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Increased temperatures associated with urbanization (the "urban heat island" effect) have been shown to impact a wide range of traits across diverse taxa. At the same time, climatic conditions vary at fine spatial scales within habitats due to factors including shade from shrubs, trees, and built structures. Patches of shade may function as microclimate refugia that allow species to occur in habitats where high temperatures and/or exposure to ultraviolet radiation would otherwise be prohibitive. However, the importance of shaded microhabitats for interactions between species across urbanized landscapes remains poorly understood. Weedy plants and their foliar pathogens are a tractable system for studying how multiple scales of climatic variation influence infection prevalence. Powdery mildew pathogens are particularly well suited to this work, as these fungi can be visibly diagnosed on leaf surfaces. We studied the effects of shaded microclimates on rates of powdery mildew infection on Plantago host species in (1) "pandemic pivot" surveys in which undergraduate students recorded shade and infection status of thousands of plants along road verges in urban and suburban residential neighborhoods, (2) monthly surveys of plant populations in 22 parks along an urbanization gradient, and (3) a manipulative field experiment directly testing the effects of shade on the growth and transmission of powdery mildew. Together, our field survey results show strong positive effects of shade on mildew infection in wild Plantago populations across urban, suburban, and rural habitats. Our experiment suggests that this relationship is causal, where microclimate conditions associated with shade promote pathogen growth. Overall, infection prevalence increased with urbanization despite a negative association between urbanization and tree cover at the landscape scale. These findings highlight the importance of taking microclimate heterogeneity into account when establishing links between macroclimate or land use context and prevalence of disease. [ABSTRACT FROM AUTHOR]

The tomato is a major crop worldwide and is one of the five most consumed vegetables in Germany. Stemphylium species including S. eturmiunum, S. gracilariae, S. lycii, S. lycopersici, S. rombundicum, S. simmonsii, S. solani, and S. vesicarium have been identified as tomato pathogens in various countries. In Germany, multiple instances of S. lycopersici and S. solani affecting tomato plants have been documented; however, only one incident of S. vesicarium has been reported in 1972. S. vesicarium is known to cause yellowish-brown spots on tomato leaves, which can ultimately lead to defoliation and reduced fruit yield. Therefore, it is crucial to identify the S. vesicarium that cause this disease accurately. In this study, S. vesicarium was isolated from necrotic tomato plants in organic farms located in northern and southern regions of Germany. Single spore isolates were generated and identified as S. vesicarium based on morphological characteristic and molecular analyses using nucleotide sequences of the internal transcribed spacer (ITS) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Koch´s postulates were fulfilled and revealed that S. vesicarium is the causal agent of brown spot on the samples adding a new account of the species. [ABSTRACT FROM AUTHOR]

The wood properties of western redcedar (Thuja plicata) (WRC) are revered in traditional practices by Pacific Coast First Nations and valued for speciality commercial purposes. In the near future, WRC harvesting will shift to second growth from old-growth, however, its cultural significance will persist, and the superior physical and chemical properties of the wood mean that it will remain in high demand. Investigating and understanding the adaptations of the species to environmental and pathogen stress in the face of changing climates can assure a sustainable supply of WRC. Of the pathogens affecting WRC, cedar leaf blight (Didymascella thujina) (CLB) is the most severe. This foliar disease infects the leaflets of seedlings and mature trees, causing a loss of photosynthetic area resulting in decreased growth or mortality. The disease is more severe on nursery seedlings than mature trees. Future projected climates in WRC's native range are expected to increase the prevalence of, and damage from CLB. This review summarizes the state of knowledge and emphasizes recent advances in the understanding of the Thuja – Didymascella pathosystem. [ABSTRACT FROM AUTHOR]

Nothophaeocryptopus gaeumannii is a common native, endophytic fungus of Douglas-fir foliage, which causes Swiss needle cast, an important foliage disease that is considered a threat to Douglas-fir plantations in Oregon. Disease expression is influenced by fungal fruiting bodies (pseudothecia), which plug the stomata and inhibit gas exchange. Trees are impacted when pseudothecia plug stomates on 1-year-old and older needles resulting in early needle abscission. Mature (100 years+) trees appear to be less impacted from disease, and we hypothesize this is due to the greater emergence of pseudothecia on older than younger needles, which allows for more needle retention. We measured the density of pseudothecia occluding stomates across 2- to 5-year-old needles from upper, middle, and lower canopy positions of mature trees at three sites in the Oregon Coast Range and two sites in the western Oregon Cascade Mountains. Binomial generalized linear mixed model (GLMM) was used to test for the effects of canopy position (upper, middle, and lower), sites, needle age (2–5 years old), and years (2016 and 2017), and their interactions on the pseudothecia density. Pseudothecia density varied annually depending on sites, needle age and canopy positions. Pseudothecia density peaked on 3-, and 4-year-old needles, however, needles emerging from the same year, like 2-year-old needles in 2016 and 3-year-old needles in 2017 both emerged in 2014, had consistently similar patterns of pseudothecia density for both years, across site and canopy positions. Canopy position was important for 3-, and 4-year-old needles, showing less pseudothecia in the lower canopy. This research confirms that N. gaeumannii pseudothecia density is greatest in 3- and 4-year old needles in mature trees in contrast to plantations where pseudothecia density usually peaks on 2-year-old needles, and that pseudothecia density (disease severity) is generally lower in mature trees. Something about mature forest canopies and foliage appears to increase the time it takes for pseudothecia to emerge from the needles, in contrast to younger plantations, thus allowing the mature trees to have greater needle retention.

Tea gray blight disease and its existing control measures have had a negative impact on the sustainable development of tea gardens. However, our knowledge of safe and effective biological control measures is limited. It is critical to explore beneficial microbial communities in the tea rhizosphere for the control of tea gray blight. In this study, we prepared conditioned soil by inoculating Pseudopestalotiopsis camelliae-sinensis on tea seedling leaves. Thereafter, we examined the growth performance and disease resistance of fresh tea seedlings grown in conditioned and control soils. Next, the rhizosphere microbial community and root exudates of tea seedlings infected by the pathogen were analyzed. In addition, we also evaluated the effects of the rhizosphere microbial community and root exudates induced by pathogens on the performance of tea seedlings. The results showed that tea seedlings grown in conditioned soil had lower disease index values and higher growth vigor. Soil microbiome analysis revealed that the fungal and bacterial communities of the rhizosphere were altered upon infection with Ps. camelliae-sinensis. Genus-level analysis showed that the abundance of the fungi Trichoderma, Penicillium, and Gliocladiopsis and the bacteria Pseudomonas, Streptomyces, Bacillus, and Burkholderia were significantly (p < 0.05) increased in the conditioned soil. Through isolation, culture, and inoculation tests, we found that most isolates from the induced microbial genera could inhibit the infection of tea gray blight pathogen and promote tea seedling growth. The results of root exudate analysis showed that infected tea seedlings exhibited significantly higher exudate levels of phenolic acids and flavonoids and lower exudate levels of amino acids and organic acids. Exogenously applied phenolic acids and flavonoids suppressed gray blight disease by regulating the rhizosphere microbial community. In summary, our findings suggest that tea plants with gray blight can recruit beneficial rhizosphere microorganisms by altering their root exudates, thereby improving the disease resistance of tea plants growing in the same soil.

Tea gray blight disease and its existing control measures have had a negative impact on the sustainable development of tea gardens. However, our knowledge of safe and effective biological control measures is limited. It is critical to explore beneficial microbial communities in the tea rhizosphere for the control of tea gray blight. In this study, we prepared conditioned soil by inoculating Pseudopestalotiopsis camelliae-sinensis on tea seedling leaves. Thereafter, we examined the growth performance and disease resistance of fresh tea seedlings grown in conditioned and control soils. Next, the rhizosphere microbial community and root exudates of tea seedlings infected by the pathogen were analyzed. In addition, we also evaluated the effects of the rhizosphere microbial community and root exudates induced by pathogens on the performance of tea seedlings. The results showed that tea seedlings grown in conditioned soil had lower disease index values and higher growth vigor. Soil microbiome analysis revealed that the fungal and bacterial communities of the rhizosphere were altered upon infection with Ps. camelliae-sinensis. Genus-level analysis showed that the abundance of the fungi Trichoderma , Penicillium , and Gliocladiopsis and the bacteria Pseudomonas , Streptomyces , Bacillus , and Burkholderia were significantly (p < 0.05) increased in the conditioned soil. Through isolation, culture, and inoculation tests, we found that most isolates from the induced microbial genera could inhibit the infection of tea gray blight pathogen and promote tea seedling growth. The results of root exudate analysis showed that infected tea seedlings exhibited significantly higher exudate levels of phenolic acids and flavonoids and lower exudate levels of amino acids and organic acids. Exogenously applied phenolic acids and flavonoids suppressed gray blight disease by regulating the rhizosphere microbial community. In summary, our findings suggest that tea plants with gray blight can recruit beneficial rhizosphere microorganisms by altering their root exudates, thereby improving the disease resistance of tea plants growing in the same soil. [ABSTRACT FROM AUTHOR]

Two foliar Phytophthora species are impacting New Zealand's pine forests. Both Phytophthora pluvialis and Phytophthora kernoviae cause similar symptoms on pine needles, however P. pluvialis is a recent arrival to New Zealand and is the primary cause of red needle cast disease in Pinus radiata. The objective of this study was to determine if Phytophthora species could be detected in archived foliage collections from plantation forests in New Zealand, to ascertain how long they have been associated with foliar disorders. Foliage samples were selected from dried collections of P. radiata and Pseudotsuga menziesii made between 1963 and 2004. From these, DNA extractions and polymerase chain reactions (PCR) were performed for both host and pathogen detection. Phytophthora species were detected in eight (of 44) pine mycological herbarium samples; of these, three contained P. kernoviae. The positive P. kernoviae samples were collected in 1999 from Northland, and in 2000 and 2002 from Gisborne. Phytophthora species were detected in an additional six archived foliage samples, collected for nutrient analysis: P. kernoviae in a 1986 sample from Riverhead, Auckland, a putative Phytophthora cactorum in a 1972 sample from Glenbervie, Northland, and other Phytophthora spp. in samples collected in 1972, 1986, 1994 and 1996. Phytophthora pluvialis was not detected in any of the samples tested. The results of this study indicate that some Phytophthora species have been present in pine foliage since at least the 1970s. The presence of P. kernoviae in pine foliage since 1986 suggests that P. kernoviae may be associated with physiological needle blight, a disorder of P. radiata with a previously unknown cause. [ABSTRACT FROM AUTHOR]

Eucalyptus spp. are undoubtedly one of the most favored plantation trees globally. Accurately identifying Eucalyptus pathogens is therefore crucial for timely disease prevention and control. Recently, symptoms of a leaf blight disease were observed on Eucalyptus trees in plantations at Jhajjar and Karnal in the state of Haryana, northern India. Asexual morphs resembling the features of the Botryosphaeriaceae were consistently isolated from the symptomatic leaves. Morphological features coupled with DNA sequence analysis confirmed a novel species, which is described and illustrated here as Botryosphaeria eucalypti sp. nov. Conidia of the new taxon are longer and wider than those of its phylogenetic neighbors. A distinct phylogenetic position for the new taxon was established through combined analysis of the internal transcribed spacer (ITS), partial translation elongation factor-1α (tef1) and partial β-tubulin (tub2) regions. Recombination analysis provided additional support for the new species hypothesis. The pathogenicity of the novel species was proved on Eucalyptus leaves, and Koch's postulates were fulfilled. The discovery of new Botryosphaeria species is important because it will help in understanding the species diversity, host range, possible threats and disease control in the long run. [Display omitted] • This study describes Botryosphaeria eucalypti sp. nov. affecting Eucalyptus in India. • Morphology and multi-locus phylogeny were employed for identification. • Koch's postulates for the novel taxon as a foliar pathogen of Eucalyptus were fulfilled. • Future research on the species diversity of Botryosphaeriaceae is imperative. [ABSTRACT FROM AUTHOR]

Abstract Background Plants are capable of building up beneficial rhizosphere communities as is evidenced by disease-suppressive soils. However, it is not known how and why soil bacterial communities are impacted by plant exposure to foliar pathogens and if such responses might improve plant performance in the presence of the pathogen. Here, we conditioned soil by growing multiple generations (five) of Arabidopsis thaliana inoculated aboveground with Pseudomonas syringae pv tomato (Pst) in the same soil. We then examined rhizosphere communities and plant performance in a subsequent generation (sixth) grown in pathogen-conditioned versus control-conditioned soil. Moreover, we assessed the role of altered root exudation profiles in shaping the root microbiome of infected plants. Results Plants grown in conditioned soil showed increased levels of jasmonic acid and improved disease resistance. Illumina Miseq 16S rRNA gene tag sequencing revealed that both rhizosphere and bulk soil bacterial communities were altered by Pst infection. Infected plants exhibited significantly higher exudation of amino acids, nucleotides, and long-chain organic acids (LCOAs) (C > 6) and lower exudation levels for sugars, alcohols, and short-chain organic acids (SCOAs) (C ≤ 6). Interestingly, addition of exogenous amino acids and LCOA also elicited a disease-suppressive response. Conclusion Collectively, our data suggest that plants can recruit beneficial rhizosphere communities via modification of plant exudation patterns in response to exposure to aboveground pathogens to the benefit of subsequent plant generations.

Heterotrimeric G proteins are best known for their role in the transduction of extracellular signals to various downstream effectors. G proteins in higher eukaryotes are intensively studied; however, their roles in foliar pathogens are still elusive. In this study, we cloned the gene Stgg1 encoding G protein γ subunit in Setosphaeria turcica and investigated its function by RNA interference technology. Three independent Stgg1 targeted RNAi mutants R3, R5 and R6 with diverse silencing efficiency were generated. Knock-down of Stgg1 resulted in a significant reduction in mRNA levels of the genes encoding Gα (Stga1, Stga2, Stga3) but not for Gβ (Stgb1). Stgg1 RNAi mutants exhibited significantly elongated hyphal cells with blocked conidium production. In addition, Stgg1 RNAi mutants all appeared in lighter colony colour compatible with inhibited secondary metabolites. Further assays demonstrated that Stgg1 was required for biosynthesis of melanin and HT-toxin activity. Furthermore, down-regulation of Stgg1 largely inhibited the inflection capacity. Thus, we proposed that Stgg1 played crucial roles in conidiation, secondary metabolite production and pathogenicity of S. turcica and is, therefore, an ideal target for drug design against foliar pathogens.

The aggressive Eucalyptus leaf pathogen, Teratosphaeria destructans, causes widespread damage in tropical and subtropical Eucalyptus‐growing regions of Indonesia, China, Thailand, East Timor, Vietnam, Lao, and South Africa. Little is known regarding the origin, pathways of dispersal, or reproductive biology of this pathogen. The aim of this study was to investigate the genetic structure of a global collection of T. destructans isolates. This was achieved by developing and using polymorphic microsatellite markers. Low genotypic diversity and a limited number of private alleles were found in all investigated populations, with the highest maximum diversity of 10.7% in isolates from South Sumatra. This supports the hypothesis that T. destructans was introduced to these regions. High levels of clonality were common in all populations, especially in isolates sampled from the recent disease outbreak in South Africa, which were all identical. The global collection of isolates grouped into three distinct clusters, corresponding largely to their sampled regions. Low levels of genotypic diversity, high levels of clonality, and strong geographic structure suggest independent introductions into all the sampled areas from an unknown source. The results imply that strict biosecurity measures are needed to avoid introductions of additional genotypes in these areas. [ABSTRACT FROM AUTHOR]

Eucalyptus spp. are widely cultivated in India and worldwide for their versatile uses. Thus, sustainable disease management requires critical knowledge of Eucalyptus pathogens. In December 2022, a leaf blight disease was observed in Eucalyptus plantations in Haryana, northern India. Isolations from the symptomatic leaves yielded Botryosphaeria -like fungal isolates. Megablast homology search and phylogenetic analysis utilizing internal transcribed spacer (ITS), partial translation elongation factor-1α (tef1), and partial β-tubulin (tub2) regions of two isolates confirmed the species as Botryosphaeria dothidea. Leaf inoculations with the two B. dothidea isolates produced disease symptoms on Eucalyptus camaldulensis clone 2023. Finally, Koch's postulates were established by re-isolation and re-identification of B. dothedia isolates from the inoculated leaves. To the best of our knowledge, this is the first report of B. dothidea causing foliar disease symptoms on Eucalyptus in India. These findings will contribute to developing disease management strategies for Eucalyptus pathogens in northern India. [Display omitted] • This is the first report of Botryosphaeria dothidea causing leaf blight disease of Eucalyptus in India. • The pathogen was identified based on microscopic features, multilocus DNA sequence analysis, and pathogenicity tests. • This is an important addition to the molecular taxonomy of Botryosphaericeae affecting Eucalyptus in India. • This study warrants screening of Eucalyptus genotypes/clones for the identification of disease-resistant sources. [ABSTRACT FROM AUTHOR]

Phytophthora pluvialis has been shown to be a foliar pathogen of various species of Pinaceae in North America and New Zealand where it has been primarily associated with red needle cast on Pinus radiata and Pseudotsuga menziesii but has also been isolated from Pinus patula and Pinus strobus. To better manage the disease and potential biosecurity implications of germplasm movement, there is much to learn about the epidemiology of the pathogen including where and how it infects hosts, affects productivity and survives during periods that are unfavourable for needle disease. While P. pluvialis is yet to be associated with root disease, most aerially dispersed Phytophthora species are known to infect and survive in roots. This study investigates the potential for P. pluvialis to infect and survive within the root system of P. radiata and its impact on the fine roots of plants up to six weeks post inoculation. Results were comparable to symptoms developed in fine roots infected by P. cinnamomi and demonstrate the potential for P. pluvialis to infect and affect the growth of P. radiata at what are likely to be sub-lethal levels. [ABSTRACT FROM AUTHOR]

Heterotrimeric G proteins are best known for their role in the transduction of extracellular signals to various downstream effectors. G proteins in higher eukaryotes are intensively studied; however, their roles in foliar pathogens are still elusive. In this study, we cloned the gene Stgg1 encoding G protein γ subunit in Setosphaeria turcica and investigated its function by RNA interference technology. Three independent Stgg1 targeted RNAi mutants R3, R5 and R6 with diverse silencing efficiency were generated. Knock-down of Stgg1 resulted in a significant reduction in mRNA levels of the genes encoding Gα (Stga1, Stga2, Stga3) but not for Gβ (Stgb1). Stgg1 RNAi mutants exhibited significantly elongated hyphal cells with blocked conidium production. In addition, Stgg1 RNAi mutants all appeared in lighter colony colour compatible with inhibited secondary metabolites. Further assays demonstrated that Stgg1 was required for biosynthesis of melanin and HT-toxin activity. Furthermore, down-regulation of Stgg1 largely inhibited the inflection capacity. Thus, we proposed that Stgg1 played crucial roles in conidiation, secondary metabolite production and pathogenicity of S. turcica and is, therefore, an ideal target for drug design against foliar pathogens. [ABSTRACT FROM AUTHOR]

ABSTRACT Foliar diseases impose severe restrictions on the persistence and productivity of Medicago sativa, both of which may be increased by developing disease resistant and more competitive genotypes that can improve pasture quality. We found Curvularia geniculata as the principal alfalfa foliar pathogen in the Brazilian state of Rio Grande do Sul (RS). Growth chamber experiments evaluated the resistance of alfalfa genotypes ‘E1C4’, ‘CPPSul’, ‘ABT 805’ and ‘CUF-101’ to C. geniculata as compared the control ‘Crioula’ genotype. These genotypes were also evaluated in field trials at a sea level site in Eldorado do Sul in central RS and at two sites £200 m above sea level, one in Bagé municipality in south west RS and the other at a farm near the town of Alto Feliz in north east RS. Plants were spray-inoculated with 1.6 x 106 ml-1 of C. geniculata spores and visually evaluated for leaf damage 14 days later. The C. geniculata infection rates varied from zero to 100%. Alfalfa persistence and forage mean dry mass (DM) production at the Eldorado site were measured during different seasons from November 2013 to January 2015 by calculating the incidence of invasive plants and morphologically separating leaves from stems and calculating both leaf and stem DM. Data were analysed using mixed statistical models. The best results for persistence and forage DM were shown by the ‘CPPSul’ genotypes (DM = 16,600 kg ha-1) and ‘Crioula’ (DM = 15,750 kg ha-1). These two genotypes will be used for subsequent investigations and selection cycles.

The increasing demand for soilless substrates and rising environmental concerns about the use of non-renewable resources such as peat has led to the search for alternative constituents of growing mixtures for containerized plants. In this report we reviewed the works concerning biochar as constituent of growing media, targeting its influence on plant growth and plant disease. Biochar mostly has positive or neutral influences on plant growth compared with peat media when present in concentrations higher than 25% (v:v). However, studies of biochar influence on plant disease reveals that while lower concentrations (≤1%) of biochar often suppressed several diseases, higher concentrations (≥3%) were mostly ineffective or induced plant disease. For use as horticultural peat replacement, it is recommended that biochar feedstocks and concentrations be standardized and the potential effect of biochar on plant disease be considered, so that growers can rely on consistent and reproducible biochars for desired effects.

The disease complex white pine needle damage (WPND), first reported in 2006, has now escalated to an epidemic state across the northeastern United States. Although this complex is composed of several fungal species, Lecanosticta acicola is considered to be the primary causal agent. Knowledge regarding the epidemiology, specific climatic factors that affect the spread of L. acicola on eastern white pine (Pinus strobus) in natural forest settings, and potential risks repeated defoliation may have on tree health is limited. Therefore, this study examined how climatic variables affect the abundance and distance of spore dispersal of L. acicola and compared litterfall caused by defoliation versus natural needle abscission. Conidia were observed on spore traps from May through August, with a peak in abundance occurring in June, corresponding to the defoliation of second- and third-year foliage measured in litter traps. During peak spore production, relative humidity and the occurrence of rainfall was found to have the greatest influence on spore abundance. Our results will aid managers in determining how far from infected trees natural regeneration will likely be affected and predicting future disease severity based on climatic conditions. [ABSTRACT FROM AUTHOR]

Soft red winter wheat (SRWW) is an important crop in the mid-Atlantic. The use of growth regulators such as trinexapac-ethyl (TE) applied with nitrogen applications at pseudo-stem erection [Zadocks (ZGS) 30] has gained more interest in the region as a means to reduce lodging and potentially improve yields. Fungicide use has also increased, with many growers applying fungicides at ZGS 30 and again at ZGS 37 or ZGS 60. The safety and utility of TE in SRWW production systems, used alone or in combination with fungicides, is unknown. We evaluated the utility and safety of TE, applied alone, tank mixed with a fungicide at ZGS 30, and in combination with a foliar fungicide at ZGS 37 or ZGS 60 for utility and safety in mid-Atlantic SRWW. Three replicated field experiments were conducted over two growing seasons in Delaware, and yield, test weight, and disease severity on the flag leaf, were assessed. No phytotoxicity was noted in any of the TE or TE x fungicide treatments tested. TE applied alone reduced plant height by nearly 7 cm, but the application of fungicide at ZGS 37 or 60 slightly negated this effect. No lodging was observed. The addition of a fungicide at ZGS 30 followed by Prosaro (prothioconazole + tebuconazole) at ZGS 60 resulted in the greatest yields and test weights. All fungicide programs significantly reduced leaf blotch complex on the flag leaves relative to untreated controls; however, no difference was detected between ZGS 37 and ZGS 60 treatments. These results indicate that TE can be used safely in SRWW production when applied alone or when tank mixed with a fungicide; however, the effect on plant height reduction and potential impact on lodging may be reduced in situations where fungicides are used. [ABSTRACT FROM AUTHOR]

The increasing demand for soilless substrates and rising environmental concerns about the use of non-renewable resources such as peat has led to the search for alternative constituents of growing mixtures for containerized plants. In this report we reviewed the works concerning biochar as constituent of growing media, targeting its influence on plant growth and plant disease. Biochar mostly has positive or neutral influences on plant growth compared with peat media when present in concentrations higher than 25% (v:v). However, studies of biochar influence on plant disease reveals that while lower concentrations (≤1%) of biochar often suppressed several diseases, higher concentrations (≥3%) were mostly ineffective or induced plant disease. For use as horticultural peat replacement, it is recommended that biochar feedstocks and concentrations be standardized and the potential effect of biochar on plant disease be considered, so that growers can rely on consistent and reproducible biochars for desired effects. [ABSTRACT FROM PUBLISHER]

Eight experimental trials have been carried out under controlled conditions in order to have a better understanding of the effect of temperature and leaf wetness duration on the incidence and severity of leaf spot caused by Fusarium equiseti on lettuce cv. Elisa and wild rocket cv. Grazia. Lettuce resulted very susceptible to F. equiseti, particularly at temperatures of 25-30 °C, with a higher disease index than 50% and a higher disease severity than 25%. At such temperatures, 1-3 h of leaf wetness were sufficient to cause a high disease incidence and severity, while at least 12 h of leaf wetness were necessary to cause high losses at lower temperatures. Disease incidence and severity were higher on the wild rocket at the highest temperatures (30-35 °C). Only one hour of leaf wetness was sufficient to cause significant levels of disease incidence and severity at the highest temperatures, while longer periods (6-12 h) were necessary to cause significant losses at lower temperatures. The possible causes of the recent spread of F. equiseti in northern Italy on a number of crops as well as the threat represented by such a pathogen are discussed hereafter. [ABSTRACT FROM AUTHOR]

The berries of Highbush Cranberry (Viburnum edule) are an important food source for wildlife and for people in rural areas. In 2012 and 2013, many Highbush Cranberry plants in northwestern British Columbia were unusually severely infected by the rust Puccinia linkii, with telia covering up to half of each leaf. Given the ecological importance of the overwintering berries, I studied the impact of the infection on the production and quality of berries in mixed forests near Smithers, British Columbia. Sites where Highbush Cranberry bushes were infected with the rust had significantly more undeveloped berries. Plants from sites with higher levels of infection produced berries with significantly less sugar. Dead leaf tissue was also significantly more prevalent in infected plants. This study provides evidence that Puccinia linkii may stress plants, leading to reduced quality and quantity of berries, especially if the severity of the infection increases with the increasingly moist springs that are projected for the region. [ABSTRACT FROM AUTHOR]

Phytophthora pluvialis was first described in 2013 and is the causal agent of red needle cast (RNC) in Pinus radiata as well as infection in Douglas fir (Pseudotsuga menziesii). A species-specific PCR is necessary for detection of this pathogen and diagnosis of RNC. To design and validate a species-specific molecular assay for P. pluvialis using isolates from infected pine needles. Species-specific PCR primers were generated from the ras-related GTP-binding protein 1 gene (y pt1) gene sequence, concentrating on DNA regions unique to P. pluvialis , and real-time and quantitative polymerase chain reaction (qPCR) were used to detect P. pluvialis from both artificially inoculated and naturally infected samples. The species-specific PCR assay was generated following P. pluvialis DNA sequence analysis. In vitro tests of the specificity of the probe-based, quantitative, polymerase chain reaction (qPCR) assay showed that no amplification was observed with other Phytophthora species including other closely-related clade 3 species, or with fungal species associated with pine or with pine DNA. The limit of detection of the qPCR assay was 2 pg/μl. When the qPCR assay was used to detect P. pluvialis in artificially-inoculated and naturally infected P. radiata needles, a PCR product was detected in all inoculated samples; the mean concentration ranges of P. pluvialis DNA in the inoculated and naturally infected samples tested were 5.9–124.5 pg/μl and 8.1–340.2 pg/μl, respectively. The assays described herein were used with serological diagnostic strips, providing the ability to identify to species level. The assay described herein detects P. pluvialis with high specificity and sensitivity from a range of DNA samples, including those extracted from infected plant material and serological diagnostic strips. The ability to detect and identify P. pluvialis , from infected tissues directly, provides value and practicality to diagnostics, biosecurity and research. • PCR assays were developed for specific detection of Phytophthora pluvialis. • The assays allow the differentiation of P. pluvialis from other foliar pine needle diseases. • The assays provides an effective tool for identification from diagnostic samples. [ABSTRACT FROM AUTHOR]

Species of eucalypts are commonly cultivated for solid wood and pulp products. The expansion of commercially managed eucalypt plantations has chiefly been driven by their rapid growth and suitability for propagation across a very wide variety of sites and climatic conditions. Infection of foliar fungal pathogens of eucalypts is resulting in increasingly negative impacts on commercial forest industries globally. To assist in evaluating this threat, the present study provides a global perspective on foliar pathogens of eucalypts. We treat 110 different genera including species associated with foliar disease symptoms of these hosts. The vast majority of these fungi have been grown in axenic culture, and subjected to DNA sequence analysis, resolving their phylogeny. During the course of this study several new genera and species were encountered, and these are described. New genera include: Lembosiniella ( L. eucalyptorum on E. dunnii, Australia), Neosonderhenia ( N. eucalypti on E. costata, Australia), Neothyriopsis ( N. sphaerospora on E. camaldulensis , South Africa), Neotrichosphaeria ( N. eucalypticola on E. deglupta , Australia), Nothotrimmatostroma ( N. bifarium on E. dalrympleana , Australia), Nowamyces (incl. Nowamycetaceae fam. nov ., N. globulus on E. globulus , Australia), and Walkaminomyces ( W. medusae on E. alba , Australia). New species include (all from Australia): Disculoides fraxinoides on E. fraxinoides, Elsinoe piperitae on E. piperita, Fusculina regnans on E. regnans, Marthamyces johnstonii on E. dunnii , Neofusicoccum corticosae on E. corticosa , Neotrimmatostroma dalrympleanae on E. dalrympleana, Nowamyces piperitae on E. piperita , Phaeothyriolum dunnii on E. dunnii , Pseudophloeospora eucalyptigena on E. obliqua , Pseudophloeospora jollyi on Eucalyptus sp., Quambalaria tasmaniae on Eucalyptus sp., Q. rugosae on E. rugosa , Sonderhenia radiata on E. radiata , Teratosphaeria pseudonubilosa on E. globulus and Thyrinula dunnii on E. dunnii . A new name is also proposed for Heteroconium eucalypti as Thyrinula uruguayensis on E. dunnii , Uruguay. Although many of these genera and species are commonly associated with disease problems, several appear to be opportunists developing on stressed or dying tissues. For the majority of these fungi, pathogenicity remains to be determined. This represents an important goal for forest pathologists and biologists in the future. Consequently, this study will promote renewed interest in foliar pathogens of eucalypts, leading to investigations that will provide an improved understanding of the biology of these fungi., (© 2019 Westerdijk Fungal Biodiversity Institute. Production and hosting by ELSEVIER B.V.)

The familial placement of four genera, Mycodidymella , Petrakia , Pseudodidymella , and Xenostigmina , was taxonomically revised based on morphological observations and phylogenetic analyses of nuclear rDNA SSU, LSU, tef1 , and rpb2 sequences. ITS sequences were also provided as barcode markers. A total of 130 sequences were newly obtained from 28 isolates which are phylogenetically related to Melanommataceae ( Pleosporales , Dothideomycetes ) and its relatives. Phylogenetic analyses and morphological observation of sexual and asexual morphs led to the conclusion that Melanommataceae should be restricted to its type genus Melanomma , which is characterised by ascomata composed of a well-developed, carbonaceous peridium, and an aposphaeria-like coelomycetous asexual morph. Although Mycodidymella , Petrakia , Pseudodidymella , and Xenostigmina are phylogenetically related to Melanommataceae , these genera are characterised by epiphyllous, lenticular ascomata with well-developed basal stroma in their sexual morphs, and mycopappus-like propagules in their asexual morphs, which are clearly different from those of Melanomma . Pseudodidymellaceae is proposed to accommodate these four genera. Although Mycodidymella and Xenostigmina have been considered synonyms of Petrakia based on sexual morphology, we show that they are distinct genera. Based on morphological observations, these genera in Pseudodidymellaceae are easily distinguished by their synasexual morphs: sigmoid, multi-septate, thin-walled, hyaline conidia ( Mycodidymella ); globose to ovoid, dictyosporus, thick-walled, brown conidia with cellular appendages ( Petrakia ); and clavate with a short rostrum, dictyosporus, thick-walled, brown conidia ( Xenostigmina ). A synasexual morph of Pseudodidymella was not observed. Although Alpinaria was treated as member of Melanommataceae in a previous study, it has hyaline cells at the base of ascomata and pseudopycnidial, confluent conidiomata which is atypical features in Melanommataceae , and is treated as incertae sedis .