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

Abstract

Powdery mildew is a significant threat to mungbean (Vigna radiata) and black gram (V. mungo) production across Australia and overseas. Despite being present in Australia for at least six decades, and being 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 (LSU) sequences of the ribosomal DNA (rDNA) and/or morphology of 57 Australian specimens were examined. Mungbean and black gram were infected by two species: Podosphaera xanthii and a newly recognised 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. Erysiphe 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 have implications for existing fungicide control measures and breeding.

Long‐term and rapid evolution in powdery mildew fungi

“…The tree is decorated with the number of accepted powdery mildew species in each genus (blue circles at tree branches; size illustrates the number of accepted species), the number of hosts (green circles, size displays the number of reported host plant genera), a stacked bar graph displaying preference for herbaceous (green), shrub (brown), or tree hosts (purple), and a stacked bar chart showing preference for annual/deciduous (light/dark brown) or perennial/evergreen (light/dark green) host plants. Data was extracted by literature review (Braun & Cook, 2012; Kelly et al, 2021; Kiss et al, 2020; Liu et al, 2021; Marmolejo et al, 2018; Meeboon et al, 2017). (b) The upper violin plot shows the number of known host genera for each powdery mildew species with primarily herbs, shrubs, or trees as hosts.…”

Beyond Nuclear Ribosomal DNA Sequences: Evolution, Taxonomy, and Closest Known Saprobic Relatives of Powdery Mildew Fungi (Erysiphaceae) Inferred From Their First Comprehensive Genome-Scale Phylogenetic Analyses

“…Others are known from many, only distantly related plants (e.g., Meeboon and Takamatsu, 2016 ; Braun et al, 2019 ; Kiss and Vaghefi, 2021 ; Young and Kiss, 2021 ). Finally, some host plants can be infected by more than one powdery mildew species, which sometimes belong to different genera (e.g., Takamatsu et al, 2007 ; Kiss et al, 2008 ; Desprez-Loustau et al, 2018 ; Kelly et al, 2021 ; Faticov et al, 2022 ). Some species have become invasive in different parts of the world ( Kiss, 2005 ; Desprez-Loustau et al, 2010 ; Kiss et al, 2020 ).…”

Thirty Years of Mungbean Genome Research: Where Do We Stand and What Have We Learned?

“…The disease is also caused by Sphaerotheca phaseoli (Z. Y. Zhao) U. Braun (Lee et al, 2002), Podosphaera xanthii (Castagne) U. Braun and Shishkoff (Sheu et al, 2021), and Erysiphe vignae sp. nov. (Kelly et al, 2021). The disease is prevalent in cool and dry environments and is favored by high-density plant populations and cloudy weather (Laosatit et al, 2020).…”