Mapping QTLs controlling physiological traits of sunflower under salinity stress

In order to study the effect of salinity on yield and physiological traits of sunflower and genetic analysis of these traits under salinity conditions, a factorial experiment based on completely randomized design with three replications were performed outside the greenhouse in an open air area under natural environmental conditions. The studied factors were included 2 salinity stress levels (normal and 6 dS/m) and sunflower recombinant inbred lines (102 lines derived from the cross PAC2 ×RHA266 together with parental lines). Traits such as grain yield per plant, chlorophyll content, net photosynthetic rate, leaf relative water content, Na+ and K+ concentrations were measured after flowering. The effect of salinity was significant on grain yield, leaf relative water content, Na+ and K+ concentrations as well as on Na+/K+ and K+/ Na+ ratios. For all traits, significant differences were observed between the genotypes studied. Genetic analysis of studied traits was done using a linkage map comprising 221 molecular markers (210 SSR/11 SNP) with an average distance of 7.44 cM between markers via composite interval mapping (CIM) procedure. Totally, 10 and 8 QTLs were detected for studied traits under normal and salt stress conditions, respectively. The phenotypic variance explained by QTLs (R2) ranged from 10.4%- 34.4%. The results showed the existence of co-localized QTLs for some of the studied traits under normal and salt stress conditions including Na+.S.4.1 with Na+/K+.S.4.1, Chl.NS.6.1 with K+.S.6.1. Using co-localized QTLs in different environmental conditions and different years could enhance the efficiency of marker-assisted selection in plant breeding programs.