Molecular linkage map of allotetraploid cotton (Gossypium hirsutum L. x Gossypium barbadense L.) with a haploid population

In the present study, a haploid population from the cross of the two cultivated allotetraploid cottons, Gossypium hirsutum L. and Gossypium barbadense L., was developed by means of Vsg, a virescently marked semigamous line of Sea island cotton, and some target haploids were successfully doubled with colchicine. A molecular linkage map was constructed with 58 doubled and haploid plants. Among the total of 624 marker loci (510 SSRs and 114 RAPDs), 489 loci were assembled into 43 linkage groups and covered 3,314.5 centiMorgans (cM). Using the monosomic and telodisomic genetic stocks, the linkage groups of the present map were associated with chromosomes of the allotetraploid genome, and some of the unassociated groups were connected to corresponding A or D subgenomes. Through the analysis of the assignment of the duplicated SSR loci in the chromosomes or the linkage groups, ten pairs of possible homoeologous chromosome (or linkage group) regions were identified. Among them, the pairs of Chrs. I and 15, Chrs. 4 and 22, and Chrs. 10 and 20 had already been determined as homoeologous by classical genetic and cytogenetic research, and the pair of Chrs. 9 and 23 had also been identified by the ISH method of molecular cytogenetics. But, from present research, it was assumed that Chrs. 5 and 18 might be a new pair of homoeologous chromosomes of the allotetraploid cotton genome detected by molecular mapping of the cotton genome.