Studying salinity stress in sunflower with focusing on mechanisms and approaches

Sunflower (Helianthus annuus L.) is an important oilseed crop that is cultivated worldwide because of its high-quality oil and be rich in linoleic acid. The present study is a review of the effects of salinity on morphological and physiological traits, resistance mechanisms, breeding, and agronomic methods to deal with salinity tolerance in sunflower. Sunflower is classified as semi-tolerant species. The negative effects of salt stress on sunflower include browning of root tips, reduction of cotyledons and root proliferation, leaf surface, accumulation of dry matter, yield, and seed oil content. Salt stress also leads to decrease in CO2 absorption, transpiration rate and stomatal conductance, and photosynthetic capacity in sunflower. The resistance reactions to salinity stress in sunflower include: modulating the expression of oubain-sensitive ATPases through calcium, delaying the degradation of membrane proteins of oil bodies, increase serotonin and melatonin, increase the expression of nitric oxide, increase S-nitrosylation of cytosolic proteins, increased content of lipid peroxide, activity of glutathione peroxidase, and the abundance of heme oxygenase-1 (HO-1) in the cells around the secretory channels . Among the important breeding approaches to cope salinity stress in sunflower are the identification of HT089, HT175, HT185, HT215, HT216, and HT227 salinity resistance genes, the identification of H. paradoxus as the most salinity resistant species, the production of HA429 and HA430 lines tolerant to salinity, the transfer of the TaNHX2 gene from wheat to sunflower that improved its salinity tolerance and the identification of genes involved in salinity stress in sunflower by next generation sequencing technology. The results of this extensive study will be important in achieving a comprehensive plan for sustainable improvement of yield and quality of sunflower oil under salt stress conditions.