Evolution and domestication of diploid cultivated cottons: molecular genetics and agronomic evidence

The Old World cotton species Gossypium arboreum (Tree Cotton) and G. herbaceum (Levant Cotton) have been cultivated in Asia, Near Est and Africa for thousands of years. They are sister-species, more or less difficult to distinguish with certainty. Phenotyping of wild/ feral and traditional cultivated gene bank accessions shows overlapping distributions for plant and fibre traits. Human selection pressure appears evident on plant earliness, compact architecture, and higher boll and seed weights in particular. Fibre traits appear very similar between cultivated types of both species for length and colour, possibly as these traits were more easily selected for in traditional systems, but fibre length appear s rather short in most-diffused traditional cultivars, while there existed and still exist high quality cultivars , for instance of G. arboreum. Geographical distributions of these two species could result from initial historic circumstances or from differential adaptations, but no precise data has been found in support of the latter hypothesis. (Résumé d'auteur