Andrea Ávila-Valdés

Climate change has intensified tomato plant infection by pathogens such as Pseudomonas syringae pv. tomato (Pst). Rootstocks may increase plant tolerance to leaf phytopathogens. The aim of this study was to evaluate the effects of the tolerant Poncho Negro (R) tomato rootstock on the physiological defence and the role of H₂S in susceptible Limachino (L) tomato plant responses to Pst attack. Ungrafted (L), self-grafted (L/L) and grafted (L/R) plants were infected with Pst. Rootstock increased the antioxidant compounds including ascorbate in the scion. Tolerant rootstock induced an increase of H₂S in the scion of the plants, which correlated with an enhanced expression of the SlAPX2 gene. A high accumulation of salicylic acid was observed in both Pst inoculated grafted plants, but in higher levels in L/R plant. The increase of H₂S during bacterial infection was associated with a reduction of ethylene in L/R plants. Our study indicated that the rootstock reduced the damage of the bacterial speck disease in the Limachino tomato plants, conferring tolerance to bacterial infection. This study provides new knowledge of the impact of rootstock in the defence of tomato plants to leaf pathogens for sustainable management of tomato cultivation.

Cultivated potato crops are sensitive to drought stress, reducing yield and tuber quality when the soil water potential drops to -0.3 MPa. However, drought not only affects plant growth and physiological activity, but this stress also induces biochemical and molecular changes in the cellular gene expression profile, triggering genes that play a direct role in plant protection and gene regulation. The genes involved in regulation include C-repeat Binding Factors/Dehydration responsive element binding (CBF/DREB) transcription factors, which increase cold, drought and salt tolerance in different plant species. The aim of this research was to evaluate whether the overexpression of the ScCBF1 gene from Solanum commersonii enhances drought stress tolerance in transgenic Solanum tuberosum and S. commersonii plantlets grown in vitro and induces drought adaptation mechanisms, such as osmoprotectors and genes for osmotic adjustment and membrane stability. Drought conditions were simulated through the addition of polyethylene glycol (PEG4000) to hormone-free MS medium. The vegetative growth, root development, proline content, and ScCBF1, Δ1-pyrroline-5-carboxylate synthetase (P5CS) and Dehydrins like genes (DNH10) expression were evaluated. The constitutive in vitro overexpression of ScCBF1 in both potato species showed better overall plantlet growth and root development under drought stress and higher proline levels in the stems and leaves. A significant increase in DNH10 expression was also associated with drought stress. In summary, the expression of ScCBF1 in potatoes induces responses associated with drought adaptation mechanisms, resulting in better overall plant growth.