A chromosome map of the European stone fruit yellows phytoplasma.

A physical map of the European stone fruit yellows phytoplasma strain GSFY1 chromosome was constructed using PFGE-purified genomic DNA from diseased tobacco and tomato plants. The map was generated with single and double digestions of the chromosome with SmaI, BssHII, ApaI, BamHI and XhoI restriction endonucleases and the fragments were resolved by PFGE. Reciprocal double digestions were used to locate 26 restriction sites on the chromosome. Southern blot analysis was also used to assist in the arrangement of the contiguous restriction fragments obtained. From the restriction fragments generated by double digestion, the circular chromosome was calculated to be approximately 635 kb. Loci of two rRNA operons, the operon containing the tuf gene, genes encoding an immunodominant membrane protein and a putative nitroreductase, and randomly cloned DNA fragments IH184 and AT67 were placed on the map. Digestion of chromosomal DNA of strain GSFY1 with MluI gave a complex restriction pattern, suggesting that this isolate consists of a population with heterogeneity with respect to MluI restriction sites. The GSFY1 physical map was different from that of the closely related apple proliferation phytoplasma but the genetic arrangement was similar.