Abstract: The karyotypes of five genomic groups in type species of Gossypium; B1 (G. anomalum), C1 (G. sturtianum), E1 (G. stocksii), F (G. longicalyx), and G (G. bickii) were analyzed in this paper. Coupled with the studies of the karyotypes A1 (G. herbaceum) and D5 (G. raimondii) in the former report, and in view of the interspecific crosses, DNA content, the electrophoretic analysis of seed proteins and morphological and geographical classification, the authors infer that the B genome distributed across Africa from North to South may be the most primitive type, with the differentiation and migration of the B genome as a radiating center, it forms the specific distribution at present time.

Key words: Gossypium, Diploid wild species, Karyotype, Evolution