An evaluation of the monophyly of Massarina based on ribosomal DNA sequences

The monophyletic status of the genus Massarina was evaluated on the basis of phylogenetic analysis of the partial small subunit gene (SSU), internal transcribed spacers (ITS 1 & 2), and 5.8S gene sequences of the ribosomal DNA. Species of Massarina used in the study clustered into two distinct clades with high bootstrap support in trees generated from maximum parsimony, weighted parsimony, maximum likelihood, and neighbor-joining analyses. The hypothesis that Massarina species belong to a phylogenetically monophyletic group is rejected. Species with narrowly fusiform ascospores form a monophyletic clade with Lophiostoma, a genus highly similar in morphology. The five species currently accepted in Massarina with such spore morphology are here transferred into the genus Lophiostoma. Massarina species with broadly fusiform to ellipsoidal ascospores are retained as Massarina s. str., lectotypified by M. eburnea. Massarina walkeri is presently excluded from both Massarina and Lophiostoma. The transfer of M. papulosa to a new genus Oletheriostrigula is verified.published_or_final_versio

Characterization and taxonomic placement of Rhizoctonia--like endophytes from orchid roots

Twenty-one Rhizoctoniu-like fungal strains were isolated from the roots of four terrestrial orchid species from various locations in Hong Kong. The cultural morpholon, uclear number of the hyphal cell, pore ultrastructure, and RAPD and CAPS analyses of rDNA fragments revealed that nlost of these isolates Tvere associated with the genera Clatorlziza and Epulorhizn. W Dan alysis showed the presence of genetic diversity between the isolates froin different hosts and locations. The compatibility between a selection of these Ceratorhiza and Epulorhiza isolates and 14 orchld species was determined using a symbiotic gerrninatlon method The germinatioil and development of three orchld species, .Arundina chinensis, Spathoglottis poubescens, and Spiranthes honkongensis, were strongly stimulated by the Epulorhiza isolates. Habenaria dentata was found to form symbionts successfully with a Ceratorhiza isolate.published_or_final_versio

Phylogenetic relationships of Pestalotiopsis and allied genera inferred from ribosomal DNA sequences

Publication no. P-2001-0089-MSA,published_or_final_versio

Dyrithiopsis lakefuxianensis gen et sp. nov. from Fuxian Lake, Yunnan, China and notes on the taxonomic confusion surrounding Dyrithium

A new taxon with Dyrithium-like characteristics was collected from Lake Fuxian in China. The taxon is typical of the Amphisphaeriaceae in that it has relatively large, ostiolate, immersed ascomata, unitunicate asci with a J+ subapical ring, and brown ascospores. It is similar to Dyrithium in that it has muriform ascospores, but considerable confusion surrounds this genus. In Dyrithium asci are bitunicate and lack a J+ subapical ring, while this was not true of our species. A new genus, Dyrithiopsis, therefore is established to accommodate this new taxon. Details of its anamorph also are provided, based on cultural studies. Parsimony analyses of part of the large-subunit rDNA provide further evidence to support the familial placement of this new genus in the Amphisphaeriaceae. The taxonomic position of Dyrithium also is discussed.published_or_final_versio

Pleosporales

One hundred and five generic types of Pleosporales are described and illustrated. A brief introduction and detailed history with short notes on morphology, molecular phylogeny as well as a general conclusion of each genus are provided. For those genera where the type or a representative specimen is unavailable, a brief note is given. Altogether 174 genera of Pleosporales are treated. Phaeotrichaceae as well as Kriegeriella, Zeuctomorpha and Muroia are excluded from Pleosporales. Based on the multigene phylogenetic analysis, the suborder Massarineae is emended to accommodate five families, viz. Lentitheciaceae, Massarinaceae, Montagnulaceae, Morosphaeriaceae and Trematosphaeriaceae

Differential disease reactions on lucerne genotypes inoculated with Phytophthora medicaginis isolates from lucerne and chickpea

Stem inoculation of clonally propagated lucerne genotypes was used to assess levels of host species and genotype specialisation in Phytophthora medicaginis. A quantitative assessment of pathogenic aggressiveness of 29 P. medicaginis isolates (from lucerne and chickpea) on 9 different clonally propagated lucerne genotypes revealed no significant difference in aggressiveness between isolates from lucerne and those from chickpea on all of the lucerne genotypes. This supported previous studies which showed that P. medicaginis isolates from lucerne and chickpea were indistinguishable using random amplified polymorphic DNA (RAPD) analysis. Analysis of pathogenic aggressiveness towards individual lucerne genotypes revealed, for the first time, specificity of individual P. medicaginis isolates. This has implications for breeding for resistance to P. medicaginis in lucerne, where screening should be done using the widest range of pathogen specificity obtainable

An evaluation of the fungal 'morphotype' concept based on ribosomal DNA sequences

In studies of fungal endophyte communities, mycelia sterilia are commonly isolated from plant substrates and grouped into morphotypes on the basis of cultural characteristics. In Polygonum multiflorum one hundred and sixty-nine strains of mycelia sterilia were isolated and grouped into 27 morphotypes. Six randomly selected morphotypes, each with 2-3 representatives, were subsequently subjected to ribosomal DNA sequence analysis. Nucleotide sequence similarities of the rDNA internal transcribed spacer (ITS) regions and the 5.8S gene were compared using UPGMA cluster analysis. Comparison of nucleotide sequences revealed high levels of similarity (ca. 91.63-99.53%) among strains within morphotypes. ITS and 5.8S sequences of species within various genera from GenBank were obtained to estimate levels of nucleotide similarity within and between well-established genera and species. This study verifies on the basis of ribosomal DNA sequence analysis the validity of these 'morphotypes' as taxonomic groups. A dendogram, illustrating relatedness of the morphotypes and reference taxa from GenBank is also presented.link_to_OA_fulltex

Specific PCR based detection of Phytophthora medicaginis using the intergenic spacer region of the ribosomal DNA

A technique based on the polymerase chain reaction (PCR) for the specific detection of Phytophthora medicaginis was developed using nucleotide sequence information of the ribosomal DNA (rDNA) regions. The complete IGS 2 region between the 5 S gene of one rDNA repeat and the small subunit of the adjacent repeat was sequenced for P. medicaginis and related species. The entire nucleotide sequence length of the IGS 2 of P. medicaginis was 3566 bp. A pair of oligonucleotide primers (PPED04 and PPED05), which allowed amplification of a specific fragment (364 bp) within the IGS 2 of P. medicaginis using the PCR, was designed. Specific amplification of this fragment from P. medicaginis was highly sensitive, detecting template DNA as low as 4 ng and in a host-pathogen DNA ratio of 1000000:1. Specific PCR amplification using PPED04 and PPED05 was successful in detecting P. medicaginis in lucerne stems infected under glasshouse conditions and field infected lucerne roots. The procedures developed in this work have application to improved identification and detection of a wide range of Phytophthora spp. in plants and soil

Phylogenetic evaluation of species nomenclature of Pestalotiopsis in relation to host association

DNA data from a number of Pestalotiopsis isolates were analysed to investigate whether isolates from the same host are phylogenetically related. The validity of naming species of Pestalotiopsis based on host association was investigated. Regions of the ITS and 5.8S of the rDNA gene were amplified from genomic DNA using PCR. DNA characters were analysed using maximum parsimony (weighted and unweighted) and maximum likelihood criteria. Isolates from the same host were not phylogenetically closely related. A close phylogenetic relationship between isolates possessing similar morphological characters was apparent. Results indicate that the naming of species based on host association is unwise and dispute the assumption that species are host-specific. When new Pestalotiopsis species are described, morphological characters should be taken into account rather than host association. The implications of the results on fungal biodiversity studies are discussed.link_to_OA_fulltex