An expanded concept of Ceratocystis manginecans and five new species in the Latin American clade of Ceratocystis

The genus Ceratocystis contains a number of emerging plant pathogens, mostly members of the Latin American Clade (LAC), in which there are several unresolved taxonomic controversies. Among the most important are Brazilian pathogens in the C. fimbriata complex, C. manginecans and C. eucalypticola. Representatives of C. manginecans and C. eucalypticola from India and China, respectively, were shown to be fully interfertile in laboratory matings, and hybrids between the putative species were identified on Punica in India. An Indian tester strain was sexually compatible with representatives of what has been considered C. fimbriata on numerous hosts across Brazil. In this revision of the LAC, the name C. fimbriata is restricted to the widely dispersed Ipomoea strain, and C. manginecans is recognized as a Brazilian species that is important on Mangifera, Eucalyptus, and many other crops. C. mangivora and C. mangicola are also considered synonyms of C. manginecans. Based on phylogenetics and mating studies, two other Brazilian species are recognized: C. atlantica, sp. nov., and C. alfenasii, sp. nov., each with wide host ranges. Three new Caribbean species are recognized based on phylogenetics and earlier inoculation studies: C. costaricensis, sp. nov., on Coffea, C. cubensis, sp. nov., on Spathodea, and C. xanthosomatis, sp. nov., on the vegetatively propagated aroids Xanthosoma and Syngonium. Some of the other Ceratocystis species were based primarily on unique internal transcribed spacer (ITS) rDNA sequences, but the unreliability of rDNA sequences was demonstrated when intraspecific crossing of isolates with differing ITS sequences generated single-ascospore progeny with intragenomic variation in ITS sequences and others with new ITS sequences. Species recognition in Ceratocystis should use phenotype, including intersterility tests, to help identify which lineages are species. Although some species remain under-studied, we recognize 16 species in the LAC, all believed to be native to Latin America, the Caribbean region, or eastern USA.

Phylogenetic analyses allow species-level recognition of Leptographium wageneri varieties that cause black stain root disease of conifers in western North America

Leptographium wageneri is a native fungal pathogen in western North America that causes black stain root disease (BSRD) of conifers. Three host-specialized varieties of this pathogen were previously described: L. wageneri var. wageneri on pinyon pines (Pinus monophylla and P. edulis); L. wageneri var. ponderosum, primarily on hard pines (e.g., P. ponderosa, P. jeffreyi); and L. wageneri var. pseudotsugae on Douglas-fir (Pseudotsuga menziesii). Morphological, physiological, and ecological differences among the three pathogen varieties have been previously determined; however, DNA-based characterization and analyses are needed to determine the genetic relationships among these varieties. The objective of this study was to use DNA sequences of 10 gene regions to assess phylogenetic relationships among L. wageneri isolates collected from different hosts. The multigene phylogenetic analyses, based on maximum likelihood and Bayesian inference, strongly supported species-level separation of the three L. wageneri varieties. These results, in conjunction with previously established phenotypic differences, support the elevation of L. wageneri var. ponderosum and L. wageneri var. pseudotsugae to the species level as L. ponderosum comb. nov. and L. pseudotsugae comb. nov., respectively, while maintaining L. wageneri var. wageneri as Leptographium wageneri. Characterization of the three Leptographium species, each with distinct host ranges, provides a baseline to further understand the ecological interactions and evolutionary relationships of these forest pathogens, which informs management of black stain root disease.

Recent and Ongoing Horizontal Transfer of Mitochondrial Introns Between Two Fungal Tree Pathogens

Two recently introduced fungal plant pathogens (Ceratocystis lukuohia and Ceratocystis huliohia) are responsible for Rapid ‘ōhi‘a Death (ROD) in Hawai‘i. Despite being sexually incompatible, the two pathogens often co-occur in diseased ‘ōhi‘a sapwood, where genetic interaction is possible. We sequenced and annotated 33 mitochondrial genomes of the two pathogens and related species, and investigated 35 total Ceratocystis mitogenomes. Ten mtDNA regions [one group I intron, seven group II introns, and two autonomous homing endonuclease (HE) genes] were heterogeneously present in C. lukuohia mitogenomes, which were otherwise identical. Molecular surveys with specific primers showed that the 10 regions had uneven geographic distribution amongst populations of C. lukuohia. Conversely, identical orthologs of each region were present in every studied isolate of C. huliohia regardless of geographical origin. Close relatives of C. lukuohia lacked or, rarely, had few and dissimilar orthologs of the 10 regions, whereas most relatives of C. huliohia had identical or nearly identical orthologs. Each region included or worked in tandem with HE genes or reverse transcriptase/maturases that could facilitate interspecific horizontal transfers from intron-minus to intron-plus alleles. These results suggest that the 10 regions originated in C. huliohia and are actively moving to populations of C. lukuohia, perhaps through transient cytoplasmic contact of hyphal tips (anastomosis) in the wound surface of ‘ōhi‘a trees. Such contact would allow for the transfer of mitochondria followed by mitochondrial fusion or cytoplasmic exchange of intron intermediaries, which suggests that further genomic interaction may also exist between the two pathogens.

Corticioid basidiomycetes associated with bark beetles, including seven new Entomocorticium species from North America and Cylindrobasidium ipidophilum, comb. nov

Seven new Entomocorticium species (Peniophoraceae) are described based on morphology and phylogenetic analyses. Along with the type species (E. dendroctoni), Entomocorticium comprises eight species of nutritional symbionts of pine bark beetles in North America. Entomocorticium cobbii is the mycangial associate of the southern pine beetle, Dendroctonus frontalis, and E. parmeteri is the mycangial associate of the western pine beetle, D. brevicomis. Entomocorticium whitneyi, E. portiae, E. kirisitsii, E. oberwinkleri and the previously described E. dendroctoni have been isolated from galleries of D. ponderosae and D. jeffreyi in western North America. Entomocorticium sullivanii forms an ambrosia-like layer of basidia and basidiospores in the pupal chambers of Ips avulsus in the southeastern USA. Entomocorticium is phylogenetically placed within Peniophora, a corticioid genus of wood decay fungi with wind-dispersed basidiospores. At least four species of Entomocorticium produce basidiospores on basidia with reduced sterigmata that apparently do not forcibly discharge basidiospores. Another basidiomycete, Gloeocystidium ipidophilum, was described from Ips typographus galleries in Europe, but it is phylogenetically and taxonomically placed in another genus of wood decay fungi as Cylindrobasidium ipidophilum (Physalacriaceae). The free-living wood-decay fungus Phlebiopsis gigantea (Phanerochaetaceae) has been occasionally associated with bark beetles but is unrelated to C. ipidophilum or Entomocorticium.

Pathogenicity, Symptom Development, and Colonization of Metrosideros polymorpha by Ceratocystis lukuohia

Extensive mortality of Metrosideros polymorpha (`ōhi`a) trees has been associated with Ceratocystis spp. on Hawai`i Island and was named rapid `ōhi`a death (ROD). Both C. lukuohia and C. huliohia have been associated with ROD, although C. lukuohia appears to be the more important pathogen. Crown observations and dissections of forest trees either wound-inoculated with, or naturally infected by, C. lukuohia were conducted to confirm pathogenicity and document patterns of host colonization. In pathogenicity trials, one of three and two of three trees inoculated with the fungus in February and August, respectively, exhibited crown wilt symptoms at 92 and 69 days after inoculation. Extensive, radial, black staining of the sapwood was found in main stems, while no crown wilt or xylem staining was found in control trees. Xylem staining, necrotic phloem, and fungus presence was noted in six trees inoculated in May to June and harvested 37 to 42 days later, and these observations were compared with those in two naturally infected trees felled in early August. Contiguous xylem staining was found in the main stems and into crowns of all diseased trees, while discontinuous streaks of xylem staining extended into the main forks and side branches. Necrotic phloem associated with xylem staining occurred on the lower stems of inoculated trees. Aside from the necrotic phloem and radial staining of the sapwood, symptom development in `ōhi`a infected with C. lukuohia is similar to other systemic wilt diseases on hardwood trees. We propose Ceratocystis wilt of `ōhi`a as the official name of the disease.

Four mycangium types and four genera of ambrosia fungi suggest a complex history of fungus farming in the ambrosia beetle tribe Xyloterini

Ambrosia beetles farm fungal cultivars (ambrosia fungi) and carry propagules of the fungal mutualists in storage organs called mycangia, which occur in various body parts and vary greatly in size and complexity. The evolution of ambrosia fungi is closely tied to the evolution and development of the mycangia that carry them. The understudied ambrosia beetle tribe Xyloterini included lineages with uncharacterized ambrosia fungi and mycangia, which presented an opportunity to test whether developments of different mycangium types in a single ambrosia beetle lineage correspond with concomitant diversity in their fungal mutualists. We collected representatives of all three Xyloterini genera (Trypodendron, Indocryphalus, and Xyloterinus politus) and characterized their ambrosia fungi in pure culture and by DNA sequencing. The prothoracic mycangia of seven Trypodendron species all yielded Phialophoropsis (Microascales) ambrosia fungi, including three new species, although these relationships were not all species specific. Indocryphalus mycangia are characterized for the first time in the Asian I. pubipennis. They comprise triangular prothoracic cavities substantially smaller than those of Trypodendron and unexpectedly carry an undescribed species of Toshionella (Microascales), which are otherwise ambrosia fungi of Asian Scolytoplatypus (Scolytoplatypodini). Xyloterinus politus has two different mycangia, each with a different ambrosia fungus: Raffaelea cf. canadensis RNC5 (Ophiostomatales) in oral mycangia of both sexes and Kaarikia abrahamsonii (Sordariomycetes, genus incertae sedis with affinity for Distoseptisporaceae), a new genus and species unrelated to other known ambrosia fungi, in shallow prothoracic mycangia of females. In addition to their highly adapted mycangial mutualists, Trypodendron and X. politus harbor a surprising diversity of facultative symbionts in their galleries, including Raffaelea. A diversity of ambrosia fungi and mycangia suggest multiple ancestral cultivar captures or switches in the history of tribe Xyloterini, each associated with unique adaptations in mycangium anatomy. This further supports the theory that developments of novel mycangium types are critical events in the evolution of ambrosia beetles and their coadapted fungal mutualists.

Taxonomic revision and multi-locus phylogeny of the North American clade of Ceratocystis

The North American clade (NAC) of Ceratocystis includes pathogenic species that infect a wide range of woody hosts. Previous phylogenetic analyses have suggested that this clade includes cryptic species and a paraphyletic C. variospora. In this study, we used morphological data and phylogenetic analyses to characterize NAC taxa, including Ceratocystis isolates causing a serious disease of almond trees in California. Phylogenetic analyses based on six gene regions supported two new species of Ceratocystis. Ceratocystis destructans is introduced as the species causing severe damage to almond trees in California, and it has also been isolated from wounds on Populus and Quercus in Iowa. It is morphologically similar to C. tiliae, a pathogen on Tilia and the most recently characterized species in the NAC. Ceratocystis betulina collected from Betula platyphylla in Japan is also newly described and is the sister taxon to C. variospora. Our six-locus phylogenetic analyses and morphological characterization resolved several cryptic species in the NAC.

A host specialized form of Ceratocystis fimbriata causes seed and seedling blight on native Carapa guianensis (andiroba) in Amazonian rainforests

Ceratocystis fimbriata Ellis & Halsted recently was recorded causing seed and seedling blight on Carapa guianensis Aubl. (andiroba), a tree species native to the Amazon Rainforest and prized for its valuable timber and medicinal seed oil. C. fimbriata more commonly causes wilt type diseases in woody hosts, especially on non-native host trees. However, on andiroba the disease occurs on seedlings and seeds, affecting the species regeneration. We studied 73 isolates of C. fimbriata on andiroba from three regions of the Amazon Basin to see if they represented natural or introduced populations. Analysis of ITS rDNA sequences and phylogenetic analysis of mating type genes revealed new haplotypes of C. fimbriata from the Latin American Clade that were closely related to other Brazilian populations of the fungus. In mating experiments, andiroba isolates were inter-fertile with tester strains of C. fimbriata from Brazil and elsewhere, confirming that they belong to a single biological species. Using microsatellite markers, 14 genotypes and populations with intermediate levels of genetic variability were found, suggesting that the fungus is indigenous to the Amazon Basin. Inoculation tests indicated that the andiroba isolates are host-specialized on andiroba, supporting the proposition of the special form C. fimbriata f. sp. carapa.

New Meredithiella species from mycangia of Corthylus ambrosia beetles suggest genus-level coadaptation but not species-level coevolution

Meredithiella norrisii (Microascales, Ceratocystidaceae) is an ambrosia fungus carried in mycangia of the North American ambrosia beetle, Corthylus punctatissimus. Reports on the identity of the fungal symbionts of other species of Corthylus have been inconsistent. This study tested the hypothesis that Meredithiella spp. are the primary symbionts of Corthylus spp. Cultures and/or internal transcribed spacer (ITS) rDNA barcode sequences of Meredithiella spp. were obtained consistently from beetles and galleries of nine Corthylus spp. The ITS sequences of three putative species of Meredithiella were associated with C. consimilis and C. flagellifer in Mexico and C. calamarius in Costa Rica. The symbiont of C. columbianus in the USA was identified as M. norrisii. Two new Meredithiella spp. are described: M. fracta from C. papulans in Florida and Honduras, and M. guianensis associated with C. crassus and two unidentified Corthylus spp. in French Guyana. The Meredithiella spp. propagate in the mycangia of adult females by thallic-arthric growth, and the ambrosia growth in larval cradles comprises bead-like hyphal swellings or conidiophores, with or without terminal aleurioconidia. Bayesian phylogenetic analysis of a combined 18S and 28S nuc rDNA and translation elongation factor 1-α (TEF1-α) data set demonstrated that Meredithiella is a distinct monophyletic clade within the Ceratocystidaceae, but its phylogenetic placement with regard to the other ambrosial genera in the family remains ambiguous. The mycangia of C. punctatissimus and C. papulans are also compared using light microscopy and micro-computed tomography (micro-CT) imaging, revealing that they differ in both size and shape, but these differences may not correlate with different lineages of Meredithiella.

Peltaster gemmifer: A new species in the sooty blotch and flyspeck species complex from the United States

Sooty blotch and flyspeck (SBFS) fungi infect the cuticle of fruit, including apple fruit, and produce pigmented colonies. A new member of this fungal complex in the genus Peltaster is described on the basis of molecular and morphological evidence. The SBFS complex is a diverse group of ectophytic fungi that reside primarily within the order Capnodiales. Sooty blotch and flyspeck isolates from apple orchards in the central United States were subjected to parsimony and Bayesian analyses based on the internal transcribed spacer regions of nuc rDNA, the partial translation elongation factor 1-α gene, and the partial mitochondrial small subunit rRNA gene. Phylogenetic analysis delineated a new species, Peltaster gemmifer, from P. cerophilus and P. fructicola. Peltaster gemmifer conidiophores bear primary conidia that produce secondary conidia either through budding or through microcyclic conidiation; these were not seen in cultures of P. cerophilus and P. fructicola. On cellulose membrane that was placed on water agar amended with apple juice, P. gemmifer produced brown to black pycnothyria in a superficial brownish mycelial mat, similar to the colonies produced on apple fruit. Findings from the present study add to the >80 named and putative SBFS species so far described worldwide.

Genetic Variation in Native Populations of the Laurel Wilt Pathogen, Raffaelea lauricola, in Taiwan and Japan and the Introduced Population in the United States

Laurel wilt is a vascular wilt disease caused by Raffaelea lauricola, a mycangial symbiont of an ambrosia beetle, Xyleborus glabratus. The fungus and vector are native to Asia but were apparently introduced to the Savannah, GA, area 15 or more years ago. Laurel wilt has caused widespread mortality on redbay (Persea borbonia) and other members of the Lauraceae in the southeastern United States, and the pathogen and vector have spread as far as Texas. Although believed to be a single introduction, there has been no extensive study on genetic variation of R. lauricola populations that would suggest a genetic bottleneck in the United States. Ten isolates of R. lauricola from Japan, 55 from Taiwan, and 125 from the United States were analyzed with microsatellite and 28S rDNA markers, and with primers developed for two mating-type genes. The new primers identified isolates as either MAT1 or MAT2 mating types in roughly equal proportions in Taiwan and Japan, where there was also high genetic diversity within populations based on all the markers, suggesting that these populations may have cryptic sex. Aside from a local population near Savannah and a single isolate in Alabama that had unique microsatellite alleles, the U.S. population was genetically uniform and included only the MAT2 mating type, supporting the single introduction hypothesis. This study suggests the importance of preventing a second introduction of R. lauricola to the United States, which could introduce the opposite mating type and allow for genetic recombination.

Genetic Bottlenecks for Two Populations of Ceratocystis fimbriata on Sweet Potato and Pomegranate in China

Chinese isolates of Ceratocystis fimbriata from sweet potato (Ipomoea batatas) and pomegranate (Punica granatum) were genetically compared with a worldwide collection of isolates from a variety of hosts. Isolates from black-rotted storage roots of sweet potato in China, Japan, Australasia, and the United States had identical internal transcribed spacer (ITS) ribosomal DNA (rDNA) sequences and only minor variation in microsatellite alleles. Sequences of their mating type genes were most similar to those of isolates from various hosts in Ecuador, a center of diversity for sweet potato. Isolates from Colocasia esculenta (taro) and pomegranate from Yunnan and Sichuan had only one ITS rDNA sequence (haplotype ITS5). This haplotype, sequences of mating type genes, and microsatellite alleles linked these isolates to isolates from Eucalyptus stumps in South China and diseased Eucalyptus trees in Brazil, supporting the hypothesis that the pomegranate population originated from Brazil via cuttings of Eucalyptus. Isolates from sweet potato and pomegranate in China were interfertile with tester strains of C. fimbriata, confirming that the causes of the two epidemics in China belong to a single biological species. However, other isolates from Eucalyptus stumps were intersterile with the tester strains and had ITS rDNA sequences typical of the Asian species, C. cercfabiensis.

Detection of Colletotrichum acutatum Sensu Lato on Strawberry by Loop-Mediated Isothermal Amplification

Colletotrichum acutatum, one of the most economically damaging pathogens of strawberry, is the primary causal agent of anthracnose fruit rot (AFR). A key challenge in managing AFR is detecting the pathogen on asymptomatic plants. To meet this need, a loop-mediated isothermal amplification (LAMP) assay was developed that incorporated two sets of primers: LITSG1, targeted on the intergenic transcribed spacer (ITS) region of ribosomal DNA, and Ltub2, on the β-tubulin 2 gene. In pure culture assays, Ltub2 was specific for detection of C. acutatum, whereas LITSG1 detected C. acutatum and two additional anthracnose pathogens, C. gloeosporioides and C. fragariae. LITSG1 had 10-fold lower detection threshold (20 pg of mycelial DNA) than Ltub2 (200 pg mycelial DNA) in detection of C. acutatum from pure culture. For detection on asymptomatic leaves, two protocols for dislodging C. acutatum for DNA extraction were compared: i) the sonicate-agitate (SA) method and ii) the freeze-incubate-sonicate-agitate (FISA) method, which initially freezes tissues, followed by 2 days of incubation at 26°C in darkness, and then, sonication and agitation. Both methods were used for greenhouse-grown plant leaves that had been spray inoculated with serial dilutions ranging from 1.5 × 10⁶ to 1.5 conidia ml^-1. The FISA method produced more repeatable results than the SA method. For the FISA method, detection limits (expressed as initial inoculum concentrations) using LITSG1 and Ltub2 were 1.5 × 10¹ and 1.5 × 10² conidia ml^-1, respectively. For composite samples comprised of inoculated (1.5 × 10⁶ conidia ml^-1) and noninoculated leaves of greenhouse-grown strawberry, the two sets of LAMP primers were compared using the SA method. Primer set LITSG1 consistently detected the pathogen from a single inoculated leaf in bulk samples of 50 or fewer pathogen-free leaves, whereas Ltub2 consistently detected one inoculated leaf in 20 or fewer pathogen-free leaves. Using primer set LITSG1, FISA was more sensitive than SA for detecting C. acutatum on leaves of field-grown plants from Florida. In an Iowa field trial using the FISA method, both primer sets detected C. acutatum in samples of asymptomatic leaves 6 days before fruit symptoms appeared. The results indicate that the LAMP assay has potential to provide a simplified method for detection of C. acutatum on asymptomatic strawberry plants.

Phenology of Infection on Apple Fruit by Sooty Blotch and Flyspeck Species in Iowa Apple Orchards

Sooty blotch and flyspeck (SBFS) is a fungal disease complex that can cause significant economic losses to apple growers by blemishing the fruit surface with dark-colored colonies. Little is known about the phenology of host infection for this diverse group of epiphytes. In 2009 and 2010, we investigated the timing of infection of apple fruit by SBFS species in six commercial apple orchards in Iowa. Five trees in each orchard received no fungicide sprays after fruit set. Within 3 weeks after fruit set, 60 apples per tree were covered with Japanese fruit bags to minimize inoculum deposition. Subsequently, a subsample of bagged apples was exposed for a single 2-week-long period and then rebagged for the remainder of the growing season. Experimental treatments included seven consecutive 2-week-long exposure periods; control treatments were apples that were either bagged or exposed for the entire season. After apples had been stored at 2°C for 6 weeks following harvest, all SBFS colonies on the apples were identified to species using a PCR-RFLP protocol. A total of 15 species were identified. For the seven most prevalent species, the number of infections per cm² of fruit surface was greatest on apples that had been exposed early in the season. Two SBFS species, Peltaster fructicola and Colletogloeopsis-like FG2, differed significantly from each other in time required to attain 50% of the total number of colonies per apple, and analysis of variance indicated a significant interaction of SBFS taxon with exposure period. Our findings are the first evidence of species-specific patterns in timing of SBFS inoculum deposition and infection on apple fruit, and strengthen previous observations that most SBFS infections resulting in visible colonies at harvest develop from infections that occur early in the fruit development period. By defining taxon-specific phenological patterns of fruit infection, our findings, when combined with knowledge of region-specific patterns of taxon prevalence, provide a foundation for development of more efficient and cost-effective SBFS management tactics.

Ancestral state reconstruction infers phytopathogenic origins of sooty blotch and flyspeck fungi on apple

Members of the sooty blotch and flyspeck (SBFS) complex are epiphytic fungi in the Ascomycota that cause economically damaging blemishes of apples worldwide. SBFS fungi are polyphyletic, but approx. 96% of SBFS species are in the Capnodiales. Evolutionary origins of SBFS fungi remain unclear, so we attempted to infer their origins by means of ancestral state reconstruction on a phylogenetic tree built utilizing genes for the nuc 28S rDNA (approx. 830 bp from near the 59 end) and the second largest subunit of RNA polymerase II (RPB2). The analyzed taxa included the well-known genera of SBFS as well as non-SBFS fungi from seven families within the Capnodiales. The non-SBFS taxa were selected based on their distinct ecological niches, including plant-parasitic and saprophytic species. The phylogenetic analyses revealed that most SBFS species in the Capnodiales are closely related to plant-parasitic fungi. Ancestral state reconstruction provided strong evidence that plant-parasitic fungi were the ancestors of the major SBFS lineages. Knowledge gained from this study may help to better understand the ecology and evolution of epiphytic fungi.

Species or Genotypes? Reassessment of Four Recently Described Species of the Ceratocystis Wilt Pathogen, Ceratocystis fimbriata, on Mangifera indica

Ceratocystis wilt is among the most important diseases on mango (Mangifera indica) in Brazil, Oman, and Pakistan. The causal agent was originally identified in Brazil as Ceratocystis fimbriata, which is considered by some as a complex of many cryptic species, and four new species on mango trees were distinguished from C. fimbriata based on variation in internal transcribed spacer sequences. In the present study, phylogenetic analyses using DNA sequences of mating type genes, TEF-1α, and β-tubulin failed to identify lineages corresponding to the four new species names. Further, mating experiments found that the mango isolates representing the new species were interfertile with each other and a tester strain from sweet potato (Ipomoea batatas), on which the name C. fimbriata is based, and there was little morphological variation among the mango isolates. Microsatellite markers found substantial differentiation among mango isolates at the regional and population levels, but certain microsatellite genotypes were commonly found in multiple populations, suggesting that these genotypes had been disseminated in infected nursery stock. The most common microsatellite genotypes corresponded to the four recently named species (C. manginecans, C. acaciivora, C. mangicola, and C. mangivora), which are considered synonyms of C. fimbriata. This study points to the potential problems of naming new species based on introduced genotypes of a pathogen, the value of an understanding of natural variation within and among populations, and the importance of phenotype in delimiting species.

Three genera in the Ceratocystidaceae are the respective symbionts of three independent lineages of ambrosia beetles with large, complex mycangia

The genus Ambrosiella accommodates species of Ceratocystidaceae (Microascales) that are obligate, mutualistic symbionts of ambrosia beetles, but the genus appears to be polyphyletic and more diverse than previously recognized. In addition to Ambrosiella xylebori, Ambrosiella hartigii, Ambrosiella beaveri, and Ambrosiella roeperi, three new species of Ambrosiella are described from the ambrosia beetle tribe Xyleborini: Ambrosiella nakashimae sp. nov. from Xylosandrus amputatus, Ambrosiella batrae sp. nov. from Anisandrus sayi, and Ambrosiella grosmanniae sp. nov. from Xylosandrus germanus. The genus Meredithiella gen. nov. is created for symbionts of the tribe Corthylini, based on Meredithiella norrisii sp. nov. from Corthylus punctatissimus. The genus Phialophoropsis is resurrected to accommodate associates of the Xyloterini, including Phialophoropsis trypodendri from Trypodendron scabricollis and Phialophoropsis ferruginea comb. nov. from Trypodendron lineatum. Each of the ten named species was distinguished by ITS rDNA barcoding and morphology, and the ITS rDNA sequences of four other putative species were obtained with Ceratocystidaceae-specific primers and template DNA extracted from beetles or galleries. These results support the hypothesis that each ambrosia beetle species with large, complex mycangia carries its own fungal symbiont. Conidiophore morphology and phylogenetic analyses using 18S (SSU) rDNA and TEF1α DNA sequences suggest that these three fungal genera within the Ceratocystidaceae independently adapted to symbiosis with the three respective beetle tribes. In turn, the beetle genera with large, complex mycangia appear to have evolved from other genera in their respective tribes that have smaller, less selective mycangia and are associated with Raffaelea spp. (Ophiostomatales).

Ceratocystis tiliae sp. nov., a wound pathogen on Tilia americana

Species in the North American clade (NAC) of the Ceratocystis fimbriata complex are mostly weak pathogens that infect native tree hosts through fresh wounds. Isolations from discolored tissue of wounded Tilia americana (basswood) in Iowa and Nebraska yielded a Ceratocystis species that was similar to but distinct from isolates of C. variospora from other hosts. Sequences of 28S rDNA showed that isolates from basswood did not differ from C. variospora, but there were minor differences in ITS rDNA sequences. The DNA sequences of a portion of the Cerato-platanin gene and TEF1α showed the basswood fungus to be a unique lineage. Cross inoculations in two experiments showed that the basswood isolates and C. variospora isolates from Quercus spp. were most aggressive to their respective hosts. Isolates from basswood grew slower and were less pigmented than C. variospora isolates from Quercus spp. The basswood fungus thus is distinguished from C. variospora based on phylogenetic analyses and phenotype and is herein described as C. tiliae sp. nov.

Genetic Analyses Trace the Yunnan, China Population of Ceratocystis fimbriata on Pomegranate and Taro to Populations on Eucalyptus in Brazil

Genotypes of the Latin American wilt pathogen Ceratocystis fimbriata have been moved around the world in vegetatively propagated material of various crop plants, including Ipomoea batatas (sweet potato), Colocasia esculenta (taro), and Eucalyptus spp. When compared to a worldwide collection of isolates of C. fimbriata, isolates from taro, Punica granatum (pomegranate), and Eriobotrya japonica (loquat) from Yunnan Province, China were found to have sequences of internal transcribed spacer (ITS) rDNA and mating type genes that were identical to isolates from Eucalyptus in Brazil. Analyses of 35 isolates with 14 microsatellite markers revealed that the Yunnan population was nearly uniform, consisting of only 19 alleles and seven closely related genotypes, suggesting that the population is not natural and is the result of an introduction. As in comparisons of sequences of ITS rDNA and mating type genes, the microsatellite alleles of the Yunnan isolates were most similar to those of Eucalyptus isolates from Minas Gerais and Bahia, Brazil, where C. fimbriata is native, soilborne, and commonly infects cuttings of Eucalyptus spp. used for rooting in nurseries. Thus, the Yunnan population, which is causing severe losses on pomegranate, may have been indirectly derived from introductions of C. fimbriata in contaminated Eucalyptus cuttings from Brazil.

Intraspecific and intragenomic variability of ITS rDNA sequences reveals taxonomic problems in Ceratocystis fimbriata sensu stricto

Fourteen new species in the Latin American Clade (LAC) of the Ceratocystis fimbriata complex recently were distinguished from C. fimbriata sensu stricto largely based on variation in ITS rDNA sequences. Among the 116 isolates representing the LAC, there were 41 ITS haplotypes. Maximum parsimony (MP) analysis of ITS sequences produced poorly resolved trees. In contrast, analyses of mating-type genes (MAT1-1-2 and MAT1-2-1) resolved a single MP tree with branches of high bootstrap and posterior probability support. Four isolates showed intragenomic variation in ITS sequences. Cloning and sequencing of PCR products from a single haploid strain identified two or more ITS sequences differing at up to 16 base positions and representing two described species. Isolates from introduced populations that appeared to be clonal based on microsatellite markers varied at up to 14 bp in ITS sequence. Strains of seven Brazilian ITS haplotypes and an isolate from Ipomoea batatas (on which the species name C. fimbriata was based) were fully interfertile in sexual crosses. These analyses support three phylogenetic species that differ in pathogenicity: C. platani, C. cacaofunesta and C. colombiana. Five ITS species (C. manginecans, C. mangicola, C. mangivora, C. acaciivora, C. eucalypticola) appear to be ITS haplotypes that have been moved from or within Brazil on nursery stock. The taxonomic status of other species delineated primarily by ITS sequences (C. diversiconidia, C. papillata, C. neglecta, C. ecuadoriana, C. fimbriatomima, C. curvata) needs further study, but they are considered doubtful species.

Wickerhamomyces arborarius f.a., sp. nov., an ascomycetous yeast species found in arboreal habitats on three different continents

Five strains representing a novel yeast species belonging to the genus Wickerhamomyces were independently isolated from Ecuador, Taiwan and the USA. One strain (CLQCA 10-161(T)) was isolated from the white flower of an unidentified plant species collected in the Maquipucuna cloud forest reserve, near Quito, in Ecuador. A second strain (GY7L12) was isolated from the leaf of a Chinese sumac or nutgall tree (Rhus chinensis 'roxburghiana') collected in the Taoyuan mountain area, Kachsiung, in Taiwan. Three additional strains (A543, A546 and A563) were isolated from two species of wood-boring beetle (Xyleborus glabratus and Xyleborinus saxeseni) collected near Clyo, Georgia, USA. Analysis of the D1/D2 domains of the LSU rRNA gene indicated that the novel species belongs to the genus Wickerhamomyces, and is most closely related to Wickerhamomyces sydowiorum, an insect-associated species predominantly found in South Africa. The North American and Taiwanese strains have identical internal transcribed spacer (ITS) sequences and can be distinguished from the Ecuadorian strain based on a single nucleotide substitution in the ITS1 region. The species name of Wickerhamomyces arborarius f.a., sp. nov. is proposed to accommodate these strains, with CLQCA 10-161(T) ( = CBS 12941(T) = NCYC 3743(T)) designated the type strain.

First Report of Laurel Wilt, Caused by Raffaelea lauricola, on Sassafras (Sassafras albidum) in Alabama

Laurel wilt, caused by Raffaelea lauricola, a fungal symbiont of the redbay ambrosia beetle, Xyleborus glabratus, is responsible for extensive mortality of native redbays (Persea borbonia and P. palustris) in the coastal plains of the southeastern United States (1). The wilt also affects the more widespread sassafras, Sassafras albidum, particularly in areas where diseased redbays are common and populations of X. glabratus are high. Because sassafras stems were thought to lack chemicals that are attractive to the beetle, and sassafras tends to be widely scattered in forests, it was believed that the advance of the laurel wilt epidemic front might slow once it reached the edge of the natural range of redbay, which is restricted to the coastal plains of the Gulf and Atlantic Coasts (2). In July and August of 2011, wilt-like symptoms (i.e., wilted and dead leaves, and streaks of black discoloration in the xylem) were observed on 1 to 10 sassafras trees (15 to 23 cm diameter; 6 to 9 m height) at each of three locations, which were approximately 6 km from one another in Marengo Co., Alabama. Samples of the discolored wood from five trees were plated on malt agar amended with cycloheximide and streptomycin (CSMA), and a fungus morphologically identical to R. lauricola was isolated from each tree (1). For confirmation, a portion of the large subunit (28S) of the rDNA region of three of the isolates was sequenced (3); in each case, the sequence matched exactly that of other isolates of R. lauricola (EU123077) from the United States. Symptomatic trees were found at all three sites when revisited in April 2012, and approximately 20 sassafras trees in various stages of wilt were observed at one location, where only one diseased tree had been noted in 2011. Bolts were cut from the main stem of a symptomatic tree, and eggs, larvae, and adults of X. glabratus were commonly found in tunnels, and R. lauricola was isolated from the discolored xylem. Three container-grown sassafras saplings (mean height 193 cm, mean diameter 2.1 cm at groundline) were inoculated as previously described (1) with conidia (~600,000) from an isolate of R. lauricola. Three additional sassafras saplings were inoculated with sterile, deionized water, and all plants were placed in a growth chamber at 25°C with a 15-h photoperiod. Inoculated plants began to exhibit wilt symptoms within 14 days, and at 30 days all inoculated plants were dead and xylem discoloration was observed. Control plants appeared healthy and did not exhibit xylem discoloration. Pieces of sapwood from 15 cm above the inoculation points were plated on CSMA, and R. lauricola was recovered from all wilted plants but not from control plants. This is the first record of laurel wilt in Alabama and is significant because the disease appears to be spreading on sassafras in an area where redbays have not been recorded (see http://www.floraofalabama.org ). The nearest previously documented case of laurel wilt is on redbay and sassafras in Jackson Co., Mississippi (4), approximately 160 km to the south. The exact source of the introduction of X. glabratus and R. lauricola into Marengo Co. is not known. The vector may have been transported into the area with storms, moved with infested firewood, or shipped with infested timber by companies that supply mills in the area. References: (1) S. Fraedrich et al. Plant Dis. 92:215, 2008. (2) J. Hanula et al. Econ. Ent. 101:1276, 2008. (3) T. Harrington et al. Mycotaxon 111:337, 2010. (4) J. Riggins et al. Plant Dis. 95:1479, 2011.

Temporal patterns in appearance of sooty blotch and flyspeck fungi on apples

Sooty blotch and flyspeck (SBFS) is a complex of about 80 fungal species that blemish the surface of apple fruit in humid regions worldwide. The dark colonies become visible in mid- to late summer, reducing the value of fresh fruit. Although many SBFS species can co-occur in the same orchard and even on the same apple, little is known about temporal patterns of these species, including the timing of colony appearance. To test the hypothesis that colonies of SBFS species appear on apples at characteristic times during the growing season, 50 apples were monitored weekly at three Iowa orchards in 2006 and six orchards in 2007 and 2008. However, a mean of 24.3 apples per orchard was assessed at harvest because of apple drop throughout the season. Colonies were marked with colored pens as they appeared. After harvest and after storage of apples at 2 °C for 3 months, SBFS colonies on each fruit were counted and classified by morphology, and a representative subset of colonies was excised from the fruit and preserved on dried peels for species identification using rDNA. Seventeen species were identified. Stomiopeltis spp. RS1 and RS2 appeared on apples 10 to 14 days before other SBFS taxa. Dissoconium aciculare was generally the last species to appear on apple fruit, and it continued to appear during postharvest storage. The most prevalent taxa in Iowa orchards were also the most abundant. Diversity of SBFS fungi in an orchard was positively correlated with cumulative hours of surface wetness hours due to rainfall or dew, which is believed to favor growth of SBFS fungi. Species-specific information about temporal patterns of appearance on apple fruit may lead to improved SBFS management strategies.

First Report of Boeremia Blight Caused by Boeremia exigua var. exigua on Pyrethrum in Australia

Pyrethrum (Tanacetum cinerariifolium) is produced for extraction of insecticidal compounds from the flower achenes. In 2004 and 2006, isolations from necrotic lesions on stems and leaves in three fields in northern Tasmania, Australia yielded four unidentified fungal isolates. Leaf lesions were medium brown and circular (2 to 4 mm in diameter) or irregular in shape (2 to 5 mm long). Stem lesions were irregular, necrotic spots, 5 to 15 mm below the flower peduncle, medium brown, 2 to 4 mm long, and 1 to 2 mm wide. Isolations were conducted on water agar following surface sterilization. Isolates were identified by colony characteristics and the presence of metabolite 'E' (1). On oatmeal agar (OA), colonies had irregular margins, were greenish olivaceous-to-olivaceous gray with sparse, white, floccose, aerial mycelia. On malt extract agar (MEA), cultures were variable in color with olivaceous black centers with soft, dense, aerial mycelia. Conidia were hyaline, ellipsoidal to oblong, mainly aseptate, but occasionally 1-septate with dimensions ranging from 2.5 to 7.5 × 1.8 to 3.8 μm (length/width ratio = 1.7 to 2.1). All isolates had moderate reactions to the NaOH test for metabolite 'E'. DNA was extracted from all four isolates with a DNeasy Plant Mini Kit (QIAGEN Inc., Valencia, CA). For identification, the internal transcribed spacer region (ITS1, 5.8s, and ITS2) and part of the translation elongation factor (TEF) region were amplified and sequenced. Primers ITS1 and ITS4 (2) were used for the ITS region and primers EFCF1 (5'-AGTGCGGTGGTATCGACAAG) and EFCF6 (3'-CATGTCACGGACGGCGAAAC) were used for the TEF. Amplicons were sequenced in both directions and consensus sequences assembled. The ITS sequence was 100% identical to Boeremia exigua var. exigua (GenBank Accession No. GU237715). Base pairs 413 to 1,214 of the TEF sequence from the pyrethrum isolates matched base pairs 1 to 802 (799 of 802 identities) of B. exigua var. exigua (GenBank Accession No. GU349080). All isolates were confirmed as B. exigua var. exigua using morphology and sequencing. Pathogenicity tests were conducted three times in separate glasshouse trials for two of the four isolates. For each isolate, conidial suspensions in water (3 ml/plant) from MEA, adjusted to 5 × 10⁵/ml were applied with Tween 20 (1 drop per 100 ml of water) to 8-week-old pyrethrum plants (five pots per isolate with four plants per pot) using a hand-held spray bottle. Twenty plants were sprayed with water and Tween 20 as nontreated controls. Plants were covered with plastic bags for 48 h after inoculation and examined for symptoms after 15 days at 20°C. Disease incidence (number of symptomatic leaves affected per total number of leaves) of the inoculated plants varied from 7.5 to 9.4%. Noninoculated plants did not develop symptoms. Isolations resulted in cultures morphologically identical on MEA and OA to those inoculated. To our knowledge, this is the first report of B. exigua var. exigua causing disease in pyrethrum. Cultures were deposited in the New South Wales Department of Agriculture collection (DAR79101 to 79104) and TEF and ITS sequences for DAR79101 in GenBank (Accession Nos. JF925328 and JF925329, respectively). Boeremia blight is likely to contribute to the fungal disease complex causing reductions in green leaf area in Australian pyrethrum production. References: (1) M. M. Aveskamp et al. Stud. Mycol. 65:1, 2010. (2) T. J. White et al. PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, 1990.

First Report of Laurel Wilt Caused by Raffaelea lauricola on Sassafras in Mississippi

Laurel wilt is caused by the fungus Raffaelea lauricola T.C. Harrin., Aghayeva & Fraedrich and is lethal to redbay (Persea borbonia (L.) Spreng.), sassafras (Sassafras albidum (Nutt.) Nees), and other species in the Lauraceae (1). The fungus is carried by the redbay ambrosia beetle (Xyleborus glabratus Eichh.), which is native to Asia. After being discovered in Georgia in 2002 (1), X. glabratus and R. lauricola have spread rapidly, causing extensive redbay mortality in South Carolina, Georgia, Florida, and Mississippi (1,4). The disease has also been confirmed on sassafras in Florida, South Carolina (1), and Georgia. Questions remain as to whether laurel wilt will continue to spread on sassafras, which often occurs as scattered trees in the eastern United States. In June 2010, a homeowner reported that a sassafras tree north of Van Cleave, MS (30.668°N, 88.686°W) had begun wilting in late May. This landscape tree had three 10-m high stems (~20 cm in diameter at breast height). Dark staining in the xylem was observed around the entire circumference of all three stems and nearly all leaves were bronze colored and wilted. No ambrosia beetle tunnels were observed in the stems. No other symptomatic Lauraceae were encountered in the wooded area within 300 m. The nearest known location with laurel wilt on redbay was ~15 km away (4). A Lindgren funnel trap baited with manuka oil (2) was placed at the site in June and monitored biweekly until November, but no X. glabratus adults were captured. Chips from discolored xylem of the sassafras were surface sterilized, plated on cycloheximide-streptomycin malt agar, and R. lauricola was readily isolated (1). Identity of the fungus (isolate C2792 in collection of T. Harrington) was confirmed by using partial sequences of the 28S rDNA (3). The sassafras sequence was identical to that of all known sequences of R. lauricola in the United States, including GenBank No. EU123076 (the holotype isolate from redbay). To confirm pathogenicity, isolate C2792 was grown on malt extract agar and three redbay (average: 141 cm high and 12 mm in diameter at soil interface) and three sassafras (average: 170 cm high and 17 mm in diameter at soil interface) potted plants were wound inoculated with 0.2 ml of a spore suspension (4.9 × 10⁶ conidia/ml) (1). Three control plants of each species were inoculated with sterile deionized water. After 8 weeks in a growth chamber at 26°C, all inoculated redbay and sassafras plants exhibited xylem discoloration above and below the inoculation point, two of the redbay and two of the sassafras had died, and the other plant of each species exhibited partial wilt (the main terminal or one or more branches). All control plants were asymptomatic. R. lauricola was reisolated from all inoculated symptomatic plants but not from controls. To our knowledge, this is the first report of laurel wilt on sassafras in Mississippi. Both redbay (4) and sassafras appear to be highly susceptible to the disease as it moves westward. Sassafras is less attractive than redbay to X. glabratus and it was thought that this might contribute to slowing the spread of laurel wilt once outside the range of redbay (2). Nonetheless, our observations confirm that sassafras can be infected where laurel wilt on redbay is not in the immediate vicinity. References: (1) S. W. Fraedrich et al. Plant Dis. 92:215, 2008. (2) J. L. Hanula et al. J. Econ. Entomol. 101:1276, 2008. (3) T. C. Harrington et al. Mycotaxon 111:337, 2010. (4) J. J. Riggins et al. Plant Dis. 94:634, 2010.

First Report of the Walnut Witches'-Broom Phytoplasma on Japanese and Black Walnut in Iowa

A single Japanese walnut (Juglans ailantifolia Carrière, an ornamental, deciduous tree) with symptoms of witches'-brooms and branch dieback, consistent with those associated with the walnut witches'-broom (WWB) phytoplasma (1), was observed near Ames, IA. No other Japanese walnut trees were present in the planting and the numerous black walnut (Juglans nigra L.) trees were asymptomatic. Leaf samples were collected in September 2009 from witches'-brooms as well as from two asymptomatic branches from the Japanese walnut tree and from three branches each from two nearby (10 m and 100 m away, respectively) black walnut trees. The presence of phytoplasma was tested using DNA extracted (sodium dodecyl sulfate and potassium acetate methods) from the midvein of individual leaves and PCR with universal phytoplasma primers P1 and P7, which amplify from the beginning of the 16S rDNA to the beginning of the 23S rDNA gene (4). Each of the five symptomatic leaves yielded a PCR product, but the two asymptomatic leaves from the sole Japanese walnut tree did not. One of the three asymptomatic leaves from a black walnut tree (100 m away) was also positive. In a subsequent round of PCR, with the nested primers R16F2 and R16R2 (4), three additional asymptomatic leaves from the two black walnut trees were positive. The P1/P7 or R16F2/R16R2 products from each of the three trees were directly sequenced or cloned into a TA vector and sequenced using vector primers. The BLAST searches (v. 2.2.2.4) of these sequences most closely matched the sequences of the WWB phytoplasma and other members of the 16SrIII group (peach X-disease). The closest matches for the full P1/P7 sequence from the Japanese walnut (GenBank Accession No. HQ221553, 1,814 bp) were with those of phytoplasmas associated with WWB from two black walnut trees in Georgia (AF190227, 1,812 of 1,815 bp matching; and AF190226, 1,808 of 1,815 bp matching), spiraea stunt (AF190228, 1,808 of 1,814 bp), and western X (AF533231, 1,807 of 1,814 bp). The iPhyClassifier restriction fragment length polymorphism similarity coefficient was 0.99 for L33733 (Canadian peach X phytoplasma) and 0.98 for AF190226. Sequence HQ221553 differed by 10 bp from the sequence from the asymptomatic black walnut tree that was 100 m away (HQ221554, 1,815 bp), which matched closest to one of the black walnut samples from Georgia (AF190227, 1,807 of 1,816 bp). A 1,029-bp fragment from the second black walnut tree (10 m away) differed by 1 or 2 bp from the Georgia WWB accessions. To our knowledge, this is the first report of WWB symptoms in Iowa and the first identification of the WWB phytoplasma outside of Georgia (1). The disease, however, is more widely known (Illinois, Indiana, and Ohio) and may cause serious reduction in nut production (1-3). It can be lethal to Juglans spp., especially to exotic species such as Japanese walnut (2,3). The native black walnut is thought to be relatively resistant to tolerant of WWB (2,3) and may only show growth decline with no symptoms, except for broom production from cut surfaces (3). Care should be taken in moving planting stock of black walnut (4) because asymptomatic trees may harbor the phytoplasma. References: (1) J. Chen et al. Plant Dis. 76:1116, 1992. (2) C. E. Seliskar. For. Sci. 22:144, 1976. (3) W. A. Sinclair et al. Diseases of Trees and Shrubs. Cornell University Press, Ithaca, NY, 1987. (4) L. Ward. Juglans (Walnut). Post-Entry Quarantine Testing Manual. Biosecurity New Zealand, Ministry of Agriculture and Forestry, Auckland, 2008.

Bur oak blight, a new disease on Quercus macrocarpa caused by Tubakia iowensis sp. nov

A newly recognized, late-season leaf disease of Quercus macrocarpa (bur oak) has become increasingly severe across Iowa and in neighboring states since the 1990s. Vein necrosis and leaf death may occur over the whole crown or only on the lower branches. Symptoms typically intensify year-to-year in individual trees, and there appears to be substantial variation in susceptibility. Distinctive conidiomata (pycnothyria with a shield of radiating, setae-like hyphae) of a Tubakia sp. are found along the necrotic leaf veins. The same species produces a second type of pycnothyrium with a crustose covering and smaller conidia on the petioles of killed leaves, which remain on the tree through the winter and provide the primary inoculum to infect newly emerging shoots and leaves in spring. Comparison of the Tubakia sp. on bur oak with T. dryina and other species of Tubakia led to the conclusion that the species on bur oak is new, distinct from T. dryina, which herein is defined more narrowly. Inoculation studies confirmed that Tubakia iowensis sp. nov. is the cause of bur oak blight. Bur oak blight appears to be particularly severe on Q. macrocarpa var. oliviformis, which is well adapted to the dry, upland sites where the disease is found most frequently. The recent climatic trend in Iowa to higher spring precipitation might have led to increased severity of the disease.

Susceptibility to Laurel Wilt and Disease Incidence in Two Rare Plant Species, Pondberry and Pondspice

Laurel wilt, caused by Raffaelea lauricola, has been responsible for extensive losses of redbay (Persea borbonia) in South Carolina and Georgia since 2003. Symptoms of the disease have been noted in other species of the Lauraceae such as the federally endangered pondberry (Lindera melissifolia) and the threatened pondspice (Litsea aestivalis). Pondberry and pondspice seedlings were inoculated with R. lauricola from redbay, and both species proved highly susceptible to laurel wilt. Field assessments found substantial mortality of pondberry and pondspice, but in many cases the losses were not attributable to laurel wilt. R. lauricola was isolated from only 4 of 29 symptomatic pondberry plants at one site, but the fungus was not recovered from three plants at another site. R. lauricola was isolated from one of two symptomatic pondspice plants at one site, and from five of 11 plants at another site, but not from any plant at a third site. Insect bore holes, similar to those produced by Xyleborus glabratus (the vector of laurel wilt), were found in some pondberry and pondspice stems, but adults were not found. Damage caused by Xylosandrus compactus was found in pondberry stems, but this ambrosia beetle does not appear to be a vector of R. lauricola. Xyleborinus saxeseni adults were found in a dying pondspice with laurel wilt, and R. lauricola was recovered from two of three adults. Isolates of R. lauricola from pondberry, pondspice, and X. saxeseni had rDNA sequences that were identical to previously characterized isolates, and inoculation tests confirmed that they were pathogenic to redbay. Because pondberry and pondspice tend to be shrubby plants with small stem diameters, these species may not be frequently attacked by X. glabratus unless in close proximity to larger diameter redbay.

Movement of genotypes of Ceratocystis fimbriata within and among Eucalyptus plantations in Brazil

Ceratocystis wilt on eucalyptus, caused by Ceratocystis fimbriata, was first recognized in 1997 in the state of Bahia, Brazil, but is now known in five other states and in four other countries. C. fimbriata is a native, soilborne pathogen in some parts of Brazil but we hypothesized that genotypes of the pathogen have been moved among plantations in rooted cuttings collected from diseased trees and within plantations on cutting tools. We used six microsatellite markers to identify 78 genotypes of C. fimbriata among 177 isolates from individual trees in 20 eucalyptus plantations. The highest gene and genotypic diversity values were found in plantations on formerly wild Cerrado forest in Minas Gerais, suggesting that the fungus was in the soil prior to planting eucalyptus. In contrast, one or only a few genotypes were found in plantations on previous pastureland (with no woody hosts) in Bahia and São Paulo, and most of these genotypes were found in a Bahian nursery or in one of two Bahian plantations that were sources for rooted cuttings. Sources of cuttings tended to be dominated by one or a few genotypes that may have been spread within the plantation on cutting tools.

Genetic variation and variation in aggressiveness to native and exotic hosts among Brazilian populations of Ceratocystis fimbriata

Ceratocystis fimbriata is a complex of many species that cause wilt and cankers on woody plants and rot of storage roots or corms of many economically important crops worldwide. In Brazil, C. fimbriata infects different cultivated crop plants that are not native to Brazil, including Gmelina arborea, Eucalyptus spp., Mangifera indica (mango), Ficus carica (fig), and Colocasia esculenta (inhame). Phylogenetic analyses and inoculation studies were performed to test the hypothesis that there are host-specialized lineages of C. fimbriata in Brazil. The internal transcribed spacer region ribosomal DNA sequences varied greatly but there was little resolution of lineages based on these sequences. A portion of the MAT1-2 mating type gene showed less variation, and this variation corresponded more closely with host of origin. However, mango isolates were found scattered throughout the tree. Inoculation experiments on the five exotic hosts showed substantial variation in aggressiveness within and among pathogen populations. Native hosts from the same families as the exotic hosts tended to be less susceptible than the cultivated hosts, but there was little correlation between aggressiveness to the cultivated and native hosts of the same family. Cultivation and vegetative propagation of exotic crops may select for strains that are particularly aggressive on those crops.

Quantification of propagules of the laurel wilt fungus and other mycangial fungi from the redbay ambrosia beetle, Xyleborus glabratus

The laurel wilt pathogen, Raffaelea lauricola, is a fungal symbiont of the redbay ambrosia beetle, Xyleborus glabratus, which is native to Asia and was believed to have brought R. lauricola with it to the southeastern United States. Individual X. glabratus beetles from six populations in South Carolina and Georgia were individually macerated in glass tissue grinders and serially diluted to quantify the CFU of fungal symbionts. Six species of Raffaelea were isolated, with up to four species from an individual adult beetle. The Raffaelea spp. were apparently within the protected, paired, mandibular mycangia because they were as numerous in heads as in whole beetles, and surface-sterilized heads or whole bodies yielded as many or more CFU as did nonsterilized heads or whole beetles. R. lauricola was isolated from 40 of the 41 beetles sampled, and it was isolated in the highest numbers, up to 30,000 CFU/beetle. Depending on the population sampled, R. subalba or R. ellipticospora was the next most frequently isolated species. R. arxii, R. fusca, and R. subfusca were only occasionally isolated. The laurel wilt pathogen apparently grows in a yeast phase within the mycangia in competition with other Raffaelea spp.

Phylogenetic placement of plant pathogenic Sclerotium species among teleomorph genera

Phylogenetic analyses and morphological characteristics were used to assess the taxonomic placement of eight plant-pathogenic Sclerotium species. Members of this genus produce only sclerotia and no fruiting bodies or spores, so Sclerotium species have been difficult to place taxonomically. Sequences of rDNA large subunit (LSU) and internal transcribed spacer (ITS) regions were determined for isolates of Sclerotium cepivorum, S. coffeicola, S. denigrans, S. hydrophilum, Ceratorhiza oryzae-sativae, S. perniciosum, S. rhizodes, S. rolfsii and S. rolfsii var. delphinii. Parsimony analysis grouped two species previously thought to be in the Basidiomycota, S. denigrans and S. perniciosum, within the Ascomycota; these species were found to have affinities with the teleomorph genera Sclerotinia and Stromatinia and the asexual Sclerotium cepivorum, which was known earlier to be related to Sclerotinia species. The other Sclerotium species were placed in one of two basidiomycetous groups, genera Athelia or Ceratobasidium. Based on rDNA analysis and morphology the basidiomycetous Sclerotium hydrophilum and S. rhizodes were transferred to genus Ceratorhiza, the anamorph of Ceratobasidium species. Sclerotium coffeicola was found to be close to S. rolfsii var. delphinii and S. rolfsii var. rolfsii, which was shown earlier to have an Athelia teleomorph.

Diversity and biogeography of sooty blotch and flyspeck fungi on apple in the eastern and midwestern United States

Sooty blotch and flyspeck (SBFS) fungi on apple fruit were sampled from nine orchards in four midwestern U.S. states during 2000 and 30 orchards in 10 eastern U.S. states during 2005 in order to estimate taxonomic diversity and discern patterns of geographic distribution. Forty apple fruit per orchard were arbitrarily sampled and colonies of each mycelial phenotype were counted on each apple. Representative colonies were isolated, cultures were purified, and DNA was extracted. For representative isolates, the internal transcribed spacer (ITS) and large subunit (LSU) regions of ribosomal DNA were amplified and sequenced. In total, 60 SBFS putative species were identified based on ITS sequences and morphological characteristics; 30 of these were discovered in the 2005 survey. Modified Koch's postulates were fulfilled for all 60 species in an Iowa orchard; colonies resulting from inoculation of apple fruit were matched to the original isolates on the basis of mycelial type and ITS sequence. Parsimony analysis for LSU sequences from both surveys revealed that 58 putative SBFS species were members of the Dothideomycetes, 52 were members of the Capnodiales, and 36 were members of the Mycosphaerellaceae. The number of SBFS species per orchard varied from 2 to 15. Number of SBFS species and values of the Margalef and Shannon indexes were significantly (P < 0.05) lower in 21 orchards that had received conventional fungicide sprays during the fruit maturation period than in 14 unsprayed orchards. Several SBFS species, including Schizothyrium pomi, Peltaster fructicola, and Pseudocercosporella sp. RH1, were nearly ubiquitous, whereas other species, such as Stomiopeltis sp. RS5.2, Phialophora sessilis, and Geastrumia polystigmatis, were found only within restricted geographic regions. The results document that the SBFS complex is far more taxonomically diverse than previously recognized and provide strong evidence that SBFS species differ in geographic distribution. To achieve more efficient management of SBFS, it may be necessary to understand the environmental biology of key SBFS species in each geographic region.

Heterobasidion annosum and H. parviporum in the Southern Rocky Mountains and Adjoining States

Collections of Heterobasidion spp. from Nebraska, Colorado, Arizona, and New Mexico were identified based on the sequence of the internal transcribed spacer region of the ribosomal DNA. The North American variant of Heterobasidion annosum sensu stricto was found on Pinus ponderosa and Juniperus virginiana in central Nebraska, southern Colorado, central Arizona, and southern New Mexico. The North American variant of H. parviporum was found on Abies concolor and Picea engelmannii in southern Colorado and central New Mexico. The pathogens were not found in a survey of conifer forests in Wyoming and the Black Hills of South Dakota. Historical records of annosus root disease are reviewed by host group to gain more insight into the potential distributions of the respective pathogens. An apparent lack of overlap in host range suggests that substitution of tree species may be a useful management approach in some cases.