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.

A global view of Gyroporus: molecular phylogenetics, diversity patterns, and new species

Gyroporus (Gyroporaceae, Boletales) is a highly diverse genus of poroid ectomycorrhizal mushrooms with a nearly worldwide distribution. Previous attempts to unravel the diversity within this genus proved difficult due to the presence of semicryptic species and ambiguous results from analysis of ribosomal RNA markers. In this study, we employ a combined morphotaxonomic and phylogenetic approach to delimit species and elucidate geographic and evolutionary patterns in Gyroporus. For phylogenetic analyses, the protein-coding genes atp6 (mitochondrial adenosine triphosphate [ATP] synthase subunit 6) and rpb2 (nuclear second largest subunit of RNA polymerase II) were selected based on their utility in studies of Boletales. We infer several distinct clades, most notably one corresponding to G. castaneus as a speciose Northern Hemisphere group, another unifying G. cyanescens and like entities, and a third group unifying G. longicystidiatus and a New World sister species. Also notable is the recovery of a sister relationship between the cyanescens and longicystidiatus clades. We formally describe five new species of Gyroporus, outline a number of provisional species, and briefly discuss distributional patterns. This study provides an important scaffold for future work on this well-known but poorly understood genus of fungi.

Sutorius: a new genus for Boletus eximius

Sutorius is described as a new genus of Boletaceae to accommodate Boletus robustus originally named illegitimately by C.C. Frost from eastern North America. The legitimate name, Boletus eximius, provided by C.H. Peck, has been used since for a dark purple to chocolate brown bolete with finely scaly stipe and reddish brown spore deposit. This iconic taxon has been documented on five continents. Despite the straightforward species identification from morphology, the interpretation of stipe macro-morphology and spore color has led to equivocal generic placement. Phylogenetic analyses of genes encoding large subunit rRNA and translation elongation factor 1α confirm Sutorius as a unique generic lineage in the Boletaceae. Two species are recognized based on multiple accessions: S. eximius, represented by collections from North America, Costa Rica, Guyana, Indonesia and Japan (molecular data are lacking for only the Guyanan and Japanese material); and S. australiensis, represented by material from Queensland, Australia. Additional collections from Zambia and Thailand represent independent lineages, but sampling is insufficient to describe new species for these entities.