Where does cotton originate and how does it evolve? What are the mysteries of cotton genome? What innovations are needed for cotton breeding and improvement in the future? Recently, Nanjing Agricultural University, University of Texas, Hassen alpha Institute of biotechnology, Texas A & M University and other units have jointly completed the mapping of high-precision reference genome of all five allotetraploid cotton species, providing an important reference basis for the exploration of polyploid plant genome evolution rules.
Now, our main cultivated cotton is allotetraploid, which has undergone a complex process of hybridization, polyploidy and domestication. About 1.5 million years ago, the diploid cotton originated in Africa crossed with the diploid cotton from America and doubled its genome to form five heterotetraploid species, namely, upland cotton, island cotton, wool cotton, brown cotton and Darwinian cotton. Among them, upland cotton and island cotton are domesticated into cultivated species, while wool cotton, brown cotton and Darwinian cotton are wild species. However, due to the complexity of quadruple genome itself and genome sequencing technology, the formation and evolution of these five species has not been accurately revealed.
This latest study found that the formation of these five species is a single origin, and after 200000-600000 years of natural evolution, gradually formed five cotton species. Among them, upland cotton and island cotton have become the most important cultivated cotton after about 8000 years of independent artificial domestication. This means that 8000 years ago, human ancestors living in different regions domesticated the two cotton species almost at the same time. Not only that, even in the two places, the human ancestors coincidentally optimized similar gene expression patterns, which made the fiber length and color of the two cultivated cotton increased.
Source: Xinhua Daily