Chapter 1 Cotton: An Introduction B.M. Khadi, V. Santhy, and M.S. Yadav 1.1 Introduction Cotton is currently the leading plant fibrecropworldwideandisgrowncommercially in the temperate and tropical regions of more than 50 countries (Smith 1999), with a total coverage of 34 million ha. The cotton seed coat extends into tubular fibre and is spun into yarn. Specific areas of production include countries such as USA, India, China, 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. Among the five major cotton growing countries, China holds the highest productivity level (1,265 kg/ha), followed by USA (985 kg/ha), Uzbekistan (831 kg/ha), Pakistan (599 kg/ha) and India (560 kg/ha) (Table 1.1). India ranks first in terms of cultivated area, occupying over a quarter of the world cotton area, followed by China, USA, and Pakistan. About 26.247 million metric tons of cotton are produced globally, and the major countries contributing the most are China, India, USA and Pakistan followed by Uzbekistan, Turkey, Australia, Greece, Brazil and Egypt. The cotton species recognized in the world are about 50, of which 4 are cultivated. Two of these (Gossypium arboreum and G. herbaceum) are diploids, and two (G. hirsutum and G. barbadense) are tetraploids. More than 80% of the world s cotton area is covered by tetraploids. However, diploid cottons are cultivated in Asia and the Middle East. India is the only country where all the cultivated species and some of their hybrid combinations are commercially grown. B.M. Khadi Dean (Post Graduate Studies), University of Agricultural Sciences, Dharwad-580005, Karnataka, India e-mail: bmkhadi@rediffmail.com V. Santhy and M.S. Yadav Central Institute for Cotton Research, Nagpur, Maharashtra, India U.B. Zehr (ed.), Cotton, Biotechnology in Agriculture and Forestry 65, DOI 10.1007/978-3-642-04796-1_1, # Springer-Verlag Berlin Heidelberg 2010 1
2 B.M. Khadi et al. Table 1.1 Major cotton growing countries of the world (2007 2008) Sl. No. Country Area (000 ha) Production Productivity (kg/ha) (000 metric tonnes) 1 China (M) 6,385 8,078 1,265 2 USA 4,245 4,182 985 3 India 9,555 5,355 560 4 Pakistan 3,082 1,845 599 5 Uzbekistan 1,450 1,206 831 6 Turkey 520 675 1,298 7 Australia 63 126 2,000 8 Brazil 1,077 1,603 1,487 9 Egypt 246 224 909 10 Greece 300 285 950 11 Argentina 311 152 489 12 Others 6,129 2,516 World average 33,363 26,247 787 Source: Cotton: World Statistics, November 2008 The diversity of cotton cultivars and cotton agro climatic zones in India is larger when compared to other major cotton growing countries in the world. 1.2 History and Taxonomy The first reference to cotton is found in a Rig-Veda hymn, which was written about the fifteenth century BC. The use of cotton in about 800 BC is recorded in Manu s Dharmashastra. The Sanskrit word karpasa,i, which is connected to kapas of modern Hindustani, was used in ancient literature. The technological and agricultural term in English, Cotton, which describes cultivated species of Gossypium, comes from the Arabic word qutum or kutum (Brown and Ware 1958). Systematic taxonomic study of cotton started with the description of Gossypium by Linnaeus in 1953. The work of Sir George Watt entitled The wild and cultivated cotton plants of the world provided a new dimension to the taxonomic studies. The cytological studies of Zaitzev (1928) cited in the paper A contribution to the classification of genus Gossypium was a landmark in cotton classification. Kohel (1973) has addressed the description of genetic mutants based on the rules of the International Committee on Genetic Symbols and Nomenclature. Among the 50 species recognized in the dicotyledonous genus Gossypium, belonging to family Malvaceae about 45 are diploids divided into three geographical groups and corresponding subgenera viz. Sturtia, Houzingenia and Gossypium, five species are tetraploids included in one subgenus viz. Karpas (Fryxell 1984; Wendel and Cronn 2003; Cronn and Wendel 2004) (Table 1.2). The diploid species with 26 chromosomes are placed in eight cytogenetic genome groups designated A G and K and tetraploids with 52 chromosomes in
1 Cotton: An Introduction 3 Table 1.2 Classification of Genus Gossypium Primary distribution No. of species Subgenus Section Subsections Examples of species Africa (Africa and Arabian peninsula) Australia (NW Kimberly region) America (West Mexico Galapagos islands and Peru) 14 Gossypium Gossypium Gossypium Asiatic diploids Pseudopambak Anamola G. anomalum Pseudopambak G. stocksii Longibola G. longicalyx 17 (16 taxonomically described) 14 (13 taxonomically described) Sturtia Sturtia G. sturtianum Grandi calys G. costulatum Hibiscoidea G. australe Houzingenia Houzingenia Houzingenia G. thurberi Integrifolia G. davidsonii Caducibractealaa G. harknessii Erioxylum Erioxylum G. aridum Selera G. gossypioides Astromericana G. raimondii American Pacific 5 Karpas All tetraploid species including New World cultivar
4 B.M. Khadi et al. one group designated AD (Endrizzi et al. 1985; Fryxell 1992; Stewart 1995; Wendel and Cronn 2003) according to the genome affinities. The five allotetraploid species are the united version of Old World A and New World D genome in A genome cytoplasm (Skovsted 1937; Brubaker et al. 1999a) (Table 1.3). Table 1.3 Gossypium species grouped according to germplasm pool Pool Species Genome Seed Notes Primary G. hirsutum AD 1 + Current and obsolete cultivars, breeding stocks, land races, referral and wild accessions G. barbadense AD 2 + Current and obsolete cultivars, breeding stocks, land races, referral and wild accessions G. tomentosum AD 3 + Hawaiian Islands G. mustelinum AD 4 + NE Brazil G. darwinii AD 5 + Galapagos Islands Secondary G. herbaceum A 1 Cultivars, landraces of Africa and Asia minor, one wild from Southern Africa G. arboreum A 2 + Cultivars, landraces from Asia minor, SE Asia and China; some African G. anomalum B 1 + Two subspecies, Sahel and SW Africa G. triphyllum B 2 + SW Africa G. capitis-viridis B 3 + Cape Verde Islands G. trifurcatum B? NE Somalia G. longicalyx F 1 + Trailing shrub, Sudan, Uganda, Tanzania G. thurberi D 1 + Sonora Desert, North America G. armourianum D 2-1 + Baja California ( San Marcos Island) G. harkenssii D 2-2 + Central Baja California G. davidsonii D 3-d + Southern Baja California G. klotzchianum D 3-k + Galapagos Islands G. aridum D 4 + Arborescent, Pacific slopes of Mexico G. raimondii D 5 + Pacific slopes valleys of Peru G. gossypioides D 6 + Central Oaxaca, Mexico G. lobatum D 7 + Arborescent, Central Michoacan, Mexico, West Central Mexico G. tumerui D 10 + NW Mexico, coastal G. schwendimanii D 11 + Arborescent, El Infiernillo Valley, SW Mexico Tertiary G. sturtianum C 1 + Ornamental, Trans central Australia arid zone G. robinsonii C 2 + Western Australia G. bickii G 1 + Central Australia arid zone G. australe G + Trans Australia, North arid zone G. nelsonii G + Central Australia G. costulatum K + North Kimberley (wet dry tropical Western Australia) G. cunninghamii K + Northern NT, Australia G. enthyle K + North Kimberley, WA G. exgiuum K + Prostrate, North Kimberley, WA G. nobile K + North Kimberley WA G. pilosum K + Terailing, Nort Kimberley, WA G. populifolium K + North Kimberley, WA (continued)
1 Cotton: An Introduction 5 Table 1.3 (continued) Pool Species Genome Seed Notes G. pulchellum K + North Kimberley, WA G. rotundifolium K + Prostrate, North Kimberley, WA G. sp. nov. K + North Kimberley, WA G. stocksii E 1 + Arabian Peninsula and Horn of Africa G. somalense E 2 + Horn of Africa to Chad G. areysianum E 3 + Yemen G. incanum E 4 + Yemen G. benadirense E Ethiopia, Somalia, Kenya G. bricchettii E Somalia G. vollesenii E Somalia 1.3 Origin and Distribution DNA-sequence phylogenetic data suggest that 6 7 million years ago, following a trans-oceanic dispersal event, a D genome diverged from the African lineage that eventually gave rise to the A genome, and became a separate lineage in the Americas (primarily Mexico) (Senchina et al. 2003; Wendel and Cronn 2003; Cronn and Wendel 2004). From another long-distance dispersal event 1 2 million years ago, a tetraploid originated through hybridization of an African plant of the A-genome group, perhaps most closely related to the present-day species G. herbaceum, with a resident plant of the D-genome group, most closely related to the present-day species G. raimondii (Wendel et al. 1992; Senchina et al. 2003; Wendel and Cronn 2003; Kebede et al. 2007). The nascent disomic AD allotetraploid from that single polyploidisation event evolved into the five present-day tetraploid species (Endrizzi 1962). Comparative RFLP mapping was used to construct genetic maps for the allotetraploids (AD genome n ¼ 26) and diploids (A & D genome n ¼ 13) (Brubaker et al. 1999b). The study showed that allotetraploid A and D genomes and A & D diploid genomes are recombinationally equivalent despite nearly two fold difference in physical size. Polypoidisation in Gossypium is associated with enhanced recombination as genetic lengths for allotetraploid genomes are over 50% greater than those of their diploid counterparts. The concept of organismal and genome relationships of diploid and allopolyploid taxa in the genus Gossypium have been given in Fig. 1.1. Gossypium raimondii, a rare species of northwestern Peru, is considered to be the diploid with the genome that has retained the most similarity to this ancestral D-genome species (Guo et al. 2007). It is one of the more recently evolved of the DD species, having diverged in isolation as a result of a long-distance dispersal event from Mexico (Wendel and Cronn 2003; Alvarez et al. 2005). Soon after separation of the D-genome lineage, African Gossypium further diverged with a long distance dispersal event resulting in establishment of an Australian lineage (which evolved into the three genome groups C, G and K). The lineage in Africa evolved further into four genome groups, first with divergence of
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