Phylogenetic relationships of Phaeochorellaparinarii and recognition of a new family, Phaeochorellaceae (Diaporthales).

Species of Phaeochorella are biotrophic leaf parasites with a tropical distribution, traditionally accepted in the family Phyllachoraceae, Phyllachorales in classifications based on morphological characters. Phylogenetic evidence presented here resolves the relationship of Phaeochorella within the Sordariomycetes, based on a multilocus analysis of partial nuc rDNA large subunit (28S) and internal transcribed spacers (ITS1-5.8S-ITS2 = ITS), the DNA-directed RNA polymerase II second largest subunit (RPB2), and the translation elongation factor 1-α (TEF1-α) gene. Phylogenetic analyses indicate that Phaeochorella belongs to the Diaporthales rather than the Phyllachorales. Phaeochorella parinarii, the type species of the genus, present on native hosts from the Brazilian Cerrado, forms a unique clade with a species of Phaeoappendicospora with high support. Thus, a new family, Phaeochorellaceae, Diaporthales, including both genera, is herein proposed. With the exception of P. parinarii and P. zonata, all other species in Phaeochorella (P. artocarpi, P. ciliata, P. machaerii) were excluded from the genus.

New neotropical species of Phyllachorales based on molecular, morphological, and ecological data.

Species of tropical tar spot fungi (Phyllachorales, Ascomycota) are obligate biotrophic plant parasitic fungi associated with living leaves of a wide range of families of host plants, mainly in tropical and subtropical regions. In this study, samples of tropical tar spot fungi were collected in forests in Costa Rica and Panamá. To identify taxa, we used morphology and information on host plants and combined multigene phylogeny of four genes: the large subunit nuclear ribosomal DNA (28S rDNA), the small subunit nuclear ribosomal DNA (18S rDNA), the complete internal transcribed spacer region of ribosomal DNA (nuc rDNA ITS1-5.8S-ITS2; ITS), and the translation elongation factor 1-α (tef1). Here we propose one new species in the genus Camarotella and eight new species in Telimena with their morphological descriptions, illustrations, and sequence data. The newly described species are Camarotella licaniae on Licania arborea (Chrysobalanaceae) and in the genus Telimena: T. billiae on Billia rosea (Sapindaceae), T. drymoniae on Drymonia multiflora (Gesneriaceae), T. hydrangeae on Hydrangea sp. (Hydrangeaceae), T. miravallensis on Symplocos panamensis (Symplocaceae), T. protii on Protium sp. (Burseraceae), T. rinoreae on Rinorea sp. (Violaceae), T. semialarii on Semialarium mexicanum (Celastraceae), and T. triseptata on Tapirira mexicana (Anacardiaceae). The new name Telimena nitens on Schlegelia brachyanta (Schlegeliaceae) is presented and 10 species of Phyllachora are transferred to Telimena, leading to the new combinations T. canarii, T. galavisii, T. insueta, T. ruelliae, T. scutiformis, T. serjaniicola, T. spicatae, T. subrepens, T. symploci, and T. symplocicola. Additionally, revisions of tar spot fungi on host families Burseraceae, Sapindaceae, and Symplocaceae are provided, and four new synonyms are proposed.

ITS phylogeny and taxonomy of Phyllachora species on native Myrtaceae from the Brazilian Cerrado.

Nine Phyllachora species found on hosts belonging to the family Myrtaceae native to the Brazilian Cerrado were described and illustrated. We sequenced nuc rDNA internal transcribed spacer barcode regions for representatives of seven species and conducted phylogenetic analyses, which provided strong support for four new species that we describe as Phyllachora cerradensis, P. ermidensis, P. furnasensis, and P. myrciariae. Catacauma nigerrimum was recombined into P. nigerrima, and a key to the common Phyllachora species on myrtaceous hosts from the Brazilian Cerrado was also included.

Characterization of Glomerella strains recovered from anthracnose lesions on common bean plants in Brazil.

Anthracnose caused by Colletotrichum lindemuthianum is an important disease of common bean, resulting in major economic losses worldwide. Genetic diversity of the C. lindemuthianum population contributes to its ability to adapt rapidly to new sources of host resistance. The origin of this diversity is unknown, but sexual recombination, via the Glomerella teleomorph, is one possibility. This study tested the hypothesis that Glomerella strains that are frequently recovered from bean anthracnose lesions represent the teleomorph of C. lindemuthianum. A large collection of Glomerella isolates could be separated into two groups based on phylogenetic analysis, morphology, and pathogenicity to beans. Both groups were unrelated to C. lindemuthianum. One group clustered with the C. gloeosporioides species complex and produced mild symptoms on bean tissues. The other group, which belonged to a clade that included the cucurbit anthracnose pathogen C. magna, caused no symptoms. Individual ascospores recovered from Glomerella perithecia gave rise to either fertile (perithecial) or infertile (conidial) colonies. Some pairings of perithecial and conidial strains resulted in induced homothallism in the conidial partner, while others led to apparent heterothallic matings. Pairings involving two perithecial, or two conidial, colonies produced neither outcome. Conidia efficiently formed conidial anastomosis tubes (CATs), but ascospores never formed CATs. The Glomerella strains formed appressoria and hyphae on the plant surface, but did not penetrate or form infection structures within the tissues. Their behavior was similar whether the beans were susceptible or resistant to anthracnose. These same Glomerella strains produced thick intracellular hyphae, and eventually acervuli, if host cell death was induced. When Glomerella was co-inoculated with C. lindemuthianum, it readily invaded anthracnose lesions. Thus, the hypothesis was not supported: Glomerella strains from anthracnose lesions do not represent the teleomorphic phase of C. lindemuthianum, and instead appear to be bean epiphytes that opportunistically invade and sporulate in the lesions.

Glomerella truncata: another Glomerella species with an atypical mating system.

In the genus Glomerella all species studied to date do not fit the usual mating system of heterothallic ascomycetes. This study investigated the mating system of G. truncata (anamorph Colletotrichum truncatum), a pathogen responsible for lentil anthracnose. Twenty-two field isolates from the Canadian prairies were crossed in all possible combinations, including selfings. All isolates also were screened for the presence of the MAT1-1 and MAT1-2 idiomorphs by targeting small conserved areas of the MAT genes (the alpha domain and the high mobility group HMG box) with degenerate primers, and a pair of G. truncata-specific HMG primers (CT21HMG) were designed. The results of the classical mating study suggested that G. truncata is heterothallic. Isolates fell into two incompatibility groups, which is consistent with a bipolar mating system but different from what has been described in other Glomerella species. Molecular screening showed that the HMG box used as a marker for the MAT1-2 idiomorph was present in both partners of fertile crosses in G. truncata, unlike in the typical ascomycete system, but as previously described for two other Glomerella species. G. truncata therefore appears to share unusual mating system characteristics with the other Glomerella species studied to date.

A Glomerella species phylogenetically related to Colletotrichum acutatum on Norway maple in Massachusetts.

A fungus isolated from Norway maple (Acer platanoides) in the Boston, Massachusetts, area was determined to be a species of Glomerella, the teleomorph of Colletotrin chum acutatum. Pure cultures of the fungus were obtained from discharged ascospores from perithecia in leaf tissue. This fungus was determined to be homothallic based on the observation of perithecial development in cultures of single-spore isolates grown on minimal salts media and with sterile toothpicks. A morphological and molecular analysis was conducted to determine the taxonomic position of this fungus. Parsimony analyses of a combined nucleotide dataset of the ITS and LSU rDNA region, and of the D1-D2 LSU rDNA region, indicated that this species has phylogenetic affinities with Colletotrichum acutatum, C. acutatum f. sp. pineum, C. lupini, C. phormii and G. miyabeana. These results are significant because C. acutatum has not been reported on Acer platanoides. In addition the consistent presence of perithecia on leaf tissue and in culture is unusual for Colletotrichum, suggesting that the teleomorphic state is important in the life cycle of this fungus.

A phylogenetic evaluation of whether endophytes become saprotrophs at host senescence.

Fungal endophytes and saprotrophs generally play an important ecological role within plant tissues and dead plant material. Several reports based solely on morphological observations have postulated that there is an intimate link between endophytes and saprotrophs. This study aims to provide valuable insight as to whether some endophytic fungi manifest themselves as saprotrophs upon host decay. Ribosomal DNA-based sequence comparison and phylogenetic relationships from 99 fungal isolates (endophytes, mycelia sterilia, and saprotrophs) recovered from leaves and twigs of Magnolia liliifera were investigated in this study. Molecular data suggest there are fungal taxa that possibly exist as endophytes and saprotrophs. Isolates of Colletotrichum, Fusarium, Guignardia, and Phomopsis, which are common plant endophytes, have high sequence similarity and are phylogenetically related to their saprotrophic counterparts. This provides evidence to suggest that some endophytic species change their ecological strategies and adopt a saprotrophic lifestyle. The implication of these findings on fungal biodiversity and host specificity is also discussed.

Glomerella truncata sp. nov., the teleomorph of Colletotrichum truncatum.

Anthracnose of lentil, caused by Colletotrichum truncatum is a serious threat to lentil (Lens culinaris) grown in western Canada. The teleomorph stage of this pathogen was induced to form under laboratory conditions. Random pairing of single conidium isolates enabled the identification of fertile isolates. The individual isolates of this fertile pair were crossed with 14 other isolates, and all isolates were also incubated alone. Self-sterility was observed for all 16 isolates tested. Three isolates did not produce perithecia with either tester isolate, and none of the isolates tested produced perithecia with both tester isolates. Perithecia were brown-black, superficial, solitary or in small groups, obpyriform to ovate or ampulliform, 200-520 x 110-320 microm (mean: 350 x 200 microm). Asci were cylindrical, narrowing slightly at the apex, unitunicate, evanescent, 53-142 x 5-14 microm (mean: 90 x 8 microm), and contained eight ascospores. Ascospores were hyaline, aseptate, oblong, 12-20 x 5-8 microm (mean: 15.7-6.7 microm). The characteristics agree with those described for the genus Glomerella, and the species was named G. truncata sp. nov. The morphology of the new species is compared with that of other species in the genus, and future research on G. truncata is described.

Heterothallic mating observed between Mexican isolates of Glomerella lindemuthiana.

Although several reports have described the occurrence of the teleomorphic state of Glomerella lindemuthiana (anamorph, Colletotrichum lindemuthianum), there has been a lack of continuity in this research. To identify G. lindemuthiana isolates capable of developing the teleomorphic state, 19 Mexican isolates were analyzed. Three types of response were observed: (i) negative, where only mycelial growth with or without acervuli was observed; (ii) potential, where in addition to the above, spherical perithecia-like structures were observed; (iii) positive, where perithecia containing asci and ascospores were observed. All strains were self-sterile and only one combination of strains produced fertile perithecia. From this fertile combination 168 individual ascospore cultures were isolated, including five from a single ascus. Forty-four monoascospore cultures were characterized with AFLP, confirming that these individuals were progeny from a sexual cross between the original two G. lindemuthiana isolates and that sexual reproduction in G. lindemuthiana is heterothallic in nature. Analysis of the parental strains with degenerate PCR primers indicated that sequences homologous to the HMG box of the MAT1-2 idiomorph are present in both parental isolates. This supports previous observations in other Glomerella species where the standard ascomycete configuration of distinct idiomorphs at the MAT locus does not hold true. The significance of these results is discussed.