Collinearity analysis of allotetraploid Gossypium tomentosum and Gossypium darwinii.

Gossypium tomentosum and G. darwinii are wild allotetraploid cotton species, characterized by many excellent traits, including fiber fineness, drought tolerance, and Fusarium and Verticillium wilt resistance. Based on the construction of F2 linkage groups of G. hirsutum x G. tomentosum and G. hirsutum x G. darwinii, two genetic linkage maps were compared. As a result, we found a total of seven inverted fragments on chr02, chr05, chr08, chr12, chr14, chr16, and chr25, and three translocated fragments on chr05, chr14, and chr26. In addition, comparison of the inverted and translocated fragments revealed that the orientation of four of seven markers in G. tomentosum were consistent with G. hirsutum or G. raimondii. The orientation of one of seven inverted markers of G. darwinii was consistent with G. hirsutum, and the orientation of one of three translocated markers of G. tomentosum was consistent with G. raimondii. These results indicate that, in comparison to G. darwinii, G. tomentosum has a closer genetic relationship to G. hirsutum. These findings will be important for our understanding on the genome structure of G. tomentosum and G. darwinii, and set the scene for further in-depth genome research such as fine mapping, tagging genes of interest from wild relatives, and evolutionary study.