Discussion
Although the phytoplasmas ´Candidatus Phytoplasma mali´,
´Ca. P. prunorum´ and ´Ca. P. pyri´ belong to the same
16SrX group their pathogenicity is quite different in their respective
host plants Malus domestica (apple), Prunus persica(peach) and Pyrus communis (pear). Apple trees can survive a
phytoplasma infection for decades whereas phytoplasma-infected peach and
pear trees often die after some weeks (quick decline of pear) to a few
years (Fiore et al., 2019; Marcone et al., 2010; Marcone & Rao
2019; Seemüller et al., 1986, 2018). This indicates that the M.
domestica /´Ca. Phytoplasma mali´-system is more adapted and
balanced in their interaction than P. persica /´Ca. P.
prunorum´ and P. communis /´Ca. P. pyri´ pointing to a
higher tolerance and survival rate for phytoplasma-infected apple. We
collected an extensive set of data (summarized in Table 3) to elucidate
anatomical and physiological responses of each plant species to a
phytoplasma infection, supporting a co-evolutionary impact.