Powdery mildew fungi (Erysiphales, Ascomycota) of Western Polissya of Ukraine

Information on powdery mildew fungi (Erysiphales, Ascomycota) recorded in Western Polissya of Ukraine throughout the history of research in the region is provided. The list included in the article comprises 85 species of 7 genera of Erysiphales, namely 43 species of Erysiphe, 19 of Golovinomyces, 15 of Podosphaera, three of Phyllactinia, two of Neoerysiphe and Sawadaea, and one species of Blumeria. For the first time, 21 species are reported for the region: Erysiphe astragali, E. azaleae, E. howeana, E. hypophylla, E. lycopsidis, E. macleayae, E. prunastri, E. russellii, E. syringae-japonicae, Golovinomyces ambrosiae, G. asterum, G. bolayi, G. fisheri, G. riedlianus, G. verbasci, Neoerysiphe galii, Phyllactinia fraxini, Podosphaera aucupariae, P. phtheirospermi, P. prunicola, and Sawadaea tulasnei. The most common species were Blumeria graminis, Erysiphe alphithoides, E. aquilegiae, E. divaricata, E. ornata, E. polygoni, Podosphaera aphanis, and P. myrtillina. Erysiphe heraclei, Neoerysiphe galeopsidis, and Podosphaera erigerontis-canadensis were recorded quite frequently. Erysiphe arcuata, E. astragali, E. azaleae, E. baeumleri, E. circaeae, E. cruchetiana, E. cruciferarum, E. grosulariae, E. hypophylla, E. lythri, E. macleayae, E. palczewskii, E. penicillata, E. pisi, E. prunastri, E. russellii, E. vanbruntiana, Golovinomyces ambrosiae, G. asterum, G. circumfusus, G. cynoglossi, G. fisheri, G. inulae, G. riedlianus, G. verbasci, Neoerysiphe galii, Phyllactinia fraxini, Ph. guttata s.str., Podosphaera amelanchieris, P. aucupariae, P. balsaminae, P. macularis, P. mors-uvae, P. prunicola, and Sawadaea tulasnei are known from one or two localities, so they are considered as rare species in Western Polissya of Ukraine.

A fungal plant pathogen overcomes conserved broad-spectrum disease resistance by rapid gene loss

Hosts and pathogens typically engage in an evolutionary arms race. This also applies to phytopathogenic powdery mildew fungi, which can rapidly overcome plant resistance and perform host jumps. Using experimental evolution, we show that the powdery mildew pathogen Blumeria graminis f.sp. hordei is capable of breaking the agriculturally important broad-spectrum resistance conditioned by barley loss-of-function mlo mutants. Partial mlo virulence is associated with a distinctive pattern of adaptive mutations, including small-sized (8-40 kb) deletions, one of which likely affects spore morphology. The detected mutational spectrum comprises the same loci in at least two independent mlo-virulent isolates, indicating convergent multigenic evolution. This work highlights the dynamic genome evolution of an obligate biotrophic plant pathogen with a transposon-enriched genome.

Checklist of powdery mildew fungi (Erysiphaceae) in Pakistan

The 10-page "Checklist of powdery mildew fungi (Erysiphaceae) in Pakistan " by Afshan, Zafar, and Khalid may now be downloaded from Mycotaxon's mycobiota webpage. This annotated species list brings to 149 the number of freeaccess fungae now available on our website: http://www.mycotaxon.com/mycobiota/index.html

First draft genome assemblies of Pleochaeta shiraiana and Phyllactinia moricola, two tree-parasitic powdery mildew fungi with hemiendophytic mycelia

Powdery mildew fungi (Erysiphaceae) are widespread obligate biotrophic plant pathogens. Thus, applying genetic and omics approaches to study these fungi remains a major challenge, particularly for species with hemiendophytic mycelium. These belong to a distinct phylogenetic lineage within the Erysiphaceae. To date, only a single draft genome assembly is available for this clade, determined in Leveillula taurica. Here, we generated the first draft genome assemblies of Pleochaeta shiraiana and Phyllactinia moricola, two tree-parasitic powdery mildew species with hemiendophytic mycelium, representing two genera that have not been investigated with genomics tools yet. Together with the draft genome of L. taurica, these resources will be pivotal for understanding the molecular basis of the lifestyle of these fungi, which is unique within the Erysiphaceae.

RACE1, a Japanese Blumeria graminis f. sp. hordei isolate, is capable of overcoming partially mlo-mediated penetration resistance in barley in an allele-specific manner

Loss-of-function mutation of the MILDEW RESISTANCE LOCUS O (Mlo) gene confers durable and broad-spectrum resistance to powdery mildew fungi in various plants, including barley. In combination with the intracellular nucleotide-binding domain and leucine-rich repeat receptor (NLR) genes, which confer the race-specific resistance, the mlo alleles have long been used in barley breeding as genetic resources that confer robust non-race-specific resistance. However, a Japanese Blumeria graminis f. sp. hordei isolate, RACE1, has been reported to have the potential to overcome partially the mlo-mediated penetration resistance, although this is yet uncertain because the putative effects of NLR genes in the tested accessions have not been ruled out. In this study, we examined the reproducibility of the earlier report and found that the infectious ability of RACE1, which partially overcomes the mlo-mediated resistance, is only exerted in the absence of NLR genes recognizing RACE1. Furthermore, using the transient-induced gene silencing technique, we demonstrated that RACE1 can partially overcome the resistance in the host cells with suppressed MLO expression but not in plants possessing the null mutant allele mlo-5.

Phytosanitary monitoring in the Arboretum of the Nikita Botanical Gardens in 2020

According to the results of phytosanitary monitoring in the Arboretum of the NBG, 26 pest species were identified on 97 tree introduced species (1039 foci). In the Arboretum of the NBG in 2020, 27 species of phytopathogenic fungi (186 foci) were identified on 65 species of woody plants. Of these, 18 species are wood-destroying fungi that cause root and trunk rot in 57 species of tree introduced species (159 foci). In the Arboretum, 5 types of powdery mildew fungi (9 foci) and 4 types of fungi that cause rust (18 foci) were identified. The results of phytosanitary monitoring for the period 2015-2020 were summed up. The number of pest species increased by 8 species and amounted to 26 species of phytophagans, the number of pest foci increased by 32%. The number of foci of phytopathogenic bracket fungi that cause root and trunk rot increased from 103 to 159 units, the increase in foci of pathogens was 56 units. Currently, the number of bracket fungi that cause root rot is 7 species (135 foci), bracket fungi that cause trunk rot - 11 species (24 foci). The number of powdery mildew and rust fungi did not change during the studies. The biology and ecology of cottony-cushion scale ( Icerya purchasi ) was studied.

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.

The barley powdery mildew effectors CSEP0139 and CSEP0182 suppress cell death and promote B. graminis fungal virulence in plants

The powdery mildew fungi secrete numerous Candidate Secreted Effector Proteins (CSEPs) to manipulate host immunity during infection of host plants. However, the function of most of these CSEPs in cell death suppression has not yet been established. Here, we identified several CSEPs from Blumeria graminis f. sp. hordei (Bgh) that have the potential to suppress BAX- and NtMEK2DD-triggered cell death in Nicotiana benthamiana. We further characterized two effector candidates, CSEP0139 and CSEP0182, from family six and thirty-two, respectively. CSEP0139 and CSEP0182 contain a functional signal peptide and are likely secreted effectors. Expression of either CSEP0139 or CSEP0182 suppressed cell death triggered by BAX and NtMEK2DD but not by the AVRa13/MLA13 pair in N. benthamiana. Transient overexpression of CSEP0139 or CSEP0182 also inhibited BAX-induced cell death and collapse of cytoplasm in barley cells. Furthermore, overexpression of either CSEPs significantly increased Bgh haustorial formation in barley, whereas host-induced gene silencing (HIGS) of the CSEP genes reduced haustorial formation, suggesting both CSEPs promote Bgh virulence in barley. In addition, expression of CSEP0139 and CSEP0182 reduced size of the lesions caused by the necrotrophic Botrytis cinerea in N. benthamiana. Our findings suggest that CSEP0139 and CSEP0182 may target cell death components in plants to promote fungal virulence, which extends the current understanding of the functions of Bgh CSEPs and provides an opportunity for further investigation of fungal virulence in relation to cell death pathways in host plants.

POWDERY MILDEW AT THE OBJECTS OF THE LANDSCAPE ARCHITECTURE OF VORONEZH

Powdery mildew is one of the pathologies of deciduous plants. In the affected plant organism, metabolic processes are disrupted. Plants lag behind in growth; lose winter hardiness and resistance to unfavorable factors. The aggressiveness of powdery mildew fungi is the basis for the study of their bioecological characteristics in various forest zones. The relevance of such studies in the conditions of the city of Voronezh is due to the dominance of deciduous plants on the objects of landscape architecture, which are more or less susceptible to powdery mildew. Studies carried out in parks have shown that the complex of pathogens (causative agents of powdery mildew) is 13 species and 2 forms of fungi. At the same time, 3 species and 1 form proved to be rare. 7 species and 1 form of pathogens were classified as common in terms of frequency of occurrence. Massive species that develop annually in parks are 3 species of powdery mildew fungi. Common barberry, English oak, ash-leaved maple and hawthorn showed weak resistance to the disease. Signs of affection were not noted on aspen, black alder, Babylonian willow, common and small-leaved elms, robinia, pear, red oak, fragrant poplar, Vangutta spirea, Buldenezh viburnum, Thunberg barberry. Measures to reduce the spread of powdery mildew in parks are monitoring, selection of planting material, the use of resistant species, agrotechnical planting care, maintaining optimal insolation and aeration regimes in plantations

First records of powdery mildew fungi (Erysiphales) on medicinal plants in Taiwan

Background Production of medicinal plants in Taiwan is not only hampered by international market competition, but also lack of knowledge of their pathogens, such as powdery mildew fungi (Erysiphales, Ascomycota). Records of these fungi in Taiwan originate from few researchers for the last one hundred years and are still incomplete. Since powdery mildews in tropical/subtropical environments rarely develop the sexual stages with morphologically diagnostic characteristics, internal transcribed spacer sequences (ITS) of the ribosomal RNA genes obtained from the asexual stages have become important modern tools for species identification. Results Powdery mildews on medicinal plants from educational and ornamental plantations in Taiwan were identified based on the anamorph morphology and ITS sequences. Four powdery mildews on medicinal plants are new records for Taiwan, Arthrocladiella mougeotii on Lycium chinense, Erysiphe glycines on Pueraria lobata, Erysiphe lespedezae on Bauhinia sp., Desmodium caudatum, and Uraria crinita, and E. lonicerae on Lonicera japonica. Eryngium foetidum is a new host for Erysiphe heraclei hitherto known on other host plants in Taiwan. Eryngium foetidum and Uraria crinita are new host plants for powdery mildews worldwide. Only specific field collection of the pathogens yielded the new records, not checking plant specimens in a phanerogam herbarium. The pathogens did not cause death of the host plants, but appeared to enhance stress by infection of mature leaves. Conclusions Taxonomic study of powdery mildews in Taiwan results into new host records of economically important medicinal plants in Taiwan with potential consequences for plant production and quarantine and also shows that host records are quite incomplete worldwide. Although ITS sequences were useful for species identification, the lack of data for several species on the same host genus on the one hand and the low variation between closely related species on the other indicate the need for further study.