Differential Drought Stress Tolerance in Five Varieties of Tomato (Solanum lycopersicum L.): An Evaluation of Photosynthesis and Antioxidant System

Among abiotic stresses, drought is the most critical threat to agricultural plants and thus to world food security. Domesticated tomato is one of the most important horticultural cash crops grown worldwide. This experiment aimed to explore the differential tolerance level of five varieties of tomato (PKM-1, K-21, Pusa-Gaurav, Pusy-Ruby, and S-22) exposed to three deficit irrigation levels.The drought stress was imposed by gravimetric method. Three different drought stress regimes (60%, 50%, and 30% field capacity, FC) were studied, along with a control, where tomato plants were normally irrigated (100% field capacity). At 40 days after transplantation, various growth, physiological and biochemical attributes were assessed. Drought stress negatively affected the growth of tomato varieties by inducing stomatal closure, decreasing photosynthetic processes, and triggering oxidative damage. In K-21 variety, severe drought stress level (30% FC) reduced shoot/root dry masses, SPAD chlorophyll value, Fv/Fm, nitrate reductase, and carbonic anhydrase activity by 49.85%, 44.48%, 50.20%, 34.36%, 42.09%, and 46.80%, whereas electrolyte leakage and hydrogen peroxide (H2O2) contents were enhanced by 39.20% and 63.44%, respectively, in comparison to respective controls, while in S-22 variety, the above-mentioned parameters were maximally affected and the values were reduced by 60.91%, 59.94%, 63.60%, 49.14%, 54.64%, and 61.53%; however, electrolyte leakage and H2O2 contents were increased by 58.90% and 70.37% respectively, in comparison to respective controls. Different varieties of tomato plants had different levels of perception and responsiveness to drought stress. The varieties followed the order in accordance with their decreasing drought tolerance as follows: K-21 > Pusa Ruby≈Pusa-Gaurav > PKM-1 > S-22.