304 Colchicine 



Interspecific hybrids between the two tetraploid species are vigor- 

 ous and fully fertile in the first generation. These species, G. hirsutum 

 and G. Ixirbadense, both carry desirable qualities.is Attempts to com- 

 bine the best features of each in a new variety have not been as success- 

 ful as one might wish.^"'' The second generation and subsequent ones 

 give rise to weak, sterile, and undesirable types. Backcrossing to 

 either parent has not led to new levels of improvement. One might 

 well ask if the combining of characters from other species, which are 



TABLE 12.2 



Genomes of Gnssjpium 

 (After Brown and Beasley, and Menzel) 



Natural Species and Tetraploid Genome 



Tri-species Hybrid Descriptions Formula 



Gossypiim herbaceum L Asiatic 1 3-chromosome 2Ai 



G. arboreiirn L Asiatic 1 3-chromosome 2A2 



G. anomolum Wawra. and Peyr African 1 3-chromosome 2Bi 



G. sturtii F. Muell AustraHan 1 3-chromosome 2Ci 



G. thurbni Tod American 1 3-chromosome 2Di 



G. aimouriamnn Kearney American 1 3-chromosome 2D2-1 



G. harknessii T. S. Brandeg American 1 3-chromosome 2D2-2 



G. davidsonii Kellogg .American 1 3-chromosome 2D3 



G. klotzchianum Anderss American 1 3-chromosome 20., 



G. arulum (Rose and Standley) Skovsted American 1 3-chromosome 2D4 



G. raimondii American 13-chromosomc 2D5 



G. slocksii M. Masi Arabian-Indian 1 3-chromosome. . . .2Ei 



G. hirsutum L American 26-chromosome 2(AD)i 



G. barhadense L American 26-chromosome 2(AD)2 



Hcxaploid G. hirsutum X herbaceum X G. harknessii 2(AD)iAi X 2D2_2 



Hexaploid G. hirsutum X arboreum X G. harknessii 2(AD)iA2 X 2D2-2 



Hexaploid G. hirsutum X anomalum X G. harknessii 2(AD)iBi X 2D2-2 



Hexaploid G. hirsutum X stocksii X G. armourianum 2(AD)iEi X 2D2-1 X 2D2-2 



G. harknessii 



Hexaploid G. hirsutum X stocksii X G. raimondii 2(AD)iEi X 2D5 



