Cytogenetic studies of N Lc1yg2R2 marker genes and chromosome deficiences in cotton

Abstract

A monosome was identified as chromosome 7 of the A genome of the tetraploid cottons by its linkage with the Lc₁yg₂R₂ markers. This makes eight chromosomes of the tetraploids now identified by monosomes. For over a decade the N locus has been considered to be linked with the Lc₁yg₂R₂ loci. Monosomic analysis, however, reveals that N is on a separate chromosome. Studies with a telocentric of chromosome 7 show that the Lc₁yg₂R₂ loci are located in the long arm. It is suggested that the R₂ locus rather than the Lc₁ locus is in the proximal position. These findings are discussed in relation to data, particularly that involving the linkage group, which supposedly illustrate the compensatory recombination phenomenon in cotton.