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The species in genus Melampsora are the causal agents of leaf rust diseases on willows in natural habitats and plantations. However, the classification and recognition of species diversity are challenging because morphological characteristics are scant and morphological variation in Melampsora on willows has not been thoroughly evaluated. Thus, the taxonomy of Melampsora species on willows remains confused, especially in China where 31 species were reported based on either European or Japanese taxonomic systems. To clarify the species boundaries of Melampsora species on willows in China, we tested two approaches for species delimitation inferred from morphological and molecular variations. Morphological species boundaries were determined based on numerical taxonomic analyses of morphological characteristics in the uredinial and telial stages by cluster analysis and one-way analysis of variance. Phylogenetic species boundaries were delineated based on the generalized mixed Yule-coalescent (GMYC) model analysis of the sequences of the internal transcribed spacer (ITS1 and ITS2) regions including the 5.8S and D1/D2 regions of the large nuclear subunit of the ribosomal RNA gene. Numerical taxonomic analyses of 14 morphological characteristics recognized in the uredinial-telial stages revealed 22 morphological species, whereas the GMYC results recovered 29 phylogenetic species. In total, 17 morphological species were in concordance with the phylogenetic species and 5 morphological species were in concordance with 12 phylogenetic species. Both the morphological and molecular data supported 14 morphological characteristics, including 5 newly recognized characteristics and 9 traditionally emphasized characteristics, as effective for the differentiation of Melampsora species on willows in China. Based on the concordance and discordance of the two species delimitation approaches, we concluded that integrative taxonomy by using both morphological and molecular variations was an effective approach for delimitating Melampsora species on willows in China.

Up-to-date information is given on the identity, occurrence, nomenclature, host ranges, geographical distribution and literature references of the Urediniomycetes in South Africa. Species of the family Melampsoraceae and all species of the family Pucciniaceae other than those in the genera Puccinia Pers. and Uromyces (Link) Unger are listed. New species records since 1945 include the following: Melampsora allii-populirui Kleb.. Melampsora coleosporioides Dietel. Melampsora laricipopulina Kleb.. Melampsora medusae Thiim., Frommea obtusa-duchesneae (Arthur) Arthur. Hemileia gardeniae-thunbergiae Maubl. & Roger. Phakopsora gossypii (Arthur) Hirats. F. Uromycladium tepperianum (Sacc.) McAlpine and Tranzschelia discolor (Fuckel) Tranzschel & M.A. Litv. Although many species of rusts have already been recorded, these are thought to represent only a small percentage of the rust population in southern Africa. Furthermore, only a small portion of rust specimens at present housed at PREM have so far been studied. Continued research on this economically important group of fungi is therefore essential.

The species in genus Melampsora are the causal agents of leaf rust diseases on willows in natural habitats and plantations. However, the classification and recognition of species diversity are challenging because morphological characteristics are scant and morphological variation in Melampsora on willows has not been thoroughly evaluated. Thus, the taxonomy of Melampsora species on willows remains confused, especially in China where 31 species were reported based on either European or Japanese taxonomic systems. To clarify the species boundaries of Melampsora species on willows in China, we tested two approaches for species delimitation inferred from morphological and molecular variations. Morphological species boundaries were determined based on numerical taxonomic analyses of morphological characteristics in the uredinial and telial stages by cluster analysis and one-way analysis of variance. Phylogenetic species boundaries were delineated based on the generalized mixed Yule-coalescent (GMYC) model analysis of the sequences of the internal transcribed spacer (ITS1 and ITS2) regions including the 5.8S and D1/D2 regions of the large nuclear subunit of the ribosomal RNA gene. Numerical taxonomic analyses of 14 morphological characteristics recognized in the uredinial-telial stages revealed 22 morphological species, whereas the GMYC results recovered 29 phylogenetic species. In total, 17 morphological species were in concordance with the phylogenetic species and 5 morphological species were in concordance with 12 phylogenetic species. Both the morphological and molecular data supported 14 morphological characteristics, including 5 newly recognized characteristics and 9 traditionally emphasized characteristics, as effective for the differentiation of Melampsora species on willows in China. Based on the concordance and discordance of the two species delimitation approaches, we concluded that integrative taxonomy by using both morphological and molecular variations was an effective approach for delimitating Melampsora species on willows in China.

In North America Melampsora rusts that parasitize willows (Salix species) have never been adequately studied and mostly have been referred to a collective species, Melampsora epitea (Kunze & Schm.) Thüm, of European origin. Even taxa that are nominally distinct from M. epitea, such as M. abieti-caprearum and M. paradoxa, currently are considered to be "races" of M. epitea. Within the range of our field surveys and collections in the Pacific Northwest and the Southwest only two species of Melampsora thus were expected: M. epitea (including its races) and M. ribesii-purpureae. In this study of Melampsora on 19 species of Salix in the western United States 14 phylogenetic species, or phylotypes, were apparent from nuclear rDNA sequencing of 140 collections or isolates. Our collections of the races of M. epitea, M. abieti-caprearum and M. epitea f. sp. tsugae belonged to one phylotype, termed lineage 'N'. Assuming that M. ribesii-purpureae represents one other phylotype, 12 phylotypes still are unaccounted for by current taxonomy. Moreover Eurasian M. ribesii-purpureae was not closely related to any of the phylotypes reported here. Even more problematic was the resistance of Eurasian species of Salix, including the type host of M. epitea, S. alba, to North American Melampsora, including phylotype 'N', in both the field and in inoculation experiments. These results suggest the need for the description of many new species of Melampsora on Salix in western North America. Additional analyses presented here might guide further research in this direction. [ABSTRACT FROM AUTHOR]

Controlled inoculations with 10 bulk inocula of Cronartium quercuum (Berk) Miyabe ex Shirai f.sp. fusiforme were carried out on open-pollinated progeny of 25 fast-growing Pinus taeda L. parents. The parents had a range of breeding values for resistance to fusiform rust in progeny field trials. There were highly significant differences among the half-sib families in response to inoculations, and these differences were very reproducible; the half-sib family-mean heritability of resistance to controlled inoculation was 0.97. All of the families that were susceptible in the field were susceptible in controlled inoculations, and most (12 of 17) of the field-resistant families were resistant in response to controlled inoculations. Significant pathogenic variability was observed among the different bulk inocula, although this accounted for only 1.9% of the total variation. Genetic differences among families within field-resistant or field-susceptible groups accounted for 13.7% of the total variation. The family by inocula interaction was highly significant, but a single field-resistant family contributed 44% of the total family by inocula interaction variance, and two other field-resistant families also showed significant interactions. [ABSTRACT FROM AUTHOR]

AFLP analysis was used to examine the genetic structure of the mycoparasite Sphaerellopsis filum on willow rust Melampsora larici-epitea using two sets of samples of a willow clone in a short-rotation coppice planting. The first set was collected from a plot (short strip) in 1998, 1999 and 2000 and the second from another plot (long strip) in 2000. In all, 228 S. filum isolates were typed, 139 AFLP loci scored and 54 AFLP genotypes identified. In the short strip, genotypes sampled in 1998 were no longer detected in subsequent years and genotype diversity fluctuated (0·25–0·68) over the years, indicating that migration had a major impact on the genotype structure. Two distinct groups (average Nei and Li's similarity coefficient between the groups = 0·047) were identified. The group B genotypes were sampled only in 2000. Within the groups, the average similarities were > 0·96. Both the index of association test and the parsimony tree length permutation test suggest that there was a significant clonality in group A while recombination cannot be ruled out in group B. Localized clusters of AFLP genotypes were detected using the software SaTScan that is based on the spatial scan statistic. Possible mechanisms involved in the spread of S. filum in willow coppice plantations are discussed. [ABSTRACT FROM AUTHOR]

The abundance of leaf rust (Melampsora sp.) was assessed on four willow clones in four experimental Estonian willow short-rotation forest plantations. Three plantations were established on poor mineral soil and one was constructed for wastewater purification. Clones 78183 and 81090 were most severely damaged in all four plantations, whereas clones 78021 and 78195 were fairly resistant to rust. In addition to clone type, the number of uredinia on leaves depended on plantation, sampling date, and fertilization. Infection increased significantly during the growing season, and the leaves collected from fertilized plants had more and larger rust pustules than those from unfertilized plants. Uredinia were smaller on older shoots and larger on younger shoots. [ABSTRACT FROM AUTHOR]

The 5' end of the large subunit (LSU) region and the entire internal transcribed spacer (ITS) region of ribosomal DNA were sequenced from 11 species or special forms of Melampsora on Salix, and three species on Populus. For all the species, except for M. larici-epitea and M. coleosporioides, the sequences in both the examined regions were identical within a species. Within M. larici-epitea, f. sp. larici-epitea typica and f. sp. larici-retusae shared the same sequences which slightly differed from that of f. sp. larici-daphnoides. In the LSU region, M. larici-epitea, M. capraearum and the stem-infecting form on S. viminalis shared the same sequence and the Far-Eastern species M. epiphylla differed from them only slightly (p distance 0.006), indicating that they may share a common ancestral lineage. M. amygdalinae and M. coleosporioides formed a distict group (bootstrap value 100% for combined ITS and LSU data). M. larici-epitea and M. ribesii-purpurea, both belonging to the M. epitea complex, appeared to be distinct. The molecular data also suggest that the differences in certain characteristics, such as the thickness of teliospore walls and host specificity, may have evolved relatively recently. [ABSTRACT FROM AUTHOR]

This article focuses on a study conducted as of February 1976, regarding the germination ability of teleutospores of melampsora pinitorqua, a fungus, overwintered in different situations and under different types of soil cover. The germination period is affected by local environmental conditions. The intensity of germination of teleutospores overwintered in the underbrush is much lower than that of teleutospores overwintered on uncovered soil. The findings may be very useful for understanding variability of disease incidence in different stations, years and types of soil coverings, besides, for obtaining the best germination ability of teleutospores in susceptibility trials of pine.

Present knowledge of host range and distribution of Melampsora pinitorqua Rostr. in Italy is reported. Melampsora larici-tremulae, which occurs at high altitude in the Apennines and the Alps and infects only larch, can infect pine also in artificial conditions. [ABSTRACT FROM AUTHOR]

Eighteen isolates of the rust fungus Melampsora from different locations in England were tested for pathogenicity to a large range of willow clones (Salix spp.) in experiments involving inoculation of leaf discs. Seventeen of the isolates were of leaf-infecting M. epitea var. epitea, 16 of which represented forms which alternated on Larix and one of which alternated on Ribes. The remaining isolate was of uncertain identity. Two experiments were carried out. In the first exp>eriment, 24 willow clones consisting of 20 Salix species and interspecific hybrids were inoculated with eight isolates from clones of S. viminalis. In the other experiment, 77 clones from 57 species or hybrids were inoculated with 10 isolates from several Salix spp. The M. epitea var. epitea isolates from S. viminalis clones were all similarly pathogenic, whilst most of the other isolates expressed distinct host specificity. Eight distinct pathotypes were recognized within M. epitea var. epitea. All except one of these alternated on Larix and could be assigned to three formae speciales which had been reported previously in Europe: four pathotypes to f.sp. larici-epitea typica, two to f.sp. larici-retusae, and one to f.sp. tarici-daphnoides. The Ribes-alternating pathotype of M. epitea var. epitea infected only S. purpurea. Nine differential willow hosts are proposed as reference clones to distinguish between the larch-alternating pathotypes, the Ribes-alternating rust and the ‘stem-infecting’ form. The extent of pathogenic variation encountered amongst sexually reproducing rusts suggests that more pathotypes probably exist and will arise in future in response to selection given by long-term clonal willow plantings. [ABSTRACT FROM AUTHOR]

Disease severity, based on six parameters (time from inoculation to flecking and eruption of uredinia, uredinial density and the amounts of urediniospores produced), was assessed on leaf discs cut from four cultivars of Populus spp. raised with either a long ( 15 h) or a short (10 h) photoperiod. The discs were inoculated with race 4 of Melampsora medusae and subsequently incubated with either a long (15 h) or a short (10 h) photoperiod. While disease severity, based on most parameters, was lower in discs from the continuing long photoperiod (15 h pre-and 15 h post-inoculation) than from the continuing short photoperiod (10 h pre- and 10 h post- inoculation), maximum seventy was developed by discs given a combination of a short pre- and a long post-inoculation photoperiod. The relative contribution of the cultivar, the pre- and the post-inoculation photoperiod and their second- and third-order interactions to variation in disease severity depended on the parameter employed to assess severity. The parameters used are elements of disease monocycles and their possible significance in modelling epidemics is discussed. [ABSTRACT FROM AUTHOR]

MeOH and water extracts were obtained from 16 species of infected leaves with rust fungi belonging to 18 species in 6 families: Pucciniaceae, Melampsoraceae, Coleosporiaceae, Pileolariaceae, Phragmidiaceae, and Phakopsoraceae. All the extracts of rust-infected plants with telia showed the teliospore-inducing activity for wheat leaf rust ( Puccinia recondita f. sp. tritici). [ABSTRACT FROM AUTHOR]

Melampsora species and their hybrids are obligate parasites of Populus and Salix species worldwide. The increasing interest in Populus and Salix for biomass and fibre production necessitates genetic markers for population studies of Melampsora spp. Libraries enriched for simple sequence repeats were used to develop five microsatellite markers for Melampsora medusae and Melampsora larici-populina. The variation detected by these markers will be valuable for phylogenetic and population genetic studies, substantiate putative hybrids, and deployment of resistant poplar clones. [ABSTRACT FROM AUTHOR]

Between 2020 and 2023, rust fungus specimens were collected from the primary forested regions of the Sanjiangyuan area in Qinghai Province, resulting in over 300 samples. A taxonomic and phylogenetic study of the rust fungi from these forests was conducted using morphological and molecular biological techniques. The investigation identified rust fungi from 7 families, 12 genera, 56 species and varieties, including 10 new host records, 1 new record for China, and 2 novel species. The host plants involved belonged to 26 families, 48 genera, and 78 species. Pucciniaceae and Coleosporiaceae were the dominant families, with the genera Puccinia, Melampsora, and Gymnosporangium being prevalent. The rust fungi in the Sanjiangyuan forests showed a biogeographical affinity with the North Temperate Zone. Floristic comparisons revealed a higher similarity with rust fungi from Inner Mongolia, Gansu, and Tibet and a lower similarity with those from Hainan. An analysis of the life forms of rust fungus host plants indicated that herbaceous plants were the most common, followed by shrubs and trees. In different regions of Sanjiangyuan, rust fungi were found as follows: Golog Prefecture with 6 families, 9 genera, and 28 species; Yushu Prefecture with 5 families, 8 genera, and 31 species; Huangnan Prefecture with 5 families, 9 genera, and 26 species; and Hainan Prefecture with 4 families, 5 genera, and 10 species. The families Pucciniaceae, Melampsoraceae, and Coleosporiaceae were common across all four regions. Moreover, the families Rosaceae, Asteraceae, Ranunculaceae, Salicaceae, and Caprifoliaceae were shared among the host plants in these regions. [ABSTRACT FROM AUTHOR]

A total of 174Salix(willow) clones belonging to 57 species and 14 interspecific hybrids were inoculated with seven pathotypes ofMelampsora larici-epiteausing the leaf disc method. Infection types were scored based on the uredinial pustule area data and the inoculum density. A close correlation (R2 = 0·82) was found between the average pustule area and the average number of spores produced. Most of the willows were also assessed in the field for rust in 1999. Most willow clones belonging to the species native to western Europe were infected by the rust. In inoculation experiments, uredinia developed on 46S. viminalisclones, out of a total of 47. In the field, all theS. viminalisclones were infected by rust. Within the subgenusVetrix, eight out of the 17 willow species that originated from North and South America produced rust pustules in inoculation experiments. Of these,S. pellitawas most susceptible.Salix irrorataandS. lasiolepsisvar.bracelinaeproduced well developed pustules after inoculation but no rust infections were detected in the field. In both leaf disc tests and field assessments, no rust infections were found onS. candida,S. cordata,S. drummondiana,S. eriocephala,S. hookeriana,S. houghtonii,S. humilis,S. rigidavar.mackenzianaandS. syrticola. Of 12 species of subgenusVetrixnative to northeast Asia and Japan, onlyS. kochianawas susceptible both in inoculation tests and in the field.Salix rossicaproduced no symptoms in leaf disc tests but showed low levels of infection in the field. The maximum infection type scores in leaf disc tests were highly significantly correlated with field disease severity scores (Spearman rank correlation coefficient was 0·76,P < 1 × 10−10). [ABSTRACT FROM AUTHOR]

Rust fungi are obligate biotrophic pathogens that cause considerable damage on crop plants. Puccinia graminis f. sp. tritici, the causal agent of wheat stem rust, and Melampsora larici-populina, the poplar leaf rust pathogen, have strong deleterious impacts on wheat and poplar wood production, respectively. Filamentous pathogens such as rust fungi secrete molecules called disease effectors that act as modulators of host cell physiology and can suppress or trigger host immunity. Current knowledge on effectors from other filamentous plant pathogens can be exploited for the characterisation of effectors in the genome of recently sequenced rust fungi. We designed a comprehensive in silico analysis pipeline to identify the putative effector repertoire from the genome of two plant pathogenic rust fungi. The pipeline is based on the observation that known effector proteins from filamentous pathogens have at least one of the following properties: (i) contain a secretion signal, (ii) are encoded by in planta induced genes, (iii) have similarity to haustorial proteins, (iv) are small and cysteine rich, (v) contain a known effector motif or a nuclear localization signal, (vi) are encoded by genes with long intergenic regions, (vii) contain internal repeats, and (viii) do not contain PFAM domains, except those associated with pathogenicity. We used Markov clustering and hierarchical clustering to classify protein families of rust pathogens and rank them according to their likelihood of being effectors. Using this approach, we identified eight families of candidate effectors that we consider of high value for functional characterization. This study revealed a diverse set of candidate effectors, including families of haustorial expressed secreted proteins and small cysteine-rich proteins. This comprehensive classification of candidate effectors from these devastating rust pathogens is an initial step towards probing plant germplasm for novel resistance components. [ABSTRACT FROM AUTHOR]

The article aims to investigate on the impact of the invasive Cronartium ribicola to the mutualism relationship of the Clark's Nutcracker and Whitebark pine in the U.S. It is reported that disruption, due to human activities, is one of the suspected cause of disturbance on the helping relationship between the two mentioned species and cites its contribution to the near extinction of these species in the forest. However, Cronartium ribicola is considered as the worst invader of mutualism, where it can infect the Whitebark pine by reducing the production of pine cones through its invasive white pine blister rust. In addition, the birds' ability to disperse the pine cones has also declined. Furthermore, ecological researchers have exerted their efforts to mitigate the invasive pathogen.

Surveys to assess the status of whitebark pine (Pinus albicaulis Engelm.) populations, with respect to white pine blister rust (Cronartium ribicola J.C. Fisch.), were conducted in Mount Rainier National Park and North Cascades National Park Service Complex between 1994 and 1999. A total of 2173 whitebark pine trees and 1029 saplings were surveyed. Blister rust was documented in every stand, but rates of blister rust infections were highly variable (0% to 70%). Overall, 22% of trees were infected, 31% were dead, and 47% of all trees showed no signs of infection. Surveys of saplings (< 2.54 cm dbh) documented infection rates of 28%, mortality rates of 10%, and uninfected rates of 62%. Generally, the percent of trees that were infected increased from west to east and with increasing elevation. Mortality rates decreased with elevation, which may be a result of shorter growing seasons at higher elevations and a longer time period for the infection to spread within the tree. A long-term monitoring program, with permanent plots, has been established to track population status and to inform restoration programs. [ABSTRACT FROM AUTHOR]

We report the discovery, characterization and validation of 118 single nucleotide polymorphisms (SNPs) for poplar leaf rust Melampsora medusae f. sp. deltoidae identified using a gene-targeted approach in an expressed sequence tag (EST) library. We developed a genotyping assay using the iPLEX™ primer extension method for two multiplex assays of 28 and 22 SNPs. [ABSTRACT FROM AUTHOR]

1 Host–pathogen interactions in isolated populations may result in the adaptation of pathogens to local hosts. However, results of earlier studies of local adaptation in plant–pathogen systems have been contradictory and it has been suggested that specific, species characteristics, for example distribution, dispersal and the degree of pathogen dependence on the host, are important for the outcome of host–pathogen interactions. In addition, the scale of the study may influence whether or not local adaptation is found. 2 We argue that local adaptation of the pathogen to the host can be expected in a system where: (i) the pathogen is host-specific with a short generation time compared with the host; (ii) populations are isolated, allowing localized evolution to occur; and (iii) the study is performed on a geographical scale exceeding the maximum dispersal range of the interacting species. 3 To test these predictions we examined the within- and among-population variation in resistance and virulence of the plant–pathogen system Salix triandra– Melampsora amygdalinae. The pathogen occurs throughout the whole distribution range of the host, and the area of interest consists of highly isolated, small natural populations. 4 Resistance and virulence differed both within and between populations and all clones showed a unique resistance pattern. We conclude that M. amygdalinae is locally adapted to the host S. triandra as all pathogen populations have a higher probability of infecting sympatric than allopatric hosts. Furthermore, high resistance in the host population was accompanied by a high virulence in the pathogen population, suggesting that high resistance levels in a host population may select for more virulent pathogen populations, or vice versa. 5 The nature of host–pathogen interactions differs among systems, and the dynamics of the interaction between S. triandra and M. amygdalinae is governed by characteristics that have resulted in the evolution of local adaptation. 6 Thus, when studying local adaptation of pathogens to their hosts it is important to consider the biology, as well as the scale of dispersal and spatial distribution of both host and pathogen. [ABSTRACT FROM AUTHOR]

We developed 15 microsatellite loci in the poplar rust fungus, Melampsora larici-populina, using two enrichment protocols. Polymorphism of each locus was assessed on a panel of 30 isolates, comprising three subpanels (world, regional and local scales). Thirteen loci were polymorphic with three to eight alleles detected. The 15 loci were also tested on five related Melampsora species, M. allii-populina, M. medusae f. sp. deltoidae, M. larici-tremulae, M. rostrupii and M. pinitorqua, and partial or global cross-amplification events were detected. [ABSTRACT FROM AUTHOR]

Abstract Using a leaf disc method, 19 isolates of the poplar rust, Melampsora larici-populina , and one isolate of M.?populnea from England were inoculated on to 25 poplar clones belonging to Populus nigra and P.?trichocarpa , and hybrids between P. deltoides and P. nigra , P. deltoides and P. trichocarpa , P.?tacamahaca and P.?trichocarpa , and P. alba and P. tremula . Disease was scored based on the pustule area and inoculum density. In terms of whether sporulating uredinia formed, the 19 isolates showed seven different patterns to the tested poplar clones. The majority of the rust isolates infected P. nigra P3090 and Vereecken, P.?nigra ?? P. deltoides Casale and Tasman, P. tacamahaca ?? trichocarpa 36 and Balsam Spire, and P.?trichocarpa Blom. Populus trichocarpa ?? P. deltoides 69039/4 was infected by only three isolates collected from southern England. No visible symptoms appeared on P. alba ?? P. tremula Tower and P.?trichcarpa? ? P. deltoides ?? P. deltoides 76028/5 in inoculations with M. larici-populina isolates. Populus alba? ?P.?tremula Tower was infected only by M. populnea . When M. larici-populina isolates were tested using AFLP, no differences were found either between isolates from different geographical regions or between those having narrow spectrum of virulence and those showing wide spectrum of virulence on the tested clones. The results suggest that the UK rust populations possess virulences which were found in races E1, E2, E3 and E4 in continental Europe and that rust having virulence patterns similar to race E4 has occurred in UK poplar plantations since 1996. [ABSTRACT FROM AUTHOR]

Uredospores of Melampsora larici-populina and Melampsora allii-populina show some reactions in common physical factors. In both species germination requires high relative humidity and darkness has adverse effects. For other characters, differences appear in their behavior. The optimum temperature for germination is 13°C for M. larici-populina but 16°C for M allii-populina. M. larici-populina uredospores germinate more slowly but their germ tubes grow faster. Above 16°C, germination of M. laricipopulnaa spores is reduced and temperatures above 30°C induce a delay in subsequent germination. However, their germination capacity is less affected by heavy and long frosts as compared with M. allii populina.

This article reports an investigation undertaken with the aid of a scanning electron microscope (SEM) to elucidate the three dimensional morphology of mature haustoria of the haploid stage of Cronartium ribicola in the different cells of Pinus monticola bark. Haustoria, particularly young small ones, are often hidden in the host cytoplasm and therefore are difficult to discern with the SEM. Haustoria were observed in almost all host cells of the densely invaded areas at or near canker centers. They were observed in all types of host cells such as cortical parenchyma , phloem parenchyma, ray parenchyma, and Sieve elements.

The article investigates haustorial morphology of the cone-rust pathogen, cronartium conigenum, among naturally infected female strobili of three Guatemalan pines, P. maxiininoi, P. pseudostrobus, and P. oocarpa. Among the three pine species, haustorial shapes and sizes were more variable in P. inaximinoi and P. oocarpa than in P. pseudosero bus. The haustorial shapes and sizes were more variable in parenchyma cells of the cortex, xylem, and pith than in the cells in the phloem, xylem rays, and tracheids. The haustoria were also present in larger numbers in the parenchyma cells of the cortex, xylem, and pith than in phloem parenchyma cells and tracheids. In living cells, the tips of some haustoria were appressed to the host nuclei.

The article analyzes the inheritance of resistance to Melampsora on Salix viminalis, the variation in resistance over space and time, and rust infection rate in relation to the geographic origin of the host. Four series of experiments located in south-central and southernmost Sweden were used for the analysis. The analysis showed that there was considerable additive genetic variation for rust resistance, that the results have low repeatability over space and time, and that the material from southernmost Sweden was most sensitive to the rusts occurring in South Sweden.

Copyright of European Journal of Forest Pathology is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of European Journal of Forest Pathology is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of European Journal of Forest Pathology is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Rust fungi in the genus Melampsora usually cause disease on hosts in the Salicaceae. Identification of Melampsora species is often complicated due to few differences in spore morphology and little publicly available comparative sequence data. Weeping willow trees (primarily Salix babylonica and its hybrids) have been reported to be infected by 11 Melampsora species; however, most of these records are based on morphological characterization. New collections of rust fungi on weeping willows from the central USA were analysed using a combination of morphology, ITS and LSU r DNA sequencing, and host data to determine that they represent an undescribed rust fungus, Melampsora ferrinii sp. nov. Additional studies of herbarium material revealed that M. ferrinii has occasionally been collected but identified as M. epitea. In addition to North America, M. ferrinii is also present in South America and has been infecting weeping willows there since at least the 1990s. [ABSTRACT FROM AUTHOR]

The article presents information on melampsora euphorbiae, a new disease found on Euphorbia rigidain in Turkey. Euphorbia rigida occurs widely in Turkey and is a weed of gardens and uncultivated areas. Symptoms include the drying of leaves before normal flowering season. It occurred mostly on the lower surface of leaves and on stems. Melampsora euphorbiae has clear potential as biological control agent against other Euphorbia species. The rust disease poses more of a threat to the horticultural trade of E. rigidain at present.

In September 2001, the uredinia sori of rust were found on alder trees in As parish, Akershus, in south-eastern Norway. Further examination of these sori, which always occurred on the lower side of the infected leaves, revealed urediniospores, which were uniformly echinulate and which had apical spines. From this morphology, Melampsoridium hiratsukanum was identified. Melampsoridium betulinum is also known to occur on A. glutinosa in As. A germination test with fresh urediniospores of M. hiratsukanum revealed four to six bizonate pores, similar to those reported for M. betulinum. However, this rust lacks spines in the apical region of its urediniospores and it is the presence of spines in the apical region that distinguishes these rust species.

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Following a request from the European Commission, the EFSA Plant Health Panel performed a pest categorisation of Melampsora medusae, a well-defined and distinguishable fungal species of the family Melampsoraceae. The pathogen is regulated in Annex IAI of Council Directive 2000/29/EC as a harmful organism whose introduction into the EU is banned. M. medusae is a heteroecious rust fungus with Populus spp. as primary telial hosts and various conifers (Larix, Pinus, Pseudotsuga, Abies, Picea and Tsuga spp.) as secondary aecial hosts. M. medusae is native to North America and has spread to South America, Africa, Asia, Oceania, as well as the EU, where M. medusae f. sp. deltoidae has been reported with a restricted distribution and low impacts from Belgium, south-west France and southern Portugal. The pest could spread to other EU countries, via dissemination of spores, movement of host plants for planting and cut branches. Climate is assumed not to be a limiting factor for the establishment of the pathogen in the EU. M. medusae is the most widespread and important Melampsora rust in North America. In western Canada, extensive damage has been reported to conifers and Populus spp. in nurseries and plantations as well as in woodlands. M. medusae is damaging in both Australia and New Zealand. The pest could have economic and environmental impacts in the EU if aggressive isolates of M. medusae were introduced into the EU. Import prohibition of host plants for planting is an available measure to reduce the risk of further introductions. Some resistant Populus cultivars are available. Moreover, increasing the genetic diversity of poplar plantations can prevent disease impacts. The main uncertainty concerns the factors explaining the low pathogenicity of the populations of M. medusae present in the EU. The criteria assessed by the Panel for consideration as a potential quarantine pest are met (the pest is present, but with a restricted distribution, and is officially under control). Given that plants for planting are not the main pathway of spread, not all criteria for consideration as a regulated non-quarantine pest are met. [ABSTRACT FROM AUTHOR]

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]

A recent study published in the New Disease Reports journal has identified Melampsora ferrinii as the cause of rust disease on Corydalis incisa, commonly known as incised fumewort, in Korea. This is the first recorded instance of M. ferrinii affecting C. incisa in Korea. The study found that the spread of C. incisa, driven by global climate change, could potentially lead to the occurrence of M. ferrinii on Salix species, which could result in ecological and economic damage. This research highlights the importance of monitoring and managing the spread of invasive species in the face of climate change. [Extracted from the article]

Honey bee workers (Apis mellifera L.) collect nectar, honeydew and pollen from plants in orderto provide the colony with, among others, carbohydrates and protein. Whenever these sources are unavailable in the environment, bees turn to alternatives. An example of this are fungi spores collected accidentally or on purpose. This last phenomenon is the aim of this study, in which we have shown that worker bees can collect willow rust (Melampsora spp.) spores. We observed as the bees obtained spores and placed them in pollen baskets. The presence of spores was demonstrated with the use of a scanning electron microscope (SEM). This observation indicates that the honey bee may use alternative sources as a potential supplement. There are few studies in this field and it requires a deeper analysis. [ABSTRACT FROM AUTHOR]

Rust fungi (Uredinales, Basidiomycetes) are one of the most diverse and economically important plant-obligated parasites. Taxonomy of this group has been under revision during the last years using molecular techniques to define phylogenetic relationships. in this study we evaluated the phylogenetic affinities of a group of 40 rust fungi obtained from different plants in the Colombian Andean region using sequence analysis of the 28S ribosomal DNA, specifically D1/D2 domains. Comparisons were undertaken with sequences of rust fungi from around the world deposited in the GenBank database. An alignment of sequences was used to build a phylogenetic tree through Maximum parsimony analysis. Our results support the taxonomical validity of families Pucciniaceae, Phakopsoraceae, Phragmidiaceae, Pileolariaceae, Mikronegeriaceae, Coleosporiaceae and Cronartiaceae, while Pucciniosiraceae represents redundant taxa with Pucciniaceae. The analyses indicated that Uropyxidaceae, Raveneliaceae, Chaconiaceae and Pucciniastraceae correspond to polyphyletic families. Melampsoraceae appear to be a basal taxon to the Uredinales. information obtained in this study will be useful to incorporate a higher number of sequences from tropical rust fungi within global efforts to redefine the taxonomy of order Uredinales. Additionally, we propose to give priority to future phylogenetic studies of taxa: Gerwasia, Hemileia, Phragmidium, Prospodium, Puccinia and Uromyces, genera that include a high number of rust fungi from the tropics. Rev. Biol. Trop. 59 (2): 517-540. Epub 2011 June 01. [ABSTRACT FROM AUTHOR]