Evaluation of The Effect of Different Calcium Doses on Yield, Antioxidant Enzyme Activity and Malondialdehyde Levels in Tomato under Salinity Stress

In soilless culture, salinity stress significantly reduces the yield and fruit quality of tomatoes. As tomatoes are sensitive to salinity, mitigation methods are required. Supplying calcium to tomato plants increases their tolerance to salinity by supporting cell membrane integrity and antioxidant defence systems. This two-year study (2021–2022) was conducted in a fully automated heated greenhouse at the Research Centre Directorate of Gaziosmanpaşa University in Tokat. The trial plots were conducted in triplicate according to the trial design. The study examined how different calcium concentrations and salinity levels affect the yield, antioxidant enzyme activities, and malondialdehyde levels of the LA4442 (Florida 8516) tomato variety. Increasing the dose of calcium between applications significantly increased the number of marketable fruits and yield in tomato plants in both years (2021–2022). The highest yields were obtained in 2021–2022, at 118.58 t ha-1 and 127.31 t ha-1 respectively, through the application of 200 mg kg-1 calcium and 2.0 dS m-1 salt. However, reductions in marketable fruit numbers and marketable yield were observed at high salinity and low calcium doses. Furthermore, significant differences were observed in antioxidant enzyme activities. In both years (2021–2022), the activity of enzymes such as catalase, glutathione reductase and peroxidase increased in the absence of calcium (0 mg kg-1) and with increasing salt concentrations (6.0 dS m-1) across treatments. However, at 200 mg kg-1 calcium doses, the activities of these enzymes decreased. Malondialdehyde levels, an indicator of oxidative stress, increased under high salinity conditions; however, they decreased significantly under high calcium and low salinity conditions. Consequently, calcium was found to reduce salt stress in tomato (Solanum lycopersicum) plants, as well as increasing yield.