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<p>Phenotypic and physiological traits play a&#xa0;crucial role in determining plant tolerance to high temperatures and are essential for identifying superior genotypes for breeding. This study provides a&#xa0;novel integrated assessment of phenotypic, physiological, and leaf micromorphological traits (including trichome architecture) under progressive heat stress, linking structural and functional responses to identify heat-tolerant genotypes. Heat stress was imposed over a&#xa0;10-day period, with temperatures gradually increased every two days across day/night regimes of 25/19 °C, 28/22 °C, 30/24 °C, 33/28 °C, and 35/30 °C, while a&#xa0;control group remained at 25/19 °C. Heat stress above 33 °C resulted in a&#xa0;significant decline in photosynthetic rate (maximum reduction of 86.4% at 35 °C) and gas exchange parameters, with the greatest decrease observed in leaf conductance (94.7%) in the susceptible genotype. These reductions were accompanied by increased stomatal limitation and vapor pressure deficit. Significant genotypic differences were detected in photosynthetic pigment concentrations, stomatal density, as well as trichome type and density. The glandular trichome type showed a&#xa0;strong negative correlation with photosynthetic pigments, particularly lutein concentration (r = −0.63). Mean performance of each trait under control and high temperature (35 °C) conditions was used to calculate the heat susceptibility index, which, together with Principal Component Analysis (PCA), grouped the genotypes into three distinct tolerance categories. Among wild species <i>S.&#xa0;pimpinellifolium</i> (PIM), and <i>S.&#xa0;habrochaites </i>(HAB) genotypes, along with the domesticated genotype BIG, were identified as heat-tolerant. These results highlight valuable genetic resources within both wild and cultivated tomatoes for improving heat tolerance in future breeding programs.</p>

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Phenotypic and Physiological Determinants of Heat Tolerance in Wild and Domesticated Tomato

  • 期刊论文

  • 发表日期：

    2026年6月20日

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  • Forouzandeh Soltani,
  • Masoud Arghavani,
  • Michelle DaCosta,
  • Masoud Hashemi

摘要

Phenotypic and physiological traits play a crucial role in determining plant tolerance to high temperatures and are essential for identifying superior genotypes for breeding. This study provides a novel integrated assessment of phenotypic, physiological, and leaf micromorphological traits (including trichome architecture) under progressive heat stress, linking structural and functional responses to identify heat-tolerant genotypes. Heat stress was imposed over a 10-day period, with temperatures gradually increased every two days across day/night regimes of 25/19 °C, 28/22 °C, 30/24 °C, 33/28 °C, and 35/30 °C, while a control group remained at 25/19 °C. Heat stress above 33 °C resulted in a significant decline in photosynthetic rate (maximum reduction of 86.4% at 35 °C) and gas exchange parameters, with the greatest decrease observed in leaf conductance (94.7%) in the susceptible genotype. These reductions were accompanied by increased stomatal limitation and vapor pressure deficit. Significant genotypic differences were detected in photosynthetic pigment concentrations, stomatal density, as well as trichome type and density. The glandular trichome type showed a strong negative correlation with photosynthetic pigments, particularly lutein concentration (r = −0.63). Mean performance of each trait under control and high temperature (35 °C) conditions was used to calculate the heat susceptibility index, which, together with Principal Component Analysis (PCA), grouped the genotypes into three distinct tolerance categories. Among wild species S. pimpinellifolium (PIM), and S. habrochaites (HAB) genotypes, along with the domesticated genotype BIG, were identified as heat-tolerant. These results highlight valuable genetic resources within both wild and cultivated tomatoes for improving heat tolerance in future breeding programs.