Detection of Plum pox virus and Characterization of Oxidative Stress Responses in Stone Fruit Trees of Azerbaijan

Sharka disease, induced by the Plum pox virus (PPV; genus Potyvirus, family Potyviridae), represents one of the most serious viral threats to stone fruit production worldwide. This study assessed PPV occurrence in major fruit-growing areas in Azerbaijan and characterized the physiological and oxidative stress responses of infected Prunus species. Symptomatic leaves from orchards in the Quba district were screened by immunochromatographic strips, DAS-ELISA, and RT-PCR. Of 60 trees surveyed, 22 (36.7%) tested positive across all three hosts, confirmed by RT-PCR amplification of a 243 bp coat protein (CP) gene fragment in peach (Prunus persica L.), plum (P. domestica L.), and apricot (P. armeniaca L.). Infection was associated with pronounced oxidative stress: hydrogen peroxide (H2O2) and malondialdehyde (MDA) contents were higher in infected trees (6.80–10.60 µmol g−1 FW and 8.0–15.2 nmol g−1 FW) than in healthy trees (3.20–3.90 µmol g−1 FW and 4.5–8.2 nmol g−1 FW). Antioxidant defenses were activated, with increased ascorbate peroxidase (APX) and catalase (CAT) activities and higher ascorbic acid (AsA) and reduced glutathione (GSH) levels. Photosynthetic performance declined markedly: total chlorophyll fell by 17.3–30.8% (greatest in apricot), maximum photosystem II quantum efficiency (Fv/Fm) was lower in infected trees (0.408–0.561) than in healthy trees (0.716–0.728), and total soluble protein was lower in infected trees (7.88–8.45 mg g−1 FW) than in healthy trees (9.38–9.58 mg g−1 FW). Collectively, PPV infection was associated with oxidative stress and lipid peroxidation, with activation of enzymatic and non-enzymatic antioxidant defenses, and with reduced photosynthetic performance in Prunus species. These findings advance understanding of host responses to PPV and support sustainable monitoring and management strategies for stone fruit production, aligned with SDG 2 (Zero Hunger) and SDG 15 (Life on Land).