Climate change is causing temperature increment in crop production areas worldwide, generating conditions of heat stress that negatively affect crop productivity. Tomato (Solanum lycopersicum), a major vegetable crop, is highly susceptible to conditions of heat stress. When tomato plants are exposed to ambient day/night temperatures that exceed 32 °C/20 °C, respectively, during the reproductive phase, fruit set and fruit weight are reduced, leading to a significant decrease in yield. Processing tomato cultivars are cultivated in open fields, where environmental conditions are not controlled; therefore, plants are exposed to multiple abiotic stresses, including heat stress. Nonetheless, information on stress response in processing tomatoes is very limited. Understanding the physiological response of modern processing tomato cultivars to heat stress may facilitate the development of thermotolerant cultivars. Here, we compared two tomato processing cultivars, H4107 and H9780, that we found to be constantly differing in yield performance. Using field and temperature-controlled greenhouse experiments, we show that the observed difference in yield is attributed to the occurrence of heat stress conditions. In addition, fruit set and seed production were significantly higher in the thermotolerant cultivar H4107, compared with H9780. Despite the general acceptance of pollen viability as a measure of thermotolerance, there was no difference in the percentage of viable pollen between H4107 and H9780 under either of the conditions tested. In addition to observations of similar pollen germination and bud abscission rates, our results suggest that processing tomato cultivars may present a particular case, in which pollen performance is not determining reproductive thermotolerance. Our results also demonstrate the value of combining controlled and uncontrolled experimental settings, in order to validate and identify heat stress-related responses, thus facilitating the development of thermotolerant processing tomato cultivars.

中文翻译：

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对比加工番茄品种在热胁迫下将产量和花粉活力分开

气候变化正在导致全球作物产区温度升高，产生对作物生产力产生负面影响的热应激条件。番茄（Solanum lycopersicum）是一种主要的蔬菜作物，对热应激条件高度敏感。当番茄植株在生殖阶段暴露于分别超过 32 °C/20 °C 的环境昼夜温度时，坐果和果实重量会减少，从而导致产量显着下降。加工番茄品种在开阔地种植，环境条件不受控制；因此，植物面临多种非生物胁迫，包括热胁迫。尽管如此，关于加工西红柿的应激反应的信息非常有限。了解现代加工番茄品种对热应激的生理反应可能有助于耐热品种的开发。在这里，我们比较了两个番茄加工品种 H4107 和 H9780，我们发现它们的产量表现不断不同。使用田间和温控温室实验，我们表明观察到的产量差异归因于热应激条件的发生。此外，与 H9780 相比，耐热品种 H4107 的坐果率和种子产量显着高于 H9780。尽管普遍接受花粉活力作为耐热性的衡量标准，但在两种测试条件下，H4107 和 H9780 之间的花粉活力百分比没有差异。除了观察到类似的花粉萌发和芽脱落率外，我们的研究结果表明，加工番茄品种可能存在一种特殊情况，其中花粉性能不决定生殖耐热性。我们的结果还证明了结合受控和非受控实验设置的价值，以验证和识别与热应激相关的反应，从而促进耐热加工番茄品种的开发。