Guinea arrowroot (Calathea allouia)

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Botanical name: Calathea allouia (Aubl.) Lindl.
Family: Marantaceae
Common names. English: Guinea arrowroot, sweet corn root (Caribbean) topeetampo, topi-tamboo, topinambour; Spanish: dale dale (Peru [Amazonia]), ague bendita, cocurito (Venezuela), lerenes (Puerto Rico), topitambo or tambu (West Indies), topinambur (Antilles); Portuguese. aria (Brazil [Amazonia]), láirem (Brazil); French: touple nambours (Santa Lucía); alleluia, 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 1 000 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 tropics - relatively high temperature and humidity throughout the year-are 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 pan it played in agroforestry systems.

Botanical description

Calathea allouia is a perennial species which forms clusters of 1 m in height. It has ovoid or cylindrical, tuberous roots which ar 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 elliptical - similar to those of rattan palm - and 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.

Ecology and phytogeography

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.

Genetic diversity

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.

FIGURE 28 Guinea arrowroot (Calathea allouia)

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 pan of its extension activities. This material comes from 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.

Cultivation practices

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 loss -29 percent after ten weeks - the 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.

Prospects for improvement

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 Pueno 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.

Lines of research

Current research projects will have to examine two aspects:

· Genetic resources: the collection of germplasm in all distribution areas in America; the establishment of at least two gene banks, one in Central America and the other in northern South America; and the carrying out of origin tests to identify agronomically superior genotypes.
· The development of production plans and research on agroforestry systems.

Production plans must be devised for Guinea arrowroot in order to define the desired biotypes in the genetic improvement programmes.

Bibliography

Bueno, C.R. 1981. Contribuição ao controle de Meloidogyne incognita (Kofoid & White, 1919) Chitwood, 1 949 (Nematoda: Heteroderidae), raça fisiológica IV, com utilização de aria (Calathea allouia (Aubl.) Lindl.). Manaus, Brazil, CNPq/INPA/Universidade do Amazonas. (thesis)

Bueno, C.R. 1989. Controle ambiental e ação de reguladores de crescimento no desenvolvimento de plantas de aria (Calathea allouia (Aubl.) Lindl.). Universidade Estadual de Campinas. (thesis)

Bueno, C.R. & Pereira, M.F.A. 1986. Efeitos do fotoperiodo e reguladores de crescimento no desenvolvimento de plantas de aria (Calathea allouia (Aubl.) Lindl.). Anais da VI Congresso da Saciedade Botânica de São Paulo, p. 75-83.

Bueno, C.R. & Weigel, P. 1981. Brotação e desenvolvimento inicial de rizomas de aria (Calathea allouia (Aubl.) Lindl.). Acta Amazónica, 11(2): 407-410.

Bueno, C.R. & Weigel, P.1981. Ariá, Calathea allouia (Aubl.) Lindl. Uma oleífera alternativa pare a região tropical. Proc . Trop. Reg. Am. Soc. Hort. Sci., 25: 77-80.

Bueno, C.R. & Weigel, P.1983. Armazenamento de tubérculos frescos de aria (Calathea allouia (Aubl.) Lindl. Acta Amazónica 13(1): 7-15.

Kay, D.E.1973. Root crops. TPI Crop and Products Digest 2. London, Tropical Products Institute.

Leon, J. 1968. Fundamentos botánicos de las cultivos tropicales. San Jose, Costa Rica, IICA, OEA.

Martin, F.W. & Cabanillas, E. 1976. Leren (Calathea allouia), a little known tuberous root crop of the Caribbean. Econ. Bot., 30: 249-256.

National Academy of Science. 1975. Underexploited tropical plants with promising economic value. Washington, DC.

Noda, H., Bueno, C.R. & Silva Filho, D.F. 1991. Genetic erosion threatens native Amazonian vegetable crops. Diversity, 62-63.

Noda, H., Paiva, W.O. & Bueno, C.R. 1984. Hortaliças da Amazônia.Ciência Hoje, 3(13): 32-37.

Pahlen, A., Kerr, W.E., Noda, H. & Bueno, C.R. 1979. Melhoramento de hortaliças na Amazônia. Ciência e Cultura. 31 (1): 17-24.

Maté (Ilex paraguariensis)

Botanical name: Ilex paraguariensis A. St-Hil. var. paraguariensis
Family: Aquifoliaceae
Common names. English maté, Brazilian tea, Paraguay tea; Guarani: ka'a; Kaingangue: kongóñ; Spanish: yerba maté, té de los jesuitas; Portuguese: congonha, erva maté

Maté, with a very restricted distribution outside America, is a tree that produces a raw material for industrialization and consumption as a stimulating infusion. So far, this has been the main use of this somewhat overlooked crop.

Although no archaeological remains have been found that show that it was used in pre-Columbian times, it is assumed that it was the Guarani Indians who taught the Spanish how to use it. However, what seems to be an indirect consequence of the discovery is the fact that the first people to have cultivated this species were the Jesuit missionaries who, around 1670, already had artificial maté plantations. In time' the settlements of Guarani Indians converted to Christianity were to become economically dependent on maté production.

The expulsion of the Jesuits from the Spanish dominions (1767) was a step backwards in the history of maté. There was a return to the forest exploitation method which utilized the natural maté plantations exclusively and inadequately. It may be said that this type of laborious and uneconomical forest management extended up to the first decades of the twentieth century, in spite of` maté planting having been renewed in Nueva Germania, Paraguay and in Santa Ana, Argentina, in 1897.

Although very much reduced, maté production did not disappear with the Jesuit plantations. During the remainder of the colonial period, the use of this herb, which had spread extensively, persisted even in the region of the Viceroyalty of Peru, where there was another methyl xanthine stimulant of the same genus: flex guayusa Loes. emend. Shemluck, also marketed by the Jesuits from that region in Quito.

It has been established that trade in maté was not interrupted and that it was commonly used in what is now Peru and Ecuador. However, following the independence of the Spanish colonies and the adoption of free trade. English tea began to be introduced into those countries and so maté gradually lost the markets of those Andean countries.

The decline and complete disappearance of the maté plantations in the settlements of Christianized Indians (which ended around 1820 after a series of wars waged in the region between the Spanish and Portuguese Crowns, followed by the struggles for independence) and the policy of` isolation and control of international trade maintained by the first governor of independent Paraguay meant that, in the 1 820s, Brazil began commercial exploitation of its natural maté plantations.

The most accessible plantations were situated in the vicinity of Curitiba, Paraná, and as they were slowly exhausted they were gradually replaced by the others located towards the west. The Brazilian product, which then began to spread on the markets as "Paranagúa maté", was considered to be of inferior quality to that from Paraguay. However, in the course of time it replaced the Paraguayan product, a development which became more marked after the war of the Triple Alliance (1870).

At the end of the nineteenth century, the limitations of the exhaustive exploitation of this forestry resource stimulated efforts to produce large plantations of I. paraguariensis once again. Eventually, these efforts were successful, especially in Argentina.

At the same time as the increase in Argentinian maté production, the extraordinary expansion of the agricultural frontiers in traditional maté growing states of southern Brazil (Paraná, Santa Catarina, Rio Grande do Sul, Mato Grosso do Sul) took place. Regrettably, the disappearance of enormous areas of natural forests in those states jeopardized the conservation of maté's genetic richness.

The complicated economic history of this crop (barely sketched out here) which is characterized by periods of scarcity alternating with periods of excessive demand, the sporadic but real existence of periods during which it was adulterated with other plants and the most common method of preparation -maté sucked through a small tube - considered by many to be unhygienic, had a bearing on the limited spread of maté outside southern South America.

Its main use is in infusions prepared as tea with leaves and dried stems which have been industrially shredded. Generally speaking, it is drunk by filling small gourds (maté gourds or cuias) with maté, to which boiling water is gradually added, the liquid being sucked up through a metal tube (the bombilla) Infusions of cimarrón, or bitter maté, are usually modified with sugar (sweet maté), milk or aromatic herbs. Other methods of consumption are boiled maté, tereré, (maté prepared with cold water, common in Paraguay and northeastern Argentina), liqueurs prepared with maté, ice-creams, desserts, etc. The industry also produces compound maté (which contains aromatic and/or medicinal herbs), soluble maté and maté teabags.

The aqueous infusion of maté owes its stimulant properties to the caffeine content (between 1 and 2 percent) so that, 60 minutes after consuming maté, an average of 80 to 120mg of this pseudoalkaloid is consumed. Its nutritional qualities are due to its content of vitamins A, C and B complex and the existence of minerals (P, Ca and Fe).

Argentina, the main producer and consumer, grows around 130 000 ha of maté in the northeast of the country (Misiones and Corrientes), which produce about 140 000 tonnes per year. Brazil is the world's second producer, followed by Paraguay. For the Argentinan province of Misiones, maté cultivation represents an important part of the country's GDP.

Botanical description

The maté is a dioecious evergreen tree which grows up to 18 m in height. The leaves are alternate, coriaceous and obovate with a serrate margin and obtuse apex. The inflorescences are in corymboid fascicles, the male ones in a dichasium with three to 11 flowers, the female ones with one or three flowers. The flowers are small, and simple, number four or five and have a whitish corolla. The fruit is in a nucule; there are four or five single seed pyrenes (propagules).

Maté flowers in the spring (from October to November), has entomophilous pollination (diptera, hymenoptera) and fruits from March to June; dissemination is endozoic (birds). There is a rudimentary embryo in many externally ripe seeds which causes a long period of germination from the time of sowing.

FIGURE 29 A) Maté (flex paraguariensis);A1) inflorescence; A2) flower; A3) fruit; A4) gourd and tube for consuming the infusion

FIGURE 30 Distribution area of flex paraguariensisvar. paraguariensis and var. vestita

Ecology and phytogeography

Prominent among the ecological requirements of this subtropical species are climatic conditions, especially mean annual precipitation and an even distribution of rainfall throughout the year. This must not be less than 1 200 mm annually and, during the driest quarter- which in the region is winter - the minimum must be 250 mm. I. paraguariensis wild distribution area is always unaffected by water shortages. The mean annual temperature of the area is approximately 21 to 22°C. The absolute minimum temperature that this species is able to tolerate is -6°C, even though winter snows are frequent on the plateaus and mountain regions to the south of Brazil and east of Misiones.

It requires lateritic, acid (pH between 5.8 and 6.8) soils that are of medium to fine texture.

Figure 30 shows the natural distribution of I. paraguariensis. The area of economic cultivation of maté coincides approximately with the main dispersion area of the var. paraguariensis.

Genetic diversity

There is still no exhaustive modern picture that explains in biological terms the infraspecific variability of this species, which is widely dispersed geographically in South America. Up to the present, taking as a basis the morphological characteristics alone, at least two varieties are recognized: I. paraguariensis A. St-Hill var. paraguariensis (cultivated maté, almost completely glabrous) and paraguariensis var. vestita (Reisseck) Loes. (not acceptable for industrialization, of dense pubescence). Both varieties coexist in limited areas of Brazil.

The wild species closest to I. paraguariensis belong to the subgenus euilex Loes., subsection repandae Loes. Only I. cognata Reisseck lives in the distribution area of maté. I. cognata is very little known; its vernacular name is chá do mato and it is used to adulterate maté.

A number of wild species of Ilex are sympatric with genuine maté and have been, or are, used to manufacture the product although, up to the present and according to the legislation in force, they are to be considered adulterations. Of those most frequently referred to, the following deserve mention: Ilex affinis Gardner (the ca' a chirí or congonha of Goyaz, a species abundant in central Brazil and northeastern Paraguay); I. dumosa Reisseck var. guaranina Loes. (yerba señorita , aperea ka'a, cauna, caá chiri), native to Paraguay, Argentina and Brazil, the producer of a bitter-tasting maté and supposedly cultivated in Misiones by the Jesuits to produce their famous "caá mini" maté; I. theezans, C. Martius ex Reisseck (cauna de folhas largas, ca'a na, congonha), a good substitute for I. paruguariensis, found in Paraguay, Argentina and Brazil.I. brevicuspis Reisseck, known as cauna or voadeira, like the previous species, is a faithful companion of I. paraguariensis in plant communities characteristic of the region -where Araucaria is also prominent - but the product obtained from its experimental industrialization is of low quality.

Outside the natural area of distribution and production of maté, in northwestern Argentina and southeastern Bolivia, Ilex argentina Lillo, a related species that is known not to accumulate caffeine but theobromine has been used to prepare maté. It is a tree characteristic of the area of transition between the forests of Myrtaceae and alder (Alnus spp.) of the phytogeographical province of the yungas.

Known cultivars of I. paraguariensis. The infraspecific classification of I. paraguariensis is still under study. Consequently, the correspondence between the biological varieties and the horticultural varieties of genuine maté is not clear. Following is a list of some of the varieties recognized as such by growers in the three countries: Erva de talo roxo, Erva de talo branco, Erva piriquita (Brazil); Caá verá, Caá manduví, Caá panambi, Caá cuatí, Caá ñu, Caá eté, Caá mi, Caá chacra, Caá-je-he-ni (Paraguay); Yerba colorada, Yerba señorita, Caá mini (Argentina).

INTA in Argentina recently began to distribute seeds of clones and selected clonal progeny which, following comparative trials, demonstrated their superiority.

In wild South American Ilex species and in the maté-growing region, the risks of genetic erosion are high because the natural forest is gradually giving way to agroforestry and livestock production, a process accentuated by the relatively low germinating capacity of many species (especially that of maté). As no suitable method has yet been discovered for maintaining the germinating capacity of I. paraguariensis for prolonged periods, there are no seed banks of the species. Nevertheless, at the Cerro Azul de Misiones experimental agricultural station in Argentina, a maté clonal garden began to be developed in 1976, complemented by the nursery started in 1986 with I. paraguariensis of various origins and with other species of Ilex.

Cultivation practices

In the wide and varied economic production area of maté, the practices for the cultivation or exploitation of natural maté vary considerably in their technical aspects, resulting in different yields per hectare.

Three methods of production can be distinguished which are arranged here in increasing order of importance reflecting the use of techniques and their yields:

Extractive exploitation of the natural forest. Here the richness of natural maté plantations is utilized. Harvesting is not mechanized and the pruning system is generally incorrect. This form of production is diffused mainly in Brazil.

Mixed system or system for the enrichment of the natural forest. This consists of increasing the number of natural plantations and reconstituting those that have been lost. In Brazil, where this method is most commonly practiced, it is called densifying the maté plantation. Since, generally speaking, this technique is accompanied by others that increase the yield, such as cultivation care and improved pruning methods, the higher production cost is compensated for.

Cultivated maté plantations. This is undoubtedly the best system, and came into general use in Argentina around 1915. In spite of higher costs, the yield per hectare greatly increases. Complemented by measures such as improvement in the layout of plantations (which have evolved from trees planted in quincunxes, with spaced out plants used by Jesuits, to cultivation following contour lines, with a high density per hectare and use of the corte mesa pruning and plant management system), with well-timed pruning, cultivation work and harvesting, this system enabled Argentinian production to exceed that of Brazil, in spite of the former being carried out in a very reduced area and even outside the environments most suited for maté. For example, rising from a density of 1 000 to 1 500 plants per hectare (still fairly widespread) to a density of 2 500 or 4 000 plants per hectare, production can increase from around 1 000 to 1 800 kg to 2 100 to 3 300 kg per hectare.

The corte mesa system not only increases the yield but is also better suited to mechanical harvesting.

Yields are improved by: planting following contours; the use of natural or introduced cover (rape, legumes, etc.); fertilization (NPK); weed control (mechanical and/or using herbicides); suitable phytosanitary treatments; and rational harvesting. The relevant experiments have been going on for some years but, regrettably, their results have not become generalized. The introduction into cultivation of improved cultivars is much less widespread.

Conventional propagation techniques. Sexual propagation ("seeds" = pyrenes). This is the most common reproduction technique. In the case of maté, the advantage of sexual propagation lies in the fact that the variability in descendants may give rise to individuals better suited to different environments (which on other occasions may not be desired).

The seeds are harvested in the region (from February to April). They must be stratified or sown immediately, otherwise they quickly lose their viability.

Stored at 5°C, they maintain a very reduced germinating capacity (1.7 to 6.6 percent) for a further 11 months. The relatively short period of viability together with the low germination rate (immature embryos, phytosanitary problems) have undoubtedly been the cause of the difficulties in its cultivation spreading to other continents in the past.

Agamic reproduction. Grafting, propagation by cuttings and layering are not very widespread. It is relatively difficult to obtain rooted cuttings and this is generally achieved by using young branches from the stools, irrespective of whether plant hormone treatment is used. Additional experiments are necessary if the intention is to increase the rooting percentage.

In vitro cultivation of I. paraguariensis is being tried out in Brazil and Argentina by various research groups, with varying results which still do not clearly indicate which are the economically viable techniques for the clonal reproduction of selected individuals.

According to the Under-Secretariat for Agriculture and Livestock, in Argentina in 1988, the average yield of semi-processed maté was 1 220 kg per hectare.

Prospects for improvement

The limitations of cultivation are due to the fact that there is no demand for the product on a macroeconomic scale. The recurrent cycles of surplus supply, low prices, disinvestment in plantations, scarcity of raw materials, high prices -very often linked with international trading terms between producer countries, which result in a greater distortion - have historically acted against a stable supply of the product in terms of quality and quantity. Even worse, they have discouraged the continuation of basic and/or applied research, which cultivation and processing require. The partial or total absence of knowledge concerning maté biology, plant chemistry, dietetics, agronomics and industrialization have made it difficult to adopt international standards which would lay down norms for the quality of the product and improve and guarantee it over time, depending on its distribution to the major international markets for the production of methyl xanthine infusions.

Potential areas for the introduction of this crop are subtropical regions with acid soils and a water supply similar to those of the species' natural area of dispersal.

It has recently been suggested that verticillata, a North American species, could be a source of biodegradable detergents because of its high saponin content. Since research regarding similar subjects is being continued on I. paraguariensis and, furthermore, since other related species are studied even less than maté from the chemical point of view, it would be advantageous to go into these aspects more deeply.

Ilex argentina is also a possible caffeine-free maté and is, moreover, remarkable for its richness in liver-protecting phenolics similar to those in artichokes (Cynara scolymus).

There are also reports of a range of non-traditional uses for I. paraguariensis, for instance as a source of edible oils, furfural and cosmetics.

Finally, the importance of the wild flex species in genetic improvement of the crop should be mentioned.

Lines of research

· Botanical. Infraspecific variability of I. paraguariensis and how it is related to other species of the genus; an updated chorology; crossing systems of I. paraguariensis and other species of Ilex; inheritance of sex.
· Physiology of the seed and micropropagation methods.
· Plant chemistry: Cycle of the xanthines in the species and its relatives; toxic and undesirable compounds of allied species; analytical determination of the infusion's flavour components.
· Updating, from the food point of view and with relation to allied species.
· Architecture of the individual of I. paraguariensis and of allied species; phenology and adaptation of these trees to mechanical harvesting.
· Industrialization: Improvements in the drying and accelerated seasoning systems without organoleptic losses; alternative industries with cultivation by-products.
· New ways of consuming and presenting the product

Bibliography

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