The Role of Repeated Polyploidization in the Evolution of Modern Cotton Species

The Role of Repeated Polyploidization in the Evolution of Modern Cotton Species

In an article entitled, “Repeated polyploidization of Gossypium genomes and the evolution of spinnable cotton fibres,” published in the 20th December, 2012 issue of Nature (492:423-427), Andrew H. Paterson and 73 authors affiliated to leading world institutions working in cotton, investigated into the role of polyploidy leading to the evolution of high quality spinnable -fibers. In that article the authors have explained how sudden 5-6 fold ploidy that occurred approximately 60 million years ago followed by allopolyploidy reuniting divergent Gossypium genomes about 1–2 million years back , ended in about 30–36-fold duplication of ancestral angiosperm genes in elite American- and Egyptian cottons, namely, Gossypium hirsutum and G. barbadens. Among sequenced angiosperms, these authors pointed out that besides cotton such genetic complexity took place only in Brassica. Previous work has shown that in the origin of tetrapoloid American cotton (2n = 4x = 52), two diploid species, namely, the spinnable –fiberd Asiatic cotton, G. herbaceum (A genome) and either of the non-spinnable G. longicalyx (F genome) or G. raimondii (D genome) have contributed their genomes. The authors have observed many non-reciprocal translocations between subgenomes which, according to them may have been responsible for their wide range ecological adaptation. Another conclusion these authors have reached is that changes in the expression of proximal groups including that of mitochondrial DNA block may account for clusters of cotton-fiber quantitative trait loci affecting various traits.

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