Salinity-induced Physiological Alterations in Tomato (Solanum lycopersicum L. cv. Karahıdır) under Hydroponic Culture: Implications for Genetic Resource Conservation and Breeding

Plants form the foundation of human nutrition, serving as the primary source of raw materials for plant- and animal-derived products. Agricultural systems are in constant flux, shaped by social, economic, industrial, and environmental drivers, and these influences are projected to intensify. Among abiotic stress factors, salinity and climate change are considered the most critical constraints to sustainable agriculture. Their impacts impair current production capacity and threaten long-term food security by reducing crop yield and quality (Dönmez et al. 2024; Şehirali and Özgen 2010; Şimşek et al. 2024; Yılmaz et al. 2012). Salinity already affects over one-third of irrigated land worldwide, with estimates suggesting that more than half of global agricultural lands will face salinization by 2050 (Guo et al. 2022; Roșca et al. 2023). Over the last two decades, salinity has emerged as a pervasive abiotic stressor across irrigated and rainfed systems, even in regions employing advanced irrigation technologies. Excessive salt accumulation degrades soil fertility, disrupts water and nutrient uptake, and directly suppresses plant growth (Acharya et al. 2024; Edelstein et al. 2011; Ulas et al. 2020). Tomato (Solanum lycopersicum L.), a member of the Solanaceae family, is one of the most economically significant vegetable crops worldwide, consumed both fresh and in processed forms. While its global demand continues to rise, tomato is categorized as moderately sensitive to salinity, with considerable yield losses occurring under salt stress conditions (Guo et al. 2022; Roșca et al. 2023; Ulas et al. 2020). The negative impacts of salinity on tomato production include reductions in biomass, fruit set, and quality, driven by disturbances in photosynthetic efficiency, mineral nutrition, and osmotic balance (Colla et al. 2006; Gong et al. 2013; Roșca et al. 2023). Studies across multiple horticultural species—melon, watermelon, cucumber, eggplant, pepper, and tomato—demonstrate that biomass production, leaf area, photosynthesis, and pigment concentrations are highly sensitive to increasing electrical conductivity (EC) levels (Al Rubaye et al. 2020, 2021; Colla et al. 2013; Del Amor et al. 1999; Yasar et al. 2006; Yetisir and Uygur 2010). Salt stress exerts its effects through both osmotic stress, limiting water uptake, and ionic toxicity, particularly due to sodium (Na+) and chloride (Cl−) accumulation, which destabilize membranes and interfere with metabolic processes (Rouphael et al. 2012; Yılmaz et al. 2011). These effects result in impaired photosynthetic activity, chlorophyll degradation, enhanced ion leakage, and reduced nitrate reductase activity, all of which compromise plant performance and yield (Ulaş 2021; Zhen et al. 2010; Zhu et al. 2008). Identifying and conserving plant genetic resources have become indispensable in this context. Local landraces are particularly valuable, as they often harbor unique adaptive traits to abiotic stress. Using such genotypes provides breeders with a genetic foundation for developing salt-tolerant cultivars, crucial for sustaining tomato production in saline environments (Kuşvuran et al. 2007). For example, the Turkish landrace ‘Karahıdır’ represents a promising genetic resource due to its long history of local cultivation and potential for adaptation under stress conditions. Therefore, this study investigates the agronomic, physiological, and root morphological responses of the Turkish landrace ‘Karahıdır’ tomato under NaCl-induced salinity in a controlled hydroponic system. By integrating classical physiological measurements—such as biomass, leaf area, chlorophyll and carotenoid contents, ion leakage, nitrate reductase activity, and membrane injury index—this research comprehensively assesses the cultivar’s response profile. Importantly, it addresses a gap in the literature by characterizing the salinity tolerance of a traditional tomato genotype, thereby generating highly relevant insights for both breeding programs and the conservation of local germplasm. The outcomes of this work are expected to inform future molecular and genomic studies, ultimately contributing to the development of salt-resilient tomato cultivars that can support sustainable production under global climate change.