EFFECT OF PLUM POX VIRUS INFECTION ON THE ANTIOXIDANT CAPACITY OF LEAF APOPLAST FROM APRICOT PLANTS

In the apoplastic space from apricot plants, the presence of both p-hydroxy mercury benzoic acid (pHMB)-sensitive and pHMB-insensitive APX, SOD, peroxidase, NADH-POX and PPO was observed. In the susceptible apricot cultivar (‘Real Fino’), a decrease in POX and SOD took place, whereas in the resistant cultivar (‘SEO’) an increase in APX, POX and SOD occurred. These results suggest that, in the apoplastic space, the resistant plants had a higher capability to eliminate AOS than the susceptible cultivar. In both cases, PPO was induced in infected plants, although the increase was much higher in the susceptible plants than in the resistant ones. In susceptible plants, the apoplastic H₂O₂ levels increased nearly 2-fold in infected leaves. This effect was accompanied by an increase in leaf electrolyte leakage. However, in the PPV-resistant cultivar, H₂O₂ levels only increased by 42% and no changes were observed in electrolyte leakage. The results suggest that long-term PPV infection produced an oxidative stress in the apoplastic space only in susceptible apricot plants.