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 centi-Morgans (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. 1 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.

Genetics of CMS fertility restoration was presented through the analysis of classic genetics and molecular markers. Based on F 2 segregation of the crosses between CMS and the restoring lines, the testcrosses and F 1 × F 1 populations, together with RAPD and SSR mapping, one dominant gene was identified to control the CMS fertility restoration in cotton. The strategy of genotype representation analysis (GRA) was put forward to screen the markers linked with the Rf 1 locus. Using 1,025 random decamer primers and 282 pairs of SSR primers, two RAPD and three SSR markers were identified to be closely linked to the Rf 1 gene. Among the five markers, three were co-dominantly inherited. Additionally, based on the analysis of monosomic and telesomic lines with one SSR maker, the Rf 1 locus could be located on the long arm of chromosome 4. The molecular markers available here are helpful in the development of the elite restoring lines in cotton by marker-assisted selection.

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Two genic male sterile (GMS) lines, Lang-A conditioned by ms 15 and Zhongkang-A conditioned by ms 5 ms 6 duplicate recessive genes in Gossypium hirsutum L., were chosen to map GMS genes. These two lines were crossed with Gossypium barbadense cv. ÔHai7124Õ to produce segregating populations. The ms 15 gene was mapped on chromosome 12, and was flanked by two simple sequence repeat (SSR) markers, NAU2176 and NAU1278, with a genetic distance of 0.8 and 1.9 cM respectively. The ms 5 and ms 6 genes were mapped to one pair of homoeologous chromosomes, ms 5 on chromosome 12 flanked by three SSR markers, NAU3561, NAU2176 and NAU2096, with genetic distances of 1.4, 1.8 and 1.8 cM, respectively, and ms 6 on chromosome 26 flanked by two SSR markers, BNL1227 and NAU460, with a genetic distance of 1.4 and 1.7 cM respectively. These tightly linked markers with the ms 15 , ms 5 and ms 6 genes can be used in the markerassisted selection among segregating populations in a breeding programme, and provide the foundation for gene isolation by mapbased cloning for these three genes.