Physical map of the chromosome of the apple proliferation phytoplasma

A physical map of the apple proliferation phytoplasma strain AT chromosome was constructed from genomic DNA extracted from diseased tobacco plants. Th e map was generated with single and double digestions of the chromosome wit h BssHII, SmaI, MluI, and ApaI restriction endonucleases and resolving the fragments by pulsed-field gel electrophoresis. Partial digestion and Southe rn blot analysis were used to assist in the arrangement of the 14 contiguou s restriction fragments obtained. From the restriction fragments generated by double digestions, the size of the circular chromosome was calculated to be approximately 645 kb. Locations of the two rRNA operons, the operon inc luding the fus and tuf genes, and three other genes were placed on the map. Genome sizes and BssHII restriction profiles of apple proliferation strain AP15 and the pear decline and European stone fruit yellows phytoplasmas we re different from that of strain AT.