3) Dr. Moshe Dubinin

Citrus fruit cracking is a major cause of yield and quality loss in mandarins, yet its physiological drivers remain poorly understood. This study investigated the relationship between plant water status (PWS) and cracking intensity in a commercial ‘Ori’ orchard in Israel over two contrasting seasons: a milder “off” year (2023) and a hotter, stress-intensified “on” year (2024). Seventy-two trees under four irrigation regimes were monthly monitored for trunk growth rate (TGR), stem water potential (SWP), stomatal conductance (SC), and plant area index (PAI) using dendrometers, pressure chambers, porometers, and SunScan measurements, respectively. Monthly UAV flights provided multispectral, thermal, and LiDAR data, integrated with meteorological and soil moisture records. Random forest models predicted PWS indicators with high accuracy (R²Pred = 0.80 for TGR; 0.76 for SWP; 0.74 for SC) and reliably explained both yield (R²Pred = 0.88) and fruit cracking (R²Pred = 0.86). Mid-season PWS indicators, particularly SWP, SC, and PAI during July and September, emerged as the strongest predictors of orchard outcomes. Cluster analysis further revealed seasonal contrasts: in 2023, high yields were attainable with only moderate cracking, whereas in 2024, frequent heatwaves, coupled with high growth and conductance, drove elevated cracking despite higher rainfall and irrigation inputs. The integration of UAV-based thermal, optical, and LiDAR data with ground-based PWS monitoring demonstrates that cracking risk is governed by dynamic water status fluctuations and atmospheric demand, rather than irrigation dose alone. This multi-sensor, tree-resolved framework provides a novel and scalable foundation for precision irrigation, emphasizing the importance of stabilizing mid-season PWS to balance productivity and fruit quality. By explicitly linking physiological indicators, fruit outcomes, and irrigation regimes, the study advances understanding of citrus cracking and offers a transferable approach for managing water stress and fruit disorders in perennial orchards under climate variability.