RETRACTED ARTICLE: Screening and differential physiological responses of tomato (Solanum lycopersicum L.) to drought stress

Water deficit stress remains an important agricultural threat worldwide, thereby identifying germplasm with proven tolerance to drought stress is imperative. Tomato (Solanum lycopersicum L.) is a prominent fruit vegetable whose growth is considerably hampered by drought stress. This study evaluated physiological responses of 14 commercial tomato cultivars subjected to drought stress. Multivariate analysis and drought susceptibility index were employed to assess differential drought tolerance among cultivars, resulting into selection of Star 9003 and Rodede as tolerant and sensitive cultivars respectively. Subsequent physiological experiments showed that cultivar Star 9003 maintained better photosynthetic parameters as opposed to Rodede under drought stress, but had lower intercellular carbon dioxide concentration indicating that available CO2 was efficiently assimilated as also shown by its higher carboxylation and instantaneous transpiration efficiencies (CE and ITE). Lower stomatal limitation values in sensitive cultivar Rodede hint at a possibility that the major photosynthetic limiting factors were non-stomatal such as oxidative stress-induced photoinhibitory damage. The present study reports that tolerance in Star 9003 was unrelated to avoidance in stomatal water losses, but in part through development of morphologically thicker leaves, accumulation of organic osmolytes for osmotic adjustment and attainment of higher efficiencies in photosynthetic water use and carbon assimilation.