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Detection and Identification of ÔCandidatus Phytoplasma prunorumÕ, ÔCandidatus Phytoplasma maliÕ and ÔCandidatus Phytoplasma pyriÕ in Stone Fruit Trees in Poland Miros irosŁawa awa Cieslinska ieśliń ska and Halina alina Morgas orgaś Abstract A survey was made to determine the incidence of phytoplasmas in 39 sweet and sour cherry, peach, nectarine, apricot and plum commercial and experimental orchards in seven growing regions of Poland. Nested polymerase chain reaction (PCR) using the phytoplasmauniversal primer pairs P1 ⁄ P7 followed by R16F2n ⁄ R16R2 showed the presence of phytoplasmas in 29 of 435 tested stone fruit trees. The random fragment length polymorphism (RFLP) patterns obtained after digestion of the nested PCR products separately with RsaI, AluI and SspI endonucleases indicated that selected Prunus spp. trees were infected by phytoplasmas belonging to three different subgroups of the apple proliferation group (16SrX-A, -B, -C). Nucleotide sequence analysis of 16S rDNA fragment amplified with primers R16F2n ⁄ R16R2 confirmed the PCR ⁄ Restriction Fragment Length Polymorphism (RFLP) results and revealed that phytoplasma infecting sweet cherry cv. Regina (Reg), sour cherry cv. Sokowka (Sok), apricots cv. Early Orange (EO) and AI ⁄ 5, Japanese plum cv. Ozark Premier (OzPr) and peach cv. Redhaven (RedH) was closely related to isolate European stone fruit yellows-G1 of the ÔCandidatus Phytoplasma prunorumÕ (16SrX-B). Sequence and phylogenetic analyses resulted in the highest similarity of the 16S rDNA fragment of phytoplasma from nectarine cv. Super Queen (SQ) with the parallel sequence of the strain AP15 of the ÔCandida-tus Phytoplasma maliÕ (16SrX-A). The phytoplasma infecting sweet cherry cv. Kordia (Kord) was most similar to the PD1 strain of the ÔCandidatus Phytoplasma pyriÕ (16SrX-C). This is the first report of the occurrence of ÔCa. P. prunorumÕ, ÔCa. P. maliÕ and ÔCa. P. pyriÕ in naturally infected stone fruit trees in Poland.

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