The effect of salicylic acid on some growth parameters and quality of strawberry grown under different shade conditions

Strawberry is a fruit that is very popular among people and consumed in different ways every season. Many practices during the cultivation stage affect plant development and fruit quality. Many practices during the cultivation stage affect plant development and fruit quality. In greenhouse strawberry cultivation, high temperatures and long photoperiods during the growing season can negatively affect many factors such as flower bud formation. In the present study, the effects on the biochemical activities of strawberries were determined by increasing the plant resistance against environmental stresses and by applying salicylic acid to strawberry plants grown by using shading nets with different permeability. The experiment was performed as a pot experiment in the growing period between April and September 2022 with 3 replications and 10 plants in each replication. Different shading conditions (0%, 35%, 55%, and 75%) and doses of salicylic acid (SA) (0.0, 0.1, 0.25, 0.5, and 1.0 mM) were applied to Albion neutral-day strawberry (Fragaria X ananassa Duch.) cultivar by foliar spraying in the experimental greenhouse. The plants were harvested in two different developmental stages (i.e., the flowering period and the fruiting period). The fruits that had reached harvest maturity were also collected and analyzed. The harvested plants were separated into roots, stems and leaves and then dried in the oven. The highest fresh weights were determined as 48.95, 3.46, 14.02 g and the dry weights were 77.03, 5.17, and 53.37 g, in the root, stem, and leaf, respectively. In general, control and 35% shading treatments were statistically significant for strawberry plant weights. The highest stem thickness and root length were determined as 9.87 mm and 22.32 cm, respectively. The effect of salicylic acid treatments on stem diameter and root length was found to be insignificant. As the level of shading increased, stem diameter decreased, and root length tended to increase on the contrary and also the highest was detected in plants grown under 75% shading application conditions. In the study, the color of the fruits was measured twice and the shading treatments did not statistically affect the color values (L, a, b, c, and h). In terms of average fruit weight, the highest value was 17.80 g at 55% shading level and 1.0 mM dose of SA. While the effect of salicylic acid doses on fruit weight was statistically insignificant, applying 55% shading to the plants gave positive results on fruit weight. The soluble solids content (TSS) value ranged between 9.30% and 7.10%. The effect of salicylic acid at a concentration of 0.25 mM on TSS was significant. The TSS value decreased as the shading level increased. The effect of salicylic acid applications on pH was insignificant, while the increase in pH value was significant as the shading level increased. The highest titratable acidity (Ta) value (0.94) was obtained from fruits in 75% shading and 1.0 mM SA treatments. The effect of both applications on titration acidity in strawberry was found to be statistically insignificant. The lowest phenolic content was obtained from the control application (166.75 mg GAE/g) during the flowering period, and the highest was determined as 252.57 mg GAE/g from the 55% shade application during the fruiting period. The total amount of flavonoids was the lowest (79.95 mg QE/g) in the 35% shade application during the fruiting period, and the highest was detected (186.37 mg QE/g) in the samples taken from the plots where no shade was applied during the flowering period. The lowest total chlorophyll content of 0.35 mg/g TA was obtained from the control application during the flowering period, and the highest was obtained from the 3.59 mg/g TA and 35% shade application during the fruiting period. The lipid peroxidation amount (MDA) was obtained at the lowest level (0.66 nmol/g TA) in the 55% shade application and the highest (2.88 nmol/g TA) was obtained from the plants harvested during the fruiting period from the plot where no shade was applied.