Levels of common antigens in determining pathogenicity of Curvularia eragrostidis in different tea varieties

AIMS: Pathogenicity of Curvularia eragrostidis, a foliar fungal pathogen of tea was studied in 24 commercially cultivated tea varieties by analysing the antigenic patterns of host and pathogen with the help of immunoserological techniques. METHODS AND RESULTS: Initial testing by cut shoot inoculation technique followed by whole plant inoculation technique showed that among the varieties tested, TV12 was the most susceptible and TV25 most resistant. Antigen preparations from tea varieties, fungal pathogens (C. eragrostidis and Lasiodiplodia theobromae) and a nonpathogen (Gliocladium virens) were compared by immunodiffusion, immunoelectrophoresis and indirect ELISA to detect common antigens shared by host and pathogen. Common antigens were detected by immunodiffusion and immunoelectrophoresis only among susceptible varieties and the pathogens. Such antigens were not found between the pathogens and the resistant varieties and also between nonpathogens and tea varieties. However, ELISA revealed the presence of low level of common antigens between all combinations. A certain minimum level of antigens was present for compatible host-pathogen interaction. Indirect labelling of antibodies with fluorescein isothiocyanate (FITC) showed that cross-reactive antigens were found to be concentrated mainly in the epidermal cells and also spread throughout the cortical cells. CONCLUSION: Pathogenicity of C. eragrostidis to different varieties of tea was found to be related to the level of common antigens present between host and pathogen. SIGNIFICANCE AND THE IMPACT OF THE STUDY: Indirect ELISA proved to be valuable in screening commercially cultivated varieties of tea for their susceptibility to C. eragrostidis.     

Pathogenicity of Colletotrichum gloeosporioides (Penz.) Sacc. causal agent of anthracnose in different varieties of eggplant (Solanum melongena L.) determined by levels of cross-reactive antigens shared by host and pathogen

Pathogenicity test of the fungal pathogen Colletotrichum gloeosporioides (Penz.) Sacc., causal agent for anthracnose in eggplant (Solanum melongena L.), was performed in 28 commercially cultivated eggplant varieties by analysing the antigenic patterns of host and pathogen. Through initial screening following detached leaf inoculation technique and whole plant inoculation technique, Pusa purple long (Ppl) variety was found to be the most susceptible while Shamala variety (Shav) was the most resistant. Cross-reactive antigens (CRA) shared by susceptible varieties and C. gloeosporioides was detected by immunodiffusion and immunoelectrophoresis and indirect enzyme-linked immunosorbent assay (ELISA). Such antigens could not be detected between the resistant varieties and the pathogen and also between a nonpathogen (Alternaria porri) and all the test varieties. However, ELISA showed that low levels of common antigens were present between all combinations. The level of CRA was found to decrease with increasing resistance. Indirect immunogold labeling followed by silver enhancement revealed that CRA were concentrated mainly in the cell wall regions throughout the tissue. The level of CRA was found to correlate to the pathogenicity of C. gloeosporioides in different eggplant varieties. ELISA may therefore be used to screen the commercially cultivated eggplant varieties for resistance to C. gloeosporioides.     

Detection of cross reactive antigens between Pestalotiopsis theae and tea leaves and their cellular location

Among the 12 varieties of tea tested against three isolates of Pestalotiopsis theae, causal agent of grey blight disease, Teen Ali-17/1/54 and TV-23 were found to be highly susceptible while CP-1 and TV-26 were resistant under identical conditions. Leaf antigens were prepared from all the tea varieties, three isolates of P. theae and a non-pathogen of tea (Bipolaris tetramera). Polyclonal antisera were raised against mycelial suspensions of P. theae (isolate Pt-2) and leaf antigens of Teen Ali-17/1/54 and CP-1. These were compared an immunodiffusion test and enzyme-linked immunosorbent assay to detect cross reactive antigens (CRA) shared the host and the parasite. CRA were found among the susceptible varieties and isolates of P. theae (Pt-1, 2 and 3). Such antigens were not detected between isolates of P. theae and resistant varieties, B. tetramera and tea varieties or isolates of P. theae. Indirect staining of antibodies using fluorescein isothiocyanate (FITC) indicated that in cross sections of tea leaves, the CRA was concentrated in the epidermal cells and mesophyll tissues. CRA was present in the young hyphal tips of the mycelia and on the setulae and appendages of the conidia of P. theae.     

Detection of cross-reactive antigens shared byFusarium oxysporum andGlycine max by indirect ELISA and their cellular location in root tissues

Pathogenicity test ofFusarium oxysporum on ten cultivars of soybean revealed Soymax and Punjab-1 to be most resistant while JS-2 and UPSM-19 were most susceptible. Antigens were prepared from the roots of all the ten varieties of soybean and the mycelium ofF. oxysporum. Polyclonal antisera were raised against the mycelial suspension ofF. oxysporum and the root antigen of the susceptible cultivar UPSM-19. Cross reactive antigens shared by the host and the pathogen were detected first by immunodiffusion. The immunoglobulin fraction of the antiserum was purified by ammonium sulfate precipitation and DEAE-Sephadex column chromatography. The immunoglobulin fractions were used for detection of cross-reactive antigens by enzyme-linked immunosorbent assay. In enzyme-linked immunosorbent assay, antigens of susceptible cultivars showed higher absorbance values when tested against the purified anti-F. oxysporum antiserum. Antiserum produced against UPSM-19 showed cross-reactivity with the antigens of other cultivars. Indirect staining of antibodies using fluorescein isothiocyanate indicated that in cross-sections of roots of susceptible cultivar (UPSM-19) cross-reactive antigens were concentrated around xylem elements, endodermis and epidermal cells, while in the resistant variety, fluorescence was concentrated mainly around epidermal cells and distributed in the cortical tissues. CRAs were also present in microconidia, macroconidia and chlamydospores of the fungus.     

Advances in understanding the mechanism of resistance to anthracnose and induced defence response in tea plants

The tea plant (Camellia sinensis) is susceptible to anthracnose disease that causes considerable crop loss and affects the yield and quality of tea. Multiple Colletotrichum spp. are the causative agents of this disease, which spreads quickly in warm and humid climates. During plant–pathogen interactions, resistant cultivars defend themselves against the hemibiotrophic pathogen by activating defence signalling pathways, whereas the pathogen suppresses plant defences in susceptible varieties. Various fungicides have been used to control this disease on susceptible plants, but these fungicide residues are dangerous to human health and cause fungicide resistance in pathogens. The problem-solving approaches to date are the development of resistant cultivars and ecofriendly biocontrol strategies to achieve sustainable tea cultivation and production. Understanding the infection stages of Colletotrichum, tea plant resistance mechanisms, and induced plant defence against Colletotrichum is essential to support sustainable disease management practices in the field. This review therefore summarizes the current knowledge of the identified causative agent of tea plant anthracnose, the infection strategies and pathogenicity of C. gloeosporioides, anthracnose disease resistance mechanisms, and the caffeine-induced defence response against Colletotrichum infection. The information reported in this review will advance our understanding of host–pathogen interactions and eventually help us to develop new disease control strategies.     

Epidemiology and disease-control under gene-for-gene plant-pathogen interaction

An introduction of disease-resistant variety of a crop plant often leads to the development of a virulent race in pathogen species that restores the pathogenicity to the resistant crop. This often makes disease control of crop plants extremely difficult. In this paper, we theoretically explore the optimal 'multiline' control, which makes use of several different resistant varieties, that minimizes the expected degree of crop damages caused by epidemic outbreaks of the pathogen. We examine both single-locus and two-locus gene-for-gene (GFG) systems for the compatibility relationship between host genotypes and pathogen genotypes, in which host haplotype has either susceptible or resistant allele in each resistance locus, and the pathogen haplotype has either avirulent or virulent allele in the corresponding virulence locus. We then study the optimal planting strategy of host resistant genotypes based on standard epidemiological dynamics with pathogen spore stages. The most striking result of our single-locus GFG model is that there exists an intermediate optimum mixing ratio for the susceptible and resistant crops that maximizes the final yield, in spite of the fact that the susceptible crop has no use to fight against either avirulent or virulent race of the pathogen. The intermediate mixture is optimum except when the initial pathogen spore population in the season consists exclusively of the virulent race. The optimal proportion of resistant crops is approximately 1/R(0), where R(0) is the basic reproductive ratio of pathogen--the rest (the vast majority if R(0) is large) of crops should be the susceptible genotype. By mixing susceptible and resistant crops, we can force the pathogen races to compete with each other for their available hosts. This competition between avirulent and virulent races prevents the fatal outbreak of the virulent race (the super-race) that can infect all the host genotypes. In the two-locus GFG control, there again exists the optimal mixing ratio for the fraction of universally susceptible genotype and the total fraction of various resistant genotypes, with the ratio close to 1/R(0).     

辽宁水稻品种抗灰飞虱鉴定及其抗性机制研究

为探明辽宁地区水稻品种对本地灰飞虱Laodelphax striatellus(Fallén)的抗性水平及其抗虫机制,本研究利用改进的苗期集团鉴定法,以IR36为抗虫对照品种、武育粳3号为感虫对照品种,对42份辽宁地区主栽水稻品种和研究待推广品种进行了水稻苗期对灰飞虱抗性鉴定,并从中选取20份不同抗性水平的品种进行了排趋性和抗生性的测定。结果表明:从42份水稻材料中仅筛选出1份抗虫材料辽优5218,中抗品种11份,其余均为感虫或高感品种。在不同水稻类型中,杂交稻的抗虫性普遍较常规稻强,而从水稻株型上看,抗性品种大多为披散型。抗虫机制研究发现,抗虫品种辽优5218和中抗品种港育129兼具排趋性和抗生性,是非常理想的抗性种质资源,中抗品种港源8号和粳优558具有很强的排趋性,也是较为理想的抗性资源,为抗性机制的深入研究提供了材料。但大部分省内主栽主推品种不具备对灰飞虱的抗性,应引起重视。     

Phenotypic and histochemical traits of the interaction between Plasmopara viticola and resistant or susceptible grapevine varieties

ABSTRACT: BACKGROUND: Grapevine downy mildew, caused by Plasmopara viticola, is a very serious disease affectingmainly Vitis vinifera cultivated varieties around the world. Breeding for resistance throughthe crossing with less susceptible species is one of the possible means to reduce the diseaseincidence and the application of fungicides. The hybrid Bianca and some of its siblings areconsidered very promising but their resistance level can vary depending on the pathogenstrain. Moreover, virulent strains characterized by high fitness can represent a potential threatto the hybrid cultivation. RESULTS: The host response and the pathogen virulence were quantitatively assessed by artificiallyinoculating cv Chardonnay, cv Bianca and their siblings with P. viticola isolates derived fromsingle germinating oospores collected in various Italian viticultural areas. The hostphenotypes were classified as susceptible, intermediate and resistant, according to the AreaUnder the Disease Progress Curve caused by the inoculated strain. Host responses in cvBianca and its siblings significantly varied depending on the P. viticola isolates, which in turndiffered in their virulence levels. The fitness of the most virulent strain did not significantlyvary on the different hybrids including Bianca in comparison with the susceptible cvChardonnay, suggesting that no costs are associated with virulence. Among the individualfitness components, only sporangia production was significantly reduced in cv Bianca and insome hybrids. Comparative histological analysis revealed differences between susceptibleand resistant plants in the pathogen diffusion and cytology from 48 h after inoculation onwards. Defence mechanisms included callose depositions in the infected stomata, increasein peroxidase activity, synthesis of phenolic compounds and flavonoids and the necrosis ofstomata and cells immediately surrounding the point of invasion and determined alterations inthe size of the infected areas and in the number of sporangia differentiated. CONCLUSIONS: Some hybrids were able to maintain an intermediate-resistant behaviour even wheninoculated with the most virulent strain. Such hybrids should be considered for further fieldtrials.     

Interactions of Apple and the Alternaria alternata Apple Pathotype

Apple is one of the most cultivated tree fruits worldwide, and is susceptible to many diseases. Understanding the interactions between the host and pathogen is critical in implementing disease management strategies and developing resistant cultivars. This review provides an update on the interactions of apple with Alternaria alternata apple pathotype, which causes Alternaria blotch, with a brief history about the discovery of the disease and pathogen and its damage and epidemiology. The focus of the review is placed on the physiological and genetic response of the host to pathogen infection, including resistance and susceptibility, and the molecular markers associated with them. Of the response of the pathogen to the host, the emphasis is placed on the role of the selective toxins on pathogenicity and their genetic controls and regulations. The review ends with a perspective on future directions in the research on the apple-A. alternata pathosystem in the era of genomics and post genomics, particularly on how to identify candidate genes from both host and pathogen for potential genetic engineering for disease resistant cultivars.     

Influence of jasmonic acid as potential activator of induced resistance against Karnal bunt in developing spikes of wheat

Induction of defense response against Karnal bunt (KB) by suppressing the pathogenesis was observed upon exogenous application of jasmonic acid (JA) as evident from decrease in the coefficient of infection and overall response value in both susceptible and resistant varieties of wheat. The ultra-structural changes during disease progression showed the signs of programmed cell death (PCD). However, JA strengthened the defense barrier by enhancing the lignifications of cell walls as observed in spikes of both varieties by histochemical analysis. Compared to the plants inoculated with pathogen alone, plants of resistant line (RJP) first treated with JA followed by inoculation with pathogen showed more lignifications and extracellular deposition of other metabolites on cells, which is supposed to prevent mycelial invasions. Contrary to this, susceptible (SJP) lines also showed lignifications but the invasion was more compared to resistant line. Induction of protease activity was higher in resistant variety than its corresponding susceptible variety. The protease activity induced during the colonization of the pathogen and its proliferation inside the host system gets inhibited by JA treatment as demonstrated by the quantitative and in-gel protease assay. The results indicate the role of JA signalling in inhibiting the proteases due to expression of certain protease inhibitor genes. SDS-PAGE analysis shows differential gene expression through induction and/or suppression of different proteins in wheat spikes of resistant and susceptible varieties under the influence of JA. Thus, exogenously applied JA provides the conditioning effect prior to the challenge of infection and induces defense against KB probably by maintaining a critical balance between proteases and protease inhibitors and/or coordinating induction of different families of new proteins.     

Olfactory cues explain differential attraction of the striped rice stem borer to different varieties of rice plant

In Iranian rice fields, different varieties of rice are cultivated which are differentially impacted by females of the rice stem borer, Chilo suppressalis. To elucidate the role odours may play in their host plant finding behaviour, female Ch. suppressalis were exposed to four varieties of rice plants and their volatiles in a four‐arm olfactometer. In whole plant tests, Ch. suppressalis were significantly attracted to the variety previously characterized as most susceptible, least attracted to one characterized as semisusceptible, and showed no attraction to those varieties characterized as semi‐ and highly resistant. Tests using headspace volatile extracts yielded similar results in the case of the most susceptible variety, but showed no attraction to the semisusceptible and highly resistant varieties, and low attraction to the semiresistant variety. Subsequent analysis of the volatile composition identified a panel of 27 components, some of which were either unique to, or abundantly present in, particular varieties, and may explain the observed variation in their attractiveness. Our findings show that rice plant volatiles can play a role in the host selection behaviour of this pest species, and we suggest compounds which may be important to this process and the future application of volatiles in rice pest management programs.     

Screening of certain barley lines for resistance to root rot disease caused by Fusarium graminearum

This investigation was conducted in 2005/2006 and 2006/2007 to test 235 barley lines plus two varieties Giza 127 and Giza 128 for resistance and susceptibility to Fusarium graminearum. All screened barley lines showed varied significant degrees of infestation to root rot pathogen. A screening system is described for identifying barley lines which are effective in controlling resistant or susceptible lines. By detecting small but consistent differences in root rot severity, the bioassay proved effective in large-scale screening for partial resistance: already 335 barley lines and two varieties have been screened. We found five groups (7.12%), 22 barley lines and both varieties are resistant (R) (8.31%); 28 barley lines are moderately resistant (MR) (19.29%); 65 barley lines are moderately susceptible (MS) (27.89%); 94 barley lines are susceptible (S) and (37.39%) 126 barley lines are highly susceptible (HS). The high degree of precision makes this an invaluable tool in the understanding of pathogen aggressiveness, host specialisation and parasitic fitness. Disease scale was strongly negative and had moderate correlation with germination (?0.309?? and ?0.649??) under normal and disease treatment. The correlation between yield and normal and disease treatment during two seasons was strong and negative (?0.834?? and ?0.847??, respectively were detected).     

Defense Reactions in Host and Nonhost Plants Against the Soybean Rust Fungus (Phakopsora pachyrhizi Syd.)

Growth and development of two races of the soybean rust fungus (Phakopsora pachyrhizi Syd.) were compared on host and nonhost plants. Both groups had several lines of defense, each of which could stop a part of attacking uredospores. Germ tubes and appressoria were produced equally well on hosts and nonhosts. A reduced formation of penetration hyphae contributed to the resistance of nonhosts and resistant host genotypes. In the epidermal cells of wheat and barley leaves, lower frequencies of penetration hyphae coincided with the production of papillae-like structures which were not penetrated. The last line of defense of all nonhosts was localized in the epidermal cell where the growth of the penetration hyphae was arrested definitively. The colony development in these species was suppressed completely. In highly resistant host genotypes the last defense reaction occurred later as a hypersensitive cell collapse which interrupted the growth of the rust colony.     

Biochemical and genetical studies on host parasite relationship: Role of tyrosinase in pathocenicity and host resistance of two mutants of fusarium vasinfectum Atk

An assay of tyrosinase activity has been carried out inFusarium vasinfectum Atk. mutants differing in their pathogenicity. The results obtained reveal that the tyrosinase activity is more in the nicotinic acid requirer which is highly pathogenic than the other two strains. The non-pathogenic paraaminobenzoic acid requirer also possesses tyrosinase activity but comparatively less.In vitro studies were carried out by growing the pathogen in presence of host extracts. The susceptible host extract forms better source for the production of tyrosinase by the pathogen. Studies on tyrosinase activity of resistant and susceptible varieties of host inoculated with the parent strain ofF. vasinfectum in comparison with the respective uninoculated types suggest that a decline of tyrosinase activity occurs in all the hosts on inoculation.This research has been financed in part by a grant made by the United States Department of Agriculture under P.L. 480.     

THE ORIGIN OF SPECIFICITY BY MEANS OF NATURAL SELECTION: EVOLVED AND NONHOST RESISTANCE IN HOST–PATHOGEN INTERACTIONS

Most species seem to be completely resistant to most pathogens and parasites. This resistance has been called “nonhost resistance” because it is exhibited by species that are considered not to be part of the normal host range of the pathogen. A conceptual model is presented suggesting that failure of infection on nonhosts may be an incidental by‐product of pathogen evolution leading to specialization on their source hosts. This model is contrasted with resistance that results from hosts evolving to resist challenge by their pathogens, either as a result of coevolution with a persistent pathogen or as the result of one‐sided evolution by the host against pathogens that are not self‐sustaining on those hosts. Distinguishing evolved from nonevolved resistance leads to contrasting predictions regarding the relationship between resistance and genetic distance. An analysis of cross‐inoculation experiments suggests that the resistance is often the product of pathogen specialization. Understanding the contrasting evolutionary origins of resistance is critical for studies on the genetics and evolution of host–pathogen interactions in human, agricultural, and natural populations. Research on human infectious disease using animal models may often study resistances that have quite contrasting evolutionary origins, and therefore very different underlying genetic mechanisms.     

Avian- and mammalian-derived antibodies against adherence-associated proteins inhibit host cell colonization by Escherichia coli O157:H7

AIM: To evaluate the potential for polyclonal antibodies targeting enterohaemorrhagic Escherichia coli (EHEC) virulence determinants to prevent colonization of host cells by E. coli O157:H7. METHODS AND RESULTS: Rats and laying hens were immunized with recombinant proteins from E. coli O157:H7, EspA, C-terminal intimin or EscF. Rat antisera (IgG) or chicken egg powders (IgY) were assessed for their ability to inhibit growth and colonization-associated processes of E. coli O157:H7. Mammalian antisera with antibodies to intimin, EspA or EscF effectively reduced adherence of the pathogen to HeLa cells (P<0.05) and prevented type III secretion of Tir. Similarly, HeLa cells treated with chicken egg powder containing antibodies against intimin or EspA were protected from EHEC adherence (P<0.05). Neither egg nor rat antibody preparations had any antibacterial effect on the growth of EHEC (P>0.05). CONCLUSIONS: Antibody preparations targeting EHEC adherence-associated factors were effective at preventing adhesion and intimate colonization-associated events. SIGNIFICANCE AND IMPACT OF THE STUDY: This work indicates that immunotherapy with anti-adherence antibodies can reduce E. coli O157:H7 colonization of host cells. Passive immunization with specific antibodies may have the potential to reduce E. coli O157:H7 colonization in hosts such as cattle or humans.     

Reaction of Some Coffea arabica Genotypes to Strains of Colletotrichum kahawae, the Cause of Coffee Berry Disease

Pathogenicity tests were performed on 11 genotypes of Coffea arabica using single‐isolate suspensions of Colletotrichum Kahawae obtained from 90 monoconidial isolates. The objective of this study was to estimate the proportion of pathogenic variation corresponding 10 differences in aggressiveness and virulence (races). A large part of the variation in the pathogen population was due to aggressiveness. The differential effects were too small to suggest conclusively that races exist. This paper discusses the possible causes for the observed small differential interaction and suggests breeding strategies that not only prevent possible adaptation of the pathogen to resistant varieties but also limit variation for resistance due to differences in aggressiveness of the pathogen.     

Optimizing In vitro Culture Conditions for the Biotrophic Fungi Exobasidium vexans Through Response Surface Methodology

The blister blight disease caused by the fungus, Exobasidium vexans has serious implications on the quality of tea production. The disease however, has been poorly studied and hence there is very limited information on the pathogen and as such the pathogenesis of blister blight infection. One of the major roadblocks in understanding E. vexans is the obligate and biotrophic nature of the fungus which limits the establishment and maintenance of in vitro cultures. To address this issue, a Central Composite Design based Response Surface Methodology (RSM) was adopted to study the modification of three fungal culture media viz. czapek dox, potato dextrose, and v8 juice, and the effect of altered media composition on growth conditions and media compositions were assessed. The response parameter for the RSM experiments was the mycelial biomass produced under different culture conditions. The uni and bi-parametric interactions among the experimental variables provided the basis for the statistically optimized conditions for maximal fungal growth. The study thus presents the recommended modifications of existing media that can lead to the successful establishment and maintenance of E. vexans in vitro cultures.     

Cytokinins in pathogenesis and disease resistance of Pyrenophora teres-barley and Dreschslera maydis-maize interactions during early stages of infection

Infection of Hordeum vulgare L. by Pyrenophora teres and of Zea mays by Dreschslera maydis were characterized by 'green island' formation, higher cytokinin levels and accumulation of metabolites in the infected areas. Higher cytokinin concentrations of the order 6-Y,Y-dimethylallylaminopurine > zeatinriboside > zeatin > dihydrozeatinriboside were detected at infection sites of susceptible hosts. By virtue of these cytokinins, infection sites may be acting as metabolic sinks helping proliferation of the pathogen. Existence of translocatory sinks at infection zones was confirmed from autoradiographic studies, where, accumulation of labeled metabolites was prominent at infection sites of susceptible hosts. Upon infection the lower cytokinin levels of resistant hosts decreased further with progress of infection. In the infected resistant hosts the concentrations of zeatin/zeatinriboside were the maximum among the four identified cytokinins. The pathogen is also capable of secreting cytokinins as evident from quantification of cytokinins in culture filtrate extracts using HPLC. Since detached leaves were used in the experiments the increase/decrease of various cytokinin levels may be attributed to pathogen influence. The increase in cytokinin levels in the susceptible host may be aiding the growth of the pathogen on one hand, while the decrease in the infected resistant host may signal the host to activate defenses against a potential pathogen at the early stage of infection.     

Puccinia coronata f. sp. avenae: a threat to global oat production

Puccinia coronata f. sp. avenae (Pca) causes crown rust disease in cultivated and wild oat (Avena spp.). The significant yield losses inflicted by this pathogen make crown rust the most devastating disease in the oat industry. Pca is a basidiomycete fungus with an obligate biotrophic lifestyle, and is classified as a typical macrocyclic and heteroecious fungus. The asexual phase in the life cycle of Pca occurs in oat, whereas the sexual phase takes place primarily in Rhamnus species as the alternative host. Epidemics of crown rust happens in areas with warm temperatures (20–25 °C) and high humidity. Infection by the pathogen leads to plant lodging and shrivelled grain of poor quality. Disease symptoms : Infection of susceptible oat varieties gives rise to orange–yellow round to oblong uredinia (pustules) containing newly formed urediniospores. Pustules vary in size and can be larger than 5 mm in length. Infection occurs primarily on the surfaces of leaves, although occasional symptoms develop in the oat leaf sheaths and/or floral structures, such as awns. Symptoms in resistant oat varieties vary from flecks to small pustules, typically accompanied by chlorotic halos and/or necrosis. The pycnial and aecial stages are mostly present in the leaves of Rhamnus species, but occasionally symptoms can also be observed in petioles, young stems and floral structures. Aecial structures display a characteristic hypertrophy and can differ in size, occasionally reaching more than 5 mm in diameter. Taxonomy : Pca belongs to the kingdom Fungi, phylum Basidiomycota, class Pucciniomycetes, order Pucciniales and family Pucciniaceae. Host range : Puccinia coronata sensu lato can infect 290 species of grass hosts. Pca is prevalent in all oat‐growing regions and, compared with other cereal rusts, displays a broad telial host range. The most common grass hosts of Pca include cultivated hexaploid oat (Avena sativa) and wild relatives, such as bluejoint grass, perennial ryegrass and fescue. Alternative hosts include several species of Rhamnus, with R. cathartica (common buckthorn) as the most important alternative host in Europe and North America. Control : Most crown rust management strategies involve the use of rust‐resistant crop varieties and the application of fungicides. The attainment of the durability of resistance against Pca is difficult as it is a highly variable pathogen with a great propensity to overcome the genetic resistance of varieties. Thus, adult plant resistance is often exploited in oat breeding programmes to develop new crown rust‐resistant varieties. Useful website : https://www.ars.usda.gov/midwest-area/st-paul-mn/cereal-disease-lab/docs/cereal-rusts/race-surveys/ .