The asexual morph and molecular phylogeny of endemic <i>Phyllactinia verruculosa</i> on <i>Indigofera tinctoria</i>

Phyllactinia verruculosa is a powdery mildew species (Erysiphaceae, tribe Phyllactinieae) so far only known from its type material collected in China on Indigofera scabrida in 1992, which only comprised the sexual morph. Two asexual morph samples were observed, one was collected on I. tinctoria on the campus of Guizhou University, Guiyang, China, and another one, on I. scabrida, was borrowed from Kunming Institute of Botany, Chinese Academy of Sciences. The anamorphic characters were observed, described and illustrated. The phylogenetic analysis of the combination of internal transcribed spacer regions (ITS) and 28S rDNA sequences showed that Ph. verruculosa is phylogenetically distantly related from other Phyllactinia species. To our knowledge, this is the first record of the asexual morph and first ITS+28S sequences for Ph. verruculosa, and I. tinctoria is a new host record for this species.

One Crop Disease, How Many Pathogens? Podosphaera xanthii and Erysiphe vignae sp. nov. Identified as the Two Species that Cause Powdery Mildew of Mungbean (Vigna radiata) and Black Gram (V. mungo) in Australia

Powdery mildew is a significant threat to mungbean (Vigna radiata) and black gram (V. mungo) production across Australia and overseas. Although they have been present in Australia for at least six decades and are easily recognized in the field, the precise identification of the pathogens causing this disease has remained unclear. Our goal was to identify the powdery mildew species infecting mungbean, black gram, and wild mungbean (V. radiata ssp. sublobata) in Australia. The internal transcribed spacer (ITS) and large subunit sequences of the ribosomal DNA and/or morphology of 57 Australian specimens were examined. Mungbean and black gram were infected by two species: Podosphaera xanthii and a newly recognized taxon, Erysiphe vignae sp. nov. Wild mungbean was infected only with P. xanthii. Mungbean and black gram powdery mildew ITS sequences from China, India, and Taiwan revealed the presence of only P. xanthii on these crops despite controversial reports of an Erysiphe species on both crops in India. Sequence analyses indicated that the closest relative of E. vignae is E. diffusa, which infects soybean (Glycine max) and other plants. E. vignae did not infect soybean in cross-inoculation tests. In turn, E. diffusa from soybean infected black gram and provoked hypersensitive response in mungbean. The recognition of a second species, E. vignae, as another causal agent of mungbean and black gram powdery mildew in Australia may complicate plant breeding efforts and control of the disease with fungicide applications.

Multi-locus phylogeny and taxonomy of an unresolved, heterogeneous species complex within the genus Golovinomyces (Ascomycota, Erysiphales), including G. ambrosiae, G. circumfusus and G. spadiceus

Background

Previous phylogenetic analyses of species within the genus Golovinomyces (Ascomycota, Erysiphales), based on ITS and 28S rDNA sequence data, revealed a co-evolutionary relationship between powdery mildew species and hosts of certain tribes of the plant family Asteraceae. Golovinomyces growing on host plants belonging to the Heliantheae formed a single lineage, comprised of a morphologically differentiated complex of species, which included G. ambrosiae, G. circumfusus, and G. spadiceus. However, the lineage also encompassed sequences retrieved from Golovinomyces specimens on other Asteraceae tribes as well as other plant families, suggesting the involvement of a plurivorous species. A multilocus phylogenetic examination of this complex, using ITS, 28S, IGS (intergenic spacer), TUB2 (beta-tubulin), and CHS1 (chitin synthase I) sequence data was carried out to clarify the discrepancies between ITS and 28S rDNA sequence data and morphological differences. Furthermore, the circumscription of species and their host ranges were emended.

Results

The phylogenetic and morphological analyses conducted in this study revealed three distinct species named, viz., (1) G. ambrosiae emend. (including G. spadiceus), a plurivorous species that occurs on a multitude of hosts including, Ambrosia spp., multiple species of the Heliantheae and plant species of other tribes of Asteraceae including the Asian species of Eupatorium; (2) G. latisporus comb. nov. (≡ Oidium latisporum), the closely related, but morphologically distinct species confined to hosts of the Heliantheae genera Helianthus, Zinnia, and most likely Rudbeckia; and (3) G. circumfusus confined to Eupatorium cannabinum in Europe.

Conclusions

The present results provide strong evidence that the combination of multi-locus phylogeny and morphological analysis is an effective way to identify species in the genus Golovinomyces.

Epitope analysis of an HLA-B27-derived synthetic peptide: a possible approach to analyzing HLA class I antigens

A monoclonal antibody, F3H7, was generated by immunizing mice with a synthetic peptide corresponding to residues 63-84 of the B*2705 allele of the HLA-B27 antigens. The reactive epitope and the contact residues on the peptide were localized by ELISA using a large panel of overlapping peptides as well as peptides with substituted amino acids. Residues corresponding to R75, D77 and L78 on the HLA-B27 protein appeared to be critical. The clarity of these results indicate that this is a potentially useful approach to the study of HLA class I epitopes.