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Fungal Biology Apr 2022Alternaria rot has been recently described as an emerging fungal disease of citrus causing significant damage in California groves. A survey was conducted to determine...
Alternaria rot has been recently described as an emerging fungal disease of citrus causing significant damage in California groves. A survey was conducted to determine latent infections on fruits, twigs, and leaves and investigate their seasonal patterns during 2019 and 2020. On fruits, latent infections were more associated with the stem end than with the stylar end, except during spring when a significantly high percentage of flowers (86%) had latent infections. Latent infections on twigs varied markedly between years (28% in 2019 and 9.5% in 2020), while Alternaria spp. were also recovered from citrus leaves. Alternaria isolates collected during the survey were identified based on multigene sequence analysis, confirming that Alternaria alternata and Alternaria arborescens are the two species associated with infections of citrus fruits. Of the 23 isolates, 19 were identified as A. alternata and demonstrated the dominance of this species over A. arborescens. Isolates representing populations of these two species were selected as representative isolates for physiological and morphological studies. A. alternata and A. arborescens showed similar conidial dimensions but differed in the number of conidia produced. Growth rates demonstrated that A. alternata grows faster than A. arborescens at all the temperatures evaluated, except at 25 and 35 °C. The growth patterns were similar for both species. The sporulation rate of the Alternaria isolates was influenced differently by temperature. This parameter also influenced conidial germination and appressorium formation, and no significant differences were observed between Alternaria species. Pathogenicity and aggressiveness tests on detached fruit demonstrated the ability of A. alternata and A. arborescens to cause internal lesions and produce fruit drop in the orchards with no quantitative differences between them (disease severity indexes of 58 and 68%, respectively). The fungicide sensitivity tests showed that DMI fungicides are the most effective fungicides in reducing mycelial growth. The SDHI fungicides had intermediate activity against the mycelial growth but also suppressed spore germination. The spore germination assay suggested that some of the isolates included in this study might have some level of resistance to QoI and SDHI fungicides. The findings of this study provide new information about the pathogens associated with the excessive fruit drop recently observed in some California citrus groves.
Topics: Alternaria; Citrus; Fruit; Fungicides, Industrial; Spores, Fungal; Virulence
PubMed: 35314059
DOI: 10.1016/j.funbio.2022.02.003 -
PloS One 2023Early blight, caused by the necrotrophic fungus Alternaria solani, is an important foliar disease that causes major yield losses of potato. Effector proteins secreted by...
Early blight, caused by the necrotrophic fungus Alternaria solani, is an important foliar disease that causes major yield losses of potato. Effector proteins secreted by pathogens to host cells can inhibit host immune response to pathogens. Currently, the function of effector proteins secreted by A. solani during infection is poorly understood. In this study, we identified and characterized a novel candidate effector protein, AsCEP50. AsCEP50 is a secreted protein that is highly expressed throughout the infection stages of A. solani. Agrobacterium tumefaciens-mediated transient expression in Nicotiana benthamiana and tomato demonstrated that AsCEP50 is located on the plasma membrane of N. benthamiana and regulates senescence-related genes, resulting in the chlorosis of N. benthamiana and tomato leaves. Δ50 mutants were unaffected in vegetative growth, spore formation and mycelium morphology. However, the deletion of AsCEP50 significantly reduced virulence, melanin production and penetration of A. solani. These results strongly supported that AsCEP50 is an important pathogenic factor at the infection stage and contributes to the virulence of Alternaria solani.
Topics: Alternaria; Biological Transport; Melanins; Agrobacterium tumefaciens
PubMed: 36877688
DOI: 10.1371/journal.pone.0281530 -
Genes May 2023Alternaria black spot disease on pecan is caused by the opportunistic pathogen and poses a serious threat to the local South African and global pecan industry. Several...
Alternaria black spot disease on pecan is caused by the opportunistic pathogen and poses a serious threat to the local South African and global pecan industry. Several diagnostic molecular marker applications have been established and used in the screening of various fungal diseases worldwide. The present study investigated the potential for polymorphism within samples of isolates obtained from eight different geographical locations in South Africa. Pecan () leaves, shoots, and nuts-in-shuck with Alternaria black spot disease were sampled, and 222 isolates were retrieved. For rapid screening to identify Alternaria black spot pathogens, polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis of the Alternaria major allergen () gene region was used, followed by the digestion of the amplicons with III and I endonucleases. The assay resulted in five (III) and two (I) band patterns. Unique banding patterns from the two endonucleases showed the best profile and isolates were grouped into six clusters using a UPGMA (unweighted pair group method with arithmetic averages) distance matrix (Euclidean) dendrogram method on R-Studio. The analysis confirmed that the genetic diversity of does not depend on host tissues or the pecan cultivation region. The grouping of selected isolates was confirmed by DNA sequence analysis. The phylogeny corroborated no speciation within the dendrogram groups and showed 98-100% bootstrap similarity. This study reports the first documented rapid and reliable technique for routine screening identification of pathogens causing Alternaria black spot in South Africa.
Topics: Alternaria; Carya; Polymorphism, Restriction Fragment Length; Haplotypes; Polymerase Chain Reaction
PubMed: 37239475
DOI: 10.3390/genes14051115 -
Plant Disease Jul 2022Brown leaf spot of potato is caused by a number of small-spored spp. , , and have been reported with increasing frequency in commercial potato fields. Potato cultivars...
Brown leaf spot of potato is caused by a number of small-spored spp. , , and have been reported with increasing frequency in commercial potato fields. Potato cultivars with resistance to small-spored spp. have yet to be developed; therefore, the application of foliar fungicides is a primary management strategy. Greenhouse inoculation assays demonstrated that isolates of these three small-spored spp. were pathogenic. Significant differences in aggressiveness were observed across isolates; however, there was no trend in aggressiveness based on species. Significant fungicide by isolate interactions in in vitro fungicide sensitivity and significant differences between baseline and nonbaseline isolates were observed in all three small-spored spp. The ranges of in vitro sensitivity of baseline isolates to boscalid (EC <0.010 to 0.89 µg/ml), fluopyram (<0.010 to 1.14 µg/ml) and solatenol (<0.010 to 1.14 µg/ml) were relatively wide when compared with adepidyn (<0.010 to 0.023 µg/ml). The baseline sensitivities of and isolates to all four fungicides were <0.065 µg/ml. Between 10 and 21% of nonbaseline isolates fell outside the baseline range established for the four succinate dehydrogenase inhibitor (SDHI) fungicides evaluated. In , 10 to 80% of nonbaseline isolates had higher sensitivities than the baseline. isolates fell outside the baseline for boscalid (55%), fluopyram (14%), and solatenol (14%), but none fell outside the baseline range for adepidyn. Evaluations of in vivo fungicide efficacy demonstrated that most isolates were equally controlled by the four SDHI fungicides. However, reduced boscalid efficacy was observed for four isolates (two each of and ) and reduced fluopyram control was observed in one isolate. Results of these studies demonstrate that isolates of all three species could be contributing to the brown leaf spot pathogen complex and that monitoring both species diversity and fungicide sensitivity could be advantageous for the management of brown leaf spot in potatoes with SDHI fungicides.
Topics: Alternaria; Drug Resistance, Fungal; Fungicides, Industrial; Solanum tuberosum; Succinate Dehydrogenase; Succinic Acid
PubMed: 34978878
DOI: 10.1094/PDIS-10-21-2292-RE -
Toxins Jun 2023Alternariol is a metabolite produced by fungus that can contaminate a variety of food and feed materials. The objective of the present paper was to provide a prediction...
Alternariol is a metabolite produced by fungus that can contaminate a variety of food and feed materials. The objective of the present paper was to provide a prediction of Phase I and II metabolites of alternariol and a detailed ADME/Tox profile for alternariol and its metabolites using an in silico working model based on the MetaTox, SwissADME, pKCMS, and PASS online computational programs. A number of 12 metabolites were identified as corresponding to the metabolomic profile of alternariol. ADME profile for AOH and predicted metabolites indicated a moderate or high intestinal absorption probability but a low probability to penetrate the blood-brain barrier. In addition to cytotoxic, mutagenic, carcinogenic, and endocrine disruptor effects, the computational model has predicted other toxicological endpoints for the analyzed compounds, such as vascular toxicity, haemato-toxicity, diarrhea, and nephrotoxicity. AOH and its metabolites have been predicted to act as a substrate for different isoforms of phase I and II drug-metabolizing enzymes and to interact with the response to oxidative stress. In conclusion, in silico methods can represent a viable alternative to in vitro and in vivo tests for the prediction of mycotoxins metabolism and toxicity.
Topics: Lactones; Oxidative Stress; Metabolomics; Alternaria; Mycotoxins
PubMed: 37505690
DOI: 10.3390/toxins15070421 -
Isolation and identification of Tussilago farfara leaf spot caused by Alternaria alternata in China.Microbial Pathogenesis Nov 2022Tussilago farfara is of vital medical value. A new leaf spot disease was observed on T. farfara leaves, in Dingxi, Gansu Province, China, in October 2019. In order to...
Tussilago farfara is of vital medical value. A new leaf spot disease was observed on T. farfara leaves, in Dingxi, Gansu Province, China, in October 2019. In order to research the pathogen, the diseased samples were collected for isolation and identification. The isolate KD3 was verified by pathogenicity test, as the pathogen causing the T. farfara leaf spot disease. Its morphological characteristics were consistent with Alternaria alternata, the colony color gray-green with concentric rings, conidia fusiform and pear-shaped, brown, with 1-7 septa and 0-3 longitudinal septa, conidia size (19. 62-44.49) μm × (6.97-10.53) μm, beak length (1.35-10.03) μm × (1.01-3.63) μm, and the spore phenotype was a dwarf tree-like chain of short conidia. Multilocus sequences analysis manifested that the internal transcribed spacer (ITS), Alternaria major allergen (Alta1), and Calcium barine (CAL) sequences of strain KD3 were most closely to A. alternata (A23), with the homology of 99.47%, 99.56% and 98.28%, respectively. Based on morphological and molecular characteristics, strain KD3 was identified as A. alternata. OA was the optimal medium for its growth and PCA medium was the optimal for sporulation. This is the first report of A. alternata causing T. farfara leaf spots in China.
Topics: Alternaria; Tussilago; Calcium; China; Allergens
PubMed: 36075342
DOI: 10.1016/j.micpath.2022.105750 -
The Science of the Total Environment Dec 2023The study is aimed at determining the potential spatiotemporal risk of the co-occurrence of airborne pollen and fungal spores high concentrations in different...
The study is aimed at determining the potential spatiotemporal risk of the co-occurrence of airborne pollen and fungal spores high concentrations in different bio-climatic zones in Europe. Birch, grass, mugwort, ragweed, olive pollen and Alternaria and Cladosporium fungal spores were investigated at 16 sites in Europe, in 2005-2019. In Central and northern Europe, pollen and fungal spore seasons mainly overlap in June and July, while in South Europe, the highest pollen concentrations occur frequently outside of the spore seasons. In the coldest climate, no allergy thresholds were exceeded simultaneously by two spore or pollen taxa, while in the warmest climate most of the days with at least two pollen taxa exceeding threshold values were observed. The annual air temperature amplitude seems to be the main bioclimatic factor influencing the accumulation of days in which Alternaria and Cladosporium spores simultaneously exceed allergy thresholds. The phenomenon of co-occurrence of airborne allergen concentrations gets increasingly common in Europe and is proposed to be present on other continents, especially in temperate climate.
Topics: Allergens; Spores, Fungal; Pollen; Seasons; Europe; Cladosporium; Alternaria; Hypersensitivity; Air Microbiology
PubMed: 37748608
DOI: 10.1016/j.scitotenv.2023.167285 -
Plant Disease Jul 2023The fungal genus , which causes a variety of crop diseases, is widely distributed in the world. Alternaria leaf blight, caused by , is one of the most common and...
The fungal genus , which causes a variety of crop diseases, is widely distributed in the world. Alternaria leaf blight, caused by , is one of the most common and destructive diseases in carrot. The infection of leads to dramatic decay on both foliage and taproot in severe cases, which results in significant yield losses. In this study, we sequenced and assembled the genome of isolate CALB1, which isolated from the major carrot producing areas of China. A total of 65 contigs were assembled, and the estimated genome size was 34.9 Mb. The draft genome of can be used for comparative genomic analysis of species and provide genetic information for further research on plant-pathogen interactions.
Topics: Alternaria; Daucus carota; Plant Diseases; China
PubMed: 36451305
DOI: 10.1094/PDIS-10-22-2438-A -
Bioorganic Chemistry Nov 2019Seven previously undescribed metabolites, designated as tricycloalternarenes Q-W (1-7), were isolated and identified from the fermented rice substrate of fungus...
Seven previously undescribed metabolites, designated as tricycloalternarenes Q-W (1-7), were isolated and identified from the fermented rice substrate of fungus Alternaria brassicicola. The planar and absolute structures of all new compounds were determined on the basis of extensive NMR spectroscopic data, a modified Mosher's method, X-ray crystallographic analysis, and electronic circular dichroism (ECD) spectral analyses. All the isolates were evaluated for in vitro cytotoxicity against five human tumor MM231, MM468, HeLa, SW1990, and SW480 cell lines, and compounds 1, 2, 5, and 7 showed selective cytotoxicity against certain human tumor cell lines with IC values ranging from 12.83 to 32.87 μM, with no obvious cytotoxicity to the normal LO2 cell.
Topics: Alternaria; Antineoplastic Agents; Cell Survival; Cells, Cultured; Crystallography, X-Ray; Dose-Response Relationship, Drug; Drug Screening Assays, Antitumor; Humans; Models, Molecular; Molecular Structure; Structure-Activity Relationship; Terpenes
PubMed: 31539746
DOI: 10.1016/j.bioorg.2019.103279 -
Microbiological Research Mar 2022The ability to cope with environmental abiotic stress and biotic stress is crucial for the survival of plants and microorganisms, which enable them to occupy multiple...
The ability to cope with environmental abiotic stress and biotic stress is crucial for the survival of plants and microorganisms, which enable them to occupy multiple niches in the environment. Previous studies have shown that transcription factors play crucial roles in regulating various biological processes including multiple stress tolerance and response in eukaryotes. This work identified multiple critical transcription factor genes, metabolic pathways and gene ontology (GO) terms related to abiotic stress response were broadly activated by analyzing the transcriptome of phytopathogenic fungus Alternaria alternata under metal ions stresses, oxidative stress, salt stresses, and host-pathogen interaction. We investigated the biological functions and regulatory roles of the bZIP transcriptional factor (TF) genes in the phytopathogenic fungus A.alternata by analyzing targeted gene disrupted mutants. Morphological analysis provides evidence that the bZIP transcription factors (Gcn4, MeaB, Atf1, the ER stress regulator Hac1, and the all development altered-1 gene Ada1) are required for morphogenesis as the colony morphology of these gene deletion mutants was significantly different from that of the wild-type. In addition, bZIPs are involved in the resistance to multiple stresses such as oxidative stress (Ada1, Yap1, MetR) and virulence (Hac1, MetR, Yap1, Ada1) at varying degrees. Transcriptome data demonstrated that the inactivation of bZIPs (Hac1, Atf1, Ada1 and Yap1) significantly affected many genes in multiple critical metabolism pathways and gene ontology (GO) terms. Moreover,the ΔHac1 mutants displayed reduced aerial hypha and are hypersensitivity to endoplasmic reticulum disruptors such as tunicamycin and dithiothreitol. Transcriptome analysis showed that inactivation of Hac1 significantly affected the proteasome process and its downstream unfolded protein binding, indicating that Hac1 participates in the endoplasmic reticulum stress response through the conserved unfolded protein response. Taken together, our findings reveal that bZIP transcription factors function as key regulators of fungal morphogenesis, abiotic stress response and pathogenesis, and expand our understanding of how microbial pathogens utilize these genes to deal with environmental stresses and achieve successful infection in the host plant.
Topics: Alternaria; Basic-Leucine Zipper Transcription Factors; Fungal Proteins; Stress, Physiological
PubMed: 34953292
DOI: 10.1016/j.micres.2021.126915