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Tea [Camellia sinensis (L.) O. Kuntze] is a major commercially important crop cultivated in both tropical and subtropical areas for the production of the famous beverage "tea". Gray blight is one of the commonly encountered foliar fungal diseases caused by Pestalotiopsis-like taxa. In this study, fungi isolated from symptomatic tea leaves were characterized based on morphological and molecular data. A combined phylogenetic analysis of the internal transcribed spacer 1, 5.8S and the internal transcribed spacer 2 of the ribosomal RNA gene cluster (ITS), β-tubulin (TUB2) and translation elongation factor 1-α (TEF1-α) revealed multiple species of Pseudopestalotiopsis associated with gray blight in Sri Lanka. Among them, the currently known species of Ps. daweiana, Ps. annellata and Ps. chinensis were identified based on the molecular data derived from ex-type isolates. Additionally, four new species of Pseudopestalotiopsis viz Ps. petchii, Ps. ratnapurensis and Ps. rossmaniae and Ps. srilankensis are introduced herein with descriptions and illustrations. Since young leaves and buds of tea plants are used in manufacturing tea, prevention of the occurrence of foliar diseases is crucial to minimize annual yield loss. This study demonstrates the significance of DNA-aided identification and enhances our understanding of the diversity and distribution of fungi associated with tea, which are crucial for implementing effective disease management strategies. [ABSTRACT FROM AUTHOR]

Crop residues colonized saprophytically by necrotrophic plant pathogens are an important primary inoculum source for epidemics of foliar diseases. Residues of crops, weeds, and litter were systematically sampled in a complex crop rotation experiment. Concentrations of DNA of major pathogens of the grown crops, Alternaria solani in potato and Cercospora beticola, Ramularia beticola , and Stemphylium beticola in sugar beet, were quantified in the residues using newly developed qPCR assays. Repeated field trials gave additional insights into the dynamics of A. solani in potato foliage residues for 2 years. The overall results demonstrate that the A. solani and C. beticola colonized crop residues of their host crops initially after harvest at high densities whereas R. beticola and S. beticola were almost absent in the field. Within several months, amounts of available host residues decreased substantially and concentrations of pathogens in the remaining host residues decreased steeply. Alternative substrates, residues of non-host crops including cover crops and weeds, were colonized saprophytically by the necrotrophic pathogens A. solani and C. beticola. It can be concluded that residues of non-hosts can potentially serve as an important bridge for pathogen populations during host-free cropping seasons in crop rotation systems. These findings contribute to the development of rational crop residue management strategies aiming at disease prevention by lowering the inoculum potential in crop rotation systems. [ABSTRACT FROM AUTHOR]

Crop residues colonized saprophytically by necrotrophic plant pathogens are an important primary inoculum source for epidemics of foliar diseases. Residues of crops, weeds, and litter were systematically sampled in a complex crop rotation experiment. Concentrations of DNA of major pathogens of the grown crops, Alternaria solani in potato and Cercospora beticola, Ramularia beticola, and Stemphylium beticola in sugar beet, were quantified in the residues using newly developed qPCR assays. Repeated field trials gave additional insights into the dynamics of A. solani in potato foliage residues for 2 years. The overall results demonstrate that the A. solani and C. beticola colonized crop residues of their host crops initially after harvest at high densities whereas R. beticola and S. beticola were almost absent in the field. Within several months, amounts of available host residues decreased substantially and concentrations of pathogens in the remaining host residues decreased steeply. Alternative substrates, residues of non-host crops including cover crops and weeds, were colonized saprophytically by the necrotrophic pathogens A. solani and C. beticola. It can be concluded that residues of non-hosts can potentially serve as an important bridge for pathogen populations during host-free cropping seasons in crop rotation systems. These findings contribute to the development of rational crop residue management strategies aiming at disease prevention by lowering the inoculum potential in crop rotation systems.

Many studies identify fungal and oomycete phytopathogens as natural enemies capable of influencing plant species composition and promoting diversity in plant communities. However, little is known about how plant‐pathogen interactions vary along regional abiotic gradients or with tree species characteristics, which limits our understanding of the causes of variation in tree species richness.We surveyed 10,756 seedlings from 272 tree species for disease symptoms along a mean annual precipitation gradient in the tropical wet forests of Central Panama for 3 months in the early wet season (June–August) and 2 months in the following dry season (March–April). Over 99% of observed disease symptoms were caused by necrotrophic foliar pathogens, while less than 1% of symptoms were attributed to soilborne pathogens. Foliar disease incidence was inversely related to mean annual precipitation, a pattern which may be due to greater disease susceptibility among dry forest species.Foliar disease incidence increased with conspecific seedling density but did not respond to the proximity of conspecific adults. Although foliar disease incidence decreased as mean annual precipitation increased, the strength of conspecific density‐ or distance‐dependence was independent of the precipitation gradient.Seedlings of common tree species and species dispersed by non‐flying mammals had a higher risk of foliar pathogen incidence. Increased disease in common species may help reduce their dominance.Synthesis. The increases in foliar pathogen incidence with conspecific seedling density, species abundance, and dispersal mechanism indicate that foliar disease incidence is non‐random and may contribute to the regulation of tropical plant communities and species coexistence. Furthermore, the relationships between foliar disease incidence, dispersal mechanism and precipitation suggest plant‐pathogen interactions could shift as a response to climate change and disruption of the disperser community. [ABSTRACT FROM AUTHOR]

Abstract Background Date palm ((Phoenix doctylifera L.) suffers from several fungal diseases. The endophytic microorganisms present in higher plants generally offer protection to their host plants against invading phytopathogenic fungi and bacteria. In the present study, endophytic bacteria associated with date palm leaves were isolated and their in vitro antagonistic potential against fungal pathogens causing leaf spots in date palm was demonstrated. Results Endophytic bacteria were isolated from date palm leaves of 3 different cultivars viz., Nighal, Khalas and Khinaizi and evaluated for their inhibitory activity against leaf spot pathogens of date palm viz., Fusarium solani, Alternaria sp., Nigrospora sp., Thieloviopsis sp., Curvularia subpapendrofii and Tilletiopsis minor using an in vitro dual culture assay. Of the 24 endophytic bacterial strains tested, the endophytes designated B1, B7, B8 and B9 obtained from cv. Nighal showed inhibitory activities (more than 55% mycelial growth inhibition) against F. solani and Alternaria sp. None of the bacterial endophytes inhibited the growth of other fungal pathogens tested. These antagonistic bacterial strains were identified as Pantoea septica on the basis of 16S rRNA gene sequence analysis. The hyphae of F. solani and Alternaria sp. exhibited morphological abnormalities such as shrinkage and disintegration when grown in the presence of antagonistic bacterial endophytes. The cell-free culture filtrates of the bacterial endophytes caused inhibition of mycelial growth and induced leakage of electrolytes from the mycelia of F. solani and Alternaria sp. This is the first study that describes inhibition of the date palm pathogens F. solani and Alternaria sp. by P. septica. Conclusion Endophytic Pantoea septica strains isolated from date palm leaves inhibited the mycelial growth of F. solani and Alternaria sp. and induced morphological changes in their mycelia. The culture filtrates of these bacterial strains also inhibited the mycelial growth and caused leakage of electrolytes from the mycelia of F. solani and Alternaria sp. These promising bacterial strains can be exploited as biocontrol agents to control F. solani and Alternaria sp.-induced leaf spot diseases of date palm.

Fungal diseases are a serious threat to Eucalyptus spp., which are cultivated worldwide for pulp and paper. Robust and timely detection of Eucalyptus pathogens is thus a crucial step in disease prevention and control. In 2022 , leaf spots were observed on Eucalyptus trees in Karnal, northern India. Fungal isolates displaying morphological characteristics similar to Neofusicoccum mangiferae were consistently recovered from the infected leaves. The morphological identification was validated by phylogenetic analysis employing internal transcribed spacer (ITS), partial translation elongation factor-1α (tef1) and partial β-tubulin (tub2) regions. Finally, Koch's postulates for N. mangiferae as a foliar pathogen of Eucalyptus were fulfilled. This is the first confirmed report of N. mangiferae affecting Eucalyptus trees in India. [Display omitted] • This study first time reports Neofusicoccum mangiferae as a foliar pathogen of Eucalyptus in India. • The pathogen was identified based on microscopic features, multilocus phylogenetic analysis and pathogenicity tests. • This is a new taxonomic addition to the diversity of Botryosphaeriaceae affecting Eucalyptus in India. • This study provides future directions to decipher the diversity of Neofusicoccum spp., their host range and testing of Eucalyptus germplasm for disease-resistance. [ABSTRACT FROM AUTHOR]

Bacterial speck caused by Pseudomonas syringae pv. tomato is a serious foliar disease on tomato. However, it is still unknown how organic fertilizers application mediates plant defense against foliar pathogens by altering the composition of the soil microbial community. We conducted a 2-cycle pot experiment involving chemical and organic fertilizers and tracked tomato foliar pathogen incidence. Using microbiome sequencing, we then compared the differences in bulk and rhizosphere microbial communities. The results showed that, compared with soils amended with chemical fertilizer, soils amended with organic fertilizer gradually and significantly presented a reduction in tomato foliar disease, and the bacterial richness and diversity significantly increased. Moreover, the bacterial and fungal compositions of the bulk soil and rhizosphere soil of the organic fertilizer and chemical fertilizer treatments were different from each other. More importantly, the abundance of some potentially beneficial bacteria, such as Luteolibacter , Glycomyces , Flavobacterium , and Flavihumibacter , increased in the organic fertilizer-amended soil, and these genera were significantly negatively correlated with the incidence of tomato foliar disease. These results suggest that organic fertilizers can alter the taxonomy of the soil microbiome and that some specific beneficial microbial communities may play an important role in reducing the infection of foliar pathogens by inducing plant resistance. [ABSTRACT FROM AUTHOR]

Bacterial speck caused by Pseudomonas syringae pv. tomato is a serious foliar disease on tomato. However, it is still unknown how organic fertilizers application mediates plant defense against foliar pathogens by altering the composition of the soil microbial community. We conducted a 2-cycle pot experiment involving chemical and organic fertilizers and tracked tomato foliar pathogen incidence. Using microbiome sequencing, we then compared the differences in bulk and rhizosphere microbial communities. The results showed that, compared with soils amended with chemical fertilizer, soils amended with organic fertilizer gradually and significantly presented a reduction in tomato foliar disease, and the bacterial richness and diversity significantly increased. Moreover, the bacterial and fungal compositions of the bulk soil and rhizosphere soil of the organic fertilizer and chemical fertilizer treatments were different from each other. More importantly, the abundance of some potentially beneficial bacteria, such as Luteolibacter, Glycomyces, Flavobacterium, and Flavihumibacter, increased in the organic fertilizer-amended soil, and these genera were significantly negatively correlated with the incidence of tomato foliar disease. These results suggest that organic fertilizers can alter the taxonomy of the soil microbiome and that some specific beneficial microbial communities may play an important role in reducing the infection of foliar pathogens by inducing plant resistance.

Recent studies have detected phylogenetic signals in pathogen-host networks for both soil-borne and leaf-infecting fungi, suggesting that pathogenic fungi may track or coevolve with their preferred hosts. However, a phylogenetically concordant relationship between multiple hosts and multiple fungi in has rarely been investigated. Using next-generation high-throughput DNA sequencing techniques, we analyzed fungal taxa associated with diseased leaves, rotten seeds, and infected seedlings of subtropical trees. We compared the topologies of the phylogenetic trees of the soil and foliar fungi based on the internal transcribed spacer (ITS) region with the phylogeny of host tree species based on matK, rbcL, atpB, and 5.8S genes. We identified 37 foliar and 103 soil pathogenic fungi belonging to the Ascomycota and Basidiomycota phyla and detected significantly nonrandom host-fungus combinations, which clustered on both the fungus phylogeny and the host phylogeny. The explicit evidence of congruent phylogenies between tree hosts and their potential fungal pathogens suggests either diffuse coevolution among the plant-fungal interaction networks or that the distribution of fungal species tracked spatially associated hosts with phylogenetically conserved traits and habitat preferences. Phylogenetic conservatism in plant-fungal interactions within a local community promotes host and parasite specificity, which is integral to the important role of fungi in promoting species coexistence and maintaining biodiversity of forest communities.

Background: Date palm ((Phoenix doctylifera L.) suffers from several fungal diseases. The endophytic microorganisms present in higher plants generally offer protection to their host plants against invading phytopathogenic fungi and bacteria. In the present study, endophytic bacteria associated with date palm leaves were isolated and their in vitro antagonistic potential against fungal pathogens causing leaf spots in date palm was demonstrated. Results: Endophytic bacteria were isolated from date palm leaves of 3 different cultivars viz., Nighal, Khalas and Khinaizi and evaluated for their inhibitory activity against leaf spot pathogens of date palm viz., Fusarium solani, Alternaria sp., Nigrospora sp., Thieloviopsis sp., Curvularia subpapendrofii and Tilletiopsis minor using an in vitro dual culture assay. Of the 24 endophytic bacterial strains tested, the endophytes designated B1, B7, B8 and B9 obtained from cv. Nighal showed inhibitory activities (more than 55% mycelial growth inhibition) against F. solani and Alternaria sp. None of the bacterial endophytes inhibited the growth of other fungal pathogens tested. These antagonistic bacterial strains were identified as Pantoea septica on the basis of 16S rRNA gene sequence analysis. The hyphae of F. solani and Alternaria sp. exhibited morphological abnormalities such as shrinkage and disintegration when grown in the presence of antagonistic bacterial endophytes. The cell-free culture filtrates of the bacterial endophytes caused inhibition of mycelial growth and induced leakage of electrolytes from the mycelia of F. solani and Alternaria sp. This is the first study that describes inhibition of the date palm pathogens F. solani and Alternaria sp. by P. septica. Conclusion: Endophytic Pantoea septica strains isolated from date palm leaves inhibited the mycelial growth of F. solani and Alternaria sp. and induced morphological changes in their mycelia. The culture filtrates of these bacterial strains also inhibited the mycelial growth and caused leakage of electrolytes from the mycelia of F. solani and Alternaria sp. These promising bacterial strains can be exploited as biocontrol agents to control F. solani and Alternaria sp.-induced leaf spot diseases of date palm. [ABSTRACT FROM AUTHOR]

Background. The article presents the results of many research’s years on leaf pathogens Syringa josikaea Jacq. and S. vulgaris L. in the urban environment and collections of Siberian arboretums. The biology, morphology and symptoms of 6 phytopathogens are given: Erysiphe syringae Schwein., Heterosporium syringae Oudem., Septoria syringae Sacc. & Speg., Ascochyta syringae Bres., Cladosporium herbarum (Pers.) Link, Alternaria alternata (Fr.) Keissl., Leptoxyphium fumago (Woron.) R. C. Srivast. Materials and methods. Phytopathological studies of plants of Syringa L. were carried out in 5 Siberian cities. Identification of pathogens was carried out by standard methods. Results. In Siberia, differences in the manifestation of symptoms and morphology of individual pathogenic micromycetes were established. It has been proven that the powdery mildew pathogen stably forms a telemorph in Siberia, in contrast to the European part of Russia. The significance of the features of the fungus development cycle in specific conditions is shown for the development of a system of measures to limit its spread and harmfulness. Conclusions. It was found that the formation of pathogenic mycobiota on lilacs in Siberia is carried out in two ways: the transfer of pathogens together with plantsintroducers to new territories and the transition of saprophytic fungi to optional parasitism.

Teratosphaeria foliar pathogens cause leaf and shoot blight on Eucalyptus trees in many parts of the world. Among them, T. destructans is one of the most aggressive pathogens causing defoliation of young Eucalyptus trees in tropic regions. Identification of T. destructans to species level is currently not possible based solely on morphological characteristics or ITS sequence data. The aim of this study was to assess T. destructans microsatellites and a newly developed T. epicoccoides microsatellite as a diagnostic tool to differentiate among T. destructans and several closely related foliar pathogens. Based on the number of markers that amplified, the T. destructans microsatellites allowed for the differentiation of T. destructans, T. epicoccoides,T. eucalypti,T. nubilosa,T. pseudoeucalypti and T. viscidus. These microsatellites provide a rapid and cost‐effective diagnostic tool that will enable the identification of a large number of isolates important in disease surveys and inoculation trials. [ABSTRACT FROM AUTHOR]

Background and Aims Biotic and abiotic stressors can cause different defoliation patterns within trees. Foliar pathogens of conifers commonly prefer older needles and infection with defoliation that progresses from the bottom crown to the top. The functional role of the lower crown of trees is a key question to address the impact of defoliation caused by foliar pathogens. Methods A 2 year artificial defoliation experiment was performed using two genotypes of grafted Pinus radiata to investigate the effects of lower-crown defoliation on carbon (C) assimilation and allocation. Grafts received one of the following treatments in consecutive years: control–control, control–defoliated, defoliated–control and defoliated–defoliated. Results No upregulation of photosynthesis either biochemically or through stomatal control was observed in response to defoliation. The root:shoot ratio and leaf mass were not affected by any treatment, suggesting prioritization of crown regrowth following defoliation. In genotype B, defoliation appeared to impose C shortage and caused reduced above-ground growth and sugar storage in roots, while in genotype A, neither growth nor storage was altered. Root C storage in genotype B decreased only transiently and recovered over the second growing season. Conclusions In genotype A, the contribution of the lower crown to the whole-tree C uptake appears to be negligible, presumably conferring resilience to foliar pathogens affecting the lower crown. Our results suggest that there is no C limitation after lower-crown defoliation in P. radiata grafts. Further, our findings imply genotype-specific defoliation tolerance in P. radiata. [ABSTRACT FROM AUTHOR]

The phylogenetic revision of the genera Petrakia and Seifertia using LSU, ITS, RPB2 and TEF1 sequences and the re-evaluation of their morphological characteristics lead to several reclassifications: The genus Pseudodidymella as well as the genera Mycodidymella and Xenostigmina are synonymized with the genus Petrakia. Based on ITS sequence comparisons, it was previously suspected that the leaf spot pathogen Pseudodidymella fagi, which occurs on the Japanese beech Fagus crenata in Japan, is conspecific to the pathogen attacking the European beech Fagus sylvatica in Switzerland and Germany since 2008. Herein, we show that Japanese and European collections represent separate species and describe the European one as Petrakia liobae new to science. Apart from that, we make the new combinations Petrakia fagi and Petrakia minima. The names Petrakia aesculi and Petrakia aceris are validated. A 60-year-old collection from Wisconsin USA, designated as Petrakia echinata on leaves of silver maple (Acer saccharinum), proved to be another species new to science and is described here as Petrakia greenei. Consequently, there is currently no evidence of the European P. echinata to occur in North America. In contrast, P. echinata was found to infect the North American big leaf maple (Acer macrophyllum) in Europe. Antromycopsis alpina, described in 1914, was rediscovered in the Swiss Alps from dry fruits of Rhododendron ferrugineum. It is combined in Seifertia as S. alpina, based on molecular phylogenetic and morphological analyses. This anamorphic fungus appears to be native to Europe and does not cause a bud disease on Rhododendron in contrast to the closely related S. azaleae. Seifertia shangrilaensis is the third species of this genus that is closely related to Petrakia. Both genera belong to the family Melanommataceae. [ABSTRACT FROM AUTHOR]

Camellia sinensis is one of the major crops grown in Taiwan and has been widely cultivated around the island. Tea leaves are prone to various fungal infections, and leaf spot is considered one of the major diseases in Taiwan tea fields. As part of a survey on fungal species causing leaf spots on tea leaves in Taiwan, 19 fungal strains morphologically similar to the genus Diaporthe were collected. ITS (internal transcribed spacer), tef1-α (translation elongation factor 1-α), tub2 (beta-tubulin), and cal (calmodulin) gene regions were used to construct phylogenetic trees and determine the evolutionary relationships among the collected strains. In total, six Diaporthe species, including one new species, Diaporthe hsinchuensis, were identified as linked with leaf spot of C. sinensis in Taiwan based on both phenotypic characters and phylogeny. These species were further characterized in terms of their pathogenicity, temperature, and pH requirements under laboratory conditions. Diaporthe tulliensis, D. passiflorae, and D. perseae were isolated from C. sinensis for the first time. Furthermore, pathogenicity tests revealed that, with wound inoculation, only D. hongkongensis was pathogenic on tea leaves. This investigation delivers the first assessment of Diaporthe taxa related to leaf spots on tea in Taiwan.

The purpose of this study was to evaluate fire ant venom alkaloids and an alarm pheromone analog against several plant pathogens, including Botrytis cinerea, Fusarium oxysporum, Phytophthora nicotianae, P. cryptogea, Pseudomonas syringae, Phytopythium citrinum, Rhizoctonia solani, Sclerotonia rolfsii, Xanthomonas axonopodis, and X. campestris. All pathogens were tested against red imported fire ant venom alkaloid extract and alarm pheromone compound for growth inhibition in in vitro assay. The venom alkaloid extract inhibited fungal and oomycete pathogens. Neither of the treatments were effective against bacterial pathogens. Three soilborne pathogens, P. nicotianae, R. solani, F. oxysporum, and one foliar pathogen, B. cinerea were selected for further in-vivo assays on impatiens (Impatiens walleriana ‘Super Elfin XP violet’). Total plant and root weight were higher in venom alkaloid treated plants compared to an inoculated control. The venom alkaloid treatment reduced damping-off, root rot severity, and pathogen recovery in soilborne pathogen inoculated plants. Similarly, venom alkaloid reduced Botrytis blight. However, higher venom rates caused foliar phytotoxicity on plants. Therefore, additional work is needed to evaluate rates of venom alkaloids or formulations to eliminate negative impacts on plants. Overall, these results suggest that red imported fire ant venom alkaloids may provide a basis for new products to control soilborne and foliar plant pathogens.

This article presents the results of 15-year observations of alien and native foliar fungal pathogens and woody plants in Siberian arboreta and urban ecosystems and discusses the possibility of using these data to determine how the pathogenic mycobiota of woody species was formed under Siberian conditions. In total, 121 species of pathogenic micromycetes affecting the leaves of woody plants in botanical gardens and city and belonging to 2 divisions, 14 orders, and 46 genera have been revealed. Most of these species belong to the Ascomycota division (86.8%). The Basidiomycota division is represented by fungi from the order Pucciniales. Among all observed pathogens, 21 species belong to powdery mildew fungi, 15 species belong to rust fungi, and 84 species represent anamorphic fungi. A study of 108 woody plant species growing in Siberian cities has revealed 101 species of leaf pathogens, while 158 woody plant species growing in arboreta have been inhabited by 105 pathogen species. All fungal species revealed during this study, except for three species (Mycopappus alni, Venturia acerina, and Phyllosticta westendorpii), have been observed in Siberia earlier. However, some fungus–host plant associations are apparently new to science, suggesting that complexes of cryptic species differing in their host range and geographic range may occur. The main sources for tree mycobiota formation in Siberia include the invasion of pathogens together with alien plant species, the transition of pathogens from native to alien plant species, the enhancement of a pathogenicity of saprotrophic fungi, and the expansion of fungi onto new hosts. The majority of pathogens (65−75% of the total number of revealed fungi) locate on native plants. Alien plants are infected mainly by (native) pathogens. Only eight pathogen species have been introduced in Siberia with alien plants; three of them originate from the Far East (Cercospora gotoana, Phyllosticta phellodendricola, and Erysiphe palczewskii), while five are of European origin (Cladosporium syringae, Phyllosticta vincae-minoris, Erysiphe syringae, Erysiphe alphitoides, and Erysiphe berberidis). In Siberia, the lateness of phenological phases of plants originating from mild climatic zones, may be favorable for the development of fungal pathogens, such as Erysiphe alphitoides, causing the powdery mildew of oak trees. [ABSTRACT FROM AUTHOR]

Climate change and the associated increase in atmospheric CO2 levels may affect the severity of plant diseases and threaten future crop yields. Here, we compared responses of the model plant Arabidopsis thaliana to leaf and root pathogens with hemi-biotrophic or necrotrophic infection strategies under pre-industrial, current, and future atmospheric CO2 conditions. Defenses against biotrophs are generally regulated by salicylic acid (SA) signaling, whereas jasmonic acid (JA) signaling controls defenses against necrotrophs. Under the CO2 conditions tested, basal expression of the JA-responsive marker gene PDF1.2 increased at increasing CO2 concentrations. The SA-responsive marker genes ICS1 and FRK1 showed an opposite behavior, being lower expressed under high CO2 and higher expressed under low CO2, respectively. Accordingly, plants showed enhanced resistance to the necrotrophic leaf pathogen Botrytis cinerea under high CO2, while resistance to the hemi-biotrophic leaf pathogen Pseudomonas syringae pv. tomato was reduced. The opposite was true for plants grown under low CO2. Disease severity caused by the soil-borne pathogens Fusarium oxysporum f.sp. raphani and Rhizoctonia solani was similar under all CO2 conditions tested. Collectively, our results stress the notion that atmospheric CO2 impacts the balance between SA- and JA-dependent defenses and concomitant resistance against foliar (hemi)biotrophic and necrotrophic pathogens. The direction of the CO2-mediated effects on SA- and JA-mediated defenses varies between reported studies, suggesting that the defense output is influenced by environmental context. These findings highlight that a wider dynamic range of climate change parameters should be studied simultaneously to harness plant traits for the development of future climate-resilient crops. [ABSTRACT FROM AUTHOR]

The foliar fungal pathogens associated with the disease complex known as White Pine Needle Damage (WPND) are causing widespread defoliation of eastern white pine ( Pinus strobus L.) in the northeastern United States and Canada. Presently, there are no specific management recommendations for addressing declining stand health relating to WPND induced defoliations. This study aims to test the effects of thinning at two different residual stocking densities (14 and 25 m 2  ha −1 ) on mitigating the negative impacts of WPND within infected stands. To quantify the impacts of WPND on individual tree health, we generated a composite health index score using response variables measured in the field and weighted according to their association with observations of WPND severity. Post-thinning changes in disease severity were used to evaluate the effectiveness of stand thinning to reduce pathogen pressure and promote overall tree vigor. Results show that thinning had a rapid positive effect on overall tree health, with no significant difference between thinning treatment levels in the first two years following tree removal. Severity of WPND was reduced by 35% in low-density residual thinnings in the second year of the study. Our findings suggest that thinning as a silvicultural tool to reduce stocking densities within infected stands can effectively promote overall tree health and maintaining proper stocking densities is recommended for stands at risk of infection. [ABSTRACT FROM AUTHOR]

The fungal pathogens Cochliobolus australiensis and Pyricularia grisea have recently been isolated from diseased leaves of buffelgrass (Cenchrus ciliaris) in its North American range, and their ability to produce phytotoxic metabolites that could potentially be used as natural herbicides against this invasive weed was investigated. Fourteen secondary metabolites obtained from in vitro cultures of these two pathogens were tested by leaf puncture assay on the host plant at different concentrations. Radicinin and (10S, 11S)-epi-pyriculol proved to be the most promising compounds. Thus, their phytotoxic activity was also evaluated on non-host indigenous plants. Radicinin demonstrated high target-specific toxicity on buffelgrass, low toxicity to native plants, and no teratogenic, sub-lethal, or lethal effects on zebrafish (Brachydanio rerio) embryos. It is now under consideration for the development of a target-specific bioherbicide to be used against buffelgrass in natural systems where synthetic herbicides cause excessive damage to native plants.

Dieback of young Abies alba seedlings was identified as an important limitation for natural regeneration of this species in the mountain regions of Central Europe. Approximately 2–4 weeks after emergence, during cool and wet weather, necrotic spots developed on seedling cotyledons. Later they expanded and merged to finally cover all above-ground tissues. Symptomatic seedlings of A . alba were sampled at 16 stands, and fungi were isolated from the cotyledons, stems, and roots. Morphological and molecular methods based on ITS rDNA sequencing were then used for isolate identification. In total, 105 distinct taxa were identified, with Ascomycota dominating, representing 97.4% of the isolates. The most frequently isolated taxa were Allantophomopsis lycopodina , Gyoerffyella rotula , Leptosphaeria sp., Phialocephala fortinii , Pseudaegerita sp., Scirrhia aspidiorum , Sydowia polyspora , Peyronellaea sp., Phomopsis sp., and Varicosporium elodeae . The frequency of colonization by individual fungal species differed among the three plant organs and among forest types. In symptomatic cotyledons, the dominant species were G . rotula , S . polyspora , and Pseudaegerita sp. whose pathogenicity, together with that of Gyoerffyella sp., V . elodeae , and Hormonema carpetanum , was tested on young A . alba seedlings. Only G . rotula and Gyoerffyella sp. caused serious dieback of above-ground seedling tissues and necrotic symptoms on cotyledons. This study is one of the few comprehensive reports showing that aquatic hyphomycetes commonly occur in forests beyond their preferred habitat. [ABSTRACT FROM AUTHOR]

Abstract: A detached leaf bioassay was used to determine the influence of several film forming polymers and a conventional triazole fungicide on apple scab (Venturia inaequalis (Cooke) G. Wint.) development under laboratory in vitro conditions, supported by two field trials using established apple cv. Golden Delicious to further assess the efficacy of foliar applied film forming polymers as scab protectant compounds. All film forming polymers used in this investigation (Bond, Designer, Nu-Film P, Spray Gard, Moisturin, Companion PCT12) inhibited germination of conidia, subsequent formation of appressoria and reduced leaf scab severity using a detached leaf bioassay. Regardless of treatment, there were no obvious trends in the percentage of conidia with one to four appressoria 5 days after inoculation. The synthetic fungicide penconazole resulted in the greatest levels of germination inhibition, appressorium development and least leaf scab severity. Under field conditions, scab severity on leaves and fruit of apple cv. Golden Delicious treated with a film forming polymer (Bond, Spray Gard, Moisturin) was less than on untreated controls. However, greatest protection in both field trials was provided by the synthetic fungicide penconazole. Higher chlorophyll fluorescence Fv/Fm emissions in polymer and penconazole treated trees indicated less damage to the leaf photosynthetic system as a result of fungal invasion. In addition, higher SPAD values as measures of leaf chlorophyll content were recorded in polymer and penconazole treated trees. Application of a film forming polymer or penconazole resulted in a higher apple yield per tree at harvest in both the 2005 and 2006 field trials compared to untreated controls. Results suggest application of an appropriate film forming polymer may provide a useful addition to existing methods of apple scab management. [Copyright &y& Elsevier]

The investigations were based on two surveys of wheat and one survey of rice. Alternaria alternata, Curvularia lunata, Helminthosporium tetramera and Bipolaris sorokiniana were isolated and identified from foliage and soil of both wheat and rice crops and their aggressiveness was studied by aggressiveness analysis screened out into different aggressiveness classes. The aggressiveness of isolated fungi was studied on wheat varieties (Inqalab-91 and Chakwal-86) and rice varieties (Basmati-385 and IRRI-6) under controlled conditions. In the foliar aggressiveness test of A. alternata, the overall number of aggressive isolates was higher on wheat varieties than rice. Bipolaris sorokiniana isolates showed foliar blight symptoms on wheat but not on rice varieties. In C. lunata, the overall number of aggressive isolates was higher on wheat. In the foliar aggressiveness test of H. tetramera, the number of non-aggressive isolates was almost the same on wheat and rice varieties. In the present study it became clear that A. alternate, B. sorokiniana, C. lunata and H. tetramera are common foliar pathogens in rice and wheat crops and can cause soil-borne and foliar diseases. [ABSTRACT FROM AUTHOR]

The article examines the effects of film-forming polymers including Bond, Designer, Spray Gard and Nu-Film-P in controlling guignardia leaf blotch and powdery mildew on horse chesnut (Aesculus hippocastanum L.). The study was conducted using a field experiment. The results show that application of a suitable film-forming polymer may furnish a useful addition to subsisting methods of plant disease control.

Ten microorganisms of the epiphytic microflora of wheat leaves in Buenos Aires Province, Argentina, were evaluated under greenhouse conditions as potential biocontrol agents of the pathogens Alternaria triticimaculans, Bipolaris sorokiniana, Drechslera tritici-repentis and Septoria tritici in two application sequences (prior to or together with the pathogens). The antagonists significantly reduced the expression of the diseases on wheat plants compared with control plants not inoculated with the antagonists. Maximum percentage of reduction of the necrotic lesion area (NLA) (40–55%) of S. tritici resulted when Cryptococcus sp., Rhodotorula rubra and Penicillium lilacinwn were sprayed on leaves prior to inoculations with the pathogen. Bacillus sp., Cryptococcus sp., Fusarium moniliforme var. anthophylium, P. lilacinum and R. rubra reduced significantly (34–52%) the NLA of B. sorokiniana in both of the application sequences. The best antagonistic effect against A. triticimaculans was shown by Aspergillus niger, Bacillus sp., Chaetomium globosum, F. moniliforme var. anthophylium and Nigrospora sphaerica, with a NLA reduction from 21% to 35% in the co-inoculation or in the sequential application. All microorganisms except N. sphaerica performed better than the control against D. tritici-repentis. The area under disease progress curve (AUDPC) of the pathogens appeared to progress similarly, but at lower values, in treated plants than in untreated controls. The two yeasts and the bacteria decreased AUDPC to 50–55% of S. tritici and B. sorokiniana compared with the control in both application sequences, whereas the maximum efficacy against A. triticimaculans was reached by N. sphaerica and A. niger for the sequential application and by F. moniliforme var. anthophylium for the co-inoculation. If the parasitism occurs also in nature, application of antagonists for biological control might provide the opportunity to compete with the pathogens and regulate their colonization in wheat leaves. [ABSTRACT FROM AUTHOR]

Camellia sinensis is one of the major crops grown in Taiwan and has been widely cultivated around the island. Tea leaves are prone to various fungal infections, and leaf spot is considered one of the major diseases in Taiwan tea fields. As part of a survey on fungal species causing leaf spots on tea leaves in Taiwan, 19 fungal strains morphologically similar to the genus Diaporthe were collected. ITS (internal transcribed spacer), tef1-α (translation elongation factor 1-α), tub2 (beta-tubulin), and cal (calmodulin) gene regions were used to construct phylogenetic trees and determine the evolutionary relationships among the collected strains. In total, six Diaporthe species, including one new species, Diaporthe hsinchuensis, were identified as linked with leaf spot of C. sinensis in Taiwan based on both phenotypic characters and phylogeny. These species were further characterized in terms of their pathogenicity, temperature, and pH requirements under laboratory conditions. Diaporthe tulliensis, D. passiflorae, and D. perseae were isolated from C. sinensis for the first time. Furthermore, pathogenicity tests revealed that, with wound inoculation, only D. hongkongensis was pathogenic on tea leaves. This investigation delivers the first assessment of Diaporthe taxa related to leaf spots on tea in Taiwan. [ABSTRACT FROM AUTHOR]

Foliar applications of alcohols have been reported to have remarkable benefits on yields of several crops. The toxifying characteristics of alcohols for many microorganisms may also potentially be of use in crop protection. Greenhouse and field experiments were conducted to determine if foliar-applied ethanol was elective against Septoria nodorum, the causal agent of leaf and glume blotch in spring wheat (Triticum aestivum). Ethanol (30 % and 60 %) decreased the disease symptoms on the leaves of wheat significantly when applied one day after the inoeulation, although reductions in disease severity were still observed until 4 days after the inoculation. In contrast, ethanol treatments before inoculation did not affect, or occasionally even enhanced, the disease development. On agar plate assay, the average sensitivity of S. nodorum on ethanol was high, as no reduction in its growth was observed at incubation times less than 10 or 20 min in 60% or 30% ethanol. respectively. Ethanol treatments did not damage the treated leaves, but a slight reduction in the leaf chlorophyll content as measured by SPAD values was observed. Ethanol application whether alone or with inoculation did not increase wheat kernel weights. [ABSTRACT FROM AUTHOR]

The purpose of this study was to evaluate fire ant venom alkaloids and an alarm pheromone analog against several plant pathogens, including Botrytis cinerea, Fusarium oxysporum, Phytophthora nicotianae, P. cryptogea, Pseudomonas syringae, Phytopythium citrinum, Rhizoctonia solani, Sclerotonia rolfsii, Xanthomonas axonopodis, and X. campestris. All pathogens were tested against red imported fire ant venom alkaloid extract and alarm pheromone compound for growth inhibition in in vitro assay. The venom alkaloid extract inhibited fungal and oomycete pathogens. Neither of the treatments were effective against bacterial pathogens. Three soilborne pathogens, P. nicotianae, R. solani, F. oxysporum, and one foliar pathogen, B. cinerea were selected for further in-vivo assays on impatiens (Impatiens walleriana 'Super Elfin XP violet'). Total plant and root weight were higher in venom alkaloid treated plants compared to an inoculated control. The venom alkaloid treatment reduced damping-off, root rot severity, and pathogen recovery in soilborne pathogen inoculated plants. Similarly, venom alkaloid reduced Botrytis blight. However, higher venom rates caused foliar phytotoxicity on plants. Therefore, additional work is needed to evaluate rates of venom alkaloids or formulations to eliminate negative impacts on plants. Overall, these results suggest that red imported fire ant venom alkaloids may provide a basis for new products to control soilborne and foliar plant pathogens. [ABSTRACT FROM AUTHOR]

The fungal pathogens Cochliobolus australiensis and Pyricularia grisea have recently been isolated from diseased leaves of buffelgrass (Cenchrus ciliaris) in its North American range, and their ability to produce phytotoxic metabolites that could potentially be used as natural herbicides against this invasive weed was investigated. Fourteen secondary metabolites obtained from in vitro cultures of these two pathogens were tested by leaf puncture assay on the host plant at different concentrations. Radicinin and (10S, 11S)-epi-pyriculol proved to be the most promising compounds. Thus, their phytotoxic activity was also evaluated on non-host indigenous plants. Radicinin demonstrated high target-specific toxicity on buffelgrass, low toxicity to native plants, and no teratogenic, sub-lethal, or lethal effects on zebrafish (Brachydanio rerio) embryos. It is now under consideration for the development of a target-specific bioherbicide to be used against buffelgrass in natural systems where synthetic herbicides cause excessive damage to native plants. [ABSTRACT FROM AUTHOR]

Phyllosticta is a geographically widespread genus of plant pathogenic fungi with a diverse host range. This study redefines Phyllosticta, and shows that it clusters sister to the Botryosphaeriaceae (Botryosphaeriales, Dothideomycetes), for which the older family name Phyllostictaceae is resurrected. In moving to a unit nomenclature for fungi, the generic name Phyllosticta was chosen over Guignardia in previous studies, an approach that we support here. We use a multigene DNA dataset of the ITS, LSU, ACT, TEF and GPDH gene regions to investigate 129 isolates of Phyllosticta, representing about 170 species names, many of which are shown to be synonyms of the ubiquitous endophyte P. capitalensis. Based on the data generated here, 12 new species are introduced, while epitype and neotype specimens are designated for a further seven species. One species of interest is P. citrimaxima associated with tan spot of Citrus maxima fruit in Thailand, which adds a fifth species to the citrus black spot complex. Previous morphological studies lumped many taxa under single names that represent complexes. In spite of this Phyllosticta is a species-rich genus, and many of these taxa need to be recollected in order to resolve their phylogeny and taxonomy., Taxonomic Novelties: New species - Phyllosticta abieticola Wikee & Crous, P. aloeicola Wikee & Crous, P. citrimaxima Wikee, Crous, K.D. Hyde & McKenzie, P. leucothoicola Wikee, Motohashi & Crous, P. mangifera-indica Wikee, Crous, K.D. Hyde & McKenzie, P. neopyrolae Wikee, Motohashi, Crous, K.D. Hyde & McKenzie, P. pachysandricola Wikee, Motohashi & Crous, P. paxistimae Wikee & Crous, P. podocarpicola Wikee, Crous, K.D. Hyde & McKenzie, P. rhaphiolepidis Wikee, C. Nakash. & Crous, P. rubra Wikee & Crous, P. vacciniicola Wikee, Crous, K.D. Hyde & McKenzie; New combinations - P. foliorum (Sacc.) Wikee & Crous, P. philoprina (Berk. & M.A. Curtis) Wikee & Crous; Epitypifications (basionyms) - P. concentrica Sacc., P. cussoniae Cejp, P. owaniana G. Winter; Neotypifications (basionyms) - Phyllosticta cordylinophila P.A. Young, Physalospora gregaria var. foliorum Sacc., Sphaeropsis hypoglossi Mont., Sphaeropsis minima Berk. & M.A. Curtis.