The first linkage map for a recombinant inbred line population in cotton (Gossypium barbadense) and its use in studies of PEG-induced dehydration tolerance

Abstract

Egyptian or Pima cotton (Gossypium barbadense L.) is grown for its superior fiber quality in arid and semiarid region where drought is prevalent. However, its genetic and genomic resources are lacking. The objectives of this study were to develop the first recombinant inbred line (RIL) population for linkage mapping and to identify quantitative trait loci (QTLs) for drought tolerance using candidate gene-based single strand conformation polymorphic (SSCP) markers. Out of 152 primer pairs designed from 92 drought-responsive genes, 80 primer pairs yielded 165 polymorphic markers in the Egyptian RIL population of drought tolerant ‘Dandara’ × drought sensitive ‘Giza-70’. Seedlings of the RILs were evaluated for plant height, fresh shoot weight, fresh root weight, chlorophyll content, evapotranspiration, and leaf temperature in two replicated tests in the greenhouse under 10 % polyethylene glycol (PEG) treatment and control (water) conditions. Significant genotypic differences were detected within the RILs, and all the traits were significantly and positively correlated with one another except between fresh root weight and leaf temperature in one test. Based on a linkage map comprised of 247 loci assembled onto 32 linkage groups, 14 QTLs on 11 chromosomes were detected under the control or PEG conditions, each explaining 14–23.5 % of the phenotypic variation. Three chromosomes each carried two QTLs in the same regions, while 7 QTLs were consistent with previous studies. Out of 25 SSCP-SNP gene markers that were significantly correlated with the traits studied, 17 were commonly correlated with more than one trait. This linkage map represents the first for G. barbadense based on a permanent mapping population, and the candidate gene markers and QTLs reported provide useful information for further studies leading to marker-assisted selection and a better understanding of molecular basis in drought tolerance in cotton.