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A survey was conducted of the rust fungus Gymnosporangium in Korea. We recollected previously known species, namely Gymnosporangium asiaticum, G. clavariiforme, G. globosum, G. japonicum and G. yamadae. Gymnosporangium nidus-avis and G. sabinae are reported for the first time from Korea, and two new species, G. monticola sp. nov. and G. unicorne sp. nov., are recognized. Previous single reports of G. miyabei and G. shiraianum could not be confirmed. The LSU rDNA was sequenced from freshly collected specimens. Phylogenetic analyses show that species of Gymnosporangium form a monophyletic group with strong bootstrap support within the rust fungi. The two new species are unique based on both A and B molecular as well as morphological characteristics. Analyses of phenotypic characters mapped onto the phylogenetic tree show that teliospore length followed by telia shape and telia length are conserved; these are morphological characters useful in differentiating species of Gymnosporangium. Each of the nine species of Gymnosporangium in Korea is described and illustrated, and keys based on aecia and telia stages are provided. Lectotype specimens for several names described in Gymnosporangium are designated.

Background Gymnosporangium asiaticum and G. yamadae can share Juniperus chinensis as the telial host, but the symptoms are completely different. The infection of G. yamadae causes the enlargement of the phloem and cortex of young branches as a gall, but not for G. asiaticum , suggesting that different molecular interaction mechanisms exist the two Gymnosporangium species with junipers. Results Comparative transcriptome analysis was performed to investigate genes regulation of juniper in responses to the infections of G. asiaticum and G. yamadae at different stages. Functional enrichment analysis showed that genes related to transport, catabolism and transcription pathways were up-regulated, while genes related to energy metabolism and photosynthesis were down-regulated in juniper branch tissues after infection with G. asiaticum and G. yamadae . The transcript profiling of G. yamadae -induced gall tissues revealed that more genes involved in photosynthesis, sugar metabolism, plant hormones and defense-related pathways were up-regulated in the vigorous development stage of gall compared to the initial stage, and were eventually repressed overall. Furthermore, the concentration of cytokinins (CKs) in the galls tissue and the telia of G. yamadae was significantly higher than in healthy branch tissues of juniper. As well, tRNA-isopentenyltransferase (tRNA-IPT) was identified in G. yamadae with highly expression levels during the gall development stages. Conclusions In general, our study provided new insights into the host-specific mechanisms by which G. asiaticum and G. yamadae differentially utilize CKs and specific adaptations on juniper during their co-evolution.

This document provides the conclusions of the pest survey card that was prepared in the context of the EFSA mandate on plant pest surveillance (M‐2020‐0114) at the request of the European Commission. The full pest survey card for non‐EU Gymnosporangium spp. is published and available online in the EFSA Pest Survey Card gallery at the following link and will be updated whenever new information becomes available: https://efsa.europa.eu/plants/planthealth/monitoring/surveillance/non-eu-gymnosporangium

The European pear (Pyrus communis) is an economically significant fruit crop. Sustainable pear cultivation is negatively affected by European pear rust caused by Gymnosporangium sabinae. The current knowledge on the variability of the pathogen and host resistance is insufficient, limiting the implementation of successful plant protection methods. This study aimed to identify Gymnosporangium species occurring in Latvia on junipers (Juniperus) and P. communis with a focus on possible hosts of G. sabinae and to assess the pathogen’s genetic diversity and pathogenicity as well as their geographic origin. Based on a large sample across the country, morphological characterization and sequences of three loci, three species were found: G. sabinae on J. sabina and P. communis, G. clavariiforme on J. communis, and G. cornutum on J. communis and Sorbus aucuparia. Resistant genotypes among seedlings consistently showed no disease symptoms in inoculation experiments, confirming the presence of resistance to G. sabinae in P. communis. Pathogenicity of G. clavariiforme on P. communis was tested and confirmed by inoculation with basidiospore inoculum from J. sabina. The methodology tested and obtained results obtained in this study using artificial inoculation will support further studies of G. sabinae and P. communis interaction.

This article is the 17th in the Fungal Diversity Notes series which allows the researchers to publish fungal collections with updated reports of fungus-host and fungus-geography. Herein we report 97 taxa with four new genera distributed in three phyla (Ascomycota, Glomeromycota and Mucoromycota), 11 classes, 38 orders and 62 families collected from various regions worldwide. This collection is further classified into taxa from 69 genera with four novel genera namely Jinshana , Lithophyllospora , Parapolyplosphaeria and Stegonsporiicola . Furthermore, 71 new species, 21 new records, one new combination and four novel phylogenetic placements are provided. The new species comprise Acrocalymma estuarinum, Aggregatorygma isidiatum, Alleppeysporonites elsikii, Amphibambusa aquatica, Apiospora hongheensis, Arthrobotrys tachengensis, Calonectria potisiana, Collariella hongheensis, Colletotrichum squamosae, Corynespora chengduensis, Diaporthe beijingensis, Dicellaesporites plicatus, Dicellaesporites verrucatus, Dictyoarthrinium endophyticum, Distoseptispora chiangraiensis, Dothiora eucalypti, Epicoccum indicum, Exesisporites chandrae, Fitzroyomyces pseudopandanicola, Fomitiporia exigua, Fomitiporia rondonii, Fulvifomes subthailandicus, Gigaspora siqueirae, Gymnopus ailaoensis, Hyalorbilia yunnanensis, Hygrocybe minimiholatra, H. mitsinjoensis, H. parviholatra, H. solis, H. vintsy, Helicogermslita kunmingensis, Jinshana tangtangiae, Kirschsteiniothelia dujuanhuensis, Lamproderma subcristatum, Leucoagaricus madagascarensis, Leucocoprinus mantadiaensis, Lithophyllospora australis, Marasmius qujingensis, Melomastia aquilariae, Monoporisporites jansoniusii, M. pattersonii, Monoporisporites valdiyae, Mucispora maesotensis, Mucor soli, Muyocopron yunnanensis, Nigrospora tomentosae, Ocellularia psorirregularis, Ophiocordyceps duyunensis, Oxneriaria nigrodisca, Oxydothis aquatica, O. filiforme, Phacidiella xishuangbannaensis, Phlebiopsis subgriseofuscescens, Pleurothecium takense, Pleurotus tuber-regium, Pseudochaetosphaeronema puerensis, Pseudodactylaria guttulate, Racheliella chinensis, Rhexoacrodictys fangensis, Roussoella neoaquatica, Rubroboletus pruinosus, Sanghuangporus subzonatus, Scytalidium assmuthi, Shrungabeeja kudremukhensis, Spirographa skorinae, Stanjehughesia bambusicola, Stegonsporiicola aurantiaca, Umbelopsis hingganensis, Vararia tenuata, Verruconis pakchongensis, Wongia bandungensis, and Zygosporium cymodoceae . The new combination is  Parapolyplosphaeria thailandica (≡ Polyplosphaeria thailandica ). The 21 new hosts, geographical and habitat records comprise Acrocalymma fici, Apiculospora spartii, Aspergillus subramanianii, Camposporium ramosum, Clonostachys rogersoniana, Colletotrichum brevisporum, C. plurivorum, Collybiopsis gibbosa, Dictyosporium tratense, Distoseptispora adscendens, Exosporium livistonae, Ganoderma gibbosum, Graphis mikuraensis, Gymnosporangium paraphysatum, Lasiodiplodia thailandica, Moesziomyces bullatus, Penicillium cremeogriseum, P. echinulonalgiovense, P. javanicum, P. lanosocoeruleum, P. polonicum, and Pleurotus tuber-regium. Graphis chlorotica, G. panhalensis and G. parilis are given as novel phylogenetic placements. In addition, we provide the morphology of Tarzetta tibetensis which was missing in the previous Fungal Diversity Notes 1611–1716. Identification of characterization of all these taxa are supported by morphological and multigene phylogenetic analyses.

Background Rust fungi constitute the largest group of plant fungal pathogens. However, a paucity of data, including genomic sequences, transcriptome sequences, and associated molecular markers, hinders the development of inhibitory compounds and prevents their analysis from an evolutionary perspective. Gymnosporangium yamadae and G. asiaticum are two closely related rust fungal species, which are ecologically and economically important pathogens that cause apple rust and pear rust, respectively, proved to be devastating to orchards. In this study, we investigated the transcriptomes of these two Gymnosporangium species during the telial stage of their lifecycles. The aim of this study was to understand the evolutionary patterns of these two related fungi and to identify genes that developed by selection. Results The transcriptomes of G. yamadae and G. asiaticum were generated from a mixture of RNA from three biological replicates of each species. We obtained 49,318 and 54,742 transcripts, with N50 values of 1957 and 1664, for G. yamadae and G. asiaticum , respectively. We also identified a repertoire of candidate effectors and other gene families associated with pathogenicity. A total of 4947 pairs of putative orthologues between the two species were identified. Estimation of the non-synonymous/synonymous substitution rate ratios for these orthologues identified 116 pairs with Ka/Ks values greater than1 that are under positive selection and 170 pairs with Ka/Ks values of 1 that are under neutral selection, whereas the remaining 4661 genes are subjected to purifying selection. We estimate that the divergence time between the two species is approximately 5.2 Mya. Conclusion This study constitutes a de novo assembly and comparative analysis between the transcriptomes of the two rust species G. yamadae and G. asiaticum . The results identified several orthologous genes, and many expressed genes were identified by annotation. Our analysis of Ka/Ks ratios identified orthologous genes subjected to positive or purifying selection. An evolutionary analysis of these two species provided a relatively precise divergence time. Overall, the information obtained in this study increases the genetic resources available for research on the genetic diversity of the Gymnosporangium genus.

Rust fungi (Basidiomycota, Pucciniales) are biotrophic plant pathogens which exhibit diverse complexities in their life cycles and host ranges. The completion of genome sequencing of a few rust fungi has revealed the occurrence of large genomes. Sequencing efforts for other rust fungi have been hampered by uncertainty concerning their genome sizes. Flow cytometry was recently applied to estimate the genome size of a few rust fungi, and confirmed the occurrence of large genomes in this order (averaging 225.3 Mbp, while the average for Basidiomycota was 49.9 Mbp and was 37.7 Mbp for all fungi). In this work, we have used an innovative and simple approach to simultaneously isolate nuclei from the rust and its host plant in order to estimate the genome size of 30 rust species by flow cytometry. Genome sizes varied over 10-fold, from 70 to 893 Mbp, with an average genome size value of 380.2 Mbp. Compared to the genome sizes of over 1800 fungi, Gymnosporangium confusum possesses the largest fungal genome ever reported (893.2 Mbp). Moreover, even the smallest rust genome determined in this study is larger than the vast majority of fungal genomes (94%). The average genome size of the Pucciniales is now of 305.5 Mbp, while the average Basidiomycota genome size has shifted to 70.4 Mbp and the average for all fungi reached 44.2 Mbp. Despite the fact that no correlation could be drawn between the genome sizes, the phylogenomics or the life cycle of rust fungi, it is interesting to note that rusts with Fabaceae hosts present genomes clearly larger than those with Poaceae hosts. Although this study comprises only a small fraction of the more than 7000 rust species described, it seems already evident that the Pucciniales represent a group where genome size expansion could be a common characteristic. This is in sharp contrast to sister taxa, placing this order in a relevant position in fungal genomics research.

1. Forest structure and diversity can regulate tree vulnerability to damage by insects and pathogens. Past work suggests that trees with diverse neighbours should experience less leaf herbivory and less damage from specialist herbivores and diseases, and that the effect of neighbourhood diversity should be strongest at small spatial scales. 2. In an early stage temperate tree diversity experiment, we monitored damage from leaf removing herbiour, specialist (gallers and leaf miners) herbivores, and two specialist fungal diseases (maple leaf anthracnose and cedar apple gall rust) over 3 years. The experimental design included treatments that varied independently in phylogenetic and functional diversity and we made our analyses across four spatial scales (1-16 m²). 3. Neighborhood diversity simultaneously increased leaf removal for some species, decreased it for other, and had no effect on yet others. Height apparency—the difference between a focal plant's height and its neighbours'—was the best single direction of its effect were also species-specific. 4. Specialist pathogens and fungal foliar diseases showed signs of associational resistance and susceptibility. Oaks (Quercus spp.) were more resistant to leaf miners and maples were more resistant to anthracnose when surrounded by diverse neighbours (associational resistance). In contrast, birches (Betula papyrifera) were more susceptible to leaf miners and eastern red cedars (Juniperus virginiana) were more susceptible to cedar apple gall rust (Gymnosporangium juniperi-virginianae) infection in diverse environments (associational susceptibility). 5. Herbivore and pathogen damage was better predicted by community structure and diversity at small spatial scales (1 and 4 m²) than large scales (9 and 16 m²), suggesting a characteristic spatial scale for these biodiversity-ecosystem functioning effects. 6. Synthesis. Humans control forest diversity through selective harvesting and planting in natural stands and plantations. Our experimental demonstration of the role of local community structure and diversity in suppressing some forms of pest and pathogen damage to trees suggests that forest management can be most effective when diversity is considered at small spatial scales and the underlying biology of particular pests, pathogens, and hosts is taken into account.

Key messageComprehensive management of urban greenery is a key approach to control fungal diseases of trees and shrubs to avoid the deterioration in their health status.Preliminary investigations on the health status related to fungal diseases of trees and shrubs growing in four green squares in Warsaw were conducted in 2017–2019. The examined plants were affected by diseases that are commonly identified in urban greenery, e.g., powdery mildew (causal agents: Sawadaea tulasnei, S. bicornis, Podosphaera leucotricha, Podosphaera sp., Erysiphe alphitoides, E. magnifica, E. berberidis, E. flexuosa and E. adunca), rusts (Gymnosporangium sabinae, Melampsora laricis-populina), apple scab (Venturia inaequalis), tar spot of maple (Rhytisma acerinum), and oyster mushroom (Pleurotus ostreatus). The causal agents of the diseases were identified based on their morphological (macro- and microscopic) features. Preventing and managing fungal plant diseases and reduction of their effects are the key tasks in conscious management of urban greenery. To address this issue, the study presents basic guidelines based on the application of various recommended actions and good practices, which constitute a comprehensive and sustainable strategy for integrated protection of trees and shrubs against these diseases. The implementation of the strategy for complex management of urban greenery is a crucial measure aimed at maintenance of a high health status of urban plants.

Anthocyanins play many roles in plants, including providing protection from biotic and abiotic stresses. Japanese apple rust (Gymnosporangium yamadae Miyabe ex G. Yamada) causes serious diseases in plants of the genus Malus and results in reduced fruit production and quality. However, few studies have been done to unravel the molecular mechanisms of anthocyanin formation in rust-infected apple leaves. To identify new regulatory genes in apple leaves that may be involved in regulating rust-induced anthocyanin biosynthesis, we measured anthocyanin content and sequenced the transcriptomes of rust-infected and uninfected tissues of Malus ‘Profusion’ leaves. Significant color changes and anthocyanin enrichment (especially cyanidin-3-galactoside chloride) occurred in infected tissues, whereas no significant color change and a low anthocyanin level were observed in uninfected tissue. We identified 10,045 differentially expressed genes (DEGs) in these two tissue types, including 6021 genes that were upregulated in the infected tissue and 4024 genes that were downregulated. We also identified five structural genes that are putative regulators of anthocyanin biosynthesis. In addition, 56 MYB genes, 36 bHLH genes, and one WD40 gene were identified among the obtained DEGs. According to the phylogeny of the amino acid sequences of transcription factors known to be involved in anthocyanin biosynthesis, one MYB gene (MYB114-like) and two bHLH genes (bHLH33 and bHLHA-like) may relate to anthocyanin biosynthesis in rust-infected apple leaves. These data will provide insights into the molecular mechanisms underlying anthocyanin accumulation upon rust infection.