Genetic mapping of new cotton fiber loci using EST-derived microsatellites in an interspecific recombinant inbred line cotton population.

There is an immediate need for a high-density genetic map of cotton anchored with fiber genes to facilitate marker-assisted selection (MAS) for improved fiber traits. With this goal in mind, genetic mapping with a new set of microsatellite markers [comprising both simple (SSR) and complex (CSR) sequence repeat markers] was performed on 183 recombinant inbred lines (RILs) developed from the progeny of the interspecific cross Gossypium hirsutum L. cv. TM1 x Gossypium barbadense L. Pima 3-79. Microsatellite markers were developed using 1557 ESTs-containing SSRs (> or = 10 bp) and 5794 EST-containing CSRs (> or = 12 bp) obtained from approximately 14,000 consensus sequences derived from fiber ESTs generated from the cultivated diploid species Gossypium arboreum L. cv AKA8401. From a total of 1232 EST-derived SSR (MUSS) and CSR (MUCS) primer-pairs, 1019 (83%) successfully amplified PCR products from a survey panel of six Gossypium species; 202 (19.8%) were polymorphic between the G. hirsutum L. and G. barbadense L. parents of the interspecific mapping population. Among these polymorphic markers, only 86 (42.6%) showed significant sequence homology to annotated genes with known function. The chromosomal locations of 36 microsatellites were associated with 14 chromosomes and/or 13 chromosome arms of the cotton genome by hypoaneuploid deficiency analysis, enabling us to assign genetic linkage groups (LG) to specific chromosomes. The resulting genetic map consists of 193 loci, including 121 new fiber loci not previously mapped. These fiber loci were mapped to 19 chromosomes and 11 LG spanning 1277 cM, providing approximately 27% genome coverage. Preliminary quantitative trait loci analysis suggested that chromosomes 2, 3, 15, and 18 may harbor genes for traits related to fiber quality. These new PCR-based microsatellite markers derived from cotton fiber ESTs will facilitate the development of a high-resolution integrated genetic map of cotton for structural and functional study of fiber genes and MAS of genes that enhance fiber quality.