Identification of phytoplasmas infecting sour cherry in Hungary

In summer 1998 symptoms resembling to phytoplasma infection were observed on Prunus mahaleb cv. Cemany in a stone fruit germplasm in Hungary. Four trees of this rootstock cultivar were sampled: on shoots of three declining plants small leaves, yellows and wilting were seen, while one tree was symptomless. Total nucleic acids, extracted from fresh leaf midribs and phloem tissue from young branches, were used in two different nested-PCR systems. In the first system (System "A"), universal phytoplasma-specific primers, developed from the 16SrDNA region (R16F1/R0, R16F2/R2), were used for general amplification. Two of the three samples from symptomatic plants were positive in these tests. During the nested-PCR assay with group-specific primers [R16(I)F1/R1, R16(III)F1/R1, R16(V)F1/R1, R15(X)F1/R1] fragments were amplified from positive controls as well as from some of the symptomatic P. mahaleb samples. In the second PCR system (system "B"), general primers from the 16SrDNA and spacer region (P1/P7, 16R(7587f)/M23SR(1804r)) were used. The nested reaction provided amplification from two of the symptomatic samples, confirming data obtained with the other PCR system. The symptomless sample and one of the symptom-showing plants were negative. RFLP analyses were carried out on nested-PCR products from both PCR systems in order to confirm the phytoplasma identification at sub-group level. Phytoplasma of 16SrX group, subgroup B (ESFY) and phytoplasma from the aster yellows group (16SrI-B) were identified.