Effect of 24- Epibrassinolide foliar application on the “Camarosa” strawberry plant growth and fruit yield under salinity stress condition in soilless culture

Salinity stress is one of the most important environmental stresses that significantly reduce growth and yield of most herbaceous species. It is considered as the most important threatening factor in production of crops in several parts of the world. Brassinosteroids are the first steroid hormones found in plants that have growth stimulator activity. They are also effective in reducing the adverse effects of environmental stresses. 24-Brassinolide is known as a reducing agent against various biological and non-biological stresses. Therefore, the present study was carried out with respect to the effect of brassinosteroids on salinity. This study was designed and implemented to investigate the effect of different concentrations of 24-epibrassinolide on the quantitative and qualitative characteristics of strawberry fruit under salinity stress. The present study investigated the effect of extrinsic application of 24-epibrassinostroide as an active 24-brassinosteroid (0, 2 and 4 μmol) on fruit yield, number of fruits, flowers and leaves, leaf area, fresh and dry weight of root, relative water content of leaves, fruit size, leaf necrosis, total soluble solid, firmness, soluble carbohydrates, proline, total chlorophyll, electrolyte leakage, superoxide dismutase and catalase under salinity stress with different concentrations (S1 = 0, S2 = 15, S3 = 30, S4 = 45 Mm). It was carried out as a factorial experiment in the form of random complete block design with 3 replications in non-greenhouse conditions of University of Maragheh. The results of this study showed that salinity of 45 mM increased necrotic leaves (15.8%), ion leakage (52%), and proline (137 µg/g) in stressed plants, i.e. the plants increase their proline content, which is part of the antioxidant system, to resist stress. Using 24-brassinolide at the concentration of 4 μm showed the greatest effect on yield (59.25 g/plant), leaf area (96.25 cm2), number of flowers (8.96), fruits (5.78) and leaves (17.41), total chlorophyll levels (1.63 μg/mg), fresh (7.01 g) and dry (1.26 g) weight of root, relative water content of leaves (60.50%), firmness (1.52 kg/cm2), total soluble solid (10.58%), fruit size (3.61 cm3), and reduction of ion leakage (43%) as well. Increasing the activity of catalase and superoxide dismutase enzymes in plants treated with 24-epibrassinolide and salinity stress versus the ones that were only exposed to salinity stress showed activation of the antioxidant system and plant protection by 24-Brosinosteroids and reduction of oxidative damage in these plants. The present study showed that using plant biochemical regulator such as brassinosteroids have successfully reduced the adverse effects of salinity stress on growth parameters and fruit yield of strawberry cv. Camarosa. Therefore, the results of this research can be used to progress cultivation of strawberry cultivars in saline areas.