Silicon Modulates Bioactive Compounds and Postharvest Quality of Cherry Tomato Grown Under Salt Stress

Salinity in irrigation water limits cherry tomato production in arid and semiarid regions, making physiological stress-mitigation strategies essential. Therefore, this study aimed to evaluate postharvest quality and bioactive compounds of cherry tomato in response to silicon management under salt stress. The experiment was conducted in a greenhouse using a randomized complete block design in a 5 × 2 factorial arrangement, consisting of five irrigation-water electrical conductivities (0.3, 1.5, 2.5, 3.5, and 4.5 dS m−1) and two foliar silicon rates (0 and 1%), evaluated over two growing cycles. Increasing salinity from 0.3 to 4.5 ds m−1 decreased fruit pH from 4.33 to 4.19 in cycle 1 and from 4.24 to 4.12 in cycle 2. Total chlorophyll decreased by 88.5% and 66.8%, and total carotenoids by 76.5% and 40.0%, in cycles 1 and 2, respectively. In contrast, soluble solids (SS) increased from 5.1 to 8.1 °Brix in cycle 1 and from 5.5 to 9.6 °Brix in cycle 2, while flavonoids increased from 2.4 to 4.4 and from 1.0 to 2.5 mg 100 g−1, respectively. Foliar silicon increased mean fruit color values from 45.09 to 47.86 in cycle 1 and from 45.07 to 49.84 in cycle 2, and also increased the SS/TA ratio. Salinity × silicon interaction affected titratable acidity (TA) and anthocyanins. Overall, salinity altered the postharvest chemical and pigment profile, reduced pH and pigment, and increased SS and flavonoid contents. Foliar silicon was associated with the maintenance of fruit color and a higher SS/TA ratio, indicating its potential for maintaining postharvest quality under saline conditions.