Evaluation of Toxicity of Tropospheric Ozone on Tomato (Solanum lycopersicum L.) Cultivars: ROS Production, Defense Strategies and Intraspecific Sensitivity

Rapid industrialization, transportation and other human activities increase the formation of Ozone (O-3) in the troposphere, causing an adverse effect on agricultural productivity. It is expected that concentration of O-3 will increase along with the rise in global surface temperature. A field experiment was performed with differentially heat sensitive tomato (Solanum lycopersicum L.) cultivars with an objective to understand the intraspecific variations in defense mechanism under elevated O-3 treatment. The selected tomato cultivars were exposed to ambient and elevated O-3 (ambient +/- 20 ppb) in open top chambers. The results depicted that elevated O-3 induced accumulation of reactive oxygen species and malondialdehyde content leading to enhanced lipid peroxidation in all the tomato cultivars, but the scale of effects varied among cultivars. In response to oxidative stress generated due to ROS under elevated O-3, activities of enzymatic and non-enzymatic antioxidants showed variable responses in differentially heat sensitive tomato cultivars. Heat tolerant cultivar, Superbug experienced highest oxidative stress under elevated O-3,O- and significantly enhanced the non-enzymatic antioxidants leading to highest reduction in fruit biomass and total fresh fruit weight. However, heat tolerant cultivar, Kashi chayan and VRT 02 with lesser oxidative stress exhibited greater induction of enzymatic antioxidants and showed less reduction in fruit biomass and total fresh fruit weight. The heat sensitive cultivars, however, were less sensitive than Superbug. This study manifested that cultivar's sensitivity under elevated O-3 was governed by the variability of defense strategies, irrespective of their sensitivity towards heat. Kashi chayan and VRT 02 may be recommended in areas under elevated O-3 to minimize the productivity losses.