Gossypium Genome
A public genome sequencing effort of cotton was initiated in 2007 by a consortium of public researchers. They agreed on a strategy to sequence the genome of cultivated, allotetraploid cotton. "Allotetraploid" means that the genomes of these cotton species comprise two distinct subgenomes, referred to as the At and Dt (the 't' for tetraploid, to distinguish them from the A and D genomes of the related diploid species). The strategy is to sequence first the D-genome relative of allotetraploid cottons, G. raimondii, a wild South American (Peru, Ecuador) cotton species, because of its smaller size due essentially to less repetitive DNA (retrotransposons mainly). It has nearly one-third the number of bases of tetraploid cotton (AD), and each chromosome is only present once. The A genome of G. arboreum, the 'Old-World' cotton species (grown in India in particular), would be sequenced next. Its genome is roughly twice the size of G. raimondii's. Once both A and D genome sequences are assembled, then research could begin to sequence the actual genomes of tetraploid cultivated cotton varieties. This strategy is out of necessity; if one were to sequence the tetraploid genome without model diploid genomes, the euchromatic DNA sequences of the AD genomes would co-assemble and the repetitive elements of AD genomes would assembly independently into A and D sequences, respectively. Then there would be no way to untangle the mess of AD sequences without comparing them to their diploid counterparts.
The public sector effort continues with the goal to create a high-quality, draft genome sequence from reads generated by all sources. The public-sector effort has generated Sanger reads of BACs, fosmids, and plasmids, as well as 454 reads. These later types of reads will be instrumental in assembling an initial draft of the D genome. In 2010, two companies (Monsanto and Illumina), completed enough Illumina sequencing to cover the D genome of G. raimondii about 50x. They announced they would donate their raw reads to the public. This public relations effort gave them some recognition for sequencing the cotton genome. Once the D genome is assembled from all of this raw material, it will undoubtedly assist in the assembly of the AD genomes of cultivated varieties of cotton, but a lot of hard work remains.
Read more about this topic: Gossypium