CHARACTERIZATION OF THE PHYSIOLOGICAL RESPONSE OF THE HIGHLY-TOLERANT TOMATO CV. ‘PONCHO NEGRO’ TO SALINITY AND EXCESS BORON

Abstract

The variety of tomato (Solanum lycopersicum) called ‘Poncho Negro’ by farmers represents an important source of genetic resources of agricultural interest, because it has managed to thrive at levels of salinity and excess B that other varieties of the same species find impossible. This work was conducted under controlled growth conditions in a greenhouse, evaluating and obtaining plant material that served for physiological, chemical, and biochemical determinations. Stress conditions were supplied by irrigation, using different concentrations of sodium chloride (NaCl; 75 and 150 mM) and excess boron (B; 5 and 20 mg L⁻¹). The rate of net carbon dioxide (CO₂) assimilation, the quantum efficiency of photosynthesis and the relative water content (RWC) were measured. In addition, B, sodium (Na⁺), potassium (K⁺), and calcium (Ca²⁺), soluble sugars, and proline were quantified. The results suggest that ‘Poncho Negro’ accumulated Na⁺ mainly in the roots, partly limiting its entry into the aerial parts. In addition, it should be noted that the interaction of B and salinity reduced the movement of Na⁺ to the leaves. The ability of cv. ‘Poncho Negro’ to minimize leaf Na⁺ accumulation, accumulate more leaf B than control plants, and maintain its K⁺ level, when grown with an excess of B, possibly allowed the observed increase in the rate of photosynthesis. In addition, these tomato plants used proline and soluble sugars as osmo-regulators under high-B and saline conditions. Under all stress conditions studied, this variety of tomato was able to regulate its water content, with RWC values of approximately 86%.

Keywords:

• salinity
• boron
• ion content
• tolerant crop
• Solanum lycopersicum

ACKNOWLEDGMENTS

This work was funded partly by AECI/CEBAS-CSIC A/6021/06, Project UTA-Mayor 9721-08, and Convenio de Desempeño-UTA-MECESUP2. E. Bastías received a fellowship from the Fundacion Séneca, 09769/IV2/08. The authors thank Dr. David Walker for his correction of the English in the manuscript.