Gossypium arboreum (PROTA)

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Plant Resources of Tropical Africa
Introduction
List of species


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Gossypium arboreum L.


Protologue: Sp. pl. 2: 693 (1753).
Family: Malvaceae
Chromosome number: 2n = 26

Vernacular names

  • Cotton, tree cotton (En).
  • Coton, cotonnier, coton arborescent, cotonnier rouge (Fr).
  • Algodoeiro, algodoeiro arbóreo (Po).
  • Pamba (Sw).

Origin and geographic distribution

Gossypium arboreum is only known in cultivation and its origin is uncertain. It may have developed from Gossypium herbaceum L., though molecular comparisons support the hypothesis that Gossypium arboreum and Gossypium herbaceum diverged from a common ancestor. Gossypium arboreum has been cultivated in Asia for many centuries. It is still found there, but has mostly been replaced by Gossypium hirsutum L. From Asia Gossypium arboreum was brought to Sudan, and from there it spread to West Africa. Nowadays it is cultivated mainly in the drier parts of India and Pakistan, and sometimes in tropical Africa, where it has occasionally naturalized. In tropical Africa it is common in yards and abandoned dwelling sites.

In this article the word ‘cotton’ refers to information referring to all 4 cultivated Gossypium species (Gossypium arboreum, Gossypium barbadense L., Gossypium herbaceum and Gossypium hirsutum); where information refers to Gossypium arboreum only, this is stated explicitly.

Uses

Cotton is the most important group of fibre plants in the world. The oldest evidence of the use of cotton as a fibre plant in the Old World was found in Pakistan and probably refers to Gossypium arboreum; it is estimated to date from about 2300 BC. The main fibres of cotton plants are the longer seed hairs (‘lint’), used for making yarn to be woven into textile fabrics, alone or in combination with other plant, animal or synthetic fibres. Cotton lint is also made into other products including sewing thread, cordage and fishing nets. Cotton textile cuttings and rags serve in the paper industry for the production of the best writing, book and drawing paper. Short fibres (‘fuzz’ or ‘linters’) are processed into a range of products, including papers, twine, automobile upholstery, explosives, plastics and photographic film. Linter pulp is made into various types of paper, depending on its grade. Linters have also been used for the production of cellulose acetate and viscose. Cotton stalks are processed into paper and paperboard, for instance in China, and into cement-bonded particle board.

Oil obtained from cotton seed is industrially used in a range of products, including margarine, mayonnaise, salad and cooking oils, salad dressing and shortening. It is also made into soap, cosmetics, lubricants, sulphonated oils and protective coatings. Locally it serves for cooking and frying. Blends of cotton-oil biodiesel and diesel fuel can be used in conventional diesel engines without any major changes. The seed cake remaining after oil extraction is an important protein concentrate for livestock. Low-grade cake is used as manure. The whole seed can be fed to ruminants, which are less sensitive to the toxic gossypol in the seed than non-ruminants, or is applied as manure. Hulls are a low-grade roughage for livestock or serve as bedding or fuel. Leftover bolls, leaves and thin twigs are grazed by ruminants. Dry stalks serve as household fuel.

Gossypium arboreum is much less important in tropical Africa than Gossypium hirsutum and Gossypium barbadense, and seems to be used for medicinal purposes and as a fetish plant more than as a fibre plant. For instance in Niger, where Gossypium arboreum is now only occasionally found in gardens, farmers remarked that in the past it was grown for fibre production, while nowadays it is only used for medicinal purposes. In West Africa the fibre of Gossypium arboreum has been made into fine cloth worn by chiefs and used for wound dressing. In Cameroon the fibre is made into cloth used for dowries and in burials. In Madagascar it is also woven into cloth. In Nigeria the seeds are made into fermented cakes, and the seed oil is used for cooking. In Kordofan (Sudan) the leaves are browsed by cattle. The flowers yield a yellow dye. Crushed with lime juice they give a red dye used for colouring cotton thread and goat leather. In Benin the flowers are used for making a black dye for leather, and the plant is sometimes grown specifically for this purpose.

Gossypium arboreum is widely used in African traditional medicine. The root is considered an emmenagogue and to cause uterine contractions, and in Ghana and Nigeria an extract of the root or root bark is taken as an abortifacient. In Côte d’Ivoire, on the other hand, a root decoction with salt obtained from ash of the rachis of oil palm is recorded to be drunk to prevent abortion. In Ethiopia an infusion of the powdered root bark is drunk for the treatment of lymphatic swellings. In Madagascar a root decoction is taken against haemorrhage. A preparation of young leaves with lemon juice is drunk in Côte d’Ivoire against constipation, but in Ghana a cold infusion of the leaf with lime juice is used for the treatment of dysentery. In Ghana the macerated leaf is taken against vomiting, while the fresh leaf is used for the treatment of ulcers, either as a covering (after heating) or as a powder dressing after heating with the fruit of Piper guineense Schumach. & Thonn. In Ghana the leaf and crushed seed are applied to sores and made into poultices for the treatment of bruises and swellings. In Cameroon a leaf decoction is drunk for the treatment of typhoid fever. In Nigeria the flower is used for relieving dysentery. In Ghana a paste of ground seeds is applied against headache. In Mauritius the bark and seeds have been used against tumours.

Production and international trade

According to FAO estimates the annual world cotton production in 2004–2008 was about 70 million t seed cotton (unginned cotton, containing seed, lint and fuzz), from 34 million ha. However, the largest part (more than 90%) of the world cotton production comes from Gossypium hirsutum, which is highly productive and shows strong yield responses to improved growing conditions, fertilizers, crop protection and supplementary irrigation. Most of the remainder comes from Gossypium barbadense. Gossypium arboreum is grown to some extent in Africa and Asia. In India, for instance, about 10–15% of the cotton area is under Gossypium arboreum. In tropical Africa Gossypium arboreum is grown for domestic use only.

Properties

Cotton fibres are unicellular extensions of epidermis cells of the seed. Two types of fibres are distinguished: long fibres (‘lint’) and short fibres (‘fuzz’ or ‘linters’). Cotton lint fibres are 10–40(–64) mm long, with a diameter of (12–)18–28(–42) μm and a length:width ratio of 1000–4000. The lint fibres of Gossypium arboreum are shorter (normally less than 25 mm long) and coarser than those of Gossypium hirsutum and Gossypium barbadense, and with thicker cell walls. Fuzz fibres are similar in appearance to lint fibres, but shorter (2–7 mm long), more cylindrical and with thicker walls.

Apart from fibre length and its uniformity, the most important properties of cotton are fineness (diameter), maturity, strength and elasticity. The combined fineness and maturity (the degree to which the secondary cell wall has developed) of cotton fibre is usually determined by resistance to air flow, and expressed in a value called ‘micronaire’, reflecting the linear density of fibres. Typical values of the tensile strength, elongation at break, and Young’s modulus of cotton fibre are 285–595 N/mm², 7.0–8.0% and 5500–12,600 N/mm², respectively. Among the world’s major textile fibres, cotton has a unique combination of properties, being strong, comfortable, washable, durable and printable. It also blends well with other fibres to give it additional strength, lustre and crease resistance. On a dry weight basis, cotton fibre contains 88–96% α-cellulose, 3–6% hemicelluloses and 1–2% lignin.

Cotton seeds remaining after ginning consist of linters (5–10%), oil (15–33%), oilcake (33–45%) and hulls (24–34%). Cottonseed oil is a semi-drying oil obtained by mechanical and/or solvent oil extraction from the seed. The principal fatty acids in cottonseed oil are linoleic acid (42–59%), palmitic acid (20–34%) and oleic acid (13–25%). Gossypium arboreum seed oil with oleic acid levels as high as 32% has been reported. Cotton seed oil also contains 0.5–1(–2)% cyclopropenoid fatty acids, which are known to cause physiological disorders in animals. The oil as well as other plant parts of Gossypium species contain gossypol, a triterpenoid aldehyde, which is toxic to humans and animals, monogastric animals in particular. Gossypol has insecticidal, antimicrobial, antifertility and antitumour properties. Gossypol and related compounds have been implicated in conferring insect tolerance or resistance and antimicrobial properties to cotton plants. Glandless, gossypol-free cultivars exist, but they are more vulnerable to pests. Gossypol can be removed from the oil by solvent extraction, following mechanical and/or solvent oil extraction from the seed. The cake and meal contain over 40% crude protein, but are not without danger for monogastric animals, because of the gossypol they contain. The gossypol in the cake can be removed or made harmless by chemical (ferrous salts) or physical (heating) means, but this is more difficult to achieve economically than removing gossypol from the oil.

Methanol and dichloromethane leaf extracts of Gossypium arboreum showed activity against the Gram-positive bacteria Bacillus subtilis and Staphylococcus aureus, the Gram-negative bacteria Escherichia coli and Pseudomonas aeruginosa and the yeast Candida albicans. In another study an aqueous extract of the leaves and seeds showed only weak antibacterial activity against Bacillus subtilis, Escherichia coli, Micrococcus flavus, Pseudomonas aeruginosa and Staphylococcus aureus, but the extract stimulated growth of human dermal fibroblast cells and had an antioxidant protective effect on these cells, which gives some support to the traditional use of Gossypium arboreum leaves and seeds for wound healing. A methanol extract of the root of Gossypium arboreum showed antibacterial activity against Bacillus polymixa and Escherichia coli. Petals and flavonoids isolated from the petals showed antibacterial activity against Pseudomonas maltophilia and Enterobacter cloacae.

Description

Shrub or small tree up to 3 m tall, extremely variable, most parts densely covered with minute stellate hairs and patent simple hairs, nearly all parts irregularly dotted with black oil glands; twigs slender, terete. Leaves spirally arranged; stipules linear to lanceolate, often falcate, 4–15 mm long, caducous; petiole 1–14 cm long; blade ovate to orbicular in outline, 2–12 cm in diameter, palmately lobed or parted with 3–7 segments, frequently with an extra tooth in the sinuses, base cordate, lobes ovate to narrowly lanceolate, apex acute or acuminate, sometimes obtuse, margin entire, pedately 5–9-veined, nectaries usually inconspicious or absent. Flowers solitary, usually on sympodial branches; pedicel 0.5–6 cm long not articulated, usually without apical nectaries; epicalyx segments (bracteoles) 3, closely embracing the corolla and fruit, rarely spreading, united for 1 cm or more, 1.5–3.5 cm × 1.5–3 cm, slightly accrescent in fruit, base deeply cordate, apex acute, margin entire or remotely toothed, glabrous inside, hairy outside, persistent; calyx cupular, 5–12 mm long, truncate to inconspicuously 5-dentate, glabrous; corolla at opening usually cream to yellow and after 1–2 days turning red or purple, with or without a purplish centre, petals 5, imbricate, obovate, 2.5–4.5 cm long; stamens numerous, forming a column 1.5–2 cm long, filaments 1.5–4 mm long, anthers 1-celled; pistil with 3–5-celled ovary and one short style with clavate, 3–5-sulcate stigma. Fruit (‘boll’) an globose, ovoid or elongate capsule 1.5–2.5 cm in diameter, beak 3–5 mm long, opening loculicidally, after dehiscing and splitting often reflexed, outside densely pitted and glabrous, 3 (–4)-celled with 5–8 seeds per cell. Seeds ovoid to globular, 5–8 mm in diameter, with a copious covering of fairly long, white or rusty, woolly hairs (lint or floss) firmly attached to the seed, and also with a fine, short tomentum (fuzz). Seedling with epigeal germination.

Other botanical information

Gossypium comprises about 50 species distributed in warm temperate to tropical zones. The origin of the genus is unknown, but 3 primary centres of diversity exist: in Australia, in north-eastern Africa to Arabia, and in western-central to southern Mexico. The 4 cultivated cottons of the world (the Old World diploids Gossypium arboreum and Gossypium herbaceum and the New World tetraploids Gossypium barbadense and Gossypium hirsutum) have been domesticated independently in different parts of the world. The taxonomy of Gossypium is complicated, partly due to the domestication of 4 distinct species and extensive interspecific hybridization. The literature is confusing and authors disagree on the identity of many species, subspecies, sections, varieties, forms, races and cultivars that have been distinguished. Currently the taxonomic system of P.A. Fryxell, with about 50 species grouped into 4 subgenera and 8 sections, is the most generally accepted one. It is mainly based on morphological and geographical data, but is confirmed by cytogenetic and molecular evidence. Cytological research has led to the recognition of 8 basic diploid ‘genomic groups’, designated A through G, plus K. In general, species within a genomic group can form fertile interspecific hybrids. Gossypium arboreum and Gossypium herbaceum are included in subgenus Gossypium: diploid Old World species with A-genome, whereas Gossypium barbadense and Gossypium hirsutum belong to subgenus Karpas: tetraploid New World species with AD-genome.

The large variation within Gossypium arboreum has been classified into 6 geographical groups, usually indicated as races:

– bengalense: annual cottons, cultivated in India and Bangladesh in regions that are subject to frost; the lint is coarse and short.

– burmanicum: perennial cottons, cultivated in north-eastern India and South-East Asia, particularly Myanmar; the lint is variable.

– cernuum: annual, long-bolled cottons, grown in northern India (Assam); included by some in race burmanicum.

– indicum: mostly perennial shrubs, although in India some annual cultivars ('Rozi’ cottons) exist; the most primitive cultivated group within Gossypium arboreum, mostly grown in Gujarat (India), along the eastern coast of Africa and in Madagascar; the lint is scanty, coarse and often coloured.

– sinense: annual, early maturing cottons, cultivated commercially in China, Korea and Japan; it provides the original Asian cotton.

– soudanense: the ‘Senaar’ tree cottons, large perennial shrubs or small trees; probably reached north-eastern Africa from India about 2000 years ago, grown in the northern part of tropical Africa; the lint varies from coarse to moderately fine.

Anatomy

Cotton lint fibres are smooth-looking, ribbon-like and twisted, with the fibre walls showing longitudinal and spiral striations. The fibre walls contain many layers of cellulose chains, which run spirally and give dry fibres their characteristic twisting appearance. The hairs are covered with a waxy cuticle, giving unprocessed fibre a greasy feel and making it water-repellent.

Growth and development

The shoot system of cotton is dimorphic, with the main axis and lower branches (emerging from axillary buds) being monopodial and vegetative, whereas the fruiting branches (emerging from extra-axillary buds) are sympodial. Fruiting branches develop as primary branches higher on the main stem and as secondary branches on vegetative branches. Generally only one fruiting branch develops at each node, with 3–5 fruits per branch. The first fruiting branch appears at node 4–5 of the main stem, between 1 and 2 months after sowing, and visible flower buds appear as small, green, pyramidal structures, known as ‘squares’. They need 20–35 days to develop into open flowers. The flowers mostly open near dawn and pollination normally occurs within a few hours. Self-pollination is the predominant mating system, but visiting insects can cause considerable outcrossing (up to 40%). Flowering peaks at 3(–6) weeks after the onset and may continue for about 6 weeks. The fruits grow very quickly after pollination, reaching their final size at about 20–25 days. After a further (20–)25–45(–60) days, depending on genotype and environmental conditions, they are ripe. Usually the dry fruits open at their sutures and the white, fluffy fibre-mass emerges. The seeds remain attached to the placenta and are only separated by picking or by very strong rain or wind.

During the first 2–4 weeks after flowering (the elongation phase) the fibres grow rapidly, reaching their full length, and during the next 4–6 weeks (the secondary thickening phase) the cell walls of the fibres thicken through deposition of cellulose in consecutive layers. The cell wall thickness of a fibre, or the degree to which the fibre has been filled with cellulose, mainly depends on plant vigour during ripening. Upon boll opening the fibre dries and the lumen collapses, resulting in the characteristic twisted, ribbon-like appearance of the fibre that makes it spinnable.

Shedding of squares and young bolls is common in cotton. It is aggravated by adverse conditions such as prolonged overcast weather, extreme temperatures, water stress, waterlogging, nutrient deficiencies, diseases and insect damage. Commonly 60% of the squares and young bolls are shed, but flowers are rarely shed. The ability to overcome adverse events by compensatory growth is characteristic for cotton. However, recovery is only partial and insignificant when severe insect damage occurs late in the season.

Ecology

Gossypium arboreum requires a temperature of (18–)26–36(–38)°C and a rainfall of (500–)750–1250(–1500) mm during the growing season. It can be grown on deep, light to heavy, well-drained soils with a moderate fertility and a pH of (5.3–)6–7.2(–8.5). In East Africa it occurs from sea-level up to 1000 m altitude.

Propagation and planting

Cotton is propagated by seed. The 1000-seed weight of Gossypium arboreum is 46–91 g. It is possible to propagate cotton vegetatively by cuttings, budding or grafting. The development of rapid, reproducible and genotype-independent systems of in-vitro propagation of Gossypium species been difficult, though methods have now been developed to produce large numbers of somatic embryos from callus from hypocotyl or cotyledon explants of Gossypium arboreum, Gossypium barbadense, Gossypium herbaceum and Gossypium hirsutum.

Management

In tropical Africa, for instance in Niger and Cameroon, Gossypium arboreum is usually not grown as a field crop, but as isolated plants near homesteads. Growing Gossypium arboreum and other cotton species as perennials was formerly very common, but it has been discouraged, because perennial cotton can act as a host reservoir for cotton pests and diseases. Locally, for instance in Cameroon, fields with perennial cotton plants can still been seen. Gossypium arboreum plants 15–20 years old have been observed, with stems up to 15 cm in diameter; they are usually pollarded.

Diseases and pests

Diseases are less important in cotton than pests. The most widespread diseases are bacterial blight, leaf spot, blackarm or boll rot caused by Xanthomonas axonopodis pv. malvacearum (synonym: Xanthomonas campestris pv. malvacearum), anthracnose caused by Glomerella gossypii (anamorph: Colletotrichum gossypii), Fusarium wilt caused by Fusarium oxysporum, and Verticillium wilt caused by Verticillium dahliae. Before resistance was found and incorporated in Gossypium hirsutum cultivars, bacterial blight caused seed cotton yield losses up to 28% in African cotton crops, and it is considered partially responsible for the sustained cultivation of Gossypium arboreum and Gossypium herbaceum in Africa and Asia. Bacterial blight is controlled by growing cotton only once every 3 or more years on the same field, removing the harvest remains and seed treatment. Anthracnose can be controlled by the same measures, but resistant cultivars are not available. Gossypium arboreum cultivars with resistance to Fusarium wilt are available. Cropping methods to control wilt diseases include crop rotation, sufficient K-fertilization and the control of nematodes. The most important virus diseases of cotton in tropical Africa are leaf curl, African cotton mosaic and cotton blue disease. Virus diseases are controlled by eliminating reservoir hosts and vectors, and by using tolerant or resistant cultivars.

Cotton suffers from a wide spectrum of pests. Bollworms are among the most serious pests. They feed inside the bolls, damaging lint and seed and so causing considerable reduction in yield and quality. The main bollworms are American bollworm (Helicoverpa armigera), pink bollworm (Pectinophora gossypiella) and spiny bollworm (Earias spp.). Spiny bollworm, to which Gossypium arboreum and Gossypium barbadense seem less susceptible than Gossypium hirsutum, has a serious early effect of tipboring in the main stem leading to excessive formation of vegetative branches and delaying the setting of bolls, which makes them vulnerable to mid-season American bollworm and stainers. Resistance to bollworms has not been achieved to the desired extent, and their control has long relied heavily on insecticides.

Leaf, stem and bud-sucking bugs can cause considerable damage. Jassids (Amrasca, Empoasca, Erythroneura, Jacobiella and Jacobisca spp.) are the first pests to appear, but a dense coating of long hairs on leaves and stems provides good protection. Whitefly (Bemisia tabaci) and cotton aphid (Aphis gossypii) are pests later in the season; the former is the vector of leaf curl and African cotton mosaic, the latter of cotton blue disease. Early sowing, weeding and harvesting and the use of short-season cultivars can reduce their damage. Cotton stainers (Dysdercus spp.) occur in all cotton-growing countries. They pierce the green bolls and inject the fungus Nematospora gossypii, which causes yellow staining of the lint, resulting in lower quality. About 4 alternating sprays of organophosphates and pyrethroids can overcome this pest. Fairly effective preventive control can be obtained by strict phyto-sanitation, early cropping of maize or sorghum followed by early ploughing and close planting of cotton using an early-maturing cultivar. Close relatives of cotton, such as Abutilon species growing nearby are alternative hosts of cotton pests, especially stainers.

Insect pests in cotton have been effectively controlled since 1945 with the use of insecticides. The repeated development of resistance of insect pests (especially the American bollworm) to new insecticides has in some countries led to excessive spraying, up to 15 sprays per season, killing all natural enemies. This may also induce outbreaks of previously minor pests, requiring additional spraying. To reduce the use of pesticides, the application of Integrated Pest Management (IPM) or Integrated Weed and Pest Management (IWPM) is advocated. Very early field preparation including repeated weeding, fertilizer application, early planting of jassid-resistant cultivars, gapping, thinning and judicious use of pesticides on the basis of insect monitoring and damage thresholds, form the basis of interacting IWPM farming practices. Preventive weed control by ploughing or hoeing promptly after clearing the preceding crop stores moisture from unexpected storms in the subsoil which makes it possible to plant early. This encourages early fruiting well ahead of the main pest, American bollworm, and provides ample time for compensatory fruiting in case of early fruit damage. As insecticides against jassids are no longer needed they do not kill the natural enemies which control American bollworm in its vulnerable young stage. By the time the later pink bollworms, stainers and whitefly occur, the main crop will be safe.

The most widely distributed economically important nematode in cotton is the root-knot nematode (Meloidogyne spp.), whereas the reniform nematode (Rotylenchus spp.) is more restricted to tropical and subtropical environments. Gossypium arboreum, Gossypium herbaceum and Gossypium barbadense are less susceptible to the reniform nematode than Gossypium hirsutum. Nematodes can be controlled by rotation and chemicals, whereas cotton genotypes have been developed with some tolerance to the reniform nematode.

Harvesting

In tropical Africa cotton harvesting is generally done by hand. After the cotton has been harvested, the cotton stems should be uprooted and burnt to prevent the build-up of pest and diseases.

Yield

A seed cotton yield of up to 4 t/ha is possible under optimal conditions, but in practice it is seldom over 2.5 t/ha and the average world yield is about 2 t/ha. In most tropical African countries the yield is around 1 t/ha. Seed cotton of primitive cultivars yields 20–25% fibre after ginning, whereas good cultivars of upland cotton have a ‘ginning-outturn’ of at least 35% and sometimes over 40%. Some modern Gossypium arboreum and Gossypium herbaceum cultivars grown in India and China also yield up to 40% lint.

Handling after harvest

Cotton lint is removed from the seeds by ginning, which can be done with a hand gin (capacity of 2–3 kg lint/hour) or mechanically. Mechanical ginning can be done with a saw gin (capacity of 300 kg lint/hour) for the shorter stapled cottons, or with the more gentle roller gin (capacity of 30 kg lint/hour) for the longer stapled fine types. In some African countries, such as Kenya and Uganda, roller ginning is common, even for shorter stapled cotton. In West and Central Africa manual ginning may be done by placing the seed cotton on a block of wood or a flat stone, and squeezing out the seeds by rolling an iron or wooden rod over it. The optimum moisture content of the fibre for ginning is 5–7%. When the moisture content is lower, excessive fibre damage occurs; when it is higher, the amount of broken seeds is higher.

Genetic resources

In India about 1900 Gossypium arboreum accessions are kept at the Central Institute for Cotton Research (CICR) in Nagpur and Coimbatore, and the National Bureau for Plant Genetic Resources (NBPGR) in New Delhi. The National Collection of Gossypium Germplasm housed at the Southern Plains Agricultural Research Center (SPARC), College Station, Texas, United States, has 1700 Gossypium arboreum accessions. In Uzbekistan the Cotton Breeding Institute, the Institute of Genetics and Plant Experimental Biology and the National University of Uzbekistan together hold about 1200 Gossypium arboreum accessions. The Chinese Academy of Agriculture Sciences (CAAS) in Nanjing, China, and the N.I.Vavilov Institute of Plant Industry (VIR) in St Petersburg, Russia, each hold about 400 accessions of Gossypium arboreum, and the genebank of the Centre de Coopération Internationale en Recherche Agronomique pour le Développement (CIRAD) at Montpellier, France, about 70.

Breeding

Until the 1930s cotton breeding was limited to crossing within the diploid and tetraploid groups. After this, polyploidization of the diploids greatly increased breeding opportunities. Crosses between Old World and New World genotypes have become important, especially for resistance breeding and the breeding of better cultivars for regions in Asia where Gossypium arboreum and Gossypium herbaceum grow well, but Gossypium hirsutum does not. F1 hybrid cultivars with considerable hybrid vigour for yield have been successfully developed. However, the available systems of cytoplasmic male sterility have been inadequate for large-scale production of hybrid seed, mainly due to incomplete expression of fertility restorer genes in the male parents. Current use of cotton hybrids is limited to South Asia and China, where seed production by manual emasculation and pollination is economically feasible because of low labour costs.

The main objectives in cotton breeding, apart from higher yields, are photoperiod-insensitivity, early maturity, adaptation to mechanical harvesting (through low growth, little branching, short flowering period, loosely attached seeds, less hairy leaves), fibre quality (length, fineness, strength and elasticity), seed quality (high oil content and low gossypol content, increased suitability of the presscake as a source of protein for humans and animals), resistance to diseases (e.g. bacterial blight and Fusarium wilt) and pests (e.g. bollworms, jassids) and tolerance to drought, cold and salinity. There has been little progress in breeding for pest resistance (except for resistance to jassids), but much success has been obtained in resistance and tolerance to Fusarium and Verticillium wilts, bacterial blight and nematodes.

Prospects

Cotton will remain very important on a worldwide scale, because of its excellent fibre properties and low price, but Gossypium hirsutum and Gossypium barbadense will remain the most important species, and the role of Gossypium arboreum will remain marginal. In tropical Africa Gossypium arboreum will probably remain to be grown for domestic use, mainly for medicinal purposes.

Major references

  • Burkill, H.M., 1997. The useful plants of West Tropical Africa. 2nd Edition. Volume 4, Families M–R. Royal Botanic Gardens, Kew, Richmond, United Kingdom. 969 pp.
  • Fryxell, P.A., 1978. The natural history of the cotton tribe (Malvaceae, tribe Gossypieae). Texas A & M University Press, College Station, Texas, United States. 245 pp.
  • Hutchinson, J., 1962. The history and relationships of the world’s cottons. Endeavour 21: 5–15.
  • Kerkhoven, G.J. & Mutsaers, H.J.W., 2003. Gossypium L. In: Brink, M. & Escobin, R.P. (Editors). Plant Resources of South-East Asia No 17. Fibre plants. Backhuys Publishers, Leiden, Netherlands. pp. 139–150.
  • Kulkarni, V.N., Khadi, B.M., Maralappanavar, M.S., Deshapande, L.A. & Narayanan, S.S., 2009. The worldwide gene pools of Gossypium arboreum L. and G. herbaceum L., and their improvement. In: Paterson, A.H. (Editor). Genetics and genomics of cotton. Springer-Verlag New York, United States. pp. 69–97.
  • Neuwinger, H.D., 2000. African traditional medicine: a dictionary of plant use and applications. Medpharm Scientific, Stuttgart, Germany. 589 pp.
  • Peeters, M.-C., van Langenhove, L., Louwagie, J., Waterkeyn, L. & Mergeai, G., 2001. Cotton. In: Raemaekers, R.H. (Editor). Crop production in tropical Africa. DGIC (Directorate General for International Cooperation), Ministry of Foreign Affairs, External Trade and International Cooperation, Brussels, Belgium. pp. 1041–1070.
  • Seignobos, C. & Schwendiman, J., 1991. Les cotonniers traditionnels du Cameroun. Coton et Fibres Tropicales 46(4): 309–333.
  • Smith, C.W. & Cothren, J.T. (Editors), 1999. Cotton: origin, history, technology, and production. John Wiley & Sons, New York, United States. 850 pp.
  • Verdcourt, B. & Mwachala, G.M., 2009. Malvaceae. In: Beentje, H.J. & Ghazanfar, S.A. (Editors). Flora of Tropical East Africa. Royal Botanic Gardens, Kew, Richmond, United Kingdom. 169 pp.

Other references

  • Adjanohoun, E.J. & Aké Assi, L., 1979. Contribution au recensement des plantes médicinales de Côte d’Ivoire. Centre National de Floristique, Abidjan, Côte d’Ivoire. 358 pp.
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Sources of illustration

  • Hochreutiner, B.P.G., 1955. Malvacées (Malvaceae). Flore de Madagascar et des Comores (plantes vasculaires), familles 129–130. Firmin-Didot et cie., Paris, France. 170 pp.

Author(s)

  • M. Brink, PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

Correct citation of this article

Brink, M., 2011. Gossypium arboreum L. [Internet] Record from PROTA4U. Brink, M. & Achigan-Dako, E.G. (Editors). PROTA (Plant Resources of Tropical Africa / Ressources végétales de l’Afrique tropicale), Wageningen, Netherlands. <http://www.prota4u.org/search.asp>.

Accessed 12 November 2020.