Cultivar-Dependent Physiological and Reproductive Responses of Mature Avocado Trees under Mediterranean Weather Extremes: A Three-Year Field Study

Abstract Background- Extreme weather events increasingly threaten avocado production, yet it remains unclear whether cultivar-dependent differences in physiological responses are accompanied by differences in reproductive survival and subsequent yield under field conditions. We therefore evaluated the physiological and reproductive responses of mature ‘Hass’, ‘BL122’ (‘BL’), ‘Gem’, and ‘Maluma’ avocado trees during a three-year field study under naturally occurring Mediterranean weather extremes in northern Israel. Results- During the study period, the orchard experienced substantial environmental variation, including a severe frost event in February 2025, when air temperature fell to − 3.47°C and remained below 0°C for approximately 10 h, and episodes of extreme summer heat, with a maximum air temperature of 47.2°C. Following the severe frost event, floral bud damage reached 88% in ‘Hass’ and 95% in both ‘BL’ and ‘Maluma’, whereas ‘Gem’ sustained significantly lower damage, with 57% injured buds. Cultivar × season interactions were significant for flowering intensity and all productivity traits. Following the frost, ‘Gem’ showed significantly higher flowering intensity and produced 37.7 kg fruit tree⁻¹, whereas yields of ‘Hass’, ‘BL’, and ‘Maluma’ remained below 2.2 kg tree⁻¹. Physiological responses varied significantly among sampling dates, with significant cultivar × sampling date interactions for CO₂ assimilation, stomatal conductance, Fv/Fm, and CCI. ‘Gem’ maintained relatively high gas-exchange values on several sampling dates, including after the frost event. Fv/Fm reached its lowest values following the frost but recovered to approximately 0.82–0.85 across all cultivars by May 2025, despite pronounced differences in subsequent reproductive performance among cultivars. ‘BL’ frequently showed a higher chlorophyll content index and produced large fruit, but these traits were not accompanied by high post-frost yield. Conclusions- Overall, the results reveal substantial cultivar-dependent differences in reproductive resilience following the severe frost event, with ‘Gem’ showing the greatest post-frost flowering intensity and yield among the evaluated cultivars. In contrast, the recovery of physiological indicators did not consistently parallel reproductive recovery across cultivars. These findings highlight the importance of integrating physiological and reproductive responses when evaluating cultivar resilience to extreme weather under field conditions.