Vegetative Growth, Flowering, and Physiological Parameters of Young Avocado ‘Hass’ and ‘Hass’-Like Cultivars Under Extreme Weather Conditions

Extreme climate events may damage foliage, floral buds, flowers, and fruit, reducing avocado yields and limiting its geographical distribution and expansion. This study evaluates the performance of young “Hass” and “Hass”-like (“Gem,” “BL122” [“BL”] and “Maluma”) avocado cultivars under extreme weather conditions. Over the two years of the experiment (2021–2023), trees experienced severe frost and heat events, with temperatures ranging from −2.49°C to 45.3°C. “Gem” trees exhibited superior frost tolerance, sustaining significantly less floral bud damage than other cultivars. Both “Gem” and “BL” consistently showed higher CO2 assimilation, stomatal conductance, and Fv/Fm values during the winter than “Maluma,” suggesting better resilience to cold stress. In contrast, “Maluma” exhibited the highest flowering intensity despite greater frost damage to floral buds. Under extreme heat conditions, “Gem” and “BL” performed better than “Hass” and “Maluma,” with higher CO₂ assimilation and stomatal conductance observed following heat events. In addition, “BL” maintained the highest chlorophyll content throughout the study, suggesting better adaptation to adverse conditions. This study highlights the potential of “Gem” and “BL” as resilient alternatives to “Hass” in extreme climates, emphasizing the importance of cultivar selection and adaptive management strategies for sustainable avocado production under changing environmental conditions.