Plant material and phytoplasma inoculation
Apple trees (Malus domestica ) cv. ‘Gala Royal’ were grown on
clonal rootstock cv. ‘M9’ (non-infected control, n=14), pear trees
(Pyrus communis L.) cv. ‘Williams Christ’ were grown on cv.
’Kirchensaller Mostbirne’ rootstocks (non-infected control, n=5), and
peach trees (Prunus persica (L.) cv. ‘South Haven’ were grown on
peach seedlings cv. ‘Montclar’ (non-infected control, n=4). Plants were
inoculated by grafting of two buds from trees infected with the
respective phytoplasmas. Apple trees were infected with a virulent
accession (3/6, n=13) in 2017 (Seemüller et al., 2010, 2011, 2013). Pear
trees were infected with ’Ca. P. pyri’ (PD-W, n=5) in 2012. Peach
trees were infected with ’Ca. P. prunorum’ (ESFYQ06, n=4) in
2017. Experiments with pear and peach trees were conducted in 2018.
Apple trees were investigated in 2019. All plants were grown under
natural conditions in an insect safe environment.