High temperatures limit the successful cultivation of the Hylocereus species on a global basis. We aimed to investigate the degree of heat tolerance in three species, namely, the diploids Hylocereus undatus and H. monacanthus, and the tetraploid H. megalanthus, and nine of their interspecific-interploid hybrids. Rooted cuttings were exposed to heat stress (45/35 °C) or control conditions (25/20 °C) for eight days. Initially, the plants were screened for their tolerance to heat stress and ranked into four heat tolerance categories: good tolerance, moderate tolerance, low tolerance, or sensitive, according to the decrease in the maximum quantum efficiency of photosystem II (F_v/F_m) and visual stem damage. The physiological and biochemical performances of the parental species and of three hybrids representing three different heat-tolerance categories were further analyzed in depth. H. megalanthus (classified as heat sensitive) showed a 65% decrease in F_v/F_m and severe visual stem damage, along with a marked reduction in total chlorophyll content, a large increase in malondialdehyde, and inhibition of catalase activity. H. undatus and H. monacanthus, (classified as low-tolerance species) exhibited slight stem “liquification.” The good-tolerance hybrid Z-16 exhibited the best performance under heat stress (21% decrease in F_v/F_m) and the absence of stem damage, coupled with a small decrease in total chlorophyll content, a slight increase in malondialdehyde, high antioxidant activity, and proline accumulation progressing with time. Our findings revealed that most of the hybrids performed better than their parental species, indicating that our breeding programs can provide Hylocereus cultivars suitable for cultivation in heat-challenging regions.

高温限制了在全球范围内成功种植Hylocereus物种。我们旨在研究三种物种的耐热性，即二倍体Hylocereus undatus和H. monacanthus以及四倍体H. megalanthus以及它们的九个种间-间倍体杂种。将生根的插条暴露在热应力（45/35°C）或对照条件（25/20°C）下八天。最初，根据光系统II（F _v / F _m）的最大量子效率的降低，对植物进行热胁迫耐受性筛选，并将其分为四个耐热类别：良好耐受，中等耐受，低耐受或敏感。）和视杆损伤。深入分析了亲本物种和代表三种不同耐热性类别的三个杂种的生理和生化性能。H. megalanthus（归类为热敏感）显示F _v / F _m降低65％，严重的视觉茎损伤，总叶绿素含量显着降低，丙二醛大幅增加，并抑制过氧化氢酶活性。H. undatus和H. monacanthus（分类为低耐受性物种）表现出轻微的茎“液化”。具有良好耐受性的杂种Z-16在热应力下表现出最佳性能（F _v / F _m降低21％）且没有茎损伤，再加上总叶绿素含量略有下降，丙二醛略有增加，高抗氧化活性以及脯氨酸积累随时间而发展。我们的研究结果表明，大多数杂种的表现都优于其亲本，这表明我们的育种计划可以提供适合在高温环境中种植的Hylocereus品种。