Attività di perossidasi di superficie e via delle ossilipine in piante di melo soggette a recovery da fitoplasmosi

Apple trees (Malus domestica Borkh) may be affected by apple proliferation (AP), caused by ‘Candidatus Phytoplasma mali’. Some plants can spontaneously recover from the disease, which implies the disappearance of symptoms through a phenomenon known as recovery. Recovered apple trees show the disappearance of the symptoms and pathogens from the canopy, but not from the infected roots, where phytoplasmas persist viable and infectious. Recovery of apple plants is linked to an overproduction of hydrogen peroxide in the phloem tissues. The high levels of hydrogen peroxide in the canopy of recovered apple plants could have a direct antimicrobial effect on pathogens and/or a signalling function, in order to activate defence responses triggered by the phytormones jasmonate and salicylate. In general, it can be stated that salicylate promotes resistance against biotrophic pathogens, whereas the jasmonate pathway induces resistance against necrotrophic pathogens and herbivorous insects. Apple plants, infected by AP-disease, initially show an induced mechanism of defence mediated by salicylate but, subsequently, during the recovery, an increase of jasmonate, sinthesized by the oxylipin pathway, occurs.