Preliminary results on identification of molecules induced in apricot trees after ESFY phytoplasma inoculation by grafting.

To identify early 'sentinel' molecules involved in the host-pathogen interaction between apricot plants and European Stone Fruit Yellows (ESFY) phytoplasma, three experiments have been performed. Eighteen trees, of eight apricot varieties grafted on Myrobalan, and maintained under insect-proof environment were patch-grafted four years ago with tissue infected by ESFY phytoplasma. As only some trees belonging to four varieties resulted infected, the healthy plants belonging to the others varieties were patch-grafted again and the plant phenolic composition was carefully monitored. After the second inoculation, all varieties resulted infectible by phytoplasmas. The qualitative and quantitative composition of the phenolic fraction in leaves harvested from all plants of four varieties ('Amal', 'Harogem', 'Baracca' and 'Brusca') was examined by means of HPLC UV-DAD analysis in order to evaluate if pre-existing or induced phenolic compounds are involved in the plant defence mechanism. The plants positive and negative to molecular test, did not show differences in accordance with the tolerance showed by all varieties. Twenty plants of four rootstocks were patch grafted with apricot and plum phytoplasma-infected trees. Yellowing and general stunting were recorded in different percentages on plants belonging to all four kinds of rootstock.