Use of real-time PCR for the characterization of variable symptoms in ESFY phytoplasma disease

'Candidatus phytoplasma prunorum', known as ESFY phytoplasma, is the agent of apricot and peach illness, with very variable symptoms. Symptom variability depends on cultivar, type of rootstock and especially on virulence and concentration of the pathogen. In this experiment a long term monitored set of 12 trees was selected for their symptoms variability and indicated by ESFY phytoplasma. The aim of the work was to find the concentration of phytoplasmatic DNA at 24 samples (taken from leaf petioles and from phloem) and finding correlation between type and intensity of symptomatic effect and concentration. The results clearly show that the concentration of pathogenic DNA is 1.36x higher in herbaceous parts - petioles - than in phloem. Generally, the highest concentration was detected in the samples taken from the trees with symptoms of chlorotic leaf roll, average 1.6x10(5) copies mu L-1 in the samples taken from phloem and 2.1x10(5) copies mu L-1 in the samples taken from petioles. The lowest concentration was in the samples from the tree with symptoms of leaf roll (beginning infection ESFY). The sample taken from the tree with latent infection had a 22.7% lower concentration of phytoplasmatic DNA than average sample (in the case of DNA isolated from petiole). Results also show that in case of the 'Poyer' tree cultivar with latent infection there may be an infection with hypovirulent strains or it is a tolerant genotype to ESFY phytoplasma.