Network-based analysis of oxidative signalling and yield stability in apricot (Prunus armeniaca L.) under postharvest deficit irrigation.

Postharvest water management is a critical yet often overlooked factor in the reproductive sustainability of perennial fruit trees and can influence subsequent-season floral development and yield potential. This study was conducted within a three-year experimental framework under semi-arid orchard conditions in Malatya, Türkiye, in which postharvest irrigation-delay treatments imposed in 2020 and 2021 were evaluated through subsequent reproductive and yield responses recorded in 2021 and 2022. The treatments consisted of irrigation immediately after harvest and irrigation delayed by 10, 20, and 30 days after harvest. To provide an integrated evaluation of treatment responses, complementary multivariate approaches, including Principal Component Analysis (PCA), correlation-based association network analysis, multiple linear regression, and mixed-effects modelling, were used to examine the relationships among biochemical, physiological, reproductive, and yield-related traits. Correlation-based association network analysis identified H₂O₂, MDA, and ABA as central variables within the stress-response association structure. ABA was positioned as an important connecting variable between oxidative stress indicators, stomatal conductance, and reproductive traits, suggesting a coordinated association between biochemical stress responses and reductions in reproductive performance. Shorter irrigation delays, particularly 10 and 20 days, were associated with increased CAT and SOD activities, indicating partial antioxidant adjustment under moderate postharvest water deficit. In contrast, the 30-day irrigation delay was associated with stronger oxidative stress responses, reduced photosynthetic performance, lower flower-quality traits, reduced fruit set, and lower yield. Compared with immediate postharvest irrigation, the 30-day irrigation delay reduced mean yield by 52.7% in the 2021 response season and by 38.8% in the 2022 response season. The regression analysis identified oxidative stress indicators, antioxidant enzyme activities, stomatal conductance, and reproductive traits as yield-associated predictors rather than direct causal regulators. Overall, the findings indicate that yield stability under postharvest irrigation delay is associated with the combined behaviour of oxidative, physiological, and reproductive traits rather than with a single isolated response variable. These results support the importance of timely postharvest irrigation for maintaining subsequent-season reproductive performance in apricots under field conditions.