Recently, the genome sequence of the cultivated cotton Gossypium hirsutum (AtDt) has been unveiled by a cotton genome consortium led by Cotton Research Institute, Chinese Academy of Agricultural Sciences, with scientists from Peking University, Wuhan University, BGI and US Department of Agriculture Southern Plains Research Center. The findings were published online in Nature Biotechnology on april 20^th of 2015 entitled “Genome sequence of cultivated upland cotton (G. hirsutum) provides insights into genome evolution”. Prior to this, the same team has completed the genome of two diploid ancestor genomes, G. raimondii (DD) and G. arboreum (AA).

Cotton (Gossypium spp.), as one of the most important industrial crops in the world, is the main source for textile industry and plays an essential role in the global economy. Upland cotton is widely grown in over 75 countries and responsible for more than 90% of the world’s cotton lint production. This genus constitutes at least five well-established tetraploid and 45 diploid species, which may have evolved from a common ancestor around 5-10 million years ago (MYA) that subsequently diversified to produce eight groups, including groups A–G and K. The tetraploid cotton was formed around 1–2 MYA by hybridization between an A-genome ancestor and a D-genome ancestor, and coupled with chromosome doubling.

Apart from its economic value, cotton is also an excellent model system for studying polyploidization, cell elongation and cell wall biosynthesis. Cotton fibers are unusually long, single-celled epidermal seed trichomes, also known as cotton lint (about 3 cm final length and 20 μm width). Fiber length is a key factor determining cotton quality with the yield of cotton fiber depends mainly on the number of fiber cells of each ovule. Comparative genomics analysis revealed that neither extremely high level of ethylene in D genome nor low level in A genome is beneficial to cotton fiber development, which suggest that fine-tuning of ethylene biosynthesis is necessary for normal cotton fiber cell elongation and maturation. These findings provided important clues for the study of allopolyploid formation in general and molecular regulatory mechanisms for cotton fiber development in particular.

The completion of genome sequencing of diploid cotton G. hirsutum will enhance the understanding of the molecular mechanisms of important characters and molecular breeding of new cotton varieties. The information will also be a solid foundation for elucidating the origin of cotton, evolution, and revealing the formation process of tetraploid cotton and other polyploid species. Also, it will be used as a template for genotyping, phenotyping, and genome-wide association studies to build more effective cotton breeding programs. It has been widely anticipated that, with the rapid accumulation of knowledge from cotton genomics, transcriptomics and proteomics studies, genomics-assisted cotton breeding will gradually accelerate from theory to practice. Potentially, understanding the whole genome will enhance cotton yield and fiber quality.