Erysiphe Species Research Articles

First Report of Powdery Mildew on Vitis bryoniifolia Caused by Erysiphe necator in China.

Grapes, belonging to the genus Vitis, are one of the world's most economically valuable fruit crops, which are widely used as the source of wine, raisins, and juice. The genus Vitis contains about 60 species mainly distributed in Asia, Europe, and North America to northern South America (Wan et al. 2013). In May 2022, severe powdery mildew symptoms were found on wild Vitis bryoniifolia plants at Guizhou Normal University, Guiyang, China. The incidence observed was approximately 85% among 50 V. bryoniifolia plants. Infected leaves appear white powdery patches, eventually leading to chlorosis to necrosis. Mycelia occurred on adaxial and abaxial leaf surfaces, petioles and young shoots. Upon microscopic observation hyphae were hyaline and 3.5-6 μm wide. Hyphal appressoria were solitary and lobed to multilobed. Conidiophores were erect, straight to somewhat flexuous and 80-130 µm long (n = 30). Foot cells were subcylindrical to curved-sinuous at the base, followed by 2-4 cells. Conidia formed singly (occasionally 2-6 in a chain) and were ellipsoid to ovoid in shape with dimensions of 22.5-38 × 12-19.5 µm (n = 50). No fibrosin bodies were observed on conidia. Based on these morphological characteristics, the powdery mildew fungus strongly resembled Erysiphe necator (Braun and Takamasu 2000; Zheng et al. 1987) that has been shown to cause powdery mildew on Vitis (Gadoury et al. 2012; Gaforio et al. 2011; Qiu et al. 2015). To confirm the identification, the ribosomal DNA internal transcribed spacer (ITS) and the ribosomal large subunit (LSU) region were amplified and sequenced using the ITS1/ITS4 primer pair (White et al. 1990) and the NL1/NL4 primer pair (Ziemiecki et al. 1990), respectively. The spliced 1250-bp ITS-LSU sequence (GenBank accession no. PP188565) shared 99.84-100% identity with ITS-LSU sequences of E. necator (LC028995, LC028996, ON073862, LC777882, and OM033353). Based on the phylogenetic analysis of the combined ITS-LSU dataset of Erysiphe species (Takamasu et al. 2015), PP188565 was grouped in a clade with E. necator strains MUMH530, MUMHs141, and VPRI19719. To perform pathogenicity analysis, leaves of three healthy, potted 1-year-old V. bryoniifolia plants were inoculated by gently pressing with diseased leaves. Three non-inoculated healthy plants served as controls. All plants were incubated in a greenhouse at 25 ± 2°C with 80% relative humidity. Powdery mildew symptoms, similar to field conditions were observed on inoculated plants 13 days after inoculation, whereas control plants remained symptomless. Fungus reisolated from inoculated V. bryoniifolia plants was morphologically identical to that on originally diseased plants, and the spliced ITS-LSU sequence of reisolated fungus shared 100% identity with PP188565, fulfilling Koch's postulates. Based on the morphological and molecular characterizations, the powdery mildew fungus was identified as E. necator. To our knowledge, this is the first report of powdery mildew caused by E. necator on V. bryoniifolia in China. This work further expands the host range of Erysiphe necator on Vitis species.

An independent Taiwanese lineage of powdery mildew on the endemic host species Koelreuteria henryi

BackgroundPowdery mildews (Erysiphaceae, Ascomycota) are common plant disease agents and also cause stress for forest and fruit trees worldwide as well as in Taiwan. The powdery mildew Erysiphe bulbouncinula on Koelreuteria host trees was considered an endemic species in China. While in China the host was K. paniculata and only the teleomorph stage found, the anamorph and the teleomorph were both recorded for the host in Taiwan, K. henryi. We aimed to clarify the relationship of the powdery mildews recorded under E. bulbouncinula with an apparently disjunct distribution.ResultsSpecimens of powdery mildew on K. henryi from Taiwan were characterized based on the anamorph morphology and DNA sequences. They revealed a new record of Sawadaea koelreuteriae for this host species and Taiwan and a new species of Erysiphe, E. formosana, sister to E. bulbouncinula from China.ConclusionsIn Erysiphe on Koelreuteria hosts, speciation of plant parasitic fungi seems to be correlated with disjunct host and geographic distribution possibly shaped by extinction of potential host species which are known only as fossils. Two of the three extant East Asian species of Koelreuteria are now known as hosts of specific Erysiphe species. We may predict a further not yet discovered Erysiphe species on the third East Asian species, K. bipinnata, in South and Southwest China. In the speciation in Sawadaea, the extinction events in Koelreuteria can be excluded from being involved.

First Report of powdery mildew of Quercus guyavifolia (Fagaceae) Caused by Erysiphe quercicola.

Oaks are the most abundant trees in naturally regenerated forests in China, play a crucial role in preventing soil erosion and maintaining ecological stability (Du et al. 2022). Quercus guyavifolia H. Léveillé (Fagaceae family, Subgenus Cerris, section Ilex), is endemic in China, distributed in the southeastern boundary of the Qinghai-Tibet Plateau, with elevations from 2, 000 - 4, 500 m a.s.l. (Denk et al. 2018; Sun et al. 2016). Powdery mildew is a prevalent disease of oaks with up to 60% of foliage infection, which can induce leaf necrosis or deformation and might contribute to oak decline (Marçais and Desprez-Loustau 2014). In September 2023, we found leaves of Q. guyavifolia near Yunnan Baima Snow Mountain covered with white fungal colonies. Diseased Q. guyavifolia plants were transplanted into a greenhouse at Yunnan University for pathogenicity tests. Conidia from diseased plants were blown into twenty healthy Q. guyavifolia seedlings by cold air blower and five non-inoculated healthy seedlings were used as control. The inoculated seedlings developed powdery mildew symptoms within ten days on both sides of the leaves. Trypan blue staining was used to identify the pathogen that infects Q. guyavifolia (Xiao et al. 2017). Microscopic examination revealed abundant conidia and extensive branched hyphae on leaves, similar to the characteristics of powdery mildew fungi. The mean length and width of conidia were 29.06 ± 3.96 × 9.52 ± 1.36 μm (n = 50). We collected fungi (YNBAIMAXS01) and extracted genomic DNA from five diseased plants (from the same location) using the CTAB method. We amplified and sequenced the ITS (Gardes and Bruns, 1993), MS294, and MS447 (two nuclear protein-encoding genes; Feau et al. 2011; GenBank numbers: PP079015, PP083693, PP083694). BLAST analysis revealed 100% identity of above three sequences with the ITS of Erysiphe quercicola isolate DACA010 (GenBank accession MT569439), MS294 of E. quercicola isolate GEM09_11_FRTB1 (GenBank accession KY348509), and MS447 of E. quercicola isolate A1I1.5 (GenBank accession KY466619). Therefore, the isolate YNBAIMAXS01 was identified as E. quercicola based on its morphological and molecular characteristics. Sequences from the above three regions for YNBAIMAXS01 and five Erysiphe species were used to construct a Maximum likelihood (ML) tree. In addition, we constructed a ML tree using only the ITS region of YNBAIMAXS01 and eight Erysiphe species from GenBank to better distinguish E. quercicola from these species. Both trees were constructed using MEGA X with K2 + G as best model. The ML trees confirmed the powdery mildew fungi isolated from Q. guyavifolia is closely related to E. alphitoides. To date, thirty-four powdery mildew species belonging to genus Erysiphe have been found affecting Quercus and nine oak species can be infected by E. quercicola (https://fungi.ars.usda.gov/). To our knowledge, this is the first report of powdery mildew caused by E. quercicola on Q. guyavifolia, thus the development of control strategies and disease management is urgently needed.

First Report of Powdery Mildew on Quercus fabri and Q. robur Caused by Erysiphe quercicola in China.

Quercus (Fagaceae) is a genus of ecologically and economically important shrub and tree species (Yin et al. 2018). In April 2022, powdery mildew symptoms were observed on Quercus fabri and Quercus robur leaves on Longwen hill, Guizhou Normal University, Guiyang, China. The incidence was 30% (Q. fabri, n = 50) and 20% (Q. robur, n = 30), respectively. Powdery mildew fungi from these two Quercus species shared similar morphological characteristics. Mycelia occurred on adaxial and abaxial leaf surfaces, forming small to large patches; hyphae were hyaline, 3-7 µm wide; hyphal appressoria were lobed to multilobed, solitary; conidiophores were erect, straight, 36-80 µm long (n = 30); foot cells were followed by 1-2 shorter cells; conidia formed singly, obovoid to ellipsoid, 24-38 × 12-27 µm (n = 50), without fibrosin bodies; no chasmothecia were observed. Based on these characteristics, powdery mildew fungi on both Q. fabri and Q. robur were identified as Erysiphe quercicola (Takamatsu et al. 2007). To confirm the identification, ribosomal DNA internal transcribed spacer (ITS) sequences of two fungal samples from Q. fabri and Q. robur were separately amplified and sequenced using primer pair ITS1/ITS4 (White et al. 1990). The obtained ITS sequences (GenBank accession nos. QR414372 and QR414373, respectively) shared 100% identity, and 99.38-99.84% identity with diverse ITS sequences of E. quercicola (Takamatsu et al. 2015). In a phylogenetic tree based on ITS sequences of Erysiphe species (Takamatsu et al. 2007), QR414372 and QR414373 were grouped in a clade with ITS sequences of E. quercicola. To fulfil Koch's postulates, leaves of three healthy potted Q. fabri plants and three healthy potted Q. robur plants were inoculated by gently pressing diseased Q. fabri and Q. robur leaves onto healthy leaves. Non-inoculated healthy Q. fabri and Q. robur plants served as controls. All plants were incubated in a greenhouse at 25 ± 2°C with 80% relative humidity. Typical powdery mildew symptoms were observed on all inoculated plants 15 days after inoculation, whereas no symptoms were observed on control plants. Fungi separately reisolated from inoculated Q. fabri and Q. robur were morphologically identical to those on their originally diseased plants, and ITS sequences of reisolated fungi shared 100% identity with QR414372 and QR414373. E. quercicola has previously been reported to infect Quercus species, including Q. robur in Australia, Q. crispula, Q. phillyraeoides and Q. serrata in Japan, and Q. phillyraeoides in Korea (Lee et al. 2011). In China, Q. fabri and Q. robur may be infected by E. alphitoides and E. hypophylla, respectively (Zheng et al. 1987). To our knowledge, this is the first report of powdery mildew caused by E. quercicola on Q. fabri and Q. robur in China. This work provides a foundation to protect Quercus plants against this fungal pathogen.

Erysipheneelamensis, a new powdery mildew fungus (Ascomycota: Erysiphaceae) from Azad Jammu and Kashmir, Pakistan

A new powdery mildew species, Erysiphe neelamensis, was found on Celtis eriocarpa in Azad Jammu and Kashmir, Pakistan. The identification was based upon morpho‐anatomical features and results of a molecular sequence analysis. This species is morphologically distinguished from phylogenetically allied Erysiphe species by having chasmothecia with fewer, shorter appendages and a small number of asci and ascospores. A phylogenetic analysis of the nrDNA of ITS region of E. neelamensis supports the involvement of a novel species of the genus Erysiphe. The new species is described, illustrated and compared with all allied species, along with a phylogram showing its inferred phylogenetic position.

First report of powdery mildew on Euonymus japonicus caused by Erysiphe euonymicola in Taiwan.

The Japanese spindle (Euonymus japonicus Thunb.) is commonly used as an ornamental hedge plant in Taiwan. In March 2020, a severe powdery mildew disease was observed on E. japonicus surrounding a city park spanning six hectares in Taichung city, Taiwan. Around 90% of the plants showed symptoms on the leaves and pedicels of young shoots. Similar symptoms were observed in other districts of Taichung city and Taipei city between March to June in subsequent years. Initial signs of infection manifest as circular chlorotic spots on the leaves, which are subsequently covered by white mycelia on either the upper or lower surfaces of the spots. In severe cases, both sides of the leaves become entirely covered by dense mycelia. Hyphal appressoria were solitary or in opposite paired, lobed to multilobed. Conidiophores grow erectly from the hyphae, consist of 2-3 cylindrical cells, 38.9 to 78.6 × 6.31 to 8.28 µm (n = 30). Foot cells are usually straight or slightly flexuous, 23.6 to 43.2 µm (n = 30), followed by 1 to 2 shorter cells. Ellipsoidal conidia are produced singly on the conidiophores, 24.1 to 36.3 × 10.6 to 14.97 µm (n = 30), without fibrosin bodies. Germ tubes are mostly subterminal, sometimes terminal, occasionally exhibiting a longitudinal pattern. Chasmothecia were not observed. These morphological characteristics correspond to the description of Erysiphe euonymicola U. Braun (Braun and Cook 2012), one of the Erysiphe species reported on E. japonicus. Genomic DNA was extracted from seven isolates obtained from different plants in the affected regions. The internal transcribed spacer (ITS) and 28S large subunit (LSU) of rDNA sequences (ITS accession nos.: OR073423-OR073429; LSU accession nos.: OR073448-OR073454) were amplified and sequenced using primer sets PMITS-1 / PMITS-2 (Cunnington et al. 2003) and NLP2 / PRM2 (Bradshaw and Tobin 2020), respectively. The resulting sequences exhibited identities ranging from 99.1 to 100% in ITS and 100% in LSU when compared to the corresponding sequences of E. euonymicola MUMH 133 (ITS: AB250228; LSU: AB250230) (Limkaisang et al. 2006). Phylogenetic analysis based on the concatenated sequences of ITS and LSU clustered the seven isolates within the same clade as three E. euonymicola isolates (MUMH 133, MUMH 6999 and MUMH 7012). Pathogenicity assays were conducted on one-meter tall E. japonicus plants by gently smearing infected leaves on all leaves of four healthy plants. Four uninoculated plants were used as control. All eight assayed plants were enclosed in plastic bags to maintain high humidity at 28 ± 2°C for 3 days. Chlorotic spots began to appear on leaves younger than one month old at 7 days post inoculation (dpi). By 28 dpi, all inoculated plants showed symptoms. Spots expanded or merged and formed a dense mycelial layer on leaves younger than three months, while mature dark green leaves were asymptomatic. No symptoms were observed on any leaves of the control plants. The morphological characteristics and sequences of ITS and LSU of the pathogen from the inoculated plants matched the above information. Based on these findings, E. euonymicola was identified as the causal agent of powdery mildew on E. japonicus, representing the first documented report of this disease in Taiwan. A voucher specimen TNM F0037001 (isolate EPM-1) was deposited in the National Museum of Natural Science, Taiwan. The pathogen has been frequently reported in recent years and significantly impacts the ornamental value of Euonymus spp. (Abbasi and Braun 2020; Lee et al. 2015; Li et al. 2011; Pei et al. 2022). This report also provides an evidence of an ongoing outbreak of the pathogen.

Phylogeny and taxonomy of the genera of Erysiphaceae, part 5: Erysiphe (the “Microsphaera lineage” part 1)

ABSTRACT In this contribution, we offer the fifth installment of a series focusing on the phylogeny and taxonomy of powdery mildews. This paper is the second segment evaluating the genus Erysiphe. The first treatment of Erysiphe focused on phylogenetically basal species in the “Uncinula lineage.” This research presents a phylogenetic-taxonomic assessment of species that form the group previously referred to as the “Microsphaera lineage.” Given the size of the group, we split the treatment of this lineage of Erysiphe species into two parts based on their phylogenetic placement. Phylogenetic trees based on ITS+28S data are supplemented by sequences of additional markers (CAM, GADPH, GS, RPB2, and TUB). Included in the analysis of the Microsphaera lineage is the “Erysiphe aquilegiae complex” (group, clade, cluster), which encompasses sequences obtained from an assemblage of Erysiphe species with insufficient resolution in rDNA analyses. Attempts have been made to resolve this group at the species level by applying a multilocus approach. A detailed discussion of the “Erysiphe aquilegiae complex” is provided. Sequences are provided for the first time for several species, particularly North American species, such as Erysiphe aggregata, E. erineophila, E. parnassiae, and E. semitosta. Ex-type sequences for Microsphaera benzoin and M. magnusii have been retrieved. Alphitomorpha penicillata, Microsphaera vanbruntiana, and M. symphoricarpi are epitypified with ex-epitype sequences. The new species Erysiphe alnicola, E. deutziana, E. cornigena, E. lentaginis, and E. sambucina are described, the new combinations E. lauracearum, E. passiflorae, and E. sambucicola are introduced, and the new name E. santali is proposed.

Phylogeny and taxonomy of the genera of Erysiphaceae, part 4: Erysiphe (the “Uncinula lineage”)

ABSTRACT This is the fourth contribution within an ongoing series dedicated to the phylogeny and taxonomy of powdery mildews. This particular installment undertakes a comprehensive evaluation of a group previously referred to as the “Uncinula lineage” within Erysiphe. The genus Erysiphe is too large to be assessed in a single paper; thus, the treatment of Erysiphe is split into three parts, according to phylogenetic lineages. The first paper, presented here, discusses the most basal lineage of Erysiphe and its relationship to allied basal genera within tribe Erysipheae (i.e., Brasiliomyces and Salmonomyces). ITS+28S analyses are insufficient to resolve the basal assemblage of taxa within the Erysipheae. Therefore, phylogenetic multilocus examinations have been carried out to better understand the evolution of these taxa. The results of our analyses favor maintaining Brasiliomyces, Bulbomicroidium, and Salmonomyces as separate genera, at least for the interim, until further phylogenetic multilocus data are available for additional basal taxa within the Erysipheae. The current analyses also confirmed previous results that showed that the “Uncinula lineage” is not exclusively composed of Erysiphe species of sect. Uncinula but also includes some species that morphologically align with sect. Erysiphe, as well as species that had previously been assigned to Californiomyces and Typhulochaeta. Numerous sequences of Erysiphe species from the “Uncinula lineage” have been included in the present phylogenetic analyses and were confirmed by their position in well-supported species clades. Several species have been sequenced for the first time, including Erysiphe clintonii, E. couchii, E. geniculata, E. macrospora, and E. parvula. Ex-type sequences are provided for 16 taxa including E. nothofagi, E. trinae, and E. variabilis. Epitypes are designated and ex-epitype sequences are added for 18 taxa including Erysiphe carpophila, E. densa, and U. geniculata var. carpinicola. The new species Erysiphe canariensis is described, and the new names E. hosagoudarii and E. pseudoprunastri and the new combination E. ampelopsidis are introduced.

Erysiphe machilicola: a new powdery mildew species on Duthie’s Bay Tree

A new species of Erysiphe infecting Duthie’s bay tree in Azad Jammu & Kashmir, Pakistan, is described and illustrated based on molecular and morphological analyses. Erysiphe machilicola sp. nov. is morphologically distinct from other Erysiphe species on hosts of the Lauraceae by having longer conidiophores, larger chasmothecia with longer appendages, above all, it is distinguished from E. machiliana, the only so far known Erysiphe species on Machilus, by lacking bristle-like appendages (remnant of anchor hyphae) and a different phylogenetic position, confirmed by sequence analyses of the type material of the latter species. The phylogenetic relationship of the new species to other closely related species is discussed based on ITS rDNA sequences, which phylogenetically supports its identity as a new species within the genus Erysiphe. A comprehensive description along with photographs and a phylogram showing its exact phylogenetic position and a comparison with closely related taxa is provided.

A critical revision of the powdery mildew fungi (Erysiphaceae, Ascomycota) of Ukraine: Erysiphe sect. Erysiphe

This is the second article in a series of critical revisions of the species composition of powdery mildew fungi (Erysiphaceae, Helotiales, Ascomycota) of Ukraine and their distribution within the country. The first article of the series dealt with the small genera Arthrocladiella and Blumeria, while here we consider species of the Erysiphe sect. Erysiphe. Representatives of the other two sections of this genus, Microsphaera and Uncinula, will be critically examined in further publications. In the present article, a list of 24 species of the section Erysiphe recorded in Ukraine, their distribution by regions of Ukraine, and a key for their identification are provided. The most common species frequently occurring in many regions of Ukraine are E. aquilegiae, E. convolvuli, E. cruciferarum, E. heraclei, E. pisi, and E. polygoni. Such species as E. buhrii, E. howeana, E. knautiae, E. limonii, E. lycopsidis, and E. urticae were recorded less often. Erysiphe betae, E. circaeae, E. lythri, E. macleayae, E. mayori, E. thesii, and E. ulmariae are relatively rare species that occurred infrequently in several regions. Erysiphe caricae, E. catalpae, E. caulicola, E. celosiae, and E. malvae are known each from one or a few localities only. A number of species are invasive fungi, most of them have been recorded in Ukraine relatively recently, within the last hundred years. These are E. betae, E. caricae, E. catalpae, E. celosiae, E. howeana, and E. macleayae.

First Report of Erysiphe betae Causing Powdery Mildew on Chard (Beta vulgaris var. cicla) in Mexico.

Chard (Beta vulgaris var. cicla; Chenopodiaceae) is a vegetable native to the Mediterranean, widely cultivated for its nutritional properties. In June 2020, an outbreak of powdery mildew was detected in a commercial crop of chard in San Martín Texmelucan, Puebla (19°14'37.1"N; 98°27'12.5"W), Mexico. The disease was present in 86% of the plants (n=400) and the pathogen was found to cover up to 95% of the surface of the leaves. Initially, small whitish patches were observed on both sides of the leaves. Subsequently, the patches grew rapidly to cover most of the leaf surface and premature senescence of infected leaves was observed. The signs of the pathogen were observed as abundant whitish masses of conidia. Microscopic analysis of the fungus showed amphigenous mycelia with lobed hyphal appressoria. Conidiophores (n=30) were simple and erect, 93133 × 7.58.5 μm. Foot cells (n=30) were cylindrical, predominately straight, and rarely somewhat curved at the base, 30.036.5 μm, followed by a longer cell and two shorter cells, and the conidium. Conidia (n=100) were hyaline, ellipsoid-ovoid, 3745 × 1416 μm. Germ tubes (n =30) were terminal, short (0.52.0 times the conidial width) and stout. Conidial appressoria (n=30) were mostly lobed, showing from 2-6 lobes. Chasmothecia were not found. The morphological characteristics observed correspond to previous descriptions of Erysiphe betae by Braun and Cook et al. (2012). A voucher specimen (accession no. UACH450) was deposited in the Department of Agricultural Parasitology Herbarium at the Chapingo Autonomous University. To confirm identification, DNA was extracted from the fungus, and the internal transcribed spacer (ITS) and the 28S gene region of rDNA from one sample were amplified by PCR, using the primers ITS1/ITS4 (White et al. 1990) and PM3 (Takamatsu and Kano 2001)/TW14 (Mori et al. 2000). The sequences obtained from our specimen were registered to the GenBank under the accession numbers ON157053 and ON157047 for ITS and LSU, respectively. Our sequences shared 100% identity for ITS (KX574674) and 99.8% for LSU (OM033348 and OM368494) with sequences of E. betae in BLAST'n search. Based on phylogenetic analysis using the Maximum Likelihood method including a published ITS + 28S dataset for Erysiphe species, the isolate UACH450 was grouped into a clade with E. betae. Takamatsu et al. (2015) found that E. betae, E. malvae and E. heraclei are phylogenetically indistinguishable (they form the E. heraclei species complex), nevertheless, E. malavae infects Lavatera and Malva (Malvaceae), E. heraclei predominately forms on hosts of Apiaceae and E. betae is commonly found on Beta and Chenopodium (Chenopodiaceae) (Braun and Cook 2012). Pathogenicity was verified by spraying a suspension of conidia (1107 conidia/ml) onto the leaves of six healthy chard plants and six plants were sprayed with sterile distilled water to serve as controls. All plants were maintained at temperatures from 28 2 °C and relative humidity of 802 %. All inoculated leaves developed powdery mildew symptoms after 14 days, whereas the control plants remained symptomless. The pathogenicity test was performed twice, observing the same results. The recovered pathogen showed the same morphological characteristics as the inoculated pathogen, thus fulfilling Koch's postulates. To our knowledge, this is the first report of Erysiphe betae causing powdery mildew on Beta vulgaris var. cicla in Mexico. This pathogen has been previously reported in Iraq (Amano, 1986) and Greece (Vakalounakis and Kavroulakis, 2017) on Beta vulgaris var. cicla. Also, Erysiphe betae has been reported in Mexico on Chenopodium and throughout the world on sugar beet (Farr and Rossman, 2022). This pathogen is a major issue as it can completely cover the leaves of the diseased plants, making them difficult to market.

Erysiphe lonicerigena sp. nov., a Powdery Mildew Species Found on Lonicera harae

A powdery mildew (Erysiphaceae) has been continuously collected on the leaves of Lonicera harae in the southern part of the Korean Peninsula, where this shrub is indigenous. Microscopic examination of the asexual morphs revealed that the current collections are differentiated from the all known Erysiphe species on Lonicera spp. by its longer conidiophores and longer conidia. Although the morphology of the chasmothecia is reminiscent of Erysiphe ehrenbergii and E. lonicerae, the specimens on L. harae differ from them in having smaller ascospores. A phylogenetic tree generated from a combined dataset of the internal transcribed spacer region and 28S rDNA gene sequences demonstrates that sequences obtained from three powdery mildew collections on L. harae clustered together as an independent species clade with high bootstrap values distant from other Erysiphe species on Lonicera, representing a species of its own. Based on morphological differences and molecular-phylogenetic results, the powdery mildew on L. harae is proposed as a new species, Erysiphe lonicerigena, and the holomorph of the fungus is described and illustrated in this study.

Mitochondrial characteristics of the powdery mildew genus Erysiphe revealed an extraordinary evolution in protein-coding genes

The genus Erysiphe was an obligate parasite causing powdery mildew disease on a wide range of higher plants. However, the knowledge of their mitogenome architecture for lifestyle adaptability was scarce. Here, we assembled the first complete mitogenome (190,559 bp in size) for rubber tree powdery mildew pathogen Erysiphe quercicola. Comparable analysis of the Erysiphe mitogenomes exhibited conserved gene content, genome organization and codon usage bias, but extensive dynamic intron gain/loss events were presented between Erysiphe species. The phylogeny of the Ascomycota species constructed in the phylogenetic analysis showed genetic divergences of the Erysiphe species. Compared with other distant saprophytic and plant pathogenic fungi, Erysiphe had a flat distribution of evolutionary pressures on fungal standard protein-coding genes (PCGs). The Erysiphe PCGs had the highest mean selection pressure. In particular, Erysiphe's cox1, nad1, cob and rps3 genes had the most elevated selection pressures among corresponding PCGs across fungal genera. Altogether, the investigations provided a novel insight into the potential evolutionary pattern of the genus Erysiphe to adapt obligate biotrophic lifestyle and promoted the understanding of the high plasticity and population evolution of fungal mitogenomes.

Fungal Infection Diseases- Nightmare for Cannabis Industries: Artificial Intelligence Applications

This review paper highlights the fungal diseases of both indoor and outdoor Cannabis cultivation environments and discusses the Artificial intelligence (AI) based crop disease detection and management. Some of the fungal pathogen that can attack Cannabis crops are Botrytis, Alternaria, Fusarium, Penicillium, Cladosporium, and Aspergillus. Fungal diseases are Powdery Mildew, Damping off, and Mildew. Of these fungal pathogens, the most common inflorescence disease is gray mold, caused by Botrytis cinerea. Botrytis cinerea and Erysiphe species complex are currently the most widespread pathogens of Cannabis worldwide. The greatest challenge facing Cannabis and hemp producers is the management of insect pests and pathogens that attack the roots, leaves and inflorescences. Pathogens are a pain in the neck of every Cannabis breeder. They affect the quality and quantity of yield, thus defeating the aim of cultivation. The common disease management strategies are-remove and destroy infected plants. Irradiate dried buds with gamma or electro-beam radiation. Another method is to apply biological control agents at rooting and vegetative stages of growth. Pesticides have been found in all Cannabis products, from flowers to edibles, vapes, and smokes. The pesticide pandemic in the Cannabis industry needs urgent attention. Cannabis can contain fungal pathogens and residues of pesticides, fungicides that cause serious and often fatal infections in persons with immunocompromised conditions, such as cancer, transplant, or infection with HIV. Contamination of Cannabis plants and products (i.e., recreational- and pharmaceutical-grades) with mycotoxigenic organisms, including species of Aspergillus, Penicillium, and Fusarium, pose serious challenges. The manual Cannabis disease identification process is time-consuming and tedious work. Instead, automated methods save both time and effort. The technology of Artificial Intelligence (AI) in the detection and management of disease has already been employed in many crops. The machine learning (ML)-based models were proposed for the identification and classification of plant diseases. The PlantVillage dataset is the largest and most studied plant disease dataset, which is used as a reference for the disease detection and management of plant diseases.

First Report of Powdery Mildew Caused by Erysiphe diffusa on Cluster Bean in India.

Cluster bean (Cyamopsis tetragonoloba (L.) Taub.) is an important vegetable crop cultivated widely in India. During a field survey in November 2021, about 60% of plants exhibited characteristic powdery mildew disease symptoms and signs in a 15 ha field in Northern Karnataka (Raichur), India. Initially, the symptoms and signs appeared as tan lesions, which later became small, circular and chlorotic. The abaxial surface turned yellow and was covered with white mycelial growth. As the disease progressed, white mycelia grew on the adaxial leaf surface, stems and pods as well. In severe infections, drying and premature defoliation of infected leaves were observed. Infected leaf samples with mycelia were collected (n=8) and the fungus was subjected to morphological and molecular observations. Mycelia on leaves was characterized as epiphytic, amphigenous, producing dense, white patches on the upper and lower leaf surfaces, stem and young pods. Hyphae were hyaline, thin-walled, 1.8 to 4.2 µm wide with erect conidiophores consisting of a cylindrical foot-cell, straight flexuous at the base and measured 20 to 36 × 6 to 9 μm (n=30), followed by 1 to 2 shorter cells. Ellipsoid conidia were produced singly and measured 28 to 42 × 12 to 20 μm (n=30) without fibrosin bodies. Chasmothecia were not observed. A reference specimen was deposited at the Institution of Excellence, University of Mysore Herbarium (UOM-IOE 2022_1). The morphology and other characteristics of conidia were consistent with an Erysiphe species (Braun and Cook 2012). Genomic DNA was isolated from a conidial suspension harvested from the powdery mildew affected cluster bean samples. The ITS region was amplified from three samples using powdery mildew-specific primer pair PN23/PN34 and sequenced directly (Chen et al. 2008). nBLAST analysis revealed that the ITS sequence shared 100% similarity with the reference sequence (E. diffusa vouchers HMJAU02177 - KM260363, BRIP 71013 - MW009058) of Erysiphe diffusa (Cooke & Peck) U. Braun & S. Takam. In addition to 100% match to voucher specimens of E. diffusa, there were no vouchers from other species that also had 100% match. The representative sequences were deposited in GenBank with accession numbers OM669776 - OM669778. Koch's postulates were conducted on healthy cluster bean plants grown under greenhouse conditions. Conidia were harvested from infected leaves, suspended in water and sprayed on 40 to 50-day-old cluster bean plants (28 ± 2°C and >70% relative humidity). The development of powdery mildew symptoms was recorded on 22 plants after 10-14 days of post inoculation. Control plants inoculated with sterile water remained healthy without powdery mildew symptoms. Microscopic observation of spores from inoculated plants confirmed the pathogen as E. diffusa. The genus Erysiphe is known to infect many crop plants. E. diffusa has been reported to infect Vigna radiata, Glycine max and Phaseolus mungo in Australia (Kelly et al. 2021). No reports are available at USDA's host-fungus database for cluster bean and E. diffusa (Farr and Rossman 2022). To the best of our knowledge, this is the first report of E. diffusa associated with powdery mildew of cluster bean in India. Further comprehensive investigations will shed a light on the economic impact of powdery mildew disease on the cluster bean in India.

Sulla Powdery Mildew: Phylogeny and Host Range

Sulla is a biannual forage legume cultivated throughout the Mediterranean Basin. It can be severely damaged by powdery mildew, but there is little understanding on its causal species or its host range. The taxonomic characterization of Erysiphe species is mainly based on the examination of chasmothecia morphology, or on the molecular analysis of ITS1 and ITS2 sequences. However, a description of chasmothecia morphology or ITS sequences is not always available to clearly assign a given isolate to an existing or novel Erysiphe species. In an attempt to clarify the identity of the powdery mildew infecting sulla crop we studied the morphology and ITS of nine populations collected over years and countries and compared them with available ITS sequences. Phylogenetic analysis showed that the powdery mildews collected on sulla clustered together with isolates collected on Coronilla varia in an independent clade between the E. guarinonii/E. trifoliorum and E. palczewskii clades, strongly suggesting that all these sequences correspond to the same Erysiphe species. Measurements of conidia and conidial foot cells of the sulla-infecting powdery mildews partially overlap those of other Erysiphe species, although they clearly differentiate from them, supporting the assumption that powdery mildews from sulla belong to a distinct species as observed from the phylogenetic analysis. As far as we know, our study is the first to report the molecular characterization of powdery mildew isolated on plants from the Hedysarum clade. Cross-inoculations confirmed a high specialization of the powdery mildew of sulla, with the sulla’s isolates infecting only the S. coronaria accessions, and none of the accessions from the other legume genera studied. All studied S. coronaria accessions were heavily infected by the sulla isolate but not by any other isolate used. All this points to E. hedysari as the causal agent of the S. coronaria powdery mildew.

Phylogeny and taxonomy of powdery mildew caused by Erysiphe species on Lupinus hosts

ABSTRACT The genus Lupinus (Fabaceae) consists of over 250 plant species located throughout the world. Powdery mildew, caused by Erysiphe species, is a common disease infecting these ecologically, ornamentally, and agriculturally important plants. In the present work, we conducted phylogenetic and taxonomic analyses on Erysiphe species colonizing hosts of the leguminous genus Lupinus, using sequences from the internal transcribed spacer (ITS) and 28S genomic regions. Powdery mildews of the genus Erysiphe on Fabaceae are taxonomically intricate and challenging. Therefore, it is necessary to phylogenetically analyze the DNA retrieved from powdery mildew on lupines in a broad context that includes common and allied powdery mildew species that occur on a range of leguminous plants such as Erysiphe astragali, E. baeumleri, E. pisi, and E. trifoliorum. A new species Erysiphe lupini, found in the USA on Lupinus lepidus, L. polyphyllus, and Lupinus sp., is described. Additionally, Erysiphe intermedia (≡ Microsphaera trifolii var. intermedia) has been confirmed as a North American lupine powdery mildew that is a sister species to E. astragali on Astragalus spp. European Erysiphe collections on lupines were often referred to as E. intermedia, but our analyses have shown that they pertain to E. trifoliorum. The E. trifoliorum clade is composed of several species (i.e. E. baeumleri, E. euonymi, E. hyperici, and E. trifoliorum), that cannot be sufficiently resolved based solely on ITS+28S sequences. Morphological and biological differences between the species are discussed and provide evidence that the species concerned should be maintained. Finally, a sequence obtained from a powdery mildew collected in Portugal on the native Lupinus micranthus pertained to the Erysiphe guarinonii clade. This collection is tentatively treated as Erysiphe sp. To fix the application of the species names E. astragali, E. baeumleri (including its synonym E. marchica), and E. intermedia, epitypes have been designated with ex-epitype sequences.

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.

Infection of papaya (Carica papaya) by four powdery mildew fungi

Papaya (Carica papaya L.) is an important fruit crop in many tropical and subtropical countries. Powdery mildew commonly affects this host, causing premature leaf loss, reduced yields and poor fruit quality. At least fifteen different fungi have been identified as the causal agents of papaya powdery mildew. Powdery mildew symptoms were detected on potted papaya plants growing in two locations in Hungary. This study aimed to identify the causal agents. Morphology of powdery mildew samples was examined, and sequences of two loci were used for molecular taxonomic identifications. Only anamophs were detected in all samples, and four morphological types were distinguished. Most samples had Pseudoidium anamorphs, while some were of the Fibroidium anamorph. Based on morphology and molecular taxonomy, the Fibroidium anamorph was identified as Podosphaera xanthii. The Pseudoidium anamorphs corresponded to three different Erysiphe species: E. cruciferarum, E. necator and an unidentified Erysiphe sp., for which molecular phylogenetic analyses showed it belonged to an unresolved species complex of E. malvae, E. heraclei and E. betae. Infectivity of P. xanthii and E. necator on papaya was verified with cross inoculations. A review of previous records of powdery mildew fungi infecting papaya is also provided. Podosphaera xanthii was known to infect, and E. cruciferarum was suspected to infect Carica papaya, while E. necator was recorded on this host only once previously. No powdery mildew fungus belonging to the E. malvae/E. heraclei/E. betae species complex is known to infect papaya or any other plants in the Caricaceae, so the unidentified Erysiphe sp. is a new record on papaya and the Caricaceae. This study indicates host range expansion of this powdery mildew fungus onto papaya.

Phylogeny and taxonomy of powdery mildew caused by Erysiphe species on Corylus hosts

ABSTRACT Erysiphe species (powdery mildews) on Corylus and Ostrya hosts (Betulaceae subfam. Coryloideae) in Asia and North America are widespread pathogens on these economically and ecologically valuable nut crops. An improved understanding of their phylogeny and taxonomy is of ecological and applied importance. Phylogenetic analyses and morphological reexaminations conducted in this study revealed a higher degree of diversity and cryptic speciation than reflected in earlier species concepts. North American collections on C. cornuta, which were previously assigned to E. corylacearum, proved to constitute a species of its own and are herein introduced as E. cornutae, sp. nov. Two additional North American species, E. coryli-americanae, sp. nov. and E. ostryae, sp. nov., have been detected on C. americana and O. virginiana and are described. They are morphologically similar to E. cornutae, but genetically distinct. Based on phylogenetic analyses, E. corylacearum is an Asian species confined to various Asian Corylus species. Sequence data retrieved from Japanese type material of E. corylicola revealed that this species clusters with sequences from E. elevata on Catalpa species, distant from all other Erysiphe species on Corylus. Morphologically similar, yet distinct, specimens on C. sieboldiana, which were previously assigned to E. corylicola, form a distinct, distant clade. The species involved is described herein as E. pseudocorylacearum, sp. nov. Additionally, an unusual infection of C. sieboldiana in Japan by E. syringae has been shown by means of sequence data. The phylogeny and taxonomy of Erysiphe species belonging to the Corylioideae are discussed in detail, and a key to the species concerned is provided.