Salt Tolerance Potential of Selected Solanum pennellii Introgression Lines: Unique Shoot and Root Responses

Salinity stress affects agricultural lands worldwide, causing serious yield losses. Investigation of the salinity response and tolerance mechanisms of crop plants and their wild relatives is important for developing tolerant varieties. In this study, three Solanum pennellii introgression lines (IL2-5, IL7-4-1, IL8-3), reported to be tolerant to abiotic stress, were investigated for their physiological and molecular responses to severe salinity (200 mM NaCl). The findings emphasized the variety of different responses that even highly genetically similar lines can have to stress. In IL2-5, a lack of significant root and shoot growth reduction due to salinity was associated with the up-regulation of vacuolar ion transporter genes (NHX1 and NHX3) and the lowest Na⁺ and Cl^- accumulation in leaves, while beneficial K⁺ levels were preserved. In IL7-4-1, lateral root development was exceptionally strong compared to the other lines, with high Na⁺ and Cl^- accumulation in leaves due to this unique root architecture. Despite this, the negative effects were lower on IL7-4-1's shoot growth than in IL8-3 and the control cultivar M82 due to effective reactive oxygen species management and increased superoxide gene expression. IL8-3's growth response was most similar to M82; however, it was better able to maintain beneficial K⁺ levels under salt stress. Overall, it was revealed that S. pennellii has multiple salt tolerance mechanisms associated with specific chromosomal segments and unique plant architecture. In addition to contributing to a better understanding of the mechanisms of salinity tolerance, these findings provide important information for increasing tolerance through targeted breeding.