QTL Mapping of Chlorophyll Content in Gossypium hirsutum and Gossypium barbadense Backcross Inbred Lines

Objective] The purpose of this study was to map quantitative trait loci (QTL) related to chlorophyll content based on Soil and Plant Analyzer Development (SPAD) readings in cotton. Method] The 195 BILs (Backcross Inbred Lines) were produced by a cross between Gossypium barbadense Hai 7124 and G. hirsutum CRI 36, using CRI 36 as the recurrent parent for backcrossing with F1 to produce BC1F1, followed by seven generations of selfing. The genetic linkage map was constructed in a previous study. QTLs of chlorophyll SPAD value in the first flowering and boll development stages were identified with inclusive composite interval mapping (ICIM) method of the BIP and MET models in IciMapping 4.1 software, respectively. Result] In total, nine chlorophyll SPAD reading QTLs were identified on 6 chromosomes. The q-SPAD-A11-1 detected at the first flowering stage overlapped with q-SPAD-A11-2 detected at the boll development stage, contributing 5.08% and 5.75% of the phenotypic variation, respectively. The q-SPAD-D08-2 physical position ranged from 48.71 to 53.65 Mb on chromosome D08, which overlapped with a chlorophyll content QTL detected in a previous study. Conclusion] The novel stable QTLs, q-SPAD-A11-1 and q-SPAD-A11-2 detected in this study provide an important piece of information for fine mapping chlorophyll content in cotton.