Physiological evaluations of tomato cultivars under high temperature stress conditions

Previous studies have demonstrated that the yield reduction of tomato under sub-high temperatures is also related to a decline in the photosynthetic rates. In this work nine tomato landraces were cultivated in two different areas in Campania under three different conditions: open field with normal (April) and late (May) sowing and under plastic tunnel. Photosynthetic parameters, maximum quantum efficiency of PSII, chlorophylls, antioxidants contents and yield were determined. All the landraces showed variable responses for almost all the traits investigated in the different conditions. In the genotypes cultivated under tunnel, where temperatures reached 38-42 °C, there was a clear correlation between some photosynthetic parameters (i.e ETR) and final yield. This correlation was not found in normal and late sown plants. High temperatures affected chlorophylls and antioxidant contents. In particular there was a reduction in the content of chlorophylls and carotenoids and an increase in the level of ascorbic acid when plants were subjected to high temperatures. Genotypes potentially tolerant to high temperatures have been identified through the various parameters investigated.