Impacts of heat and water stresses on the cultivated tomato Solanum lycopersicum and its wild relative Solanum chilense

Climate change causes an increase in global temperatures and drought occurrence. Water stress and heat stress are among the most common and impactful environmental stresses on plant growth and development, and the combination of the two can have drastic effects. The cultivated tomato Solanum lycopersicum is threatened by climate change. One of its wild relative species has an interesting potential for introgression of traits linked to tolerance to water and heat stress: Solanum chilense, a wild tomato native to the Atacama Desert in Chile. Individuals of both species were subjected to heat stress (21°C vs. 28°C) as well as water stress (well-watered conditions vs. water stress) implemented by using 10% polyethylene glycol in hydroponics. Morphological parameters and biomass were measured on shoots and roots. Physiological parameters were measured, such as water content, osmolality, malondialdehyde content, sugar content and photosynthesis-linked parameters. Under heat stress, very few differences between the two investigated species have emerged. These differences were essentially about morphological impacts: both species had a lower leaf area and S. chilense had a higher stomatal density under heat stress than temperate conditions while S. lycopersicum did not seem to adapt. Water stress results were more informative and highlighted that even though both species were negatively affected, S. chilense was impacted less severely than S. lycopersicum on most indicators. Moreover, differences in the response of aerial and root systems were observed. The conclusion of this work is that S. chilense is a promising crop wild relative to S. lycopersicum for trait introgression in a context of water stress tolerance. The study of the root system of S. chilense as well as the comparison of aboveground and belowground responses to stresses are an open field to be explored.