RESUMO

New species of Amanita subgen. Lepidella are described from Guyana. Amanita cyanochlorinosma sp. nov., Amanita fulvoalba sp. nov., and Amanita guyanensis sp. nov. represent the latest additions to the growing body of newly described ectomycorrhizal fungi native to Dicymbe-dominated tropical rainforests. Macro- and micromorphological characters, habitat, and DNA sequence data for the ITS, nrLSU, rpb2, and ef1-α are provided for each taxon, and ß-tubulin for most. Distinctive morphological features warrant the recognition of the three new species and a molecular phylogenetic analysis of taxa across Amanita subgen. Lepidella corroborates their infrageneric placements.

RESUMO

The cacao pathogen Moniliophthora roreri belongs to the mushroom-forming family Marasmiaceae, but it has never been observed to produce a fruiting body, which calls to question its capacity for sexual reproduction. In this study, we identified potential A (HD1 and HD2) and B (pheromone precursors and pheromone receptors) mating genes in M. roreri. A PCR-based method was subsequently devised to determine the mating type for a set of 47 isolates from across the geographic range of the fungus. We developed and generated an 11-marker microsatellite set and conducted association and linkage disequilibrium (standardized index of association, IA(s)) analyses. We also performed an ancestral reconstruction analysis to show that the ancestor of M. roreri is predicted to be heterothallic and tetrapolar, which together with sliding window analyses support that the A and B mating loci are likely unlinked and follow a tetrapolar organization within the genome. The A locus is composed of a pair of HD1 and HD2 genes, whereas the B locus consists of a paired pheromone precursor, Mr_Ph4, and receptor, STE3_Mr4. Two A and B alleles but only two mating types were identified. Association analyses divided isolates into two well-defined genetically distinct groups that correlate with their mating type; IA(s) values show high linkage disequilibrium as is expected in clonal reproduction. Interestingly, both mating types were found in South American isolates but only one mating type was found in Central American isolates, supporting a prior hypothesis of clonal dissemination throughout Central America after a single or very few introductions of the fungus from South America.

Assuntos

Agaricales/genética , Cacau/microbiologia , Genes Fúngicos Tipo Acasalamento , Agaricales/fisiologia , América Central , DNA Fúngico/genética , Marcadores Genéticos , Desequilíbrio de Ligação , Repetições de Microssatélites , Feromônios/genética , Filogenia , Receptores de Feromônios/genética , América do Sul

RESUMO

The rust fungus Phragmidium tuberculatum Jul. Müll. is a common pathogen on Rosa spp., on which all life cycle stages are formed. Symptoms occur in spring and may include distorted stems, yellow spots on the upper leaf surface, and a bright orange spore mass formed on the abaxial leaf surface. In late summer, sori become speckled with black as fascicles of teliospores develop. The current known distribution of P. tuberculatum is mostly limited to Europe with some occurrence in Asia and into Australasia (2). There is some documented occurrence in North America (Alaska, Connecticut, and Canada [2]), where most rose rust disease is attributed to P. mucronatum (Pers.) Schltdl. This study used a combination of molecular and morphological analyses on newly collected material from across North America (California: BPI877978, PURN7783; Oregon: BPI877980; Massachusetts: BPI877977; and Quebec: BPI877979) and herbarium material from South and Central America (Honduras: BPI864186; and Argentina: BPI843677; both previously identified as P. mucronatum) to document a much broader distribution of P. tuberculatum. Collectively, teliospores from these collections are 4 to 6 celled, dark to black-brown, warted, elongated to cylindrical, 64.7 to 92.4 µm in length by 23.1 to 39.3 µm in width (average 77.6 × 30.0 µm) (30 teliospores from 2 leaves), with 2 to 3 pores/cell and a pronounced hyaline apiculus 4.6 to 18.5 µm long (average 8.3 µm). P. tuberculatum is similar morphologically to P. mucronatum, but sensu Gäumann (3) differs in having wider (30 to 36 µm) and longer (65 to 110 µm) teliospores with an average of 6 to 8 cells/spore. However, the two are easily distinguished by DNA analyses (4). The 28S sequences were amplified using the protocols described in Aime (1) and compared phylogenetically to 28S sequences available in the GenBank database for P. tuberculatum, P. mucronatum, and other Phragmidium spp. (4). In a maximum likelihood analysis, all isolates formed a 99% bootstrap supported clade with P. tuberculatum sequences from Germany, and shared 100% sequence identity with JF907675 P. tuberculatum. In contrast, comparison with HQ421646 P. mucronatum produced only 92% identity (e.g., 836/911 bp for PURN7783). This information indicates that P. tuberculatum is likely to be widespread in the Americas but simply misidentified as P. mucronatum, as was found to be the case for the two herbarium specimens sampled. Detailed examination of historical herbarium material may help to pinpoint how long the fungus has been present and the current extent of its distribution. The rose rust fungus is not considered to be a problem economically, but its spread within North America may be an indicator of commercial practices that serve as a vector for other diseases on ornamental plants. Voucher specimens have been deposited in the U.S. National Fungus Collections (BPI) and Arthur Fungarium (PUR); voucher sequences are deposited in GenBank (Accession Nos. KJ841917 to 23). References: (1) M. C. Aime. Mycoscience 47:112, 2006. (2) J. F. Arthur. Manual of the rusts in United States and Canada. Purdue Research Foundation, 1934. (3) E. Gäumann. Die Rostpilze Mitteleuropas mit besonderer Berücksichtigung der Schweiz. Büchler, Bern, 1959. (4) C. M. Ritz et al. Mycol. Res. 109:603, 2005.

RESUMO

Orange rust, Puccinia kuehnii (W. Krüger) E.J. Butler, is an important disease of sugarcane (complex hybrid of Saccharum L. species) that causes up to 53% yield loss (3), and can eliminate sugarcane clones in breeding programs. Initially confined to the Asia-Oceania region, P. kuehnii was reported in Florida in June 2007 (2) followed by confirmation in Central and South America. Orange rust pustules were observed on August 5, 2011, in commercial sugarcane fields located in the Ecuadorian Pacific coast of South America. Pustules were observed on cultivar SP79-2233 and sugarcane clones of the CINCAE breeding program (EC06-351, EC06-340, and EC01-744). Low levels of disease incidence and severity were observed in the sugarcane germplasm. Observation under a light microscope showed typical irregularly echinulate urediniospores that were pale in color with thickened apices and paraphyses inconspicuous to absent, such as those reported to be P. kuehnii (4). DNA of urediniospores were extracted and amplified using Pk1F and PK1R qPCR primers (5). Additionally, the 28s large ribosomal subunit DNA was sequenced (1), resulting in a qPCR and 100% sequence identity with a partial sequence of the P. kuehnii 28S ribosomal RNA gene, accession GU058010 (932/932 base pairs, GenBank Accession No. KF202306). Based on urediniospore morphology, DNA amplification, and sequence analysis, the causal agent of the rust observed in Ecuador was confirmed to be P. kuehnii. Commercial varieties have not yet shown symptoms of infections. However, a survey conducted in 2011 and 2012 showed an increase of disease severity from 3% to 28% in the susceptible cv. SP79-2233. Disease symptoms were evident from stalk growth to maturity (7 to 12 months), especially at the beginning of the harvesting season. To our knowledge, this is the first report of the presence, distribution, and disease spread by the sugarcane orange rust pathogen P. kuehnii in Ecuador. References: (1) M. C. Aime. Mycoscience 47:112, 2006. (2) J. C. Comstock et al. Plant Dis. 92:175, 2008. (3) J. C. Comstock et al. ASSCT. 29:82, 2009. (4) L. Dixon and L. Castlebury. Orange Rust of Sugarcane - Puccinia kuehnii. Syst. Mycol. Microbiol. Lab. Retrieved from /sbmlweb/fungi/index.cfm, August 12, 2011. (5) N. C. Glynn et al. Plant Pathol. 59:703, 2010.