Isolating Water and Nitrogen Stress Tolerant Genotypes Among Tomato Landraces and Solanum pennellii Backcross Inbred Lines

Improving crop adaptation to reduced agricultural inputs is a fundamental goal of current and future cropping systems, which must cope with resource scarcity and feed an increasing world population. Landraces and wild species showing tolerance traits are an important source of underexploited genetic traits that may contribute to pursue this goal. In this work, we exposed tomato lines of different origin to nitrogen and water deficiency to identify stress tolerance traits. Out of 10 accessions, we identified two genotypes, T292 and T150, with remarkable tolerance to nitrogen and water shortage, respectively. Under nitrogen deficiency genotype T292 did not show significant reduction of the shoot biomass vs a 20.2% reduction observed in the control genotype M82. An increased antioxidant activity and the ability to mobilize nitrogen from roots to the shoot were correlated with the sustained growth of T292 under low nitrogen. In response to drought stress, line T150 was the best performer with no significant reduction of biomass compared with control, well-watered conditions, whereas a 27.6% reduction was observed in M82. Under water deficiency, key adaptive traits of line T150 included the ability to improve the root:shoot ratio by allocating more biomass to the roots, which was correlated with lower levels of key markers of osmotic stress (proline and LEA) compared to control plants. Overall, we identified key physiological/molecular traits that mediate nitrogen and water use under resource shortage, and we confirmed that landraces represent a valuable genetic resource to be used in modern sustainability-based tomato breeding.