235 Changes in the Quality Characteristics of Tomato (Solanum lycopersicum L.) Fruits Affected by NaCl Salinity F. Casierra-Posada, C.A. Pachón and R.C. Niño-Medina Faculty of Agricultural Sciences Pedagogical and Technological University of Colombia (UPTC) Tunja Colombia Keywords: protein content, fruit quality, osmotic stress, water content Abstract Salt stress creates serious problems in crop production. Salinity can reduce growth. A primary cause of it is the alteration of plant-water relations, which frequently occurs in plants growing under greenhouse conditions. Here, fertigation may cause salt accumulation in root environment. This study was done to assess the effects of NaCl-salinity on fruits of four tomato hybrids (Solanum lycopersicum L). The study was carried out in a greenhouse of the Pedagogical and Technological University of Colombia in Tunja. Four tomatoes were cultivated in 3.5 kg substrates containing 40 or 80 mmol NaCl. This treatment induced 5.2 and 8.8 dS m -1 electrical conductivity, respectively. To the control plants NaCl was not added and the conductivity of its substrate was 1.8 dS m -1 on average. Evaluated hybrids were Supermagnate, Marimba, Gloria and Astona. Results showed that percentage of protein, fiber, fat and carbohydrates were higher in fruits of NaCl-treated plants than in those of control plants, while water content was reduced by salinity. There were no statistical differences between the hybrids or within the interaction hybrid* salinity. INTRODUCTION Environmental stresses, such as salinity, significantly affect crop growth and productivity (Tawfik, 2008). The study of salinity stress incorporates research ranging from adaptations of plants to salinity to genetic screening and manipulation (Habashy et al., 2008). Agricultural areas affected by soil salinity are increasing in the world and irrigation is one of the management techniques contributing to this phenomenon. Over 6% of the world’s land is affected by either salinity or sodicity. Of the current 230 million ha of irrigated land, 45 million ha are salt-affected and of the 1500 million ha under dryland agriculture, 32 million are salt-affected to varying degrees (FAO, 2000; Munns and Tester, 2008). In Colombia, soils susceptible to salinization cover approximately 86,592 km 2 , of which 90.39% is located in dry regions. Areas susceptible to salinization are located in the Caribbean region, inter-Andean valleys and highlands, and current and future agricultural production zones (Ministerio de Ambiente, Vivienda y Desarrollo Territorial de Colombia, 2004). Many crop plants including tomato are susceptible to soil salinity and cannot survive under conditions of high salinity or can survive only with decreased yields. In order to alleviate the deleterious effects of salinity, some rehabilitation techniques, such as reclamation of salinized lands, improved irrigation with saline water and special cultural techniques, are applied (Bohnert et al., 1999; Greenway and Munns, 1980). Yield reductions induced by salinity may be due to both the osmotic stress that results from relatively high solute concentrations in the root growing medium and specific toxicity due to the accumulation of high concentrations of Na + and Cl − in plants, which causes a wide variety of physiological and biochemical alterations inhibiting plant growth and production (Maggio et al., 2004; Munns, 2005). Tomato fruit is mainly composed of water, carbohydrates, and salts (Dorais et al., 2001). Fruit growth is closely associated with relative accumulation of water, inorganic ions and assimilates. Any research on fruit growth must consider processes involved in Proc. IS on Tomato in the Tropics Eds.: G. Fischer et al. Acta Hort. 821, ISHS 2009