PCR-RFLP and sequence analysis of a non-ribosomal fragment for genetic characterization of European stone fruit yellows phytoplasmas infecting various Prunus species

A 927 bp non-ribosomal fragment was used to assess the genetic variability of the European stone fruit yellows (ESFY) phytoplasma infecting 14 differe nt Prunus species. For this, 175 isolates originating from four different M editerranean countries were tested by PCR-RFLP analysis with seven restrict ion enzymes. No polymorphism among the ESFY phytoplasma could be observed b ut 12 out of 18 restriction sites differed between the homologous fragments of ESFY and apple proliferation (AP) phytoplasmas. An 846 bp fragment of a French ESFY isolate was sequenced, it included the 3'-end of a putative ni troreductase gene, an intergenic region and a truncated open reading frame. This ESFY phytoplasma sequence showed 89.7% identity with the equivalent A P phytoplasma nucleotide sequence (83.9% identity at the amino acid level). The G+C content of the entire sequence was extremely low (15.4%) and A+T-r ich codons were highly preferred in codon usage, in this paper, we report t he presence of the ESFY phytoplasma for the first time in Turkey and in fiv e Prunus hosts never reported previously. Our results also indicate that th e ESFY phytoplasma isolates affecting Various Prunus species are geneticall y homogenous but can be distinguished from the AP phytoplasma. Therefore, t hey are likely to represent different taxons. (C) 2000 Academic Press.