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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.

Two fungi associated with bark beetles, Graphium pseudormiticum (described in 1994) and Rhexographium fimbriisporum (described in 1995), have two micromorphological characters in common. Both species produce conidia with conspicuous basal frills, and the conidia align in chains, despite being produced in slime. The association of G. pseudormiticum with the pine bark beetle, Orthotomicus erosus, and the association of R. fimbriisporum with the spruce bark beetle, Ips typographus, suggest ecological differences between the two fungal species. Analyses of micromorphology and phylogenetic analyses of aligned 18S and ITS sequences suggest that these two species are congeneric and should be classified in Graphium but that they represent distinct species. A collection of strains tentatively identified as Graphium spp., isolated from Ips typographus on Picea abies, Ips cembrae on Larix decidua and Tomicus minor on Pinus sylvestris in Austria share the same unusual basal conidial frills and conidial chains. Isolates from spruce were identified as G. fimbriisporum and those from pine as G. pseudormiticum. The strains from Ips cembrae on Larix decidua, distinguished by the reddish color of their colonies, microscopic structures and molecular characteristics, are described as the new species Graphium laricis sp. nov., and the close relationship of this species with the other two species is confirmed.

Species of Leptographium Lagerberg & Melin are characterized by mononematous conidiophores with dark stipes and conidiogenous apparatuses with complex series of branches. These fungi generally inhabit woody substrates, are associated with bark beetles (Coleoptera: Scolytidae) and cause blue-stain in conifers. Few phylogenetic studies have been conducted on Leptographium species, and those that have been undertaken have been focused on a small number of species. The objective of this study was to investigate the phylogenetic relationships among species in Leptographium based on partial DNA operon sequences and to ascertain whether morphological characters are congruent with DNA-based phylogeny. Morphological characters were analyzed and compared with results from DNA sequence analysis. Results indicate that there are three groups within Leptographium based on DNA sequence analysis. There was, however, no congruence between these groups and those emerging from morphological characters. Data from this study strongly support the connection between Leptographium and Ophiostoma Sydow & Sydow. They also provide us with an objective means to confirm the identity of many Leptographium species that are difficult to distinguish based on morphological characters.Key words: Leptographium, phylogeny, morphology, Ophiostoma, rRNA.