Analysis of ˈCandidatus Phytoplasma prunorumˈ titer in the tissues of apricot trees (Prunus armeniaca L.) during the year.

This study focused on monitoring ˈCa. P. prunorumˈ detection rate and titer over the course of the year in one-year-old (January-May) or annual shoots (June-December) of apricot trees. As an experimental material, 3 apricot selections (H990/95, H990/177 and H980/74) each represented by 3 trees of the same age grown in the same orchard were selected and analysed monthly. The real- time PCR assay was used for absolute quantification of ˈCa. P. prunorumˈ. The results showed, that phytoplasma was detectable in high rates (above 90 %) from August until December in annual shoots and from January to March and in May in one-year-old shoots. Lower detection rates were observed in April and in June and July, showing, that these months are not reliable for phytoplasma detection. Phytoplasma titer remained the same from January to May in one-year-old shoots. In annual shoots the lowest titers were observed in June, while in the rest of the year, the titers were significantly higher and not differing from the titers in one-year-old shoots collected from January to May. ˈCa. P. prunorumˈ quantification also showed, that H990/95 selection had significantly lower phytoplasma titer than the H990/177 and H980/74 selections. This was also supported by the detection rates and symptoms, where H990/95 selection was showing lower values of these parameters than the rest of the selections.