The authors of this chapter are H. Noda, C R. Bueno and D F. Silva Filho (INPA, Manaus, Brazil).
Common names. English: Guinea arrowroot, sweet corn root (Caribbean) topeetampo, topi-tamboo, topinambour; Spanish: dale dale (Peru [Amazonia]), agua bendita, cocurito (Venezuela), lerenes (Puerto Rico), topitambo or tambu (West Indies), topinambur (Antilles); Portuguese: ariá (Brazil [Amazonia]), láirem (Brazil); French: touple nambours (Santa Lucía); alléluia. curcuma d'Amérique (France)
Guinea arrowroot or sweet corn root (Calathea allouia) is an oleiferous species which has been known and cultivated for a long time by the indigenous peoples of tropical America. It is sustaining a loss of genetic variability because its cultivation is increasingly being abandoned. In Brazilian Amazonia up to the end of the 1950s, Guinea arrowroot was a vegetable cultivated on a small scale by traditional growers in their vegetable gardens and the tuberous roots were eaten cooked, accompanied by coffee. At present, in communities further away from towns in Amazonia it is rare to meet a grower who still keeps Guinea arrowroot in his garden. For cultural reasons, it is precisely the indigenous populations who are continuing to grow the species.
Distributed throughout the world, Guinea arrowroot has been well accepted, but has not reached the point of being an important crop anywhere.
In Brazilian Amazonia, its increasing abandonment seems to have been caused by two main factors: its very long vegetative cycle (ten to 12 months) and its replacement in the diet of small rural producers by other types of food (sweet potato, care, yam or other industrialized products such as wheat biscuits and bread). Even in its region of origin where its cultivation dates back 1000 years, Guinea arrowroot is at present used only in subsistence farming by traditional growers and indigenous populations.
The tuberous roots of Guinea arrowroot are eaten cooked and their texture remains crisp even after long cooking, a characteristic which makes it very palatable. It is cooked in water for 15 to 20 minutes and its flavour is similar to that of cooked green maize. As well as being eaten on its own, Guinea arrowroot can be an ingredient of salads, mayonnaise and fish dishes.
In South America, the leaf dye is used in traditional medicine to treat cystitis and as a diuretic. The fresh leaves are used to make baby clothing, as they are strong and durable.
Generally speaking, the prevailing climatic conditions in the humid tropicsrelatively high temperature and humidity throughout the yearare unfavourable for the cultivation of vegetables from a temperate or subtropical climate and, at the same time, encourage the development of pests and phytopathogenic micro-organisms. It is in this context that the potential of little-known species should be evaluated. In the plantations of INPA in Manaus, no pest attacks or presence of diseases causing significant damage to Guinea arrowroot have been found during the last 15 years.
The study of agroforestry systems has intensified in recent years. These systems benefit from the techniques and plant species used by traditional and indigenous growers. They are thought to constitute land management methods which are more ecologically suited to the humid tropics. Guinea arrowroot is a vegetable which was grown in vegetable gardens for centuries, and historical evidence has shown the important part it played in agroforestry systems.
Calathea allouia is a perennial species which forms clusters of I m in height. It has ovoid or cylindrical. tuberous roots which are 2 to 8 cm long and 2 to 4 cm in diameter. The leaves have an enveloping base forming short pseudostems; the petioles are long and striated, the leaf blades ellipticalsimilar to those of rattan palmand measure 20 to 60 x 5 to 20 cm. The flowers are white. approximately 2 to 5 cm long, with a staminode and trilocular ovary. Tuberization begins at the end of the fibrous roots.
The tuberous roots contain 13 to 15 percent starch and 6.6 percent proteins (in the dry matter). Of the amino acids (the tryptophan content has not been measured), only cystine deficiency has been noted: this is of no great importance because Guinea arrowroot is not a food in regular use. There are high levels of all the other amino acids. chiefly the essential ones.
In the INPA collection. the plants flower only in some 2 percent of the specimens and do not produce viable seeds. Guinea arrowroot is reproduced vegetatively, through rhizomes, on each side of which about 20 shoots appear.
Figure 28. Guinea arrowroot (Calathea allouia)
Shade may facilitate the growth of the plants, but the best growth is achieved under cultivation conditions with full exposure to sunlight when the humidity, nutrients and soil drainage are not limiting factors. The cycle from planting to harvesting lasts nine to 14 months, depending on the climatic conditions. Some authors have reported that water shortages can reduce the plant's cycle. causing a reduction in the production of tubers. With introductions from Lábrea and Tefé and with irrigated cultivation beginning in the rainy season, tubers have been harvested after 253 days in Solimões. Brazil.
Guinea arrowroot requires soils of medium texture because very clayey soils impair the development of the tuberous roots while in sandy soils its growth is deficient.
Guinea arrowroot is distributed geographically through Puerto Rico, the Antilles and countries situated in northern South America (the Guyanas, Venezuela, Colombia, Ecuador, Peru and Brazil)countries in which it is assumed to have originated. There are records of Guinea arrowroot's introduction into India, Sri Lanka, Malaysia, Indonesia and the Philippines.
The genus Calathea has wide genetic diversity. Over 100 species have been described. chiefly in tropical America. C. lutea, a species of the same genus, known as cauassú, casupo, white leaf or bijão, is a tall shrub of the lower region of Amazonia, used to produce wax. Another two species of economic interest from the Marantaceae family are Ischnosiphon arouma, known as tiriti, the branches of which are used to make baskets, and Maranta arundinacea, known as arrowroot or araruta (in Brazil), whose rhizome yields a starch of high viscosity.
Although it is cultivated only on a small scale by some traditional growers and indigenous populations, Guinea arrowroot can be found practically throughout the Amazon region. The tuberous roots are usually sold at the open fairs and markets of towns such as Manaus, Belém, Porto Velho. Santarém, Tefé and Benjamin Constant, in Brazil, and in Iquitos in Peruvian Amazonia. There are no bibliographic records on the use of cultivars genetically intended for commercial exploitation. In the last 15 years, INPA has carried out research and distributed reproductive material to small farmers as part of its extension activities. This material comes trom collections gathered within Amazonia.
Observations made on the basis of research and collection maintenance programmes suggest the presence of a certain genetic variability among the different introductions, particularly when morphological characteristics and tuber size are examined.
Owing to its status as a crop of limited economic importance, Guinea arrowroot has undergone little research, and bibliographies relating to the species are scant. Genetic resources are maintained practically in situ by traditional growers and indigenous populations. Mention should be made of a collection at the USDA's Mayaguez Institute of Tropical Agriculture in Puerto Rico as well as of INPA's efforts aimed at widening the genetic variability of its collection through new introductions.
It may be assumed that, at present, genetic erosion is high. In the last 30 years, traditional growers have gradually abandoned cultivation of Guinea arrowroot.
The species is propagated by rhizomes. When the tuberous roots have been harvested, they are stored in a cool, dry place until they are transplanted.
Guinea arrowroot is normally grown in small areas where subsistence farming is frequently carried out in association with cassava, plantain or fruit-trees. In Puerto Rico, it is sown in the shade of coffee trees. Its association with woody species is due to the fact that total or partial shade is necessary for good vegetative development.
After planting, Guinea arrowroot needs little care. In areas infested with phytoparasitic nematodes, Guinea arrowroot shows no symptom of pest attack. It is antagonistic to the gall nematode, Meloidogyne incognita, because of its root secretions which impair the larvae's hatching, penetration and reproduction.
The physical and chemical qualities of the soil affect Guinea arrowroot's productivity. Productivity of the tuberous roots is quadrupled if they are grown on plots treated with organic fertilizers (fruit and vegetable waste). The right soil for growing Guinea arrowroot seems to be clayeyloam, which retains nutrients and allows good drainage, although organic matter also needs to be added.
The plants are generally planted with 0.6 m between rows and 0.45 to 0.80 m apart. In research carried out by INPA in Manaus, distances of 1 m between rows and 0.50 m between plants are being adopted. Observations indicate that denser plantings are to be more recommended.
Water supplements are a necessary condition for good yields. Low yields are mainly due to drought at the end of the rainy season. By irrigating the plantation in critical periods, a product yield of close to 15 tonnes per hectare and with more uniform roots has been achieved in Manaus.
The yield from the experimental plantations of INPA in Manaus has been very variable. Productivity per plant is between 100 and 2200 g. Planting in sandy soil with the addition of organic matter has achieved yields of 936 g per plant. Product yields of 10 tonnes per hectare, and on small plots of 2 to 12 tonnes per hectare, have been reported.
The underground part may be subject to sporadic insect attack. The larvae of coleoptera and lepidoptera cause lesions in the rhizomes and tubers while mite damage has been seen on the leaves and causes the plants to die.
Tuberous roots in clayey soils can be harvested by simply pulling up the plants. However, the most usual way is to hoe the soil carefully around the plant so as to facilitate its removal without damaging the tuberous roots. After harvesting, these may remain for up to ten weeks in open and ventilated environments. In spite of the marked weight loss29 percent after ten weeksthe best method of storing the tubers is to put them in the vegetable fibre baskets which farmers use to store roots, tubers and meal, and which are lined on the outside with dry leaves. Storage in special preservation units reduces weight loss, but seriously damages the tuberous roots, impairing the characteristics which are considered to be good for marketing.
Knowledge concerning the genetic improvement of Guinea arrowroot is still incipient. Its commercial exploitation is rare and its cultivation using modern techniques is little developed. In fact. the gradual abandonment of its cultivation by traditional farmers may lead to an extreme reduction in genetic variability and even to extinction of the species.
Basic biological studies that can form the basis for phytotechnical improvements need to be encouraged and new vegetative propagation techniques researched. For example, immersion of the rhizome in hot water at 48°C for ten minutes before planting increases sprouting by 24 percent compared with an untreated control. This experiment shows. furthermore, that too prolonged an immersion also has harmful effects.
Other research shows that the photoperiod has a pronounced influence on the initiation of the tuberization process which is caused by short days, whereas rhizome formation is favoured by long days. Nocturnal temperatures of 10°C reduce the plants' general growth and inhibit tuber formation. In Puerto Rico, it has been noted that, when the rhizomes are planted during the November-December period, no dormancy is exhibited, and tuberization is high with sowing in mid-November and in full sun. Irrigation is an important factor in the productive process and must be constant throughout the plant's cycle. Guinea arrowroot is a species very sensitive to small water shortages and a greater availability of water has the effect of bringing forward and stimulating growth of the tuberous roots and encouraging the formation of new rhizomes.
The evolution of Guinea arrowroot has the exceptional characteristic of being included within the limits of a traditional agriculture or an indigenous agriculture. This aspect of the crop is a challenge to the researcher who must carefully choose the most appropriate direction for the development of the species. What is its place to be in the agriculture of the future? It will undoubtedly depend on the evolution of agriculture itself. It is improbable that its place is in monoculture with an intensive use of inputs and with high yields, and it is probably only a matter of time before it is completely abandoned in that context. The solution for its survival can be found only within the framework of traditional indigenous agriculture. The current renewal of farming activities in fragile and complex environments such as the humid tropics, and more especially those of the Amazon region. represents an effort of synthesis in which science interprets traditional agricultural techniques, reconstructing them at a higher level. However, this new method of management alters the models on which agroforestry was conceived: self-sustainability, the integration in space and time of its component elements, the optimization of the use of available resources and the adaptation of production agents to ecological processes.
Guinea arrowroot is a vegetable that is especially recommended for use in agroforestry systems where its agronomic limitations, considered from the point of view of conventional monoculture (for example its shade requirement and its method of propagation), could be changed into advantages.
Current research projects will have to examine two aspects: