Soil salinity is a serious threat to agricultural products worldwide. Agricultural biotechnology mainly aims at developing plants with higher tolerance in order to face the challenging environmental conditions, such as drought and salinity. Identification of marker-character associations is the first step towards marker-aided selection in plant improvement programs. In the current study, quantitative trait loci (QTLs), associated with salt tolerance, were identified using 84 common sunflower (Helianthus annuus L.) inbred lines, collected from different geographical origins. The lines were fingerprinted with 30 simple sequence repeat (SSR) markers. This generated 71 clear and scorable bands, 87% of which were polymorphic. Associations between SSR markers and 18 agronomic characters were analysed using mixed linear model (MLM). Based on SSR markers data, the association panel was subdivided into two subpopulations (K = 2). About 2.06% of the 435 possible locus pairs of the studied SSRs represented significant linkage disequilibrium (LD). Six and 13 SSR loci showed significant (P ≤ 0.01) association with the assessed characters under natural and salt stress conditions, respectively. Several molecular markers were significantly associated with more than one phenotypic character, suggesting the possible presence of genetic linkage or pleiotropic effects. The identified and associated markers are expected to be helpful in marker-aided selection in sunflower breeding programmes.

One of the effective indirect selections methods for improving grain yield and its components is the selection index. In order to develop a suitable selection index for simultaneously increasing yield and its related traits, 100 sunflower inbred lines from different geographical origins were evaluated in randomized complete block designs with three replications at Urmia University in 2015 under normal and salt stress (8 dS/m) conditions. Smith-Hazel and Pesek-Baker indices based on 6 traits including plant high, head diameter, leaf number, one hundred seed weight, head dried weight and grain yield, as well as direct and correlated response of these traits were calculated in each one of salt stress conditions. Correlations between grain yield and selection indices were computed. The highest correlated responses were observed for plant height via seed yield (32.16) and for grain yield via head diameter (14.21) at normal and salt stress conditions, respectively. Head diameter with the highest correlated response for seed yield at normal and salt stress conditions can be considered as a suitable indirect trait for improving seed yield under both conditions. Smith-Hazel's third indices and Pesek-Bakker's third indices showed high heritability (0.76, 0.78), genetic correlations (0.87, 0.88) and relative efficiency (0.87, 0.88) and they help to identify the most superior genotypes same to direct selection by grain yield (16, 18) under both conditions. So, selection based on these indices potentially screens the high yielding lines. Based on results, the line '71' is introduced as superior line in normal and salt stress conditions.