Responses of Eight Differentially Heat Sensitive Tomato Cultivars against Chronic Ozone Exposure in the Indo-Gangetic Plain: Growth, Physiology, and Yield

Tropospheric ozone (O3) is an important abiotic stress to plants and its rising concentration adversely affects crop yield. The studies associated with differential responses of tomato (Solanum lycopersicum L.) cultivars to chronic elevated O3 are lacking and need to be further explored for the recognition of O3 resistant cultivars as an adaptive strategy. In the present research, differentially heat sensitive tomato cultivars were treated with elevated O3 (ambient + 20 ppb) to determine their responses by estimating the foliar injury symptoms, variations in growth, physiology, reproductive and yield related attributes. All the tomato cultivars exhibited foliar injury symptoms under elevated O3 treatment, and the intensity of injury corroborated with yield loss. Elevated O3 treatment negatively impacted biomass, growth, physiological and reproductive characteristics of all cultivars. The hierarchal cluster analysis, cumulative stress response index and yield indices differentiated cultivars into sensitive, moderately sensitive and O3 tolerant categories. The thermotolerant, VRT02 and Kashi chayan cultivars (O3 resistant) demonstrated lower yield losses, whereas the thermotolerant (O3 sensitive) Superbug exhibited higher foliar injury, greater alterations in physiology, growth and reproductive traits resulting in greater yield losses than other cultivars. The cultivars with different heat sensitivity did not respond similarly towards O3 stress. Cultivars VRT 02 and Kashi chayan can be recommended for cultivation in areas experiencing high O3 vis-à-vis high temperature conditions.