QTL Mapping For Salt Tolerance In Gossypium Tomentosum At Seedling Stage

Cotton is the most important textile fiber crop and one of the most salt-tolerant crop in the world. However, excessive salts in the soil severely affects its growth and development which eventually leads to reduction in yield. The seedling stage of cotton is the most sensitive to salinity and the effects can be quantified by measuring morphological and physiological traits. Tremendous domestication has resulted in narrow genetic base of modern cultivated cotton which has limited the improvement of its resistance to stress and yield.There is therefore the need to exploit the many valuable agronomic traits and abundant gene resources available from wild cotton species. Due to their potential as a resource of useful genes, the wild species have been used in different breeding programs for the improvement of cultivated cotton. It is however, quite difficult to transfer important traits directly into cultivated cotton from the wild species by conventional breeding due to segregation distortion, suppression of recombination and linkage drag. DNA marker technology provides a useful tool for detecting and resolving complications encountered with conventional breeding. The identification of quantitative trait loci(QTLs) for traits related to salt tolerance could facilitate the development of cotton cultivars with salt tolerance. Many studies have reported on cotton salt tolerance mechanisms, but little has been reported on mapping of salt tolerance-related genes. However, salt tolerance related genes in crops such as wheat, rice and barley have been positioned. The objective of this study was to map QTLs for salt tolerance in an F2:3 population derived from an interspecific cross between an upland cotton, CRI-12(G09091801-2), of upland cotton(Gossypium hirsutum) and an accession, AD3-00(P0601211), of wild cotton Gossypium tomentosum. One thousand two hundred and ninety five simple sequence repeat(SSR) markers, which amplified 1342 loci, distributed on 26 chromosomes and covered 3328.24 cM with an average inter-marker distance of 3.0cM, were utilized for molecular genotyping. Salt tolerance was evaluated in a hydroponic at a young seedling stage for two weeks at 150 mM NaCl concentration in three environments. Mapping of QTLs related to salt tolerance was carried out on 7 traits by composite interval mapping(CIM) using Windows QTL Cartographer 2.5. Eleven consistent QTLs were detected on 8 chromosomes(9, 11, 15, 16, 21, 23, 24 and 26) in at least two environments. qRL-Chr16-1 for RL was a major QTL explaining the Phenotypic variance of 11.97% and 18.44% in two environments. Of the 11 QTLs, 10 were located on the D subgenome, indicating that genes responsible for salt tolerance in the allotetraploid cotton AD genome were mainly derived from the D subgenome. The information derived from these studies may be useful in facilitating breeding of salt tolerant cotton lines.