The increased incidence of extreme temperature events due to global climate change poses a major challenge for crop production. Ability to increase temperature tolerance through genetic improvement requires understanding of how crops and their wild relatives respond to extreme temperatures. We developed a high-throughput technique to evaluate tolerance to freezing stress (FS) and heat stress (HS) in wild, crop–wild hybrid and cultivated sunflower (Helianthus annuus L.). We also investigated whether trade-offs exist between stress tolerance and growth under benign conditions. Eleven experiments were performed under a combination of growth-chamber and field conditions. In growth-chamber experiments, FS and HS consisted of exposing acclimated plants at the 2–4-leaf stage to temperatures ranging from to –2.5°C to –4°C for 2–4 h and from 52°C to 54°C for 2–3 h. In the field, plants were grown for 32 days during midwinter (FS: average T_mean = 9.9°C and T_min = 3.8°C) or for 10 days in a heat tent (HS: average T_mean = 30.1°C and T_max = 43.3°C). We observed large differences in tolerance to FS and HS between wild and cultivated sunflower. Wild sunflower showed higher FS tolerance than cultivated in both growth-chamber and field experiments, whereas cultivated sunflower showed higher HS tolerance in growth-chamber experiments. No differences in HS tolerance were observed in the field. Crop–wild hybrids generally showed intermediate HS and FS tolerance. We found no evidence of a growth-tolerance trade-off, which suggests that tolerance might be introgressed into elite germplasm without growth penalties. The study reveals that wide genetic variation for the tolerance to extreme temperatures exists in the primary gene pool of sunflower.

由于全球气候变化而导致的极端温度事件发生率增加，对作物生产构成了重大挑战。通过遗传改良提高耐温性的能力要求了解农作物及其野生近缘种如何应对极端温度。我们开发了一种高通量技术来评估野生，作物-野生杂种和栽培向日葵（向日葵）对冰冻胁迫（FS）和热胁迫（HS）的耐受性L.）。我们还研究了在良性条件下压力承受能力和增长之间是否存在权衡。在生长室和田间条件的结合下进行了11个实验。在生长室实验中，FS和HS包括将2–4叶片阶段的适应植物暴露于–2.5°C至–4°C的温度下2–4 h和52°C至54°C的温度。 2-3小时。在田间，植物在仲冬期间生长32天（FS：平均T_均值= 9.9°C，T _min = 3.8°C），或在帐篷中生长10天（HS：平均T_均值= 30.1°C和_最高= 43.3°C）。我们观察到野生和栽培向日葵对FS和HS的耐受性差异很大。在生长室和田间试验中，野生向日葵均显示出比栽培向日葵更高的耐FS性，而在生长室实验中，栽培向日葵显示出更高的HS耐受性。在现场没有观察到HS耐受性的差异。作物-野生杂种通常表现出中等的HS和FS耐性。我们没有发现生长耐受性折衷的证据，这表明耐受性可能会渗入到优良种质中而没有生长惩罚。该研究表明，向日葵的主要基因库中存在对极端温度耐受性的广泛遗传变异。