Basappa Adi

Local olive germplasm of the southern Levant includes wild populations of Olea europaea var. sylvestris and traditional cultivars that are believed to be well-adapted to the region’s arid and variable climate. In this study, we evaluated the drought response of the Barnea cultivar, two local traditional cultivars (MLL1 and MLL7), and var. sylvestris by applying controlled irrigation at three evapotranspiration (ETa) levels: 100%, 33%, and 10%. Physiological measurements—including stomatal conductance, relative water content, stem water potential, and net photosynthesis—revealed that Barnea exhibited the strongest negative response to water stress, while MLL1, MLL7, and sylvestris maintained more stable performance. Under full irrigation (100% ETa), MLL1 showed significantly higher net photosynthesis than MLL7, supporting its historical dominance in traditional orchards as the widely cultivated Souri cultivar, while MLL7 remains rare due to lower productivity. Beyond drought tolerance, chilling requirements also influence cultivar suitability under changing climates. Our findings suggest that MLL7 has a lower chilling requirement compared to MLL1 and Barnea, which may allow it to flower successfully under warmer winter conditions. To explore the molecular basis of this trait, transcriptomic analysis is underway using floral buds collected at different chilling stages from MLL7 and MLL1 to identify differentially expressed genes associated with low chilling requirements. This integrated approach combining physiological traits and gene expression profiling emphasizes the adaptive potential of southern Levantine olive germplasm and supports its use in breeding programs aimed at improving resilience to both drought and insufficient winter chilling under future climate scenarios.