Contrasting warming tolerance and drought resilience in Coffea arabica Castillo and Caturra varieties

Colombia, one of the world’s leading coffee producers, is increasingly threatened by climate change. By 2050, some northern regions are projected to experience higher temperatures and reduced rainfall, posing risks to coffee production. Understanding how different coffee varieties respond to heat and drought is therefore essential for sustaining coffee production in the country. We evaluated the thermotolerance and drought response of two Coffea arabica L. varieties, Castillo and Caturra, under controlled conditions. Thermotolerance was quantified using T 50 , the temperature causing a 50% reduction in the maximum quantum efficiency ( F v / F m ) of photosystem II. Drought response was assessed by withholding water from 18 plants per variety for 27 days (day/night temperatures of 23/19 °C) and comparing them with well-watered controls. We measured leaf water potential ( Ψ L ), gas exchange parameters, and relative growth rates ( RGR ) during drought and after rehydration. Our findings indicate that both varieties showed similar T 50 values (52.6 and 52.5 °C for Castillo and Caturra, respectively), indicating high leaf-level thermotolerance. Under drought, Caturra exhibited earlier stomatal closure, lower photosynthetic rates and reduced RGR , whereas Castillo maintained higher Ψ L and gas exchange parameters for a longer period. After rehydration, both varieties recovered to physiological values comparable to those of control plants, indicating no lasting impairment of hydraulic or photosynthetic function under the conditions evaluated. These results show that, although Castillo and Caturra differ in their drought responses, both possess substantial physiological resilience. This information may help guide varietal selection and management decisions under warmer and drier conditions.