Interest of traditional tomato cultivars adapted to the Mediterranean environmental constraints for their improvement of fruit quality under high temperatures and water scarcity conditions

Given the expected increase in world population, horticultural crops will be the main source of phytonutrients for millions of people in the near future. Tomato (Solanum lycopersicum) is one of the horticultural species that supplies most of these functional compounds to the human diet due to its so high per capita consumption. Agriculture is nowadays facing a major challenge due to climate change, and its effects will be more pronounced in arid/semiarid areas like the Mediterranean basin. As a result of genetic erosion, a loss of genetic diversity has occurred in tomato, which is becoming a serious setback in breeding for heat and water stresses. One way to overcome this is making use of landraces adapted to harsh conditions of Spanish Southeast semiarid area, with very hot summers and water scarcity. The traditional cultivars 'Murciano Rojo' (MR), 'Muchamiel Aperado' (MA) and 'Tomate de Almaciles' (TA), together with commercial 'Moneymaker' (MM) used as reference, were grown in spring-summer season where very high temperatures (HT) are reached (>40 degrees C at midday). In addition, plants were irrigated in optimal conditions and under water deficit (WD) conditions. From an agronomic point of view, the most interesting characteristics were the maintenance of fruit number in MR and the lowest reduction in fruit weight in MA and TA under WD, with respect to standard irrigation. Another interesting characteristic is the absence of Blossom End Rot in landraces while an incidence of 40% was observed in MM under HT and HT+WD conditions. Regarding nutritional fruit quality, remarkable results are the increased levels of amino acids and a-tocopherol found in fruits of local accessions when the plants were grown under HT + WD. In summary, these tomato traditional cultivars constitute a rich reservoir for breeding focused at improvement of fruit quality of tomato produced in a scenario of climate change.