Search

Powdery mildews on oaks, caused by Erysiphe species, have serious ecological consequences on a range of Quercus hosts. In addition to Erysiphe quercicola, E. alphitoides is one of the most common and widespread species of Erysiphe having a wide host range among oak species, and a clear economic significance in applied ecology, forestry, and forest pathology. There are many publications addressing these important tree pathogens. Previous phylogenetic examinations have shown that E. alphitoides refers to a complicated species assemblage with insufficient taxonomic resolution in ITS + 28S analyses; the associated sequences form an insufficiently resolved species complex. The majority of species within the E. alphitoides complex cannot be unequivocally identified based solely on ITS + 28S analyses. Most of the additional species of the E. alphitoides complex are distributed in Asia, with a concentration in Japan. The question posed is whether there is a single widespread powdery mildew species, E. alphitoides, or an assemblage of closely allied species. To answer this question, specimens of related recognized species, particularly those from Japan, have been subjected to phylogenetic multilocus examinations, including CAM, GAPDH, GS, ITS + 28S, RPB2, and TUB sequences. An analysis of the concatenated sequences resulted in the confirmation of several distinct species. These species form highly supported clades that include E. alphitoides, E. aucubae, E. euonymicola, E. ipomoeae, E. menispermi var. dahurica, E. orixae, E. pseudolonicerae, E. sinomenii and E. wallrothii. Erysiphe akebiae as well as the relationship between Japanese and North American collections requires further examinations. [ABSTRACT FROM AUTHOR]

Chemical control of grape black rot, caused by Phyllosticta ampelicida, relies mainly on the use of demethylation inhibitors (DMIs) and quinone outside inhibitors (QoIs). The effectiveness of QoI fungicides is influenced by alternative respiration activity, and the exon/intron structure and point mutations in the target protein's gene, the cytochrome b (cytb) gene. Our study aims to investigate the QoI fungicide sensitivity of 48 P. ampelicida isolates in vitro by measuring EC50 and the molecular characteristics of the cytb gene and its mRNA in P. ampelicida and other Phyllosticta species. Mycelial growth tests revealed that the P. ampelicida isolates were sensitive to both azoxystrobin and trifloxystrobin; baseline EC50 values were 0.029 and 0.022 μg/mL, respectively. Addition of salicylhydroxamic acid (SHAM) resulted in lower EC50 values (0.024 and 0.017 μg/mL, respectively). None of the typical point mutations conferring resistance to QoIs in some fungi were detected. A group I intron was present right after the 143rd codon in the cytb gene in four of the six Phyllosticta species examined. The sequence and exon/intron structure of the cytb gene of P. ampelicida isolated from Vitis vinifera is studied in detail and published here. Our results indicate a low risk of QoI resistance development via the G143A mutation in P. ampelicida. [ABSTRACT FROM AUTHOR]

The demand for common hazel (Corylus avellana) fruit increases constantly. Powdery mildew (PM) on hazels in Hungary and throughout Europe was previously caused mainly by Phyllactinia guttata. However, less than a decade ago, another fungus of Asian origin, Erysiphe corylacearum, appeared on hazels in Europe, including Hungary. Our investigation aimed to develop a species-specific PCR (ssPCR) to aid the identification of P. guttata and E. corylacearum, and to assess the presence of the latter, non-native fungus in Hungary. For this study, 59 samples were collected from Hungary between 2021 and 2023. The chasmothecial morphology of the PM fungi was observed, and the internal transcribed spacer (ITS) of ribosomal DNA was sequenced in representative samples. Morphological analysis distinguished two types of chasmothecia. Parts of the chasmothecia, typical of P. guttata, were flattened and spherical with bristle-like appendages, while other chasmothecia, characteristic of E. corylacearum, were distinctly smaller, bearing appendages with branched apices. Sequence data also verified the presence of P. guttata and E. corylacearum in our samples. The developed ssPCR revealed that E. corylacearum was present in more than three-quarters of the samples, more than a quarter of the samples contained both fungi and about one-fifth carried solely P. guttata. The alien fungus E. corylacearum was found in all but one of the sampled regions and was found on C. avellana and also on C. colurna. Erysiphe corylacearum spreads rapidly and can be considered an invasive pathogen. Its practical importance lies in its ability to infect hazelnuts, potentially causing economic losses. Our ssPCR ensures accurate and quick identification of the fungus, which is essential for effective plant protection. [ABSTRACT FROM AUTHOR]

During a four-year project conducted to identify fungal species associated with grapevine trunk diseases (GTDs) in Hungarian vineyards, two non-sporulating strains isolated from vines exhibiting typical GTD symptoms were identified as Dothiorella omnivora based on their nrDNA ITS and EF1-α sequences. Conidial production of these strains was induced on pine needle medium where production of spermatia has also been observed. Pathogenicity tests confirmed their virulence on potted vines. Dothiorella omnivora is a recently described species of the Botryosphaeriaceae, known to infect hazelnut, ash, walnut, and other woody hosts. This is the first European record of D. omniovora from vines exhibiting GTD symptoms. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]