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Objectives: Spiroplasma citri is a bacterium with a wide host range and is the causal agent of citrus stubborn and brittle root diseases of citrus and horseradish, respectively. S. citri is transmitted in a circulative, persistent manner by the beet leafhopper, Neoaliturus (Circulifer) tenellus (Baker), in North America. Five strains of S. citri were cultured from citrus, horseradish, and N. tenellus from different habitats and times. DNA from cultures were sequenced and genome assembled to expand the database to improve detection assays and better understand its genetics and evolution., Data Description: The whole genome sequence of five strains of S. citri are described herein. The S. citri chromosome was circularized for all five strains and ranged from 1,576,550 to 1,742,208 bp with a G + C content of 25.4-25.6%. Characterization of extrachromosomal DNAs resulted in identification of one or two plasmids, with a G + C content of 23.3 to 27.6%, from plant hosts; and eight or nine plasmids, with a G + C content of 21.65 to 29.19%, from N. tenellus. Total genome size ranged from 1,611,714 to 1,832,173 bp from plants and 1,968,976 to 2,155,613 bp from the leafhopper. All sequence data has been deposited in DDBJ/ENA/GenBank under the accession numbers CP046368-CP046373 and CP047426-CP047446.

A disease with symptoms similar to elm yellows (EY) was noticed in the early 1990s in suburban Chicago, IL. More than 1,000 mature American elms (Ulmus americana) have since died. Infected trees varied in the incidence and severity of canopy yellowing, leaf epinasty, butterscotch discoloration, and wintergreen odor of the phloem, but all developed a sparse and clumpy crown, uniformly necrotic phloem, and died within 2 years of showing canopy symptoms. Because symptoms were expressed irregularly and phytoplasma detection results by a commercial diagnostic company were inconsistent, a study was initiated to determine if EY phytoplasma was the causal agent. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) methods using universal or EY phytoplasma specific primers were employed to detect putative phytoplasma(s) associated with 10 trees of varied disease severity within the outbreak region and 10 asymptomatic trees from an uninfected area (controls). Nested PCR using universal primers revealed that 90% of trees from the outbreak region were positive for phytoplasma while asymptomatic elms from another location (controls) tested negative. Phytoplasma-positive trees ranged in disease severity from 1 (asymptomatic) to 5 (near death). Inner bark samples chiseled from the lower trunk had higher phytoplasma detection rates than foliage or drill shavings. RFLP analyses and DNA sequencing of 16S rDNA indicated that the phytoplasma recovered from dying elms in Arlington Heights is not related to the reference EY phytoplasma (group16SrV). It is most closely related to clover proliferation (CP) phy-toplasma (group 16SrVI), and we have designated it Illinois Elm Yellows (ILEY) phytoplasma, and assigned it to a new taxonomic subgroup (16SrVI-C). EY phytoplasma was not detected in any samples, but two ILEY phytoplasma positive trees also were positive for aster yellows (AY) phytoplasma. ILEY phytoplasma was not detected in local leafhopper populations trapped in elm trees between May and September 2000. This is the first report of a phytoplasma related to CP phytoplasma causing elm yellows disease symptoms.