Detection and characterization of phytoplasmas infecting fruit plants in Poland

Abstract: Plants of strawberry, raspberry, blackberry and hybrids of the Rubus species, sweet cherry, sour cherry, plum, peach, apricot, nectarine, apple and hazelnut growing in the orchards, on commercial, experimental, and amateur plantations located in various regions of the country were the research objects. Phytoplasma identification and classification was based on the PCR/RFLP analysis of 16S rRNA gene. It was shown that the tested fruit plant species were infected by phytoplasmas classified into four 16Sr groups. Most positively tested stone fruit trees (cherry plum, peach, apricot, nectarine) were infected with ‘Candidatus Phytoplasma prunorum’ belonging to the subgroup B of the apple proliferation phytoplasma group (16SrX-B). In individual nectarine and sweet cherry trees apple proliferation phytoplasma (‘Ca. P. mali’, 16SrX-A) and pear decline phytoplasma (‘Ca. P. pyri’, 16SrX-C) were identified, respectively. Two phytoplasmas were associated with witches-broom disease of apple trees: ‘Ca. P. mali’ and ‘Ca. P. asteris’ classified in subgroup B of the aster yellows (AY) phytoplasma group (16SrI-B). In the course of the research ‘Ca. P. asteris’ was also identified in hazel, and blackberry plants. Most positively tested Rubus species plants were infected by rubus stunt phytoplasma (‘Ca. P. rubi’) classified in elm yellows group (16SrV), but phytoplasma belonging to X-disease group (16SrIII), less-known in the horticultural crops in Europe, was detected in Rubus hybrid loganobaccus plant.