diversified and colonized arid and semi-arid regions
around the globe it underwent extensive
Collective observations of
chromosome size, and relative fertility in
led to the
designation of single-letter genome symbols for related clusters of
species. Presently, eight diploid genome groups (A through G, plus
K) are recognized among the 50 species in the genus. These genome
groups have been shown to correspond to natural lineages, and in
most cases, these lineages are also geographically cohesive.
has occurred in CottonFiber. Gossypium hirsutum and
G. barbadense are classic
tracing to an improbable
hybridization of an African/Asian A-genome and an American D-genome
species perhaps 1-2 MYA.