Genetic Mapping of Traits Associated with Water Stress Tolerance from Wild Tomato (Solanum habrochaites)

Limited freshwater resources and global climate change pose significant challenges to agricultural production.  Tomatoes bred for tolerance to water stress would contribute to agricultural sustainability by decreasing crop water requirements. Wild tomato (S. habrochaites) exhibits tolerance to abiotic stresses, including limited water and chilling temperatures. Rapid-onset water stress induced by root chilling (6°C) reduces water movement from roots to shoots. S. habrochaites responds to root chilling by closing stomata and maintaining shoot turgor, while cultivated tomato (S. lycopersicum) fails to close stomata and wilts. This trait is controlled by a major QTL (stm9) on chromosome 9, which was high-resolution mapped to a 0.32 cM region using recombinant sub-NILs. These sub-NILs were also evaluated in replicated field experiments under restricted irrigation. Traits evaluated included shoot dry weight, total yield, and maturity traits. QTLs for traits associated with tolerance to restricted irrigation were closely linked (but not coincidental) to stm9 and located within a 1.28 cM region. Genome sequence information for S. habrochaites is not currently available, but in S. lycopersicum this chromosome 9 region is gene-rich. Evidence to date suggests that genetic elements within this region in S. habrochaites play important roles in plant responses to abiotic stress tolerance. Further characterization and dissection of these QTLs are ongoing. This research will aid crop improvement efforts in tomato required to help offset the negative effects of limited fresh-water resources.