, opuntia is used to treat pimples and other skin problems.
Other utilization. Prickly pear are sometimes cultivated as hedge or ornamental plants. The wood of opuntia is more or less porous and usually of open lace-ike structure. It is used to some extent in the manufacture of ornaments and rustic work, taking advantage of its curious formation.
OUTLOOK AND EXPECTATION
Bailey, 1916, stated four reasons for which the tunas and their allies are worthwhile to be considered as a horticultural crop. First, they produce large crops of edible fruits; second, plants with few or no spines and edible joints are the general rule in some species; third, spineless forms make valuable forage; and fourth, Opuntia spp. are strong, vigorous plants that will thrive in situations in which few other plants will grow.
With these and more qualities to recommend, it yet remains for horticultural enterprise to develop spineless and bristle-free cultivars that will not only be of value for forage, but will produce large crops of fruits which are attractive to the educated palate. There are many areas in the world where drought and irregularity of rain make food production difficult. The desert advances, and soil erosion causes continued damage to wildlife.
Luther Burbank once stated that opuntia is the answer to all our needs in converting the desert to lush pasture and orchard combined. With the approaches of modern genetic engineering technologies, rapid progress toward this goal is feasible.
The application of growth regulators such as thidiazuron and benzyladenine on cultivated plants, resulted in significant increase in the number of branches. This later may be useful to increase crop production. Moreover, the application of biotechnology could speed the progress of opuntia breeding through selection for desirable traits such as disease resistance, and high nutritive values; and through rapid cloning and propagation of the selected cultivars. New cultivars with desirable traits can be obtained through somaclonal variation or DNA recombination.
DATE: January 1995
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