Search

Sphaerellopsis species are putative hyperparasites of rust fungi and may be promising biological control agents (BCA) of rust diseases. However, few detailed studies limit potential BCA development in Sphaerellopsis. Here, we explored the biogeography, host-specificity, and species diversity of Sphaerellopsis and examined the early infection stage of one species, S. macroconidialis, to infer its trophic status. We randomly screened 5,621 rust specimens spanning 99 genera at the Arthur Fungarium for the presence of Sphaerellopsis. We identified 199 rust specimens infected with Sphaerellopsis species on which we conducted morphological and multi-locus phylogenetic analyses. Five Sphaerellopsis species were recovered, infecting a total of 122 rust species in 18 genera from 34 countries. Sphaerellopsis melampsorinearum sp. nov. is described as a new species based on molecular phylogenetic data and morphological features of the sexual and asexual morphs. Sphaerellopsis paraphysata was the most commonly encountered species, found on 77 rust specimens, followed by Sphaerellopsis macroconidialis on 56 and S. melampsorinearum on 55 examined specimens. The type species, Sphaerellopsis filum, was found on 12 rust specimens and Sphaerellopsis hakeae on a single specimen. We also recovered and documented for the first time, the sexual morph of S. macroconidialis, from a specimen collected in Brazil. Our data indicate that Sphaerellopsis species are not host specific and furthermore that most species are cosmopolitan in distribution. However, S. paraphysata is more abundant in the tropics, and S. hakeae may be restricted to Australia. Finally, we confirm the mycoparasitic strategy of S. macroconidialis through in-vitro interaction tests with the urediniospores of Puccinia polysora. Shortly after germination, hyphae of S. macroconidialis began growing along the germ tubes of P. polysora and coiling around them. After 12 days of co-cultivation, turgor loss was evident in the germ tubes of P. polysora, and appressorium-like structures had formed on urediniospores. The interaction studies indicate that Sphaerellopsis species may be more effective as a BCA during the initial stages of rust establishment. [ABSTRACT FROM AUTHOR]

In the face of evolving agricultural practices and climate change, tools towards an integrated biovigilance platform to combat crop diseases, spore sampling, DNA diagnostics and predictive trajectory modelling were optimized. These tools revealed microbial dynamics and were validated by monitoring cereal rust fungal pathogens affecting wheat, oats, barley and rye across four growing seasons (2015–2018) in British Columbia and during the 2018 season in southern Alberta. ITS2 metabarcoding revealed disparity in aeromycobiota diversity and compositional structure across the Canadian Rocky Mountains, suggesting a barrier effect on air flow and pathogen dispersal. A novel bioinformatics classifier and curated cereal rust fungal ITS2 database, corroborated by real‐time PCR, enhanced the precision of cereal rust fungal species identification. Random Forest modelling identified crop and land‐use diversification as well as atmospheric pressure and moisture as key factors in rust distribution. As a valuable addition to explain observed differences and patterns in rust fungus distribution, trajectory HYSPLIT modelling tracked rust fungal urediniospores' northeastward dispersal from the Pacific Northwest towards southern British Columbia and Alberta, indicating multiple potential origins. Our Canadian case study exemplifies the power of an advanced biovigilance toolbox towards developing an early‐warning system for farmers to detect and mitigate impending disease outbreaks. [ABSTRACT FROM AUTHOR]

We detected isolates with SdhC-I87F-conferring mutations that were slightly SDHI-adapted in the barley leaf rust Puccinia hordei in France and the UK in 2019. SdhC-I87F of P. hordei is orthologous to SdhC-I86F in Phakopsora pachyrhizi, and SdhC-I88F in Puccinia horiana induced SDHI resistance. Nevertheless, the field performance of SDHIs against P. hordei was good, although strains with SdhC-I87F dominated the field. The sensitivity ranges were narrow for wheat leaf rust and Puccinia triticina in 2019; however, isolates with slightly higher EC50 values were obtained in southern France and the eastern UK in 2021. These isolates of P. triticina harbored an orthologous SdhC-I87F-conferring mutation. The range of EC50 values for the SDHI fungicide inpyrfluxam overlapped between the wild type and SdhC-I87F isolates. Further analyses are currently underway. [ABSTRACT FROM AUTHOR]

Members of Puccinia (Pucciniaceae, Pucciniales) are known as plant pathogens worldwide, which are characterized by their morphology, host association, and molecular data of various genes. In the present study, 10 specimens of Puccinia were collected from four herbaceous plants (Anaphalis hancockii, Anthriscus sylvestris, Halenia elliptica, and Pilea pumila) in China and identified based on morphology and phylogeny. As a result, 10 samples represent four undescribed species of Puccinia, viz., P. apdensia, P. decidua, P. dermatis, and P. lianchengensis, spp. nov. P. apdensia is characterized by its smooth teliospores with thickened apex. P. decidua represents the first Puccinia species inhabiting the host Anaphalis hancockii and is distinguished from the other Puccinia species by its telia and uredinia surrounded by the epidermis. P. dermatis from Halenia elliptica differs from the other Puccinia species on the host genus Halenia by the telia that have epidermis and teliospores with sparsely irregular granulated protrusions. P. lianchengensis is characterized by its teliospore surface with fishnet ornamentation and urediniospores without prominent caps. All of the new species are described and illustrated in this study. [ABSTRACT FROM AUTHOR]

Oats (Avena sativa L. cv. Joyang), cultivated during June 2023 in experimental fields of Naju County, South Korea, exhibited crown rust symptoms resembling those caused by isolates of Puccinia coronata. Yellow urediniospores measuring 15.3 ± 3.2 × 13.6 ± 3.0 μm were identified through microscopic examination. Multilocus sequence typing of housekeeping genes in the DNA of this fungal isolate showed identity with P. coronata var. avenae f.sp. avenae, a pathogen of oats in South Korea previously lacking in taxonomic classification. This finding raises concerns of escalated crown rust disease in South Korea due to enhanced temperatures and humidity from climate shifts. Addressing these emerging concerns may require proactive strategies to protect oat cultivation in South Korea. [ABSTRACT FROM AUTHOR]

Rust fungi (Pucciniales, Basidiomycota) are a species-rich (ca. 8000 species), globally distributed order of obligate plant pathogens. Rust species are host-specific, and as a group they cause disease on many of our most economically and/or ecologically significant plants. As such, the ability to accurately and rapidly identify these fungi is of particular interest to mycologists, botanists, agricultural scientists, farmers, quarantine officials, and associated stakeholders. However, the complexities of the rust life cycle, which may include production of up to five different spore types and alternation between two unrelated host species, have made standard identifications, especially of less-documented spore states or alternate hosts, extremely difficult. The Arthur Fungarium (PUR) at Purdue University is home to one of the most comprehensive collections of rust fungi in the world. Using material vouchered in PUR supplemented with fresh collections we generated DNA barcodes of the 28S ribosomal repeat from > 3700 rust fungal specimens. Barcoded material spans 120 genera and > 1100 species, most represented by several replicate sequences. Barcodes and associated metadata are hosted in a publicly accessible, BLAST searchable database called Rust HUBB (Herbarium-based Universal Barcode Blast) and will be continuously updated. [ABSTRACT FROM AUTHOR]

Background: Rye (Secale cereale L.) is a cereal crop highly tolerant to environmental stresses, including abiotic and biotic stresses (e.g., fungal diseases). Among these fungal diseases, leaf rust (LR) is a major threat to rye production. Despite extensive research, the genetic basis of the rye immune response to LR remains unclear. Results: An RNA-seq analysis was conducted to examine the immune response of three unrelated rye inbred lines (D33, D39, and L318) infected with compatible and incompatible Puccinia recondita f. sp. secalis (Prs) isolates. In total, 877 unique differentially expressed genes (DEGs) were identified at 20 and 36 h post-treatment (hpt). Most of the DEGs were up-regulated. Two lines (D39 and L318) had more up-regulated genes than down-regulated genes, whereas the opposite trend was observed for line D33. The functional classification of the DEGs helped identify the largest gene groups regulated by LR. Notably, these groups included several DEGs encoding cytochrome P450, receptor-like kinases, methylesterases, pathogenesis-related protein-1, xyloglucan endotransglucosylases/hydrolases, and peroxidases. The metabolomic response was highly conserved among the genotypes, with line D33 displaying the most genotype-specific changes in secondary metabolites. The effect of pathogen compatibility on metabolomic changes was less than the effects of the time-points and genotypes. Accordingly, the secondary metabolome of rye is altered by the recognition of the pathogen rather than by a successful infection. The results of the enrichment analysis of the DEGs and differentially accumulated metabolites (DAMs) reflected the involvement of phenylpropanoid and diterpenoid biosynthesis as well as thiamine metabolism in the rye immune response. Conclusion: Our work provides novel insights into the genetic and metabolic responses of rye to LR. Numerous immune response-related DEGs and DAMs were identified, thereby clarifying the mechanisms underlying the rye response to compatible and incompatible Prs isolates during the early stages of LR development. The integration of transcriptomic and metabolomic analyses elucidated the contributions of phenylpropanoid biosynthesis and flavonoid pathways to the rye immune response to Prs. This combined analysis of omics data provides valuable insights relevant for future research conducted to enhance rye resistance to LR. [ABSTRACT FROM AUTHOR]

Helictotrichon sempervirens (blue oatgrass) is a perennial grass widely grown for ornamental use in Canada. Rusted blue oatgrass plants with diseased leaves covered with uredinia were collected from two locations at metropolitan Vancouver, British Columbia (BC), in summer 2022. The rust fungus was identified as Puccinia gibberosa (= P. coronata var. gibberosa) based on combined results of morphological characteristics and molecular analyses. The internal transcribed spacer two (ITS2) and partial large subunit ribosomal DNA were amplified and sequenced. The sequence obtained for the rust fungus showed 99.9% identity with the previously reported P. coronata var. gibberosa from USA. This is the first report of rust caused by P. gibberosa on blue oatgrass in Canada. Evidence from phylogenetic analyses supports the recognition of this rust at the species level. A revised description for P. gibberosa is provided, including synonyms, host range and distribution across the globe, and incorporating comprehensive molecular and morphological results for several North American and European specimens. In addition, a lectotype and an epitype are designated here for the rust species. [ABSTRACT FROM AUTHOR]

Cereal rust is one of the most damaging diseases of small-grain cereals. The fungus Puccinia hordei causes leaf rust in barley and other small grain crops. Puccinia hordei causes serious yield losses in the cultivating areas where susceptible and late-maturing barley varieties are cultivated. Therefore, rust-resistant barley cultivar is highly demandable for sustainable small-grain crop production. Improving barley yields and quality is one of the major objectives of barley breeding programs in our country. Exotic and indigenous germplasm is one of the best sources of resistance to biotic stresses in barley particularly leaf rust caused by Puccinia hordei. Hence, the present investigation was carried out to identify the resistance sources to P. hordei and incorporate them into the breeding programs for higher barley yields under changing climatic scenarios. The study aimed to identify new resistant cultivars in barley and other small grain crops. In this study, 100 barley genotypes (Hordeum vulgare L.) were considered for screening susceptibility to P. hordei causing rust disease. Several biochemical responses were analyzed in P. hordei infected barley genotypes. However, the variable response was observed among the 100 barley genotypes while those were screened against leaf rust disease under high altitude cold arid conditions of Ladakh, India. The efficiency of the 100 barley genotypes were categorized into different classes including high resistance (4 genotypes)>resistance (14 genotypes)> moderately resistance (20 genotypes)> moderately susceptible (33 genotypes)>moderately susceptible to susceptible (19 genotypes)> and susceptible (10 genotypes) based on plant response to P. hordei. Among the total genotypes, SHEIKH/KP-706, SHEIKH-B1, SHEIKH-636, and IC-062190 showed high resistance (8.07-8.63) as per the international leaf rust scale, while EC-667381, EC-667390, EC-667392, EC667396, EC-667417, Jyoti, EC-667434, EC-667442, EC-667445, and EC-667446 were found as susceptible (3.13-3.97) to P. hordei. The highly resistant genotypes accumulated a high level of phenols and flavonoids and cooperated with susceptible and other rest of the genotypes in response to P. hordei rust. The efficiency of plant immune response and or fitness to P. hordei was correlated to the disease susceptibility index of particular genotypes. This provides a new insight and the mechanistic basis of genotype-specific rust disease susceptibility against P. hordei. A large number of genotype-based studies at the field level could be useful to plant breeders and farmers for improving rust resistance in barley and other small-grain cereals. [ABSTRACT FROM AUTHOR]

Peanuts play a pivotal role as an economic crop on a global scale, serving as a primary source of both edible oil and protein. Peanut rust (Puccinia arachidis Speg.) disease constitutes a significant global biotic stress, representing a substantial economic threat to the peanut industry by inducing noteworthy reductions in seed yields and compromising oil quality. This comprehensive review delves into the distinctive characteristics and detrimental symptoms associated with peanut rust, scrutinizing its epidemiology and the control strategies that are currently implemented. Notably, host resistance emerges as the most favored strategy due to its potential to surmount the limitations inherent in other approaches. The review further considers the recent advancements in peanut rust resistance breeding, integrating the use of molecular marker technology and the identification of rust resistance genes. Our findings indicate that the ongoing refinement of control strategies, especially through the development and application of immune or highly resistant peanut varieties, will have a profound impact on the global peanut industry. [ABSTRACT FROM AUTHOR]

Puccinia graminella is one of several rusts considered as potential biocontrol agents for the grass weed Nassella neesiana in Australia and New Zealand. While Uromyces pencanus was chosen as the most promising candidate, results of our studies on P. graminella in Argentina (where the rust and grass are native) could be useful if a complementary agent is eventually needed. P. graminella produces aecidioid urediniospores, which morphologically resemble aeciospores but behave like the urediniospores of other rusts i.e. they are repetitive and the main (perhaps only) source of new infections. To improve the consistency of previous laboratory results, we aimed to locate accessible sources of spores in the field, and to determine optimal conditions for their collection, production and storage in the laboratory. Aecidioid urediniospores were found to germinate most readily at temperatures between 10 and 15°C. It was possible to store them in a refrigerator (4°C) or a freezer (−70°C), but already-low germination rates decreased over time using both methods. The appearance of host leaves affected inoculum quality, with green healthy leaves yielding aecidioid urediniospores with good germination rates. Best results in inoculation tests were obtained when spores and plants came from the same site. The presence of qualitative resistance in the pathosystem is suspected. P. graminella is not easy to manipulate in the laboratory, its impact on Nassella neesiana in the field is variable and the nature of its life cycle remains elusive. Remaining gaps in knowledge are identified and future directions for research are discussed. [ABSTRACT FROM AUTHOR]

Hemerocallis citrina Baroni (daylily) is an important cash crop in many regions of China. Daylily rust caused by Puccinia hemerocallidis (Ph) is a major disease in H. citrina. Rust infection on the leaves of two resistant and susceptible varieties of H. citrina was examined. Transcriptome sequencing and defense enzyme activity were used to analyze the differential expression of related genes after 0, 72, 144, 192, and 288 h, to reveal the response mechanism of H. citrina to rust infection and screen-related resistance genes. The results suggested that 72 h after Ph infection was the key time point for determining differences between resistant and susceptible varieties. DEGs were significantly enriched in phenylpropanoid biosynthesis, plant–pathogen interaction, plant hormone signal transduction, and the MAPK signaling pathway. TFs WRKY33 and CYP98A are key genes closely related to the disease-resistance response of H. citrina. This study is the first large-scale transcriptomic analysis of H. citrina. [ABSTRACT FROM AUTHOR]

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 Puccinia pittieriana is published and available online in the EFSA Plant Pest Survey Cards Gallery at the following link and will be updated whenever new information becomes available: https://efsa.europa.eu/plants/planthealth/monitoring/surveillance/puccinia-pittieriana [ABSTRACT FROM AUTHOR]

In China, about 500 Puccinia species have been discovered, with over 200 species distributed in Shaanxi province. In 2023, a rust disease of Alcea rosea was discovered in Shaanxi Province, China, and the pathogen was identified as Puccinia modiolae through morphological characterization and phylogenetic analysis. This is the first documented report of rust disease on A. rosea caused by P. modiolae in China. [ABSTRACT FROM AUTHOR]

Background Puccinia arachidis fungus causes rust disease in the peanut plants (Arachis hypogaea L.), which leads to high yield loss. Metabolomic profiling of Arachis hypogaea was performed to identify the pathogen-induced production of metabolites involved in the defense mechanism of peanut plants. In this study, two peanut genotypes, one susceptible (JL-24) and one resistant (GPBD-4) were inoculated with Puccinia arachidis fungal pathogen. The metabolic response was assessed at the control stage (0 day without inoculation), 2 DAI (Day after inoculation), 4 DAI and 6 DAI by Gas Chromatography-Mass Spectrometry (GC-MS). Results About 61 metabolites were identified by NIST library, comprising sugars, phenols, fatty acids, carboxylic acids and sugar alcohols. Sugars and fatty acids were predominant in leaf extracts compared to other metabolites. Concentration of different metabolites such as salicylic acid, mannitol, flavonoid, 9,12-octadecadienoic acid, linolenic acid and glucopyranoside were higher in resistant genotype than in susceptible genotype during infection. Systemic acquired resistance (SAR) and hypersensitive reaction (HR) components such as oxalic acid was elevated in resistant genotype during pathogen infection. Partial least square-discriminant analysis (PLS-DA) was applied to GC-MS data for revealing metabolites profile between resistant and susceptible genotype during infection. Conclusion The phenol content and oxidative enzyme activity i.e. catalase, peroxidase and polyphenol oxidase were found to be very high at 4 DAI in resistant genotype (p-value < 0.01). This metabolic approach provides information about bioactive plant metabolites and their application in crop protection and marker-assisted plant breeding. [ABSTRACT FROM AUTHOR]

Switchgrass (Panicum virgatum L.) can be infected by the rust pathogen (Puccinia novopanici) and results in lowering biomass yields and quality. Label-free quantitative proteomics was conducted on leaf extracts harvested from non-infected and infected plants from a susceptible cultivar (Summer) at 7, 11, and 18 days after inoculation (DAI) to follow the progression of disease and evaluate any plant compensatory mechanisms to infection. Some pustules were evident at 7 DAI, and their numbers increased with time. However, fungal DNA loads did not appreciably change over the course of this experiment in the infected plants. In total, 3830 proteins were identified at 1% false discovery rate, with 3632 mapped to the switchgrass proteome and 198 proteins mapped to different Puccinia proteomes. Across all comparisons, 1825 differentially accumulated switchgrass proteins were identified and subjected to a STRING analysis using Arabidopsis (A. thaliana L.) orthologs to deduce switchgrass cellular pathways impacted by rust infection. Proteins associated with plastid functions and primary metabolism were diminished in infected Summer plants at all harvest dates, whereas proteins associated with immunity, chaperone functions, and phenylpropanoid biosynthesis were significantly enriched. At 18 DAI, 1105 and 151 proteins were significantly enriched or diminished, respectively. Many of the enriched proteins were associated with mitigation of cellular stress and defense. [ABSTRACT FROM AUTHOR]

In recent years, with the increase in parks, gardens, recreation areas, picnic areas and refuges with urbanization, the interest in turfgrass areas that beautify the aesthetic appearance of these areas has also increased. In these areas, rust diseases are also becoming increasingly common and causing problems. Rust diseases are an important pathogen group that needs to be monitored due to their ability to create new races and their airborne transmission. In this study, surveys were conducted in turfgrass areas in 8 provinces of Türkiye and 110 turfgrass leaf samples showing rust symptoms were collected. As a result of DNA isolation and qPCR analysis from pustules on the leaf surface, 37 Puccinia coronata, 32 P. graminis, 18 P. striiformis and 23 Puccinia spp. have been detected. It was determined that the most common rust species that causes disease in turfgrass areas in Türkiye is P. coronata. This species was followed by P. graminis and P. striiformis, respectively. While P. striiformis was mostly isolated from Kayseri and Istanbul provinces, P. coronata and P. graminis were mostly isolated from İstanbul. [ABSTRACT FROM AUTHOR]

Six quantitative trait loci (QTLs) for adult plant resistance against oat crown rust (Puccinia coronata f. sp. avenae) were identified from mapping three recombinant inbred populations. Using genotyping-by-sequencing with markers called against the OT3098 vl reference genome, the QTLs were mapped on six different chromosomes: ChrlD. Chr4D. Chr5A, Chr5D. Chr7A, and Chr7C. Composite interval mapping with marker cofactor selection showed that the phenotypic variance explained by all identified QTLs for coefficient of infection range from 12.2 to 46.9%, whereas heritability estimates ranged from 0.11 to 0.38. The significant regions were narrowed down to intervals of 3.9 to 25 cM. equivalent to physical distances of 11 to 133 Mb. At least two flanking single-nucleotide polymorphism markers were identified within 10 cM of each QTL that could be used in marker-assisted introgression, pyramiding, and selection. The additive effects of the QTLs in each population were determined using single-nucleotide polymorphism haplotype data, which showed a significantly lower coefficient of infection in lines homozygous for the resistant alleles. Analysis of pairwise linkage disequilibrium also revealed high correlation of markers and presence of linkage blocks in the significant regions. To further facilitate marker-assisted breeding, polymerase chain reaction allelic competitive extension (PACE) markers for the adult plant resistance loci were developed. Putative candidate genes were also identified in each of the significant regions, which include resistance gene analogs that encode for kinases, ligases, and predicted receptors of avirulence proteins from pathogens. [ABSTRACT FROM AUTHOR]

Puccinia, which comprises 4000 species, is the largest genus of rust fungi and one of the destructive plant pathogenic rust genera that are reported to infect both agricultural and nonagricultural plants with severe illnesses. The presence of bi-celled teliospores is one of the major features of these rust fungi that differentiated them from Uromyces, which is another largest genus of rust fungi. In the present study, an overview of the current knowledge on the general taxonomy and ecology of the rust genus Puccinia is presented. The status of the molecular identification of this genus along with updated species numbers and their current statuses in the 21st century are also presented, in addition to their threats to both agricultural and nonagricultural plants. Furthermore, a phylogenetic analysis based on ITS and LSU DNA sequence data available in GenBank and the published literature was performed to examine the intergeneric relationships of Puccinia. The obtained results revealed the worldwide distribution of Puccinia. Compared with other nations, a reasonable increase in research publications over the current century was demonstrated in Asian countries. The plant families Asteraceae and Poaceae were observed as the most infected in the 21st century. The phylogenetic studies of the LSU and ITS sequence data revealed the polyphyletic nature of Puccinia. In addition, the presences of too short, too lengthy, and incomplete sequences in the NCBI database demonstrate the need for extensive DNA-based analyses for a better understanding of the taxonomic placement of Puccinia. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the effect of the rust fungus Puccinia lagenophorae on total phenols, phenolic acids, and defense-related enzymes in the leaf tissues of the host, Senecio aegyptius. The infection increased the total phenol and defense-related enzymes in the host leaf tissues when compared to healthy tissues. The analysis using HPLC revealed the existence of 10 phenolic acids in healthy and infected host leaves. The infection increased the amounts of caffeic, chlorogenic, ferulic, p-coumaric, and salicylic acids. The examination by TEM revealed the presence of peroxidase activity on the host microbodies, Golgi bodies, endoplasmic reticulum, and the thickening of xylem vessels. After the infection, the activity was localized at the penetration sites of fungal haustoria and in amorphous materials found between the intercellular hyphae and the host cell wall. The heaviest peroxidase activity was detected in heavily infected vascular tissue, due to the monokaryotic infection. [ABSTRACT FROM AUTHOR]

Austropuccinia psidii, the causal agent of myrtle rust, has emerged as a significant threat to Myrtaceae in planted and natural woody ecosystems. The first detection of A. puccinia in South Africa was from severely infected ornamental Myrtus communis. This raised concern that M. communis, the sole Myrtaceae species native to Europe and an important component of vegetation in Mediterranean regions, could be threatened by the rust. In light of the potential threat to this unique species, seed was collected from 12 Italian provenances of M. communis, including mainland and island (Sardinia and Sicily) populations. We assessed the susceptibility of these provenances to both the pandemic and South African strains of A. psidii. In Colombia, where the pandemic strain of A. psidii is native, seedlings rapidly became infected by natural inoculum. In South Africa, a preliminary screening of seedlings by artificial inoculation with a single-uredinium isolate produced high levels of disease. Finally, plants of each of the 12 provenances were planted and monitored in Florence, Italy. To date, these showed no signs of disease, but will continue to be monitored. This study highlights the significant threat that both the pandemic and South African strains of A. puccinia pose to M. communis in Europe. [ABSTRACT FROM AUTHOR]

During the years 2017 and 2018, leaves and stems with dark brown lesions containing hypophilic telia surrounded by chlorotic halos were collected from Sphaeralcea angustifolia plants located in Axapusco, State of Mexico. Based on the morphological characteristics, the fungus Puccinia sherardiana was identified. Uredinal stage was not detected during the observation period. Verification of the identity of the fungus was carried out by means of a phylogenetic analysis with part of a sequence of the 28S gene of ribosomal DNA. Pathogenicity tests were performed on S. angustifolia plants by inoculating teliospores. The inoculated plants developed symptoms and signs 15 days after inoculation, beginning with the presence of eruptive aecia in the epidermis of the host and later the formation of telia, completing Koch's Postulates. The fungus P. sherardiana was previously described as a rust with a microcyclic life cycle on species of the genera Alcea, Malvastrum, Sidalcea and Sphaeralcea, belonging to the Malvaceae family; however, in this study the pathogen behaved differently. P. sherardiana will continue to be studied to determine if its life cycle is demicyclic in Mexico. [ABSTRACT FROM AUTHOR]

Objectives: RNA sequencing of two organisms in a symbiotic interaction can yield insights that are not found in samples from each organism alone. We present a sequencing dataset focusing on the small RNA fraction from wheat plants (Triticum aestivum) infected with the biotrophic pathogen wheat stem rust fungus (Puccinia graminis f.sp. tritici). Simultaneous small RNA sequencing of this agronomically important crop and its adversary can lead to a better understanding of the role of noncoding RNAs in both plant and fungal biology. Data description: Small RNA libraries were constructed from infected and mock-infected plant tissue and sequenced on the Ion Torrent platform. Quality control was performed to ensure sample and data integrity. Using this dataset, researchers can employ previously established methods to map subsets of reads exclusively to each organism's genome. Subsequent analyses can be undertaken to discover microRNAs, predict small RNA targets, and generate hypotheses for further laboratory experiments. [ABSTRACT FROM AUTHOR]

Rust fungi are characterized by large genomes with high repeat content and have two haploid nuclei in most life stages, which makes achieving high‐quality genome assemblies challenging. Here, we described a pipeline using HiFi reads and Hi‐C data to assemble a gigabase‐sized fungal pathogen, Puccinia polysora f.sp. zeae, to haplotype‐phased and chromosome‐scale. The final assembled genome is 1.71 Gbp, with ~850 Mbp and 18 chromosomes in each haplotype, being currently one of the two giga‐scale fungi assembled to chromosome level. Transcript‐based annotation identified 47,512 genes for the dikaryotic genome with a similar number for each haplotype. A high level of interhaplotype variation was found with 10% haplotype‐specific BUSCO genes, 5.8 SNPs/kbp, and structural variation accounting for 3% of the genome size. The P. polysora genome displayed over 85% repeat contents, with genome‐size expansion and copy number increasing of species‐specific orthogroups. Interestingly, these features did not affect overall synteny with other Puccinia species having smaller genomes. Fine‐time‐point transcriptomics revealed seven clusters of coexpressed secreted proteins that are conserved between two haplotypes. The fact that candidate effectors interspersed with all genes indicated the absence of a "two‐speed genome" evolution in P. polysora. Genome resequencing of 79 additional isolates revealed a clonal population structure of P. polysora in China with low geographic differentiation. Nevertheless, a minor population differentiated from the major population by having mutations on secreted proteins including AvrRppC, indicating the ongoing virulence to evade recognition by RppC, a major resistance gene in Chinese corn cultivars. The high‐quality assembly provides valuable genomic resources for future studies on disease management and the evolution of P. polysora. [ABSTRACT FROM AUTHOR]

Barley leaf rust (Puccinia hordei Otth.) is considered a harmful disease that occurs in barley-growing regions worldwide. In Russia, the disease is among the most prevalent in the Krasnodar region, which is the leader in the production of barley grain and has a favorable climate for disease development. In this paper, we studied the efficiency of 17 varieties and lines of barley from the International and Australian sets containing currently known Rph resistance genes or their combinations to P. hordei in the field, and 15 varieties and lines in the seedling phase in greenhouse conditions during 2019–2021. We concluded that the lines carrying the Rph7 and Rph13 genes remained immune throughout the three years of studies in the seedling and adult plant stages. The Rph1 and Rph23 genes showed moderate efficiency during the three years. The Rph2, Rph3, Rph4, Rph5, Rph6+2, Rph8, Rph12, Rph19, and Rph21+2 genes showed low efficiency over the three years. This was also confirmed by the results of their assessment in the seedling phase: the number of monopustular isolates virulent to lines with the majority of the studied genes for three years was above 90%. Fluctuations in the virulence of the P. hordei population were observed under sufficiently unfavorable weather for disease development in 2019, 2020, and 2021. This proves the ability of the fungus to adapt to changing conditions. Therefore, annual monitoring of the response of lines and varieties carrying resistance genes and studying the virulence of the pathogen are crucial for the selection of rust-resistant varieties, and, hence, the prevention of barley leaf rust epidemics in all grain-producing regions worldwide. [ABSTRACT FROM AUTHOR]

Rust infection results in decreases in photosynthesis and stress volatile emissions, but how these changes vary among host species has not been studied. We demonstrated that the impact of the obligate biotrophic fungus, Puccinia coronata f. sp. avenae , on foliage physiological processes is stronger in the primary host, Avena sativa (cultivated oat), than in the alternate host, Rhamnus frangula (alder buckthorn). Photosynthesis decreased with increasing percentage of damaged leaf area (D A) in both species, but reductions were greater in A. sativa. In A. sativa , photosynthetic reductions resulted from reductions in stomatal conductance and photosynthetic capacity; in R. frangula , reductions were due to reduced capacity. Infection reduced photosynthetic biomass and key nutrients in A. sativa , but not in R. frangula. In A. sativa , stress-elicited emissions (methyl jasmonate, green leaf volatiles, long-chain saturated aldehydes, mono- and sesquiterpenes, benzenoids, and carotenoid breakdown products) increased with increasing D A from 0% to 40%, but decreased with further increases in D A. In R. frangula , volatile emissions were slightly elicited but, surprisingly, constitutive isoprene emissions were enhanced. Different hosts had characteristic volatile fingerprints, indicating differential activation of biochemical pathways. Fungal-elicited reductions in photosynthesis scale uniformly with stress severity. In the sensitive host, biphasic scaling of volatiles indicates that heavy spread of chlorosis/necrosis leads to an overall cessation of physiological functioning. [ABSTRACT FROM AUTHOR]

Nowadays, population growth, the global temperature increase, and the appearance of emerging diseases in important crops generate uncertainty regarding world food security. The use of agrochemicals has been the "go-to" solution for the control of phytopathogenic microorganisms, such as Magnaporte oryzae, causing blast disease in rice and other cereals; Botrytis cinerea, causing gray mold in over 500 plant species; and Puccinia spp., causing rust in cereals. However, their excessive use has harmed human health, as well as ecosystems (contaminating water, and contributing to soil degradation); besides, phytopathogens can develop resistance to them. The inoculation of plant growth-promoting microorganisms (PGPMs) to crops is a sustainable strategy for increasing the yield and quality of crops and mitigating biotic stresses. Likewise, PGPMs, such as Pseudomonas, Bacillus, and Trichoderma, can trigger a series of signals and reactions in the plant that lead to the induction of systemic resistance, a mechanism by which plants react to microorganism stimulation by activating their defense system, resulting in protection against future pathogen attack. These plant defense mechanisms help to mitigate biotic stresses that threaten global food security. Thus, the study of these mechanisms at molecular, transcriptomic, and metabolomic levels is indispensable to elucidate how stresses affect globally important crops. [ABSTRACT FROM AUTHOR]

Summary: Sequencing herbarium specimens can be instrumental in answering ecological, evolutionary, and taxonomic inquiries. We developed a protocol for sequencing herbarium specimens of rust fungi (Pucciniales) and proceeded to sequence specimens ranging from 4 to 211 yr old from five different genera.We then obtained sequences from an economically important biological control agent, Puccinia suaveolens, to highlight the potential of sequencing herbarium specimens in an ecological sense and to evaluate the following hypotheses: (1) The population structure of a plant pathogen changes over time, and (2) introduced pathogens are more diverse in their native range.Our efforts resulted in sequences from 87 herbarium specimens that revealed a high level of diversity with a population structure that exhibited spatial–temporal patterns. The specimens sequenced from Europe showed more diversity than the ones from North America, uncovering an invasion pattern likely related to its European native host in North America. Additionally, to the best of our knowledge, the specimen from France collected in c. 1811 is the oldest herbarium specimen sequenced from kingdom Fungi.In conclusion, sequencing old herbarium specimens is an important tool that can be extrapolated to better understand plant–microbe evolution and to evaluate old type specimens to solidify the taxonomy of plant pathogenic fungi. [ABSTRACT FROM AUTHOR]

This study investigated the impact of the rust fungus, Puccinia lagenophorae on its host, Senecio aegyptius using both light (LM) and transmission (TEM) electron microscopy. The chloroplast numbers decreased during the aecial and telial stages of the pathogen (53.7 and 56.6%, respectively). The nucleus volumes were increased during both stages (10.9 and 14.1%, respectively). Infected chloroplasts and nuclei showed changes in their shape and ultrastructure. Instead of the M-haustorium, a collar was created around the D-haustorium. A neck encasing developed in both types of necrotic haustoria. This encasement may serve as the host cell's protection against toxins created after the death of haustoria. The severe changes in the chloroplasts and nuclei of this host plant after infection by this pathogen may give this pathogen the possibility of controlling this serious weed. Future research in the molecular mechanism may explore the biological control of weeds for local farm agroecology. [ABSTRACT FROM AUTHOR]

All plant tissues from leaves, stems, and roots are hosting a wide diversity of fungal species. Our understanding of the assembly of this diversity of fungi during the plant growth cycle is limited. Here, we characterized the mycobiome of three spring barley cultivars grown in Zealand, Denmark, at weekly intervals during a growth season from seedling emergence to senescence and seed maturity. A notable proportion of members of the fungal communities were shared among different plant organs, but community dynamics were tissue-specific. A severe attack of Puccinia hordei occurring during the vegetative stage had profound effects on the mycobiome, and P. hordei biomass displaced that of other taxa. Plant tissue type was the most important factor determining the mycobiome, but also plant age was contributing significantly. Using a random forest model, we found that specific members of the mycobiome were responding differently to plant age, for instance, Olpidium and Articulospora in roots, Dioszegia and Sporobolomyces in leaves, Pyrenophora in stems, and Epicoccum in heads. A co-occurrence network analysis revealed complex interactions among fungal OTUs, and network connectivity was changing as per plant growth stage and plant tissue type. This study contributes to the understanding of assembly of fungal communities in cereals by providing a detailed description of fungal communities associated with barley. This knowledge will be vital for microbiome assisted plant health management and our study will serve as an important baseline for future efforts to harness microbiota in cereal health. [ABSTRACT FROM AUTHOR]

Southern corn rust (SCR) caused by Puccinia polysora is one of the most devastating diseases in the world. In recent years, SCR has been upgraded from a minor to a major disease around the world, including in China. However, little is known about its population genetics and structure in China. In this study, we analyzed 288 isolates collected from various localities during 2017 in seven Chinese provinces: Guangxi, Guangdong, Anhui, Hunan, Shandong, Henan, and Shaanxi. The isolates were analyzed using nine microsatellite markers. The population structure, genetic diversity, and reproduction mode of P. polysora were investigated based on genotype data. Strong genotypic diversity was detected and clonal reproduction was dominant. The populations collected from the pathogen's winter-reproductive regions harbored more genotypes than those collected from the pathogen's epidemic regions. The spatial differences in genotypic richness, and evenness among the populations were significant, and showed a decreasing trend from south to north. Most isolates were clustered into two clonal groups. Two high-frequency multilocus genotypes (MLGs), MLG1 and MLG2, were widely distributed in all populations. Our analyses confirmed that P. polysora employed clone dispersal from the pathogen's winter-reproductive regions to the pathogen's epidemic regions, and in addition to the sources from the pathogen's winter-reproductive regions, the pathogen in Anhui and Hunan might also have other sources from areas such as Taiwan, China, or/and Southeast Asia, and the pathogen went through a genetic bottleneck during its dispersal. These findings provide initial insights into the reproduction mode and dispersal pathways of P. polysora in China. [ABSTRACT FROM AUTHOR]

Although the causal pathogen of the widespread rust on Chinese chive (Allium tuberosum) in Japan has been reported as Puccinia allii, the pathogen is restricted to A. tuberosum and differs from P. allii that causes rust on other Allium species. Here we collected isolates from A. tuberosum from various localities in Japan and examined the morphology and phylogenetically analyzed the large subunit of the ribosomal RNA gene. Based on the results, causal pathogen was re-identified as of P. tuberosa, for which we report the telial stage the first time based on authentic specimens. [ABSTRACT FROM AUTHOR]

The telial stage of Puccinia chunjiei was described in 2012 from a single specimen collected in China (DAOM 240982). This species is the closest relative of P. graminis but differs in telial morphology on their grass hosts and in DNA sequences. As part of a DNA-barcoding project for rust herbarium specimens, collections of the aecial stage of P. graminis on Berberis were processed. For one specimen, BPI 1103856, the ITS sequence matched that of P. chunjiei and the aecial morphology differed from P. graminis. An expanded description of P. chunjiei is presented with photographs of the aecial stages of both species. [ABSTRACT FROM AUTHOR]

Lysine-ε-acetylation (Kac) is a reversible post-translational modification that plays important roles during plant-pathogen interactions. Some pathogens can deliver secreted effectors encoding acetyltransferases or deacetylases into host cell to directly modify acetylation of host proteins. However, the function of these acetylated host proteins in plant-pathogen defense remains to be determined. Employing high-resolution tandem mass spectrometry, we analyzed protein abundance and lysine acetylation changes in maize infected with Puccinia polysora (P. polysora) at 0 h, 12 h, 24 h, 48 h and 72 h. A total of 7412 Kac sites from 4697 proteins were identified, and 1732 Kac sites from 1006 proteins were quantified. Analyzed the features of lysine acetylation, we found that Kac is ubiquitous in cellular compartments and preferentially targets lysine residues in the -F/W/Y-X-X-K (ac)-N/S/T/P/Y/G- motif of the protein, this Kac motif contained proteins enriched in basic metabolism and defense-associated pathways during fungal infection. Further analysis of acetylproteomics data indicated that maize regulates cellular processes in response to P. polysora infection by altering Kac levels of histones and non-histones. In addition, acetylation of pathogen defense-related proteins presented converse patterns in signaling transduction, defense response, cell wall fortification, ROS scavenging, redox reaction and proteostasis. Our results provide informative resources for studying protein acetylation in plant-pathogen interactions, not only greatly extending the understanding on the roles of acetylation in vivo, but also providing a comprehensive dynamic pattern of Kac modifications in the process of plant immune response. [ABSTRACT FROM AUTHOR]

However, at higher outbreak disease levels, >1% of the total possible infections at the outbreak onset, the power law dispersal kernel projections suggested that the outbreak and at-risk population susceptibility properties may exert a roughly equal contribution to the end epidemic severity and at higher outbreak disease levels the at-risk population was projected to have a greater influence than the outbreak (Figure 2A vs. Keywords: disease gradient; disease outbreak; Puccinia; wheat stripe rust; plant epidemic; dispersal ecology EN disease gradient disease outbreak Puccinia wheat stripe rust plant epidemic dispersal ecology 1727 11 11/17/22 20221101 NES 221101 1. Regardless, when applying a modified power law dispersal kernel, which empirical data strongly supports over an exponential dispersal kernel [[17], [32]], it is clear that the most biologically accurate of the two dispersal kernels yields unintuitive WSR disease projections even though there was no anisotropic disease dispersal (a well-known feature of wind dispersed pathogens [[49], [57]]), homogenous host distribution, and host plants with invariant physiological states (both of which are not biologically true). [Extracted from the article]

Crown rust, caused by Puccinia coronata f. sp. avenae (Pca), is a significant impediment to global oat production. Some 98 alleles at 92 loci conferring resistance to Pca in Avena have been designated; however, allelic relationships and chromosomal locations of many of these are unknown. Long-term monitoring of Pca in Australia, North America and elsewhere has shown that it is highly variable even in the absence of sexual recombination, likely due to large pathogen populations that cycle between wild oat communities and oat crops. Efforts to develop cultivars with genetic resistance to Pca began in the 1950s. Based almost solely on all all-stage resistance, this has had temporary benefits but very limited success. The inability to eradicate wild oats, and their common occurrence in many oat growing regions, means that future strategies to control Pca must be based on the assumption of a large and variable prevailing pathogen population with high evolutionary potential, even if cultivars with durable resistance are deployed and grown widely. The presence of minor gene, additive APR to Pca in hexaploid oat germplasm opens the possibility of pyramiding several such genes to give high levels of resistance. The recent availability of reference genomes for diploid and hexaploid oat will undoubtedly accelerate efforts to discover, characterise and develop high throughput diagnostic markers to introgress and pyramid resistance to Pca in high yielding adapted oat germplasm. [ABSTRACT FROM AUTHOR]

Wheat rusts are considered major biotic stresses due to immense yield losses incurred by the rust pathogens. Continuous incursions and evolution among populations of rust pathogen have challenged several resistance genes deployed in wheat mega-varieties. A substantial amount of wheat production is being saved by rust resistance wheat varieties. Breeding for rust resistance aimed to transfer potential genes in wheat elite lines and discover novel alleles to diversify resistance gene stock for future wheat breeding. This class of research was initiated worldwide after the discovery of mendelian genetics. Over a century, several genetic and genomic approaches were discovered and subsequently applied in wheat research to better understand the nature of rust pathogens and accordingly deployed major and minor rust resistant genes in combination in wheat varieties. Over 240 rust resistance genes have been catalogued and several alleles/QTL have been reported. Various statistical tools and consensus maps have been designed to precisely allocate novel alleles, as well as known genes on the wheat physical map. With the advancement in genomics and next generation sequencing (NGS) technology, more than 20 rust resistance genes have been cloned in the last two decades. The mutational genomics approach was found competitive and parallel to modern NGS technology in isolating rust resistance loci. In this review, evolutionary trends of rust pathogens, source of rust resistance genes, methodology used in genetic and association mapping studies and available cutting-edge techniques to isolate disease resistance genes have been summarised and discussed. [ABSTRACT FROM AUTHOR]

Identification of fungi infecting Zea mays leaves and sub-classifying them to have correct course management in the earlier stages is lucrative. To develop a nondestructive and low-cost classification model of corn leaves infected by Setosphaeria turcica (ST), Cercospora zeae-maydis (CZM), and Puccinia sorghi (PS) fungi using image filtering and transfer learning model. Corn leaf images were categorized based on fungal-infection and stored in an image library. All images were then processed to show different intensities and then utilized to filter the images. An original RGB-based CNN model has been compared with selected pre-trained models of VGG16 and EfficientNet-b0 with inputs of both unfiltered and filtered RGB images. Results showed that the EfficientNet-b0 with filtered images model (fMaize) exhibited the highest accuracy of 97.63%, sensitivity of 97.99%, specificity of 97.38, quality index of 97.68%, and F-score of 96.48%. Consequently, the experimental results revealed that deep transfer learning models fed with filtered images produced higher accuracy than models that simply employed RGB images. Thus, transfer learning was proven to be a valuable tool in enhancing CNN image classification accuracy. [ABSTRACT FROM AUTHOR]

Key message: We mapped three adult plant resistance (APR) loci on oat chromosomes 4D and 6C and developed flanking KASP/PACE markers for marker-assisted selection and gene pyramiding. Using sequence orthology search and the available oat genomic and transcriptomic data, we surveyed these genomic regions for genes that may control disease resistance. Sources of durable disease resistance are needed to minimize yield losses in cultivated oat caused by crown rust (Puccinia coronata f. sp. avenae). In this study, we developed five oat recombinant inbred line mapping populations to identify sources of adult plant resistance from crosses between five APR donors and Otana, a susceptible variety. The preliminary bulk segregant mapping based on allele frequencies showed two regions in linkage group Mrg21 (Chr4D) that are associated with the APR phenotype in all five populations. Six markers from these regions in Chr4D were converted to high-throughput allele specific PCR assays and were used to genotype all individuals in each population. Simple interval mapping showed two peaks in Chr4D, named QPc.APR-4D.1 and QPc.APR-4D.2, which were detected in the OtanaA/CI4706-2 and OtanaA/CI9416-2 and in the Otana/PI189733, OtanaD/PI260616, and OtanaA/CI8000-4 populations, respectively. These results were validated by mapping two entire populations, Otana/PI189733 and OtanaA/CI9416, genotyped using Illumina HiSeq, in which polymorphisms were called against the OT3098 oat reference genome. Composite interval mapping results confirmed the presence of the two quantitative trait loci (QTL) located on oat chromosome 4D and an additional QTL with a smaller effect located on chromosome 6C. This mapping approach also narrowed down the physical intervals to between 5 and 19 Mb, and indicated that QPc.APR-4D.1, QPc.APR-4D.2, and QPc.APR-6C explained 43.4%, 38.5%, and 21.5% of the phenotypic variation, respectively. In a survey of the gene content of each QTL, several clusters of disease resistance genes that may contribute to APR were found. The allele specific PCR markers developed for these QTL regions would be beneficial for marker-assisted breeding, gene pyramiding, and future cloning of resistance genes from oat. [ABSTRACT FROM AUTHOR]

Senecio madagascariensis and S. vulgaris plants were observed to be parasitized by a rust disease in the Cundinamarca department of Colombia in April 2019. The identification of the fungus growing on the hosts was conducted by morphological characterization of the spores on the host tissues, and molecular sequencing of the internal transcribed spacer (ITS) region. The fungal pathogen was identified as Puccinia lagenophorae. This is the first record of P. lagenophorae causing disease in Colombia, and the first report of this rust fungus parasitizing S. madagascariensis and S. vulgaris in South America. [ABSTRACT FROM AUTHOR]

The specific pre- and post-cold storage treatments needed to maintain the viability of urediniospores of rust fungi during storage are species dependent. Urediniospore collections are critical to assess pathogen evolution over time, but most importantly, to determine the efficacy of resistance genes in host plants. Puccinia sorghi, the causal agent of common rust of maize, can cause yield losses of up to 40% in susceptible varieties. The purpose of this study was to optimize the pre- and post-cold storage requirements of P. sorghi urediniospores. Here, we report that dried urediniospores had an 87% decrease in germination compared with undried spores. Urediniospores of P. sorghi were successfully stored at −80°C for 24 months and remained infectious, and did not require cold shock in liquid nitrogen pre-cold storage, nor a heat shock to revive them from dormancy. Urediniospores removed from storage in a freezer at −80°C germinated readily between 22°C and 55°C. [ABSTRACT FROM AUTHOR]

Wheat is one of the most important crops in the world and was considered the major grain crop grown in Egypt. Nowadays, Egypt is the largest wheat importer in the world and consumes an extensive amount of it. To decrease the gap between production and consumption and increase the yield, we need to control wheat diseases, especially stripe rust, due to its major damage to wheat. Further, we need to advise farmers as early as we can to control and treat them. The paper proposed an interactive intelligent system to monitor, predict and give the correct advice at the right time to farmers. This system is called MISSR (Mentoring Interactive System for Stripe Rust). The system is considered an important means to effectively prevent risks in agricultural production. It also plays an important role in guiding farmers and decision-makers to plan and implement suitable practices to increase yield and mitigate stripe-rust disease. On the other hand, it can acquire relevant and timely information in the areas where this information or data is unavailable. To build this model for the wheat crop in Egypt, we used wheat experts' knowledge and climate data API. MISSR is available as a mobile application to provide access for more farmers and increase its availability. [ABSTRACT FROM AUTHOR]

The genus Cerradoa (type species Cerradoa palmaea) was established in 1978 by Hennen and Ono and named after the Brazilian Cerrado biome. The holotype collected in Planaltina, Federal District, Brazil, belonged to the first rust fungus reported on palms (Arecaceae). For decades, the status of Cerradoa as a distinct genus has been regarded as doubtful, representing a synonym of Edythea (Uropyxidaceae) starting with the second edition of the Illustrated Genera of Rust Fungi in 1983. Our molecular phylogenetic analyses, as well as our morphological investigations, allowed us to reject this synonymy, leading to the reinstatement of Cerradoa within the Pucciniaceae. Cerradoa, together with morphologically similar genera such as the newly established Pseudocerradoa with two species (Ps. paullula and Ps. rhaphidophorae) infecting araceous hosts, the fern rust Desmella, and also P. engleriana, could not be assigned to any of the seven identified major lineages within the Pucciniaceae. Edythea, instead of being maintained as a member of the Uropyxidaceae, was herein placed in Pucciniaceae, shown phylogenetically in close relationship to Cumminsiella mirabilissima, both infecting the Berberidaceae. Additionally, our extensive phylogenetic analyses add guidance for future taxonomic revisions in the highly polyphyletic genus Puccinia and other established taxa within the family Pucciniaceae. [ABSTRACT FROM AUTHOR]

Surveys were carried out in garlic cultivation areas of Gaziantep province in April 2018 and April 2019 to determine the prevalence of fungal diseases of garlic. After the isolation process was conducted according to routine mycological methods, fungi were identified according to their cultural and morphological characteristics. Fungi belonging to genera of Fusarium, Rhizoctonia, Macrophomina and Puccinia were determined in garlic production areas. The most prevalent genus among all fungi was determined as the Fusarium isolated from all areas. The rust disease caused by Puccinia porri has not been detected in the Islahiye district and its prevalence in other areas varies between 5,1-18 %. [ABSTRACT FROM AUTHOR]

The study was conducted in the Department of Plant Pathology, College of Agriculture, Rajendranagar, Professor Jayashankar Telangana State Agricultural University, Hyderabad, India to understand the histopathological mechanisms of initial interaction of Puccinia arachidis with six groundnut genotypes. Fully expanded quadrifoliate leaves were inoculated with P. arachidis using the detached leaf assay. Five-mm leaf discs were cut at 6 hours after inoculation (hai) and each day until 5 days after inoculation (dai) and examined for histopathological interactions. Germination of urediniospores was detected during 6–8 hai and continued until 24 hai. There were no differences in pre-penetration and penetration among all the six genotypes. Differences in post-penetration were observed among the genotypes during 3–5 dai. In genotypes TMV 2 and K 6, extensive hyphal colonization was observed in the intercellular spaces of mesophyll cells by 4–5 dai indicating compatible interaction and susceptibility to rust disease. Sparse hyphal growth and corresponding mesophyll cell death at 3–5 dai in genotypes ICGV 171015 and ICGV 13229 indicated defense response by the host and moderate resistance. In genotypes ICG 11426 and GPBD 4, complete arrest of hyphal growth by 4–5 dai due to extensive mesophyll necrosis suggested incompatible interaction and resistance to rust. This is the first documentation of the histopathological description of the initial infection strategies of P. arachidis in the selected groundnut genotypes. [ABSTRACT FROM AUTHOR]

Puccinia caricis-smilacis, a new species of caricicolous rust fungus was described based on morphological characteristics and nuclear rDNA sequences from Japan. The heteroecious life cycle of P. caricis-smilacis was elucidated via field observations, inoculation experiments and molecular analyses. This rust fungus produces uredinial and telial stages on Carex fibrillosa, and spermogonial and aecial stages on Smilax china. [ABSTRACT FROM AUTHOR]

Advances in sequencing technologies as well as development of algorithms and workflows have made it possible to generate fully phased genome references for organisms with nonhaploid genomes such as dikaryotic rust fungi. To enable discovery of pathogen effectors and further our understanding of virulence evolution, we generated a chromosome-scale assembly for each of the 2 nuclear genomes of the oat crown rust pathogen, Puccinia coronata f. sp. avenae (Pca). This resource complements 2 previously released partially phased genome references of Pca, which display virulence traits absent in the isolate of historic race 203 (isolate Pca203) which was selected for this genome project. A fully phased, chromosome-level reference for Pca203 was generated using PacBio reads and Hi-C data and a recently developed pipeline named NuclearPhaser for phase assignment of contigs and phase switch correction. With 18 chromosomes in each haplotype and a total size of 208.10 Mbp, Pca203 has the same number of chromosomes as other cereal rust fungi such as Puccinia graminis f. sp. tritici and Puccinia triticina, the causal agents of wheat stem rust and wheat leaf rust, respectively. The Pca203 reference marks the third fully phased chromosome-level assembly of a cereal rust to date. Here, we demonstrate that the chromosomes of these 3 Puccinia species are syntenous and that chromosomal size variations are primarily due to differences in repeat element content. [ABSTRACT FROM AUTHOR]

• Canada thistle is one of the worst weeds threatening temperate regions of the world. • Puccinia punctiformis is known to cause systemic disease of Canada thistle, ultimately killing individuals and reducing stand densities. • A statewide biological control program was developed, in which telia were harvested and released at invaded sites with subsequent population monitoring. • Canada thistle stands exhibited significant declines following treatment, however these declines were associated with local site conditions and method of treatment. Canada thistle (Cirsium arvense (L.) Scop., CT) is one of the worst weeds threatening temperate regions of the world. A host-specific rust fungus, Puccinia punctiformis (F. Strauss) Rohl., is known to cause systemic disease of CT, ultimately killing individuals and reducing stand densities. In 2013, it was demonstrated that fall inoculation of rosettes with coarsely ground leaves bearing P. punctiformis telia can successfully initiate epiphytotics. In the same year, a cooperative project between the Colorado Department of Agriculture and United States Department of Agriculture was initiated, in which CT patches across the state of Colorado (USA) were inoculated and tracked over subsequent years for changes in stem density. Here, we report our findings from 8 years (2014–2021) of monitoring effort. At most sites (N = 87), CT stem densities declined, from a mean (±SE) of 87.9 (±6.5) stems to 44.7 (±4.2). These declines however were spatially-autocorrelated, and likely attributable to local growing conditions, as mean annual daily maximum temperature and standard deviation of elevation, as well as climatic conditions around the times of both treatment and monitoring, were found to be important predictors of CT decline. Further, we observed that the amount of inoculum deployed, timing since last release, and method in which it was spread locally at a site were also associated with the magnitude of CT stem decline. These results are indicative of the value of P. punctiformis as a CT biological control agent. [ABSTRACT FROM AUTHOR]

In India, systematic wheat yellow rust survey and pathotype (race) analysis work began in 1930. However, information on population structure and genetic diversity of yellow rust pathogen has not been available. To address this, we conducted studies on population structure and genetic diversity of Puccinia striiformis f. sp. tritici (Pst) pathotypes using 38 simple sequence repeat primer-pairs. Bayesian assignment and discriminant analysis of principal components indicated the presence of two distinct Pst subpopu-lations (Popl and Pop2) along with 37.9% admixed pathotypes. The unweighted pair-group method with arithmetic mean also categorized these pathotypes into two major clusters. Principal coordinates analysis explained 20.06 and 12.50% variance in horizontal and vertical In total, 102 alleles were detected, with the expected heterozygosity (Hcxp) per locus ranging from 0.13 to 0.73, with a mean of 0.47. The average polymorphic information content value of 0.40 indicated high genetic diversity among pathotypes. Analysis of molecular variance revealed 12% of the total variance between subpopulations, 11% among the pathotypes of each sub-population, and 77% within pathotypes. A significant moderate level of genetic differentiation (FsT = 0.122, P < 0.001) and gene flow (N,„ = 1.80) were observed between subpopulations. The Pst virulence phenotypes showed a weak positive correlation (R2 = 0.027, P < 0.02) with molecular genotypes. coordinates, respectively. Index of association (IA) and the standardized index of association (fd) values showed that Pst subpopulations reproduced asexually (clonally). [ABSTRACT FROM AUTHOR]

[Objective] This research focused on the pathogens, occurrence and distribution of sugarcane rust disease in low latitude plateau of Yunnan, and phylogenetic relationships between sugarcane rust fungi and other rust fungi of Pucciniaceae. [Method] The pathogens of sugarcane rust disease collected from different planting areas in Yunnan were identified based on symptoms observation, urediniospore morphology observation and molecular detection. The phylogenetic relationships between sugarcane rust fungi and other rust fungi of Pucciniaceae were analyzed by constructing the Neighbor-joining (NJ) tree. [Result] The uredinium of four sugarcane rust samples of Haiyin1 collected from Menghai, Yunnan were orange, their urediniospores were pyriform, cinnamon-brown or golden yellow in color, with thorns on the surface, and thickened apex by 10 μm, with four to five equatorial pores as (25-50) μm × (16-35) μm. Their nucleotide sequence shared more than 99.9% sequence identity with an isolate of Puccinia kuehnii (GU058021), which indicated that these four rust samples might accounted for sugarcane orange rust disease; And the pathogen were identified as P. kuehnii. The uredinium of other 53 sugarcane rust samples were reddish-brown, their urediniospores were spherical, red-brown or dark brown with numerous small spines, comprised of a uniform thickness of the entire wall, containing colorless and cochlear-form paraphysis, with four or fewer equatorial pores measuring (20-40) μm× (13-25) μm. Their nucleotide sequence was more than 99.8% similar with that of an isolate of P. melanocephala (GU058001), which indicated that all of the other 53 rust samples might accounted for sugarcane brown rust disease, and were identified as P. melanocephala. The phylogenetic tree showed that four P. kuehnii isolates and P. polysora (GU058024) were clustered into one group, showing that their phylogenetic relationship was close. Fifty-three P. melanocephala isolates were closely related to P. nakanishikii (GU058002), P. rufipes (AJ296545), Aecidium deutziae (KU309317) and P. coronata (DQ354526) and clustered into one group. However, the phylogenetic relationships between these two sugarcane rust fungi were not close. [Conclusion] This study is the first report to identify P. kuehnii, which caused sugarcane orange rust disease, in low latitude plateau of Yunnan. It is also confirmed that P. melanocephala, which caused sugarcane brown rust, is the primary sugarcane rust pathogen in low latitude plateau of Yunnan. [ABSTRACT FROM AUTHOR]