Repeated polyploidization of Gossypium genomes and the evolution of spinnable cotton fibres.

Polyploidy often confers emergent properties, such as the higher fibre productivity and quality of tetraploid cottons than diploid cottons bred for the same environments. Here we show that an abrupt five- to sixfold ploidy increase approximately 60 million years (Myr) ago, and allopolyploidy reuniting divergent Gossypium genomes approximately 1-2 Myr ago, conferred about 30-36-fold duplication of ancestral angiosperm (flowering plant) genes in elite cottons (Gossypium hirsutum and Gossypium barbadense), genetic complexity equalled only by Brassica among sequenced angiosperms. Nascent fibre evolution, before allopolyploidy, is elucidated by comparison of spinnable-fibred Gossypium herbaceum A and non-spinnable Gossypium longicalyx F genomes to one another and the outgroup D genome of non-spinnable Gossypium raimondii.

Use of diversity arrays technology markers for integration into a cotton reference map and anchoring to a recombinant inbred line map.

A diversity array technology (DArT) marker platform was developed for the cotton genome, to evaluate the use of DArT markers compared with AFLP markers in mapping and transferability across the mapping populations. We used a reference genetic map of tetraploid Gossypium L. that already contained ~5000 loci, which coalesced into 26 chromosomes, to anchor newly developed DArT and AFLP markers with the aim of further improving utility and map resolution.