Stephen G. REYNOLDS and Enrique ARIAS
Stephen G. REYNOLDS
Crop and Grassland Service
Horticultural Crops Group
Plant Production and Protection Division, FAO
The utilization by man of the cactus Opuntia was recorded in Mexico in pre-Hispanic times, where it played a major role in the agricultural economy of the Aztec empire; with maize (Zea mays) and agave (Agave spp.), opuntias are the oldest cultivated plants in Mexico. There are three crucial steps in the transition from the use of wild plants to planned cultivation, namely:
* the gathering of wild plants;
* cultivation of (wild) plants near human settlements, and
* cultivation of varieties, altered by selective propagation methods, in intensive farming for the purpose of marketing.
Opuntias are now part of the natural landscape and the agricultural systems of many regions of the world. Typically, there are three main production systems: wild cactus communities; family orchards; and intensive commercial plantations. Opuntias have adapted perfectly to arid zones characterized by droughty conditions, erratic rainfall and poor soils subject to erosion. They thus contribute in times of drought, serving as life saving crops for both humans and animals. Some species are even naturalized weeds in countries such as South Africa and Australia, where the environmental conditions are particularly favourable.
In recent years, plantations for fruit or forage production, as well as for vegetable or nopalitos and cochineal, have been developed in many countries of Africa, America, Asia and Europe. There is increasing interest in opuntias, and O. ficus-indica in particular, and the important role they play and are likely to play in the success of sustainable agricultural systems in arid and semi-arid zones, where farmers and shepherds must look to those few species that can profitably survive and produce. Thus opuntias have become an endless source of products and functions, initially as a wild plant and, later, as a crop for both subsistence and market-oriented agriculture, contributing to the food security of populations in agriculturally marginalized areas.
There are almost 300 species of the genus Opuntia (Scheinvar, 1995). In Mexico alone, Bravo (1978) recorded 104 species and varieties.
According to Scheinvar (1995), the name Opuntia comes from an ancient Greek village in the region of Leocrid, Beocia: Opus or Opuntia, where Tournefort found a spiny plant which reminded him of the American opuntias. Opuntia includes 11 subgenera: Opuntia, Consolea, Austrocylindropuntia, Brasiliopuntia, Corynopuntia, Cylindropuntia, Grusonia, Marenopuntia, Nopalea, Stenopuntia and Tephrocactus.
The taxonomy is difficult for a number of reasons: their phenotypes, which vary greatly according to ecological conditions; their polyploidy, with a great number of populations that reproduce vegetatively and sexually; and the existence of numerous hybrids, as almost all species blossom during the same period of the year and there are no biological barriers separating them. Scheinvar (1995) mentions nine wild species of Opuntia (O. hyptiacantha Web; O. joconostle Web; O. lindheimeri (Griff. and Haare) Bens.; O. matudae Scheinv.; O. robusta Wendl. var. robusta; O. sarca Griff. ex Scheinv.; O. streptacantha Lem.; O. tomentosa SD. var. tomentosa and var. herrerae Scheinv.) and three cultivated species (O. albicarpa sp. nov.; O. ficus-indica (L.) Mill.; O. robusta Wendl. var. larreyi (Web.) Bravo), as well as one cultivated species of the subgenus Nopalea (O. cochenillifera (L.) Mill.), providing detailed descriptions of each.
The evolution of members of the subgenus Opuntia in arid and semi-arid environments has led to the development of adaptive anatomical, morphological and physiological traits, and particular plant structures, as described by Sudzuki Hills (1995).
The species of the Opuntia spp. subgenus have developed phenological, physiological and structural adaptations favourable to their development in arid environments, in which water is the main factor limiting the development of most plant species. Notable among these adaptations are asynchronous reproduction, and Crassulacean Acid Metabolism (CAM), which, combined with structural adaptations such as succulence, enables this plant to survive long periods of drought, and to reach acceptable productivity levels even in years of severe drought.
In this book opuntia is used to refer to the whole genus, of which the most widely known is Opuntia ficus-indica. Previously, opuntia was used almost interchangeably with cactus pear and prickly pear. Here, while these terms are occasionally used, the term opuntia is preferred because cactus pear can sometimes refer to the fruit, and also not all opuntias are prickly pears, there being many spineless clones.
Other terms used include the following:
* cactus pear - opuntia plant
* cladode - shoots or stem-like organs
* jarabe - a syrup product from the fruit
* melcocha - jam
* miel de tuna - cactus pear honey
* nocheztli - highly prized red dye obtained from the body of the cochineal insect (Dactylopius coccus) living on some opuntias. Called grana cochinilla by the early Spanish in Mexico, now called cochineal
* nochtli - opuntia fruit
* nopal - opuntia plant (mainly Mexico)
* nopalitos - young cladodes used as vegetables
* nopalli - opuntia plant in Nahuatl language
* notuatl - the original Mexican word (from Aztec times) for opuntia
* prickly pear - opuntia plant
* queso de tuna - cactus pear cheese
* tenochtli - sacred opuntia in early Mexico
* tun/tunas - Caribbean word for fruit or seed
* Spanish: nopal, cardón de México, chumbera, chumbo, chumbua, higo chumbo, higo de pala, higo México, higuera de pala, nopal de castilla, tuna de España, tuna española, tuna mansa, tuna, higo chimbo, tuna real.
* Portuguese: palma forrageira, figo da India, figo de pitoira, figueira da India, palmatoria sem espinhos, tabaido.
* English: Barbary fig, Indian fig, prickly-pear.
* French: chardon dInde, figue de Barbarie, figuier à raquettes, figuier dInde, opunce, raquette.
* Italian: Fichi dIndia
* German: frucht des feigenkactus, Indianische feige.
Upon the request of member countries, an international network, CACTUSNET, was established in Guadalajara, Mexico, in 1993, under the auspices of FAO, to increase cooperation among scientists, technicians and growers from different countries, and to facilitate the exchange of information, knowledge and technical cooperation on cactus. Cooperation in the collection, conservation, evaluation and utilization of germplasm, and the promotion of the ecological and social benefits of opuntias are also aims of the network. Twenty-two countries have since joined. The University of Guadalajara, Mexico, and the University of Reggio Calabria/University of Palermo have hosted the general coordination; from October 2000, the coordinating institution became the National Institute for Agricultural Research of Tunisia. Meetings normally take place in conjuction with the International Congress on Cactus Pear and Cochineal, held every fourth year, but additional regional meetings and working group meetings are also held, such as those in Angola, Argentina, Chile, Italy, Mexico, Peru and South Africa on a range of topics, including post-harvest aspects, genetic resources, cochineal, forage, fruit production, etc.
Tangible results of cooperation through CACTUSNET have been the preparation for publication in 1995 of the FAO book Agro-ecology, cultivation and uses of cactus pear (which has been translated into Spanish and is being translated into Arabic), the production of a Descriptor List, and the annual CACTUSNET Newsletter. The fifth edition, published in March 2000, focused on the use of opuntia as forage and is available on the website of the FAO Grassland Group:
The present publication is also an example of voluntary cooperation of institutions and individuals participating in the CACTUSNET.
Felker (1995) has provided an excellent introduction to Opuntia as forage and a synthesis of common recommendations for cactus use and management for livestock feed. He mentions a number of excellent regional reviews covering the uses of cactus for forage in North Africa (Monjauze and Le Houerou, 1965), South Africa (De Kock, 1980; Wessels, 1988), Mexico (e.g. Flores and Aguirre, 1979; Fuentes, 1991), Brazil (Domingues, 1963) and the United States (e.g. Russell and Felker, 1987a, b; Hanselka and Paschal, 1990). Much of the progress stemmed from the work of Griffiths in Texas in the first two decades of the 1900s.
Opuntia is particularly attractive as a feed because of its efficiency in converting water to dry matter, and thus to digestible energy (Nobel, 1995). Cactus is useful not only because it can withstand drought, but also because its conversion efficiency is greater than C3 grasses and C4 broadleaves. Biomass generation per unit of water is on average about three times higher than for C4 plants and five times higher than for C3 plants. Under optimal conditions, the various types of plants can produce similar amounts of dry matter per surface area, but under arid and semi-arid conditions, CAM plants are superior to C3 and C4 plants.
Cacti, and specifically Opuntia spp., have been extremely useful livestock forage in times of drought, primarily by providing digestible energy, water and vitamins. Although mainly used for cattle, opuntia has also been used as forage for pigs. However, it must be combined with other foods to complete the daily diet because opuntias are poor in proteins, although rich in carbohydrates and calcium. Since it grows in severely degraded land, its use is important because of its abundance in areas where few crops can grow. It is estimated that, worldwide, 900 000 ha are cultivated with opuntia for forage production.
While spineless types need to be protected against herbivory, the more cold-hardy, slower growing spiny types require no such protection, although it is necessary to burn off the spines before using for livestock feed.
Felker (1995) noted the lack of serious R&D and suggested priority areas for research into the use of cactus for forage.
Opuntia spp. are being utilized in programmes to prevent soil erosion and to combat desertification; they have a great capacity for adaptation, growing in severely degraded soils which are inadequate for other crops and are ideal for responding to global environmental changes such as the increase in atmospheric CO2 levels. Opuntias are also important as cover in arid and semi-arid areas because they can survive and spread under conditions of scarce and erratic rainfall and high temperatures and can play an important role in the protection of local fauna.
However, this capacity for adaptation and rapid spread has caused problems, mainly where introduced Opuntia spp. have established and thrived in the absence of natural enemies and appropriate management to become noxious weeds in a number of counties. In the previous FAO publication Agro-ecology, cultivation and uses of cactus pear, a chapter by Brutsch and Zimmermann focused on naturalized Opuntia spp. which threaten native plant genetic resources, and also on the biological, chemical, mechanical or integrated means of control which have been developed. Biological control has been particularly successful in countries such as Australia and South Africa. However, the problems of developed countries are not necessarily the same as those of less developed countries, and what may be considered a weed in one country may be an important economic source of food in another. Therefore different countries and even areas within countries may view Opuntia spp. differently.
This book emphasizes Opuntia as a valuable natural resource, which in many countries is underutilized, and which can provide forage for livestock and enable economic activities to be undertaken and may contribute to the food security of populations in agriculturally marginalized areas.
Several publications have dealt with opuntia. Previously, through CACTUSNET, FAO published Agro-ecology, cultivation and uses of cactus pear. The present publication focuses solely on the use of opuntia as forage and aims to present much of the recent findings and research in one volume. From chapters dealing with its early use as forage in Mexico and its ecophysiology, the book presents material on germplasm resources and breeding for forage production, then deals at length - through eight chapters - with its use as forage in Mexico, Brazil, USA, Chile, Argentina, Western Asia and North