An interspecific Gossypium hirsutum x Gossypium barbadense backcross population of 75 BC1 plants was evaluated for 1014 markers. The map consists of 888 loci, including 465 AFLPs, 229 SSRs, 192 RFLPs, and 2 morphological markers, ordered in 37 linkage groups that represent most if not all of the 26 chromosomes, altogether spanning 4400 cM. Loci were not evenly distributed over linkage groups, and 18 of the 26 long groups had a single dense region. This paper proposes a partially revised list of the 13 pairs of homoeologous A/D chromosomes of the 2n = 4x = 52 tetraploid cotton genome. The major revisions, which involve the c3-c17, c4-c22, c5-D08, and c10-c20 homoeologous pairs, are based on the mapping of 68 SSR and RFLP loci with a known chromosome assignment, as well as on comparative alignments with previously published G. hirsutum x G. barbadense maps. The overall congruency in the locus orders and distances of common SSR and RFLP loci in these maps allows for an estimation of the consensus length that reaches a minimum of 5500 cM, and is encouraging for future efforts aimed at developing an integrated map of cultivated cotton. The present map also provides a firm framework for precision mapping of Mendelian components of quantitative traits in cotton

Microsatellite [simple-sequence repeat (SSR)] markers were developed and positioned on the genetic map of tetraploid cotton. Three hundred and ninety-two unique microsatellite sequences, all but two containing a (CA/GT) repeat, were isolated, and the deduced primers were used to screen for polymorphism between the Gossypium hirsutum and G. barbadense parents of the mapping population analyzed in our laboratory. The observed rate of polymorphism was 56%. The 204 polymorphic SSRs revealed 261 segregating bands, which ultimately gave rise to 233 mapped loci. The updated status of our genetic map is now of 1,160 loci and 5,519 cM, with an average distance between two loci of 4.8 cM. The presence of a total of 466 microsatellite loci, with an average distance of 12 cM between two SSR loci, now provides wide coverage of the genome of tetraploid cotton and thus represents a powerful means for the production of a consensus map and for the effective tracking of QTLs.

Cotton fiber properties are essential predictors of yarn performance. The suite of fiber quality traits that collectively affect the utility of the fiber for the textile industry include the length, the strength, the fineness and the color. These properties have been shown to be moderately to highly heritable. In an attempt to overcome the limitations of conventional breeding we undertook a marker‐assisted selection program aimed at introgressing fiber quality QTLs from Gossypium barbadense L. into G. hirsutum L. We describe the QTL analysis of 11 fiber properties measured on three phenotypic data sets. The three populations studied were the 1st (BC1) and 2nd (BC2 and BC2S1) backcross generations derived from the cross between ‘Guazuncho 2’, G. hirsutum, and ‘VH8’, G. barbadense Collectively we detected 80 QTLs, of which 50 surpassed the permutation‐based LOD thresholds (3.2–5.7). The most economically important traits, length (two correlated properties), strength, fineness (four properties), and color (two properties) were influenced by 15, 12, 21, and 16 QTLs, respectively, that could be detected in one or more populations. As expected, for the majority of QTLs, the favorable alleles came from the G. barbadense parent. Altogether one third (26) of the QTLs confirmed the map position and phenotypic effect of QTLs reported in the literature also detected in interspecific G. hirsutum × G. barbadense populations. Cases of colocalization of QTLs for different traits were more frequent than isolated positioning. Taking these QTL‐rich chromosomal regions into consideration, 19 regions on 15 different chromosomes, were identified as target regions for the marker‐assisted introgression strategy.

Leaf pubescence in cotton have a potential for insect pest management. Varying degrees of leaf trichome density in Gossypium species and cultivars have been associated to a series of five genes, referred to as t(1)-t(5). We used two segregating interspecific G. hirsutum x G. barbadense backcross populations developed in our laboratory to assess qualitatively and quantitatively leaf and stem pubescence. QTL analyses were performed using simple and composite interval mapping. Based on both types of measurements and under both types of QTL analyses, nine QTLs met permutation-based thresholds. The nine QTLs mapped to four different chromosome regions. Highest LOD values corresponded to the QTLs detected on c6 (four colocalized QTLs) and on D03 (two QTLs) for which the higher pubescence in the progeny derived from the pubescent G. hirsutum parent alleles. Conversely, on c17 (one QTL) and A01 (two QTLs), the G. hirsutum parental alleles affected negatively pubescence. These results combined with another published study confirm (1) the location in a center region of chromosome 6 of the t(1) locus as a major locus/gene determining leaf pubescence, and (2) additional genes located on seven additional chromosomes have been shown to impart trichome density either positively or negatively. The existence of a high density of PCR-based loci in most of the regions identified as harboring leaf pubescence QTLs, particularly that on chromosome 6, will facilitate future efforts for map-based cloning.