History of Cotton

History, origin and diffusion of cotton

History and origin

Cotton is harvested from almost 32.4 million hectares in more than 40 nations of the temperate and tropic regions of the world (Anonymous, 1981). The crop is grown as far as 470 degrees N latitude in the Ukraine and 370 N latitude in the USA. In the Southern hemisphere production extends to about 320 S latitude (Niles and Feaster, 1984). Cotton grows at an optimum temperature of 300C, where 150C is the minimum temperature for cottonseed germination and growth (Munro, 1987).

Various theories have been advanced to explain the selective value of lint in the evolution of the species, but there is no convincing evidence that it is of any use to a cotton plant growing wild in its natural habitat (Munro, 1987). However, the primary centres of diversity for the genus are west central and southern Mexico (18 species), northeast Africa and Arabic (14 species) and Australia (17 species) (Brubaker et al., 1999). Brown et al. (1999) reported that Gossypium hirsutum L. and G. barbadense L. are natives of Mexico where they were domesticated originally.

In the light of increased knowledge of the distribution and relationships of primitive cottons, Santhanam and Hutchinson (1974) reported that the Asiatic species and races probably differentiated before domestication. Fryxell (1968) reported that cottonseeds can survive floating in seawater for at least a year with undiminished viability and can thus be distributed by ocean currents. Pursegloves (1968) agreed that the most likely explanation was that cottonseeds floated across the Atlantic from Africa to South America. The development of Old World cotton as a major raw material took place in Sind. This was found during excavation in Pakistan that was dated at approximately 3000 BC (Gulati and Turner, 1928). In Peru the New World tetraploid cottonseeds dated back to 2500 BC (Hutchinson, 1959). In Southern Mexico, cotton was dated around 3500 BC (Smith, 1968). Linted cotton species have been used for cotton fabrics between 4000 and 3000 BC (Munro, 1987). The oldest archaeological remains of G. hirsutum are from the Tehuacan Valley of Mexico, 4000 to 5000 years ago (Munro, 1987).

It is assumed that G. hirsutum was probably first domesticated by pre-Columbian people of the Yucatan peninsula

(Verhalen et al., 2002). Variation determination for cotton varieties in Tanzania has been done morphologically using phenotypic descriptors. This knowledge has been important mainly for selecting parental material for crossing to improve available varieties

(Lukonge et al., 1999). Morphological properties mainly used were disease resistance, pest resistance, fibre quality, adaptability and yield components (boll size, boll number and branch number). Environment and cultivation practices had an effect on most of these morphological characteristics. Variation observed in farmers’ fields indicated a seed-mixing problem, but since the characters were unknown, it was difficult to identify individual varieties (Hau, 1997). Therefore, the objectives of this study were to characterise and quantify genetic diversity in 30 varieties collected from different areas using agronomical and morphological markers. Information obtained was compared with molecular markers in Chapter 6 to assess the relatedness between these two methods of characterisation.

(Iqbal et al., 2001; Allen and Auld, 2002). Improved cotton varieties are urgently needed to improve the cotton market through cotton yield, high ginning percentages and good cotton quality as these factors affect lint price on the world market. The success of a breeding programme is mainly due to knowledge on the available germplasm especially genetic diversity (Meredith and Bridge, 1984; Pillay and Myers, 1999). The above knowledge is important to a plant breeder.

(Farooq and Azam, 2002; Murtaza et al., 2005). DNA fingerprinting involves the display of sets of fragments from specific DNA samples. It is an effective tool to increase the speed and quality of backcrossing conversion, thus reducing the time taken to produce crop varieties with desirable characteristics

Altaf Khan et al., 2002; Rana and Bhat, 2004. With the use of molecular techniques, it is now possible to hasten the transfer of desirable genes among varieties and to introgress novel genes from related species. Using DNA fingerprinting, polygenic characteristics can be easily tagged and genetic relationships between sexually incompatible crop plants can be established .

Bruce et al., 2001.AFLP analysis has been applied in cotton to identify genes for resistance to fungal wilt diseases. It showed a greater potential compared to conventional breeding since it reduced the selection time and used small numbers of plants for detection of resistance genes.

AUison et al. (1999) estimated the trans fatty acid intake of Americans by using food intake data from the 1989-1991 Continuing Survey of Food Intakes by Individuals (CSPII) and the trans fatty acid contents of foods contained in a database compiled by the USDA. It was found that the mean percentage of energy ingested as trans fatty acids was 2.6% and the mean percentage of total fat ingested as trans fatty acids was 7.4%o (5.3 grams of trans fatty acids per day). Of this value, only 20-25% of the trans fatty acid intake comes from naturally occurring sources (basically animal fats), where as the majority of the intake comes from altered fats.

Ascherio et al. 1999.Since the 1960s, levels of trans fatty acids in margarines have declined as softer margarines have arrived on the market due to health concerns.

Lichtenstein et al. 1999 In the mid 1980s, manufactures replaced partially hydrogenated vegetable oils used in household salad and cooking oils with unhydrogenated vegetable oils (ASCN 1995). The majority of trans fatty acids consumed today come from fiied foods, margarine, snacks and baked products (Table 6). For example, a large cake doughnut has 3 g of trans fatty acids and a large order of French fries has 5 grams of trans fatty acids (Lichtenstein et al. 1999). Trans fatty acids should be Umited to no more than 3 g/day).

(UPOV, 1991; Van Esbroeck et al., 1999; Murtaza et al., 2005). This knowledge is important for germplasm collection and conservation (Pillay and Myers, 1999). Accurate morphological characterisation of varieties is an important process in breeding as variety characteristics like resistance to insect pests and diseases can be determined. For example, hairy leaf or stem varieties are resistant to insects like jassids while smooth leaf varieties reduce the trash content in harvested cotton

(Gregory et al., 1990; Pillay and Myers, 1999).

Cotton is harvested as seedcotton, which is then ginned to separate the seed and lint. The long lint fibres are processed by spinning, to produce yarn that is knitted into fabrics. The short fibres (fuzz), covering the seeds are known as ‘linters’. Delinted cottonseed can be processed to produce oil, meal and hulls. Cottonseed 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 Cosmetics Act because of its common use prior to 1958 (ANZFA, 2002). Cottonseed oil is used in a variety of products including edible vegetable oils and margarine, soap and plastics. Cottonseed cake, meal flour or hulls derived from it is used in food products and for animal feed as carbohydrate roughage, but is limited by the presence of natural toxicants in the seeds (gossypol and cyclopropenoid fatty acids) (Pillay and Myers, 1999).

Brubaker et al. 1999; Cotton belongs to the order Malvales, family Malvaceae and genus Gossypium. Gossypium includes about 45 diploid (2n=2x=26) species and five allotetraploid (2n=4x=52) species (cultivated and wild)

(Meredith et al., 1997). Utilising these morphological characteristics in breeding programmes help cotton growers to obtain high yields and good fibre quality with reduced dependence on pesticides. Meredith et al. (1997) reported a higher photosynthesis rate and improved fibre quality characteristics in varieties with subokra leaves compared to varieties with normal leaves.

Morphological markers can be monitored visually without specialised biochemical or molecular techniques. Although agronomical characterisation provides useful information to users, these characteristics are normally subjected to environmental influences and must be assessed during a fixed vegetative phase of the crop. (Jackson et al., 1998).

Accumulation of tolerance to a number of stresses is the key to wideadaptation and consequently selection in multiple environments is the best way to breed stable genotypes (Romagosa and Fox, 1993). When the effects of environmental differences are large, it may be expected that the interaction of G x E will be large. As a result it is not only average performance that is important in genotype evaluation programmes, but also the magnitude of interactions (Gauch and Zobel, 1997).

Jixiang et al. (1996) and Hussain et al. (1998); observed that ginning outturn and lint index were positively and significantly correlated with each other. Fibre strength was correlated with seedcotton yield. Tang et al. (1996) observed a high positive genetic correlation for boll weight with lint percentages, fibre strength and micronaire. Lint yield showed a genetic correlation with fibre strength and boll weight. Dedaniya and Pethani (1994) and Carvalho et al. (1995) observed that seedcotton yield per plant was positively correlated with number of bolls, plant height, boll weight, lint weight per plant and bundle strength tenacity. Negative correlation was observed among fibre strength and earliness, fibre length and fibre fineness, fibre length and fibre percentage as well as fibre fineness and fibre percentage

Bunyecha and Tamminga, 1995; Ramadhani et al., 1998

Infrastructure shortcomings severely impede the development of the cotton sector. Firstly, because most cotton must be transported by rail, the quality of rail services is vital to sectoral performance. Greater efficiency in rail transport will lower costs to growers. Secondly the road network in the Mwanza region, where most cotton is produced, requires considerable upgrading. As with rail transport, road improvements will increase efficiency and reduce costs, thereby leading to higher producer prices (Baffes, 2002).

Declining input, caused by removal of input price subsidies at farmer level, (mainly insecticides and fertilizers) led to poor quality cotton and low yields. Any quality decline due to reduced input use reflects relative prices and hence market forces .

Following reforms, as cotton prices rose in the late 1990’s, price competition and overcapacity in ginning caused abandonment of zoning, leading to the mixing of infected and uninfected seed and ultimately reduction in cotton fibre quality. The northern and southern area varieties, which were released for specific agroclimatic conditions of the area, were mixed (Government of Tanzania, 1999a; TCL and SB, 2002).

Endrizzi et al., 1985; Pillay and Myers, 1999; Iqbal et al., 2001 The entire worldwide cotton production is from G. barbadense and G. hirsutum though G. hirsutum comprises 90-95% of the world cotton production.

In allotetraploid species, the D-genome has 13 small chromosomes and the A-genome has 13 moderately large chromosomes in the haploid complement of 26. D and A genomes differ in the amounts of moderately repetitive DNA sequences.

(Brubaker et al., 1999).; Mexican G. hirsutum types may have been grown in the Stephens Austin colony in Texas as early as 1821. Numerous introductions were probably made by soldiers returning from the Mexican-American war (1846-1848). These cultivars were subjected to strict selection to create varieties adapted to local conditions in various cotton growing regions of Northern America. Throughout these periods, outcrossing occurred between cultivars (Endrizzi et al., 1985), collectively known as American Upland cotton. The resulting high yielding and adaptable varieties were dispersed to Europe, Asia and Africa. The limited genetic diversity of cultivated upland G. hirsutum has been observed by several researchers (Multani and Lyon 1995; Iqbal et al., 1997; Iqbal et al., 2001; Lu and Myers, 2002). A hypothesis to explain this is that genetic bottlenecks occurred upon importation of small quantities of seed from Mexico to America in the 19th century. For example, Burling’s cotton in 1806 was smuggled out of Mexico in the stuffing of dolls. More bottlenecks may have occurred during the late stages of development of G. hirsutum Latifolium possibly as a result of rigorous selection (Lewis, 1962).

Meredith et al. (1997) stated that cotton yield has greatly increased since 1935 because of improved crop management and breeding. In South Africa, cotton is one of the five major crops produced commercially in the country and makes a significant contribution to the economy (Dippenaar-Schoeman, 1999).

In Tanzania, cotton is of great economical importance as it is the second most important cash crop after coffee, representing 15% of the country’s total exports and almost 40% of agricultural exports (Bunyecha and Tamminga, 1995; Baffes, 2002). Following liberalisation of the cotton industry, strong competition from village to market level resulted in the deterioration of cotton quality. Furthermore, mixing of different types of cotton varieties led to poor cotton properties (TCL and SB, 2002). Available varieties have medium yields (1200 kg/ha at research level and 300-500 kg/ha at farmers level), medium ginning percentages (36.8-39.6%) and medium fibre strength (22-25g/tex). Based on improved spinning machines, a fibre strength above 28 g/tex is recommended for international cotton fibre markets (Deussen, 1992; Hau, 1997).

(Powell et al., 1996; Rana and Bhat, 2004).

Molecular markers are becoming increasingly attractive markers in molecular breeding and diversity assessment

Tang et al. (1993a), and Baloch et al. (1996) observed positive and negative GCA effects exerted by parents on boll weight, boll number, lint yield and lint percentage. SCA effects for lint percentage observed were significant and consistent across the environment. Theoretically the presence of significant GCA and SCA in the F1 generation is a consequence of fluctuations in additive and dominance relationships among parents (Tang et al., 1993a).

Zock et al. (1995).; It has been known for years that dietary fat and cholesterol influence blood cholesterol concentrations. Extensive research has been done not only on fats as a class, but on individual fatty acids and their effects on blood lipid levels and lipoprotein concentration. The length of the chain and the degree of unsaturation of a particular fatty acid molecule contribute to the ability of the fatty acid to promote or delay the development of atherosclerosis. Scientists now agree that total dietary fat intake itself is a poor predictor of CHD risk (Nelson 1998). Small differences in fatty acid stmctures may have huge influences on their metabolic effect (Pederson 2001). For example, myristic acid (14:0) and palmitic acid (16:0) are potent cholesterol increasing fatty acids, while stearic acid (18:0) and oleic acid (cis 18:1) have no effect on semm cholesterol, and linoleic acid (18:2) decreases semm cholesterol (Pederson 2001). Laurate, myristate, and palmitate constitute the majority of saturated fatty acids consumed in the Westem diet (Nelson 1998). Trans fatty acids are metabolized in the same manner as saturated fatty acids. A study by Mensink and Katan (1990) found that consumption of trans fatty acids increases blood cholesterol levels. Other studies have shovm that saturated fatty acids and trans fatty acids are equal in their effects on blood cholesterol. Large scale epidemiological surveys and resuhs from human feeding studies all point to the same conclusion, that an increased risk from coronary heart disease is associated v^th dietary intake of trans fatty acids (Nelson 1998).

(Carvalho et al., 1995). Ibragimov (1989) observed close genetic correlation between relatively short fibre and high fibre outturn and high yield. Chen et al. (1991) observed that days from sowing to standard flowering date, days from sowing to practical flowering date, plant height and sympodia per plant were significantly positively correlated with each other and negatively correlated with first peak in cotton harvest.

Zock et al., 1994.; Polyunsaturated oils can, however, be converted into stable cooking oils by hydrogenation in which the carbon double bonds (unsaturated) are reduced to single bonds (saturated). However, partial hydrogenation results in the breakdown of naturally occurring cis carbon bonds and occasional reformation in trans configuration (Ray and Carr, 1985), forming trans-fatty acids (the two hydrogen constituents are on opposite sites) (Gurr and Harwood, 1991). In contrast to cis-unsaturated fatty acids, trans-fatty acids are known to be as potent as palmitic fatty acid in raising plasma LDL cholesterol levels (Noakes and Clifton, 1998) and lowering plasma high density lipoprotein (HDL) cholesterol

Although cotton is grown mostly for fibre, the seeds are an important source of oil. The estimated world production of cottonseed oil in 1985 was 3.57 million metric tons ranking fifth in vegetable oil production after soybean, palm, rapeseed and sunflower (Hatje, 1989). World production of cottonseed oil was about 4 million metric tons in both 1997 and 1998 (Jones and Kersey, 2002).

(Brubaker et al., 1994). The wild G. hirsutum variety is ‘Yucatanense’, a sprawling perennial shrub with reproductive development controlled by photoperiod flowering under short day conditions. Variety ‘Punctatum’ arose from ‘Yucatanense’. These early-domesticated varieties dispersed to the rest of Mesoamerica, northern South America and the Caribbean basin. Ethno botanical evidence suggested that landrace ‘Latifolium’ arose from this germplasm. Some accessions classified as ‘Latifolium’ show photoperiodic flowering while others are photoperiodic independent. In Guatemala, cotton was traditionally intercropped with pepper (Capsicum spp.). Cotton plants were removed as soon as first bolls began to open in order to prevent competition with the developing pepper. This practice would have eliminated late maturing genotypes. Selection for early maturity would have reduced seed dormancy and possibly photoperiod dependent flowering. The early maturing Latifolium genotypes diffused into the highlands of southern central Mexico

Kapoor (1994) and Turner et al. (1976) indicated that epistasis for seedcotton yield per plant, boll weight and ginning outturn was of duplicate type, thus additive and dominance gene effects have been found to be important in upland cotton. However, it varied from characteristic to characteristic. Gad et al. (1974) and Singh and Singh (1980) reported additive genetic variation for seedcotton yield, number of bolls, ginning outturn and lint index. Sayal and Sulemani (1996) reported over-dominance on lint percentage, seed index, lint index and staple length from a 8 x 8 diallel cross and additive effects for seedcotton yield. Carvalho and De-Carvalho (1995) studied fibre percentage and boll size in four varieties of G. hirsutum and 12 hybrids from a complete diallel set of crosses. Both traits showed incomplete dominance. Additive gene effects predominated in the control of both traits. Ahmad et al. (1997) observed additive gene action with partial dominance for bolls per plant, boll weight, seedcotton yield and seed index. Epistatic effects were involved in the expression of all characteristics except for boll weight.

Mensink and Katan, 1992; Zock et al., 1994). However, it was revealed that stearic acid (C18:0) does not raise LDL-cholesterol like other saturates and may lower the total cholesterol, thus is considered to be neutral with respect to risk of cardiovascular disease (Dougherty et al., 1995; Liu et al., 2002). On the other hand, unsaturated fatty acids, such as monounsaturated oleic acid (C18:1) and polyunsaturated linoleic acid (C18:2) and α-linolenic acid (C18:3), have the beneficial property of lowering LDL-cholesterol, thus reducing the risk of cardiovascular disease (Mensink and Katan, 1992).

Wang et al., 1989; Stanton et al., 1994.; Gossypium arboreum (A2 genome) is still grown in Pakistan and India on marginal land for use in non-woven material and is helpful in breeding programmes as a donor of host-plant resistance genes. The A-genome cotton enhances genetic diversity of tetraploid cotton breeding programmes (Stanton et al., 1994), especially with the development of techniques for introgressing A-genome germplasm into AD-genome cultivars (Stewart, 1992). Hybrids between G. hirsutum and G. arboreum have led to the selection of genotypes with earlier maturity and an increased range of fibre traits

Poehlman, 1987; Abdalla et al., 2001.; Cotton is primarily a self-pollinated crop but there is about 1-32% natural outcrossing during field cultivation that depends mainly on location and pollinator availability.

Lin et al., 1986; Becker and Léon, 1988).; Eberhart and Russell (1966) proposed the use of two stability parameters to describe the performance of a variety over an array of environments. They proposed the regression of each cultivar on an environmental index as a function of the squared deviation. Breeders search for genotypes that show a stable high yield over years and locations. In general a genotype is considered stable when its performance across environments does not deviate from the average performance of a group of standard genotypes. Eberhart and Russell (1966) proposed pooling the sum of squares for environments and G x E interactions and subdividing it into a linear effect between environments [with 1 degree of freedom (df)], a linear effect for G x E (with G-1 df) and a deviation from regression for each genotype (with E-2 df). The residual mean squares from the regression model across environments is used as an index of stability and a stable genotype is one in which the deviation from regression mean squares (S2di) is small.

Chang et al., 1978

Highly unsaturated oils are unstable when exposed to high temperatures and oxidative conditions for long periods of time. This results in the development of short chain aldehyde, hydroperoxide and keto derivatives, imparting undesirable flavours and reducing the frying performance of the oil by raising the total level of polar compounds .

Andries et al. (1971) reported that row spacing affects plant height. For such characteristics, conclusive results are obtained by repeats over years and/or locations. However, other traits like leaf colour, leaf shape and boll shape are consistent over environments and data from one or two tests normally give a good indication of relative performance

Hutchinson et al., 1947 Cotton improvement has always been directed towards yield and yield components like locules, boll size, number of bolls per plant, seeds per boll, seed size, lint index, seed index and ginning outturn. Therefore, breeders applied different breeding methods for improvement like pedigree breeding (Munro, 1987), bulk population breeding (Allard, 1960), backcross breeding (Sikka and Joshi, 1960) and interspecific and intraspecific breeding for hybrid vigour or heterosis that is found in F1 crosses within and between species .