Mapping of the cl₁, r₁, yg₁, and Dw loci in the long arm of chromosome 16 of cotton

In cotton (Gossypium hirsutumL.), telocentric chromosomes are used to assign genes to specific chromosome arms and to map the genes in relationship to their centromeres. The genes for clustered flowers (cl₁), red plant color (R₁), yellow-green plant(yg₁), and dirty white lint (Dw)are on chromosome 16 of the D_h genome. A genetic stock homozygous for the cl₁R₁Yg₁Dwand yg₂ alleles was crossed to a monotelodisomic 16L stock, deficient for the short arm (Df 16S) and homozygous for the Cl₁r₁yg₁dw and yg₂ alleles; testcross populations of both the Df16S and 2n F₁s were scored for segregation of the four loci. The four loci are in the long arm of chromosome 16 and, including the centromere, the map order and map distances between loci were determined to be: centromere 30.0 ± 6.3 cl₁ 18.6 ±1.3 R₁ 19.8 ± 1.4 yg₁ 33.8 ± 1.6 Dw. When combined with previously reported map positions of three additional genes, the revised complete map is centromere 6.0 cl₃ 24 cl₁ 18.6 R₁ 19.8 yg₁ 5 ms₃ 33 ac 17 Dw. Positive interference (0.32) was observed in the R₁yg₁Dw segment of the progeny of the 2n F₁ but not in the progeny of the Df 16S F₁. Triple chiasmata occur, essentially unrestricted, in the long arm of chromosome 16. The genetic length of chromosome 16 is at least 173 cM.