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The Biology of
Gossypium hirsutum L. and Gossypium barbadense L. (cotton)

Version 2 February 2008

This document provides an overview of baseline biological information relevant to risk assessment of genetically modified forms of the species that may be released into the Australian environment.

For information on the Australian Government Office of the Gene Technology Regulator visit


Table of Contents


Section 1 Taxonomy

1.1 Taxonomy and distribution of native Australian cotton species

Section 2 Origin and Cultivation

2.1 Centre of diversity and domestication

2.2.1 Origin in Australia

2.2 Commercial uses

2.3 Cultivation in Australia

2.3.1 Commercial propagation

2.3.2 Scale of cultivation

2.3.3 Cultivation practices

2.4 Crop Improvement

2.4.1 Breeding

2.4.2 Genetic modification

Section 3 Morphology

3.1 Plant morphology

3.2 Reproductive morphology

Section 4 Development

4.1 Reproduction

4.1.1 Asexual reproduction

4.1.2 Sexual reproduction

4.2 Pollination and pollen dispersal

4.2.1 Pollen

4.2.2 Pollination

4.2.3 Out-crossing rates

4.3 Fruit/seed development and seed dispersal

4.3.1 Fruit development

4.3.2 Seed dispersal

4.4 Seed dormancy and germination

4.4.1 Seed dormancy

4.4.2 Germination

4.4.3 Seedling survival

4.5 Vegetative growth

Section 5 Biochemistry

5.1 Toxins

5.1.1 Gossypol

5.1.2 Cyclopropenoid Fatty Acids

5.2 Allergens

5.3 Beneficial phytochemicals

5.3.1 Medicines

5.3.2 Stock feed

Section 6 Abiotic Interactions

6.1 Nutrient requirements

6.2 Temperature requirements and tolerances

6.3 Water use

6.4 Other tolerances

Section 7 Biotic Interactions

7.1 Weeds

7.1.1 Weed Control

7.2 Pests and pathogens

7.2.1 Pests

7.2.2 Pathogens

7.3 Other interactions

Section 8 Weediness

8.1 Weediness status on a global scale

8.2 Weediness status in Australia

8.3 Weediness in agricultural ecosystems

8.4 Weediness in natural ecosystems

8.5 Control measures

Section 9 Potential for Vertical Gene Transfer

9.1 Intraspecific crossing

9.2 Natural interspecific and intergeneric crossing

9.2.1 Crosses between G. barbadense and G. hirsutum

9.2.2 Crosses with native Gossypium spp

9.3 Crossing under experimental conditions

9.3.1 Cross-pollination with G- and K-genome natives

9.3.2 Cross-pollination with C-genome natives

9.3.3 Cross-pollination with other plant taxa


Appendix A Weeds of Cotton


This document describes the biology of Gossypium hirsutum (upland cotton) and Gossypium barbadense (pima cotton), with particular reference to the Australian environment, cultivation and use. Information included relates to the taxonomy and origins of cultivated G. hirsutum and G. barbadense, general descriptions of their morphology, reproductive biology, development, biochemistry, biotic and abiotic interactions. This document also addresses the potential for gene transfer to occur to closely related species. The purpose of this document is to provide baseline information about the parent organism in risk assessments of genetically modified G. hirsutum or G. barbadense that may be released into the Australian environment.

In this document, the word “cotton” is used to refer to information relevant to both G. hirsutum and G. barbadense, where the information only relates to one species it will be stated as G. hirsutum or G. barbadense.

In nature, G. hirsutum and G. barbadense are perennial shrubs. However, in the agricultural system both species are cultivated as annuals, with destruction of plants after harvesting the fruit for seed and fibre. The plants are mainly grown for their fibre, cotton lint, which is used in textiles and clothing. Neither species is native to Australia, but grown as a mostly irrigated crop in northern New South Wales (NSW) and Queensland (QLD).

Section 1 Taxonomy

The genus Gossypium was named by Linneaus in the middle of the 18th century. It is in the Family Malvaceae, Order Malvales and Tribe Gossypieae. (Smith 1995). Gossypium hirsutum L. was named due to its hairiness (hirsute), although it has also been referred to as Gossypium hirsutum ssp. latifolium, Gossypium hirsutum var. punctatum, Gossypium jamaicense, Gossypium mexicanum, Gossypium morrillii, Gossypium punctatum, Gossypium purpurascens, Gossypium religiosum, Gossypium schottii, Gossypium taitense and Gossypium tridens. It is commonly known as upland cotton, American cotton or Mexican cotton.

G. barbadense L. was named after its assumed habitat of Barbados. It has been known by alternative scientific names as Gossypium evertum, Gossypium peruvianum, Gossypium vitifolium and Gossypium brasiliense (USDA 2006). It is commonly known as Creole cotton, Egyptian cotton, extra long-staple or ELS cotton, Indian cotton, Sea Island cotton or pima cotton.

The common name cotton comes from the Arabic ‘quotn’ and generally refers to species that produce spinnable fibres (lint) on their seed coat (Lee 1984). The oldest known words for cotton are ‘karparsa-i’, in the language Sanskrit, and ‘Karapas’ used in early Bible manuscripts (Smith 1995).

The taxonomy of Gossypium is still a subject for debate. Smith (Smith 1995) described the genus Gossypium as containing 43 species consisting of 37 diploid species (2n = 2x = 26) and six tetraploid (2n = 4x = 52) species. This is in contrast to Fryxell (Fryxell 1992) who lists 50 species in total or other authors (Percival et al. 1999; Brubaker et al. 2002) who list 49 species in total but include only five tetraploids. The different number of tetraploids relates to discussion on the status of G. lanceolatum Todaro and the evidence presented that it is actually a locally developed, domesticated form of G. hirsutum and should be classified as G. hirsutum race ‘palmeri’ not a separate species (Brubaker & Wendel 1993). There has also been debate about the status of G. nandewarense and whether it should be classified as separate species (Fryxell 1992; Brown et al. 1997) or as a variety of G sturtianum (Fryxell 1965). The Gossypium genus is commonly grouped into eight diploid genomic groups, designated A–G and K, and one tetraploid genomic group, based on chromosomal similarities (Edwards & Mirza 1979; Endrizzi et al. 1985; Stewart 1995). Each genome represents a group of morphologically similar species that can only rarely form hybrids with species from other genomic groups ().

  1. Taxonomy of Gossypium Speciesa


Genomic Group

DistributionDiploid speciesG. herbaceum L.A1Old World cultigen, Africa, Asia MinorG. arboretum L. (syn. G. aboreum L.)A2Old World cultigen, Asia Minor, SE Asia, China, AfricaG. anomalum Wawr. and Peyr.B1AfricaG. triphyllum (Harv. And Sand.) HochrB2Africa G. captis-viridis MauerB3Cape Verde IslandsG. trifurcatum Vollesen bB?SomaliaG. sturtianum J.H. WillisC1AustraliaG. robinsonii F. Muell.C2WA, AustraliaG. nandewarense Derera cCAustraliaG. thurberi Tod.D1Mexico, ArizonaG. armourianum Kearn.D2-1MexicoG. harknessii Brandg.D2-2MexicoG. davidsonii Kell.D3-dMexicoG. klotzschianum Anderss.D3-kGalapagos IslandsG. aridum (Rose & Standl.) SkovD4MexicoG. raimondii UlbrD5PeruG. gossypioides (Ulbr.) Standl.D6MexicoG. lobatum GentryD7MexicoG. laxum PhillipsD8MexicoG. trilobum (DC.) Skov.D9MexicoG. turneri Fryx.D10MexicoG. schwendimanii Fryxell & S. KochD11MexicoG. stocksii Mast.ex. Hook.E1ArabiaG. somalense (Gϋrke) Hutch.E2ArabiaG. areysianum (Defl.) Hutch.E3ArabiaG. incanum (Schwartz) Hille.E4ArabiaG. benadirense MatteiESomalia, Kenya, EthiopiaG. bricchettii (Ulbrich) VollesenESomaliaG. vollesenii FryxellESomaliaG. longicalyx Hutch. and LeeF1AfricaG. bickii ProkhG1Central AustraliaG. nelsonii Fryx.GAustraliaG. australe F. Muell.GAustraliaG. anapoides Stewart, Wendel and CravenKAustraliaG. costulatum Tod.KAustraliaG. cunninghamii Tod.KNorthern NT, AustraliaG. enthyle Fryxell, Craven & J.M. StewartKWA, AustraliaG. exgiuum Fryxell, Craven & J.M. StewartKWA, AustraliaG. londonderriense Fryxell, Craven & J.M. StewartKAustraliaG. marchantii Fryxell, Craven & J.M. StewartKAustraliaG. nobile Fryxell, Craven & J.M. StewartKWA, AustraliaG. pilosum Fryx.KWA, AustraliaG. populifolium (Benth.)Tod.KWA, AustraliaG. pulchellum (C.A. Gardn.) Fryx.KWA, AustraliaG. rotundifolium Fryxell, Craven & J.M. StewartKWA, AustraliaAllotetraploid speciesG. hirsutum L.(AD)1Cultivars, Central AmericaG. barbadense L.(AD)2Cultivars, South AmericaG. tomentosum Nutt. ex Seem.(AD)3Hawaiian IslandsG. mustelinum Miers ex Watt(AD)4BrazilG. darwinii Watt(AD)5Galapagos Islands? G. lanceolatum Tod d(AD)Mexicoa Modified from (Endrizzi et al. 1985; Stewart 1995; Seelanan et al. 1999; Percival et al. 1999)

b Retained in Gossypium genus as (Rapp et al. 2005).

c May be classified as a subspecies of G. sturtianum (Fryxell 1965).

d May be classified as a subspecies of G. hirsutum (Brubaker & Wendel 1993).

G. hirsutum and G. barbadense, the two species cultivated in Australia, are in the AD allotetraploid genomic group, subgenus Karpas Rafinesque (Seelanan et al. 1999). Like the other AD genome species, G. hirsutum and G. barbadense contain one genome similar to those of the A-genome diploids, and one similar to those of the D genome diploids (Endrizzi et al. 1985; Wendel et al. 1989; Wendel 1989). The identity of the progenitor diploid species, and when these progenitors may have come into physical contact sufficient to enable hybridisation is unknown as, at present, A and D diploid species exist in different hemispheres (Endrizzi et al. 1985).

1.1 Taxonomy and distribution of native Australian cotton species

The Australian flora contains 17 native Gossypium species that are all members of a distinct group found exclusively in Australia — Gossypium subgenus Sturtia. They are distant relatives of the cultivated cottons that originated in the Americas (Fryxell 1979b; Fryxell 1992; Seelanan et al. 1999; Brubaker et al. 1999a; Brubaker et al. 1999b). The Australian Gossypium species are all diploid (2n = 26) and fall within the three taxonomic sections of the subgenus Sturtia, C, G or K: Section Sturtia (C genome) contains two species including Sturt’s desert rose, (G. sturtianum, the floral emblem of the Northern Territory (NT)); Section Hibiscoidea (G genome) contains three species and Section Grandicalyx (K genome) contains 12 species (Wendel & Cronn 2003).

The centre of Gossypium diversity in Australia is in northern Western Australia (WA) and NT. Including G. robinsonii, which is indigenous to the Port Hedland area of WA, and G. rotundifolium, which occurs in the Broome region, 13 of Australia’s 17 Gossypium species occur in this northern region. Of the remaining four species, G. sturtianum is the most widely distributed. It is a shrubby species, occurring as small isolated populations, widely scattered across the sub-tropical to warm temperate arid zones of Australia, in QLD, NSW, South Australia (SA) and WA (Seelanan et al. 1999). Like G. sturtianum, G. australe has a broad east coast – west coast distribution, but its indigenous range is north of that of G. sturtianum, extending from southern areas of the NT to Katherine, in the north of the NT. Finally, G. bickii occurs largely within central NT, while G. nelsonii is distributed in a band from central NT to central QLD.

Section 2 Origin and Cultivation

2.1 Centre of diversity and domestication

The word ‘cotton’ is used in this document to refer to G. hirsutum and G. barbadense, however, generally ‘cotton’ refers to four species in the genus Gossypium (Malvaceae) - G. hirsutum L., G. barbadense L., G. arboreum L. and G. herbaceum L. - that were domesticated independently as source of textile fibre (Brubaker et al. 1999a). Today, G. hirsutum and G. barbadense are the major cultivated cotton species, with G. hirsutum accounting for 90% of world production (Jenkins 2003). G. barbadense represents approximately 5% of world fibre production (Wu et al. 2005) and is cultivated primarily in Egypt, Peru, Sudan, USA and parts of the former Soviet Union. G. arboreum is grown mainly in India and G. herbaceum is grown in the drier regions of Africa and Asia (Jenkins 2003). Only G. hirsutum and G. barbadense are grown commercially in Australia with G. hirsutum comprising 99% of plantings in 2006/2007 (Information supplied by Monsanto).

The place of origin of the Gossypium genus is not known, however the primary centres of diversity for the genus are west-central and southern Mexico (18 species), north-east Africa and Arabia (14 species) and Australia (17 species). The genus Gossypium is thought to have separated from Kokia and Gossypioides, the most closely related genera in the Gossypieae, approximately 12.5 million years ago in the Miocene period (Wendel & Albert 1992; Seelanan et al. 1997) or slightly more recently in the Pliocene (Cronn et al. 2002). There is still debate regarding when the allelotetraploids originated (reviewed inWendel & Cronn 2003). Some authors have suggested an ancient origin (60–100 million years ago - Cretaceous or early Tertiary period), so that hybridisation of the A and D genomes took place prior to separation of the South American and African continents. Alternatively, human transfer of African or Asian A genome plants may have occurred followed by accidental or deliberate hybridisation with a D genome species. This would have occurred much more recently, approximately 6000 years ago. However, neither of these theories is supported by molecular evidence such as DNA sequence data which estimates and supports a mid-Pleistocene origin (1 2 million years ago) (Wendel 1989). This period was characterised by fluctuating sea levels due to glaciation, and the coastal distribution of the allelotetraploids may have enabled them to exploit the disturbed littoral areas (Fryxell 1979b).

Archaeological records indicate that Gossypium fibre has been used since 6000 BC. A Gossypium thread, used to string copper beads, from Mehrgarh in Pakistan has been dated at 6th millennium BC (Moulherat et al. 2002). It is unknown whether this is from a domesticated cotton species, but it suggests that cotton fibre was known and used at this time. Cotton was probably used as wadding, packing or for dressing wounds prior to being used for spinning into yarn (Smith 1995). Gossypium remains in the form of cloth, string, assorted bits of fibre and boll fragments were found in different layers of deposits in caves in Techuacan Valley in Mexico (Smith, Jr. & MacNeish 1964). These have been identified as being from tetraploid Gossypium, with the earliest bolls dating from approximately 5800 BC. Archaeological remains of scraps of fabrics and cords, unprocessed fibres formed into plugs and cotton boll segments from a site in Peru are thought to be the earliest forms of domesticated G. barbadense. The finds show a continuum of increasing seed size and fibre diameter from the earlier (2500 BC) to later (1000 BC) levels (Stephens & Moseley 1973).

The geographic centre of origin for G. hirsutum is North and Central America and Mexico, and for G. barbadense is South America (Jenkins 2003). G. hirsutum was probably first domesticated by pre-Columbian people of the Yucatan peninsula (Brubaker & Wendel 1994). These early semi-domesticated forms dispersed into the rest of Mesoamerica as well as northern South America and into the Caribbean (Iqbal et al. 2001). Selection then occurred for reduced seed dormancy, annualised growth habit and photoperiod independent flowering creating genotypes more similar to modern cultivars. Interestingly, modern North American G. hirsutum has a very limited genetic diversity, thought to be due to a genetic bottleneck resulting from the selection pressure of domestication (Iqbal et al. 2001). This is hypothesised to partly result from the Kekchi Indians of Guatemala intercropping cotton with capsicums and harvesting the cotton as soon as the first bolls developed to prevent competition with the capsicums, thus rigorously selecting for early maturity along with reduced seed dormancy and annual growth.

The maritime subsistence for the Andean civilisations, depending in part on cotton fishing nets, has led to the perception that the domestication of G. barbadense took place along the coastline (Westengen et al. 2005). Cotton seed, fibres, fabric and fishing nets have been found at Huaca Prieta on the north coast of Peru, dating from 1500–2400 BC. From this centre G. barbadense dispersed into South America, West Indies and the Galapagoes. This may have been carried by humans or naturally by ocean currents (Smith 1995).

Cotton remains from archaeological excavation sites from northern and central coastal Peru show a continuum to a strongly reduced fuzz layer (tufted seed) with a kidney shaped seed which was more easily ginned by hand, with no hard seeds and no delayed germination. Later domestication introduced higher percentage lint, longer and stronger lint and different colour fibres (Westengen et al. 2005).

It is believed that G. hirsutum was cultivated by the Pueblo Indians in the south west USA as early as the first century AD (Fryxell 1979a). Most wild cottons have a short day photoperiod response for flowering so during domestication cotton has been selected to be insensitive to photoperiod (Lee 1984). Annuals are unknown amongst the wild species of Gossypium (Fryxell 1979a). Annual growth habit and the concomitant day-neutral flowering response is a major evolutionary step which occurred due to human selection and enabled growth of these plants outside of the tropics. Wild species of cotton have a fairly high percentage of ‘hard’ or dormant seed which can persist in a seed bank prior to germination (Jenkins 2003). This trait has been bred out of modern cotton cultivars as it is advantageous for all the seed planted to germinate immediately after sowing. Similarly, modern annual cultivars have seed aggregated in compact locks which remain in bolls to aid harvesting whereas the wild species have seeds that drop individually and scatter freely (Stephens 1965; Stephens 1970). Data suggests that a doubling of seed size has led to a 3-fold increase in lint index (g lint/100 seed) and an 80% increase in mean fibre length during domestication (Stephens 1965). This increased fibre length has been achieved by a prolonging of the fibre elongation period and greater growth rate early in fibre development in modern cultivars compared to wild G. hirsutum (Applequist et al. 2001).

Today, indigenous G. hirsutum is widely distributed in Central and South America, the Caribbean and some Pacific Islands. G. barbadense has a more southerly indigenous range centred on the northern third of South America but with a large region of overlap with G. hirsutum in the Caribbean (Wendel and Cronn 2003). However, both species are cultivated commercially in many countries.

2.2.1 Origin in Australia

Cotton was introduced to Australia as a source of textile fibre. Although sporadic attempts were made to produce cotton in the years following European settlement in 1788, commercial cotton cultivation began in QLD and NSW in the 1860s when the American Civil War caused shortages in world cotton supplies (Constable et al. 2001). Subsequently, cultivation was attempted in the NT (1882) and the Kimberley’s, Western Australia (1947), although in these northern regions, the prevalence and impact of insect pests limited the commercial viability of continued plantings (Wood & Hearn 1985). It was not until the 1960s that the modern intensive Australian cotton industry was established, primarily in northern NSW and southern QLD (Hearn & Fitt 1992).

G. hirsutum also may have arrived in northern Australia naturally, via ocean currents from Central America (Fryxell 1966; Fryxell 1979b). When this may have occurred is unknown, and it has not been substantiated. The primary evidence for this supposition is the presence along coastal river and beach strands in northern Australia of ‘naturalised’ populations of agronomically primitive cotton with morphological features that suggest they are not derived directly from modern, elite G. hirsutum cultivars. They may be descendants of long-distance transoceanic immigrants as proposed by Fryxell, or alternatively, feral derivatives of primitive varieties introduced for cultivation before 1900.

2.2 Commercial uses

Cotton is currently the leading plant fibre crop worldwide and is grown commercially in the temperate and tropical regions of more than 50 countries (Smith 1999). It is estimated that cotton is cultivated on approximately 2.4% of the World’s arable land (Blaise 2006). Specific areas of production include countries such as USA, India, China, America, the Middle East and Australia, where climatic conditions suit the natural growth requirements of cotton, including periods of hot and dry weather and where adequate moisture is available, often obtained through irrigation.

Average world cotton production was at 24.88 Mt (mega tons) in 2005–06 and is forecast to rise to 28.04 Mt by 2011–12 (Wood et al. 2007). Ninety-five percent of Australian cotton production is exported ( Australia exported 650 kt (kilo tons) of raw cotton in 2005–06 worth $1137 million (ABARE 2007). In 2005–06 Australian exports comprise only approximately 7% of the world cotton export market with most cotton being exported from USA (3821 kt), sub-Saharan Africa (1422 kt) and Uzbekistan (1045 kt) (ABARE 2006). The major markets for Australian cotton are (in descending order) China, Indonesia, Thailand, Republic of Korea and Japan (ABARE 2006). No cotton was imported into Australia in 2005–06, although a small amount (0.1–0.4 kt) was imported in the previous five seasons.

G. barbadense is grown for its fibre quality as it has longer staple length (44–46 staple length) and higher fibre strength than G. hirsutum (Smith 1999). G. barbadense fibre had a price premium in the USA of approximately 80% more than G. hirsutum fibre in 2004 (ICAC 2004). The world production for extra fine cotton was estimated to be 774,000 t (metric tons) for 2004. This included 224,000 t of G. hirsutum cotton grown in Egypt which has fibre long enough to be classified as extra fine cotton. The main producers of G. barbadense cotton in 2004 were estimated to be the USA (157,000 t), China (98,000 t), India (90,000 t) and Egypt (68,000 t). Australia, Israel and Peru were estimated to produce 24,000 t in total in 2004. (ICAC 2004).

Cotton is primarily grown as a fibre crop. It is harvested as ‘seed cotton’ which is then ‘ginned’ to separate the seed and lint. The long ‘lint’ fibres are further processed by spinning to produce yarn that is knitted or woven into fabrics. Cotton fabrics, used in clothing, upholstery, towels and other household products, are made from cotton lint.

The ginned G. hirsutum seed is covered in short, fuzzy fibres, known as ‘linters’. These must be removed before the seed can be used for planting or crushed for oil. The linters are produced as first-cut or second-cut linters. The first-cut linters have a longer fibre length and are used in the production of mattresses, furniture upholstery and mops. The second-cut linters have a much shorter fibre length and are a major source of cellulose for both chemical and food uses. They are used as a cellulose base in products such as high fibre dietary products as well as a viscosity enhancer (thickener) in ice cream, salad dressings and toothpaste. In the chemical industry the second-cut linters are used with other compounds to produce cellulose derivatives such as cellulose acetate, nitrocellulose and a wide range of other compounds (Gregory et al. 1999). G. hirsutum ginned seed comprises 17% crude oil, 45% meal, 10% linters and 28% hulls (Smith 1995). It should be noted that G. barbadense cotton seed does not produce linters and therefore is only processed into oil, meal and hulls.

De-linted cotton seed (ie. seed with no lint or linters) is processed into oil, meal and hulls (Cherry & Leffler 1984). The processing of cotton seed oil involves a series of steps including heating, addition of sodium hydroxide, bleaching with clay, filtering and treating with steam under vacuum (OECD 2004). Cotton seed oil has been in common use since the middle of the nineteenth century and achieved GRAS (Generally Recognised As Safe) status under the United States Federal Food Drug and Cosmetic Act because of its common use prior to 1958 (ANZFA 2002). It is used in a variety of products including edible vegetable oils and margarine, soap, and plastics (Frank 1987).

Cotton seed meal is the product remaining once the oil has been removed by crushing and can contain up to contain 41% protein (Smith 1995). Cotton seed, or meal, flour or hulls derived from it, is used in food products and for animal feed, but this is limited by the presence of natural toxicants in the seeds (gossypol and cyclopropenoid fatty acids; see Section 5). Although cotton seed meal is not used for human consumption in Australia or New Zealand, it has been approved for use in human food in the USA and other countries, when derived from gossypol-free varieties of cotton or after processing to remove the gossypol. The FAO and WHO permit up to 0.6 μg/mg (600 ppm) free gossypol in edible cotton seed products, whereas the FDA has a lower limit of 450 ppm (Lusas & Jividen 1987). Human consumption of cotton seed meal is reported mainly in central American countries and India where it is used as a low cost, high quality protein ingredient (Frank 1987).

Cotton trash can be used as a bulking agent to improve the efficacy of animal manure composting (Brampton 2001). In the USA, cotton trash has been investigated as a fuel. The cotton stalks have a similar specific energy (17.1–18.1 mJ/kg) to wood (Coates 2000) which has led to the proposal that the trash could be used as an industrial fuel for a power plant (Gomes et al. 1997) or combined with pecan shells to produce BBQ briquettes (Coates 2000). There has also been some interest in using cotton waste to ferment to produce ethanol (Jeoh & Agblevor 2001).

Extracts from cotton plants, which would be primarily gossypol, have been used as a medicine. In traditional medicine G. barbadense leaves have been used as a treatment for nausea during pregnancy or for ‘proud flesh’ (swollen tissue around a wound) (Sawyer 1955). G. barbadense extracts are still sold for treatment of hypertension, fungal infection and menstrual stimulant (Tropilab Inc 2007) (See Section 5.4 for more information).

2.3 Cultivation in Australia

2.3.1 Commercial propagation

Cotton is generally propagated by seed. In Australia, seed can be ordered with various seed treatments such as fungicides, systemic insecticides or a plant activator, thought to provide increased plant resistance against diseases (Cotton Seed Distributors 2007).

Seed for planting is generally delinted. This can be achieved using a mechanical, flame or acid delinting process (Gregory et al. 1999). Sulphuric acid delinting is used most commonly and is a commercial process carried out in Australia at plants in WeeWaa and Narromine. Acid delinting heats up the seed and slightly scarifies the seed coat which can help break dormancy and improve germination rates (Gregory et al. 1999).

The isolation distances for production of certified seed of G. hirsutum and G. barbadense in Australia are different. In the USA, only minimal (5 m) separation is required between different varieties unless there is obvious differences in morphology, such as flower colour or leaf shape when 536 m between varieties is required (Jenkins 2003). The OECD recommends separation distances of 800 m for certified commercial seed production of G. barbadense and 600 m for G. hirsutum (OECD 2007) and this standard has been adopted by some seed companies in Australia (Cotton Seed Distributors 2007). QSEED specify 600 m for G. barbadense and 200 m for G. hirsutum (QSEED 2004). This difference is thought to reflect the higher value of G. barbadense cotton lint and the low tolerance to the presence of G. hirsutum genes (Brett Ross 2007 pers. comm.) rather than a greater likelihood of out-crossing by G. barbadense.

Hybrid cotton, consisting of either intraspecific or interspecfic hybrids between G. hirsutum and G. barbadense is widely grown in some countries including India and China. It was estimated in 2006 that 50% of the cotton acreage in these countries is planted to hybrid cotton (Blaise 2006). In India seeds of hybrid cotton are commercially produced by hand emasculation and pollination, or hand pollination of male sterile lines. However in Australia and other countries where labour costs are high, this process is considered economically unfeasible. Research into insect pollination of male sterile lines in Arizona, USA (Moffett et al. 1975) indicated that insect pollination rates were probably not high enough for hybrid cotton production.

2.3.2 Scale of cultivation

The total area planted to cotton varies from season to season with 150 000 ha planted in 2006–07 compared with over 500 000 ha planted in 2000–01 as can be seen in . The size of cotton farms in Australia range from 300–4400 ha, with an average size of 800 ha (Hearn & Fitt 1992). In 2004–05, Australia yielded a world record of 2,038 kg/ha (9.2 cotton bales/ha). This figure was three times the world average (732 kg/ha). The next highest yielding countries were Syria (1,571 kg/ha), Mexico (1,312 kg/ha) and Turkey (1,289 kg/ha) (Cotton Australia 2006b).

In Australia, the bulk of the cotton industry is concentrated in northern NSW and southern QLD. G. hirsutum is grown commercially from Hillston in southern NSW to Emerald in central QLD, as far west as Bourke and Lake Tandou in NSW. G. barbadense is cultivated around Bourke, Tandou and Hillston in NSW.

  1. Seasonal cotton crop in Australia1

1 Compiled from data from Cotton Australia and International Cotton Advisory Committee (ICAC)

The major cotton growing regions in Australia are listed in . Cotton Australia produce an annual report with detailed information about cotton production and the individual valleys where cotton is grown commercially each season (Cotton Australia 2005). A map showing the local government areas in which cotton is grown is available on the OGTR website
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This document provides an overview of baseline biological information relevant to risk assessment of genetically modified forms of the species that may be iconCommercial release of canola genetically modified for herbicide tolerance and a hybrid breeding system (InVigor® X Roundup Ready® canola)

This document provides an overview of baseline biological information relevant to risk assessment of genetically modified forms of the species that may be iconPlease reference your comments to the relevant policy or paragraph of the document

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