Drought stress is one of the factors which influence sunflower (Helianthus annuus L.) production. Breeding for tolerance to drought stress has become a major focus. In the present investigation, combining ability, gene action and genetic analysis of several characteristics were studied in six pure lines of sunflower and their 15 hybrids. The materials were evaluated in two separate experiments using a randomized complete block design (RCBD) with three replications in two states (well-watered and water-stressed) under controlled conditions. Comparison of mean values exhibited that under water- stressed condition the average performance of sunflower genotypes were decreased for all studied traits. In well-watered condition the highest value for seed yield per plant (SY) was observed in the cross 'LR4?LR25', whereas in water-stressed condition the highest value for this trait was observed in the hybrid 'C104?LR25'. Combining ability analysis revealed that most of agronomical traits such as head diameter, number of achene per head, head weight and seed yield inherited differently in stressed and non-stressed conditions. In water-stressed conditions, the non-additive effects played a more important role for controlling the number of achene per head (NA), seed yield per plant (SY), head diameter (HD), and days from flowering to physiological maturity (DFM) than additive. Based on results yield improvement for water-stressed conditions requires selection under drought conditions. In well-watered condition, the cross 'LR4?C10' showed the best SCA value for seed yield per plant (SY). In water-stressed conditions, 'RHA266?C100' had the highest SCA for seed yield per plant (SY) and number of achene (NA) per head.

Primary Trans Chromosomal Tritipyrum (PTCT) amphiploid is a new cereal grown in saline soil and brackish water for grain and forage production. We evaluated the tolerance to seed deterioration in 13 promising PTCT lines, assessing accelerated aging (AA) tests by using AA boxes with 100% relative humidity at 40 °C for 72 h. The (Ma/b)(Cr/b)F4 and (St/b)(Cr/b)F4) PTCT lines, more sensitive to seed aging, were primed with NaCl, Salicylic Acid (SA), and Polyethylene Glycol (PEG) to increase the seed vigor of artificially aged seeds. Germination and emergence traits, biochemical parameters, and chromosomal abnormalities induced by artificial aging were measured in deteriorated and not-deteriorated seeds. The highest reduction percentages related to seed vigor were observed in (Ka/b)(Cr/b)F2 (34.52) and La(4B,4D)/b (28.15) lines, while the lowest was found in (Ma/b)(Cr/b)F4 (7.65) and (St/b)(Cr/b)F4 (7.46) lines. Seed aging also increases electrolytes, potassium, and protein leakages. Chromosomal abnormalities are caused by seed aging that interferes with chromosome behaviors during cell division. Seed priming on aged seeds revealed an increase in the germination percentage (GP) with PEG treatment, while the priming by SA showed an increase in seedling traits, such as the seedling length (SL2). In conclusion, we highlighted the potential use of different PTCT lines and the effective use of seed priming on deteriorated seed to enhance seed viability and seedling vigor as a useful tool for sustainable agriculture.