Phytopathology

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ISSN / EISSN : 0031-949X / 0031-949X
Published by: Scientific Societies (10.1094)
Total articles ≅ 12,920
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Lu Yu, Dasen Wen, Yuchen Yang, Xiaolin Qiu, , Chengming Tian
Published: 3 October 2022
Journal: Phytopathology®
Abstract:
Mitogen-activated protein kinase (MAPK) cascades are highly conserved signal transduction pathways that mediate cellular responses to various biotic and abiotic signals in plant pathogenic fungi. Here, we identified the orthologs of two MAPK genes (CcHog1 and CcSlt2) and assessed their functions by gene deletion and transcriptional analysis methods in Cytospora chrysosperma, the causal agent of canker disease in a wide range of woody plants. We found that the MAPKs shared convergent and distinct roles in fungal development, stress responses and virulence. For example, CcHog1, CcSlt2 and CcPmk1 were all involved in conidiation and response to stresses, including hyperosmotic pressure, cell wall inhibition agents and H2O2, but only CcPmk1 and CcSlt2 were required for hyphal growth and fungal pathogenicity. RNA-Seq data showed that numerous hyperosmosis and cell wall related genes significantly reduced their expression levels in ΔCcHog1 and ΔCcSlt2, respectively. Importantly, RNA and ribosome related processes were significantly enriched in the up-regulated genes of ΔCcSlt2, while they were significantly enriched in the down-regulated genes of ΔCcPmk1. Moreover, some secondary metabolite biosynthesis core genes (20/68) and two gene clusters were regulated by at least one among CcPmk1, CcHog1 and CcSlt2. Importantly, some virulence-associated genes were significantly down-regulated in ΔCcPmk1 and/or ΔCcSlt2, such as candidate effector genes. Collectively, these results suggest that the similar and distinct phenotypes of each MAPKs mutant may result from the transcriptional regulation of a series common or specific downstream genes, which provide a better understanding of the regulation network of MAPKs in C. chrysosperma.
Published: 29 September 2022
Journal: Phytopathology®
Abstract:
Apple blotch (AB) is a major disease of apple in Asia and recently emerged in Europe and the USA. It is caused by the fungus Diplocarpon coronariae (Dc) (formerly: Marssonina coronaria; teleomorph: Diplocarpon mali) and leads to severe defoliation of apple trees in late summer resulting in reduced yield and fruit quality. To develop effective disease management strategies, a sound knowledge of the pathogen’s biology is crucial. Data on the early phase of disease development is scarce: no data on spore dispersal in Europe is available. We developed a highly sensitive TaqMan qPCR method to quantify Dc conidia in spore trap samples. We monitored temporal and spatial dispersal of conidia of Dc, and progress of AB in spring and early summer in an extensively managed apple orchard in Switzerland in 2019 and 2020. Our results show that Dc overwinters in leaf litter and spore dispersal and primary infections occur in late April and early May. We provide the first results describing early-season dispersal of conidia of Dc, which, combined with the observed disease progress, helps to understand the disease dynamics and will be a basis for improved disease forecast models. Using the new qPCR method, we detected Dc in buds, on bark, and on fruit mummies, suggesting that several apple tissues may serve as overwintering habitats for the fungus, in addition to fallen leaves.
Wenyuan Yan, , , Xiao Guo, , ,
Published: 29 September 2022
Journal: Phytopathology®
Abstract:
Hormones play an important role in plant disease resistance and defense. Transcriptome data of late blight resistant potato genotype SD20 treated by ethylene (ET), jasmonate (JA), salicylic acid (SA), and Phytophthora infestans CN152 was analyzed to assess the role of the ET/JA/SA regulatory network in plant disease resistance and defense and predict key resistant genes. The results show that there was significant crossover of differentially expressed genes (DEGs) between all treatments, and common and specific plant disease interaction genes for the ET, JA, and SA treatments were differentially expressed in the CN152 treatment. The resistance and defense genes of the potato genotype SD20 could be induced to regulate metabolic and hormone signaling pathways by alternative splicing in all treatments. Further analysis found that JA and ET pathways can work together synergistically, JA/ET and SA pathways antagonize each other to initiate the expression of calmodulin-domain protein kinases (CDPK), calmodulin/calmodulin-like (CaM/CML), and RPM1-interacting protein 4 (RIN4) genes, and activate HSP-mediated HR response and defense-related genes. Meanwhile nine defense genes, including wound-responsive AP2 like factor, glutathione-s-transferase, serine/threonine-protein kinase BRI1, and Avr9/Cf-9 rapidly elicited protein genes were obtained using WGCNA, which provided reliable targets for functional verification. This study provides a theoretical reference for the comprehensive application of plant hormones to improve resistance to potato late blight disease.
Hongke Huang, Dongxue Li, Shilong Jiang, Rui Yang, Yuqin Yang, Zhongqiu Xia, Xinyue Jiang, Yongtian Zhao, Delu Wang, Baoan Song, et al.
Published: 29 September 2022
Journal: Phytopathology®
Abstract:
Because effective control measures are lacking, tea leaf spot caused by Didymella segeticola results in huge tea [Camellia sinensis (L.) O. Kuntze] production losses on tea plantations in Guizhou Province, southernwest China. Screening for natural anti-microbial agents with higher control effects against this pathogen and studying their modes of action may contribute to disease management. Here, Penicillium griseofulvum-derived antimicrobial griseofulvin (GSF) can inhibit the hyphal growth of D. segeticola strain GZSQ-4, with a half-maximal effective concentration of 0.37 μg/ml in vitro and a higher curative efficacy at a lower dose of 25 μg/ml for detached tea twigs. GSF induces deformed and slightly curly hyphae with enlarged ends, with protoplasts agglutinated in the hyphae, and higher numbers of hyphal protuberances. GSF altered hyphal morphology and the subcellular structure’s order. The integrated transcriptome and proteome data revealed that the transport of materials in cells, cellular movement, and mitosis were modulated by GSF. Molecular docking indicated that beta-tubulin was the most potent target of GSF, with a binding free energy of −13.59 kcal/mol, and microscale thermophoresis indicated that the Kd value of GSF binding to beta-tubulin 1, compared with beta-tubulin 2, was significantly lower. Thus, GSF potentially targets beta-tubulin 1 to disturb the chromosomal separation and fungal mitosis, thereby inhibiting hyphal growth.
Wankuan Shen, Yichang Cai, Feng Bai, , Wenjia Li, Han Bao, ,
Published: 29 September 2022
Journal: Phytopathology®
Abstract:
Sugarcane smut is a serious disease caused by Sporisorium scitamineum, which causes significant losses to sugar industry. It is critical to reveal the molecular pathogenic mechanism of S. scitamineum to explore a new control strategy for sugarcane smut. Based on transcriptome sequencing data of two S. scitamineum strains with different pathogenicity, we identified the gene, SsCI51640, which was predicted to encode kynurenine 3-monooxygenase. In this study, we obtained knockout mutants and complementary mutants of this gene and identified gene function. The results showed that the sporidial growth rate and acid production ability of knockout mutants were significantly higher and stronger than those of the wild-type and complementary mutants. The growth of knockout mutants under abiotic stress (osmotic stress and cell wall stress) was significantly inhibited. In addition, the sexual mating ability and pathogenicity of knockout mutants was significantly reduced, while this phenomenon could be restored by adding exogenous cyclic adenosine monophosphate (cAMP). It is thus speculated that the SsCI51640 gene may regulates the sexual mating and pathogenicity of S. scitamineum by cAMP signaling pathway. Moreover, the SsCI51640 gene enhanced the sporidial environmental adaptability, which promoted sexual mating and development of pathogenicity. This study provides a theoretical basis for the molecular pathogenesis of S. scitamineum.
Published: 27 September 2022
Journal: Phytopathology®
Abstract:
Brown and black spots, caused by Stemphylium and Alternaria species, are important fungal diseases affecting European pear (Pyrus communis L.) in orchards. Both fungal genera cause similar symptoms, which could favour misidentification, but Alternaria spp. are increasingly reported due to the changing climatic conditions. In this study, Alternaria spp. were isolated from symptomatic leaves and fruits of European pear, and their pathogenicity was evaluated on pear fruits from cultivar ‘Abate Fétel’ and molecular and chemical characterization were performed. Based on Maximum likelihood phylogenetic analysis, 15 out of 46 isolates were identified as A. arborescens species complex (AASC), 27 as A. alternata and four were named Alternaria sp. Both species were isolated from mature fruits and leaves. In pathogenicity assays on pear fruits all isolates reproduced the symptoms observed in the field, both by wound inoculation and direct penetration. All but one isolates were produced Alternaria-toxins on European pears, including tenuazonic acid and alternariol (89.1% of the isolates), alternariol monomethyl ether (89.1%), altertoxin I (80.4%), altenuene (50.0%) and tentoxin (2.2%). These isolates also produced at least two mycotoxins and 43.5% produced four mycotoxins, with an average total concentration of the Alternaria-toxins exceeding 7.58×106 ng/kg. Our data underline the potential risks for human health related to the high mycotoxin content found on fruits affected by black spot. This study represents also the first report of AASC as agent of black spot on European pear in Italy.
Published: 26 September 2022
Journal: Phytopathology®
Abstract:
Scab, caused by the plant-pathogenic fungus Venturia effusa, is a major disease of pecan in South America, resulting in loss of quantity and quality of nut yield. Characteristics of the populations of V. effusa in South America are unknown. We used microsatellites to describe the genetic diversity and population structure of V. effusa in South America, and determined the mating type status of the pathogen. The four hierarchically sampled orchard populations from Argentina (AR), Brazil (BRC and BRS), and Uruguay (UR) had moderate to high genotypic and gene diversity. There was evidence of population differentiation ( Fst = 0.196) but the correlation between geographic distance and genetic distance was not statistically significant. Genetic differentiation was minimal between the UR, BRC, and BRS populations, and these populations were more clearly differentiated from the AR population. The MAT1-1 and MAT1-2 mating types occurred in all four orchards and their frequencies did not deviate from the 1:1 ratio expected under random mating; however, multilocus linkage equilibrium was rejected in three of the four populations. The population genetics of South American populations of V. effusa has many similarities to the population genetics of V. effusa previously described in the United States. Characterizing the populations genetics and reproductive systems of V. effusa are important to establish the evolutionary potential of the pathogen and, thus, its adaptability—and can provide a basis for informed approaches to utilizing available host resistance and determining phytosanitary needs.
Published: 26 September 2022
Journal: Phytopathology®
Abstract:
Management of cucurbit downy mildew (CDM) caused by Pseudoperonospora cubensis, relies on an intensive fungicide program. In Michigan, CDM occurs annually due to an influx of airborne sporangia; timely alerts of airborne inoculum can assist growers in assessing the need to initiate fungicide sprays. This research aimed to improve the specific detection of airborne P. cubensis sporangia by adapting qPCR-based assays to distinguish among P. cubensis clade I and II and P. humuli in spore trap samples from commercial production sites and research plots. We also evaluated the suitability of impaction spore traps in comparison to Burkard traps for detection of airborne sporangia. A multiplex qPCR assay improved the specificity of P. cubensis clade II detection accelerating the assessment of field spore trap samples. After two years of monitoring, P. cubensis clade II DNA was detected in spore trap samples before CDM symptoms were first observed in cucumber fields (July and August), while P. cubensis clade I DNA was not detected in air samples before or after the disease onset. In some commercial cucumber fields, P. humuli DNA was detected throughout the growing season. The Burkard spore trap appeared to be better suited for recovery of sporangia at low concentrations than the impaction spore trap. This improved methodology for the monitoring of airborne Pseudoperonospora spp. sporangia could be used as part of a CDM risk advisory system to time fungicide applications that protect cucurbit crops in Michigan.
, Bingxuan Li, Xuemei Zhao, Liqiang Yao, Yuanyuan Kong, Wenkui Liu, Rong Zhang,
Published: 26 September 2022
Journal: Phytopathology®
Abstract:
In ascomycetes, 1,8-dihydroxynaphthalene (DHN) melanin plays important protective functions and its production is usually coupled with development and environmental stress responses. The regulation of melanin biosynthesis, however, remains obscure. Colletotrichum fructicola is a phytopathogen with a broad host range that produces melanized appressoria and perithecia. In this study, we annotated melanin genes in a high-quality C. fructicola genome and characterized two zinc finger transcription factors (TFs) (cmr1 and cmr2) that form a loosely organized gene cluster with several melanin biosynthesis genes. Deleting either TF abolished melanization in both mycelia and perithecia but did not affect appressoria. The deletion mutants also showed perithecial development defects. Overexpressing cmr1 in Δcmr2 strongly activated the expression of melanin biosynthesis genes including pks1, scd1, t4hr1, and thr1 and caused hyper-accumulation of charcoal to black pigment(s). On the other hand, overexpressing cmr2 in Δcmr1 activated pks1, t4hr1, and thr1, but not scd1. We conclude that proper DHN melanin accumulation in C. fructicola requires the cooperative function of two in-cluster TFs that also regulate perithecial development. The study clarifies DHN melanin regulations in C. fructicola and expands the function of melanin in-cluster TFs to sex regulation.
, , , , , Hamid Abachi, Rachel A. Herschlag, Kevin Hockett, Carolee T. Bull,
Published: 21 September 2022
Journal: Phytopathology®
Abstract:
Mycopathogenic bacteria play a pivotal role in the productivity of edible mushrooms grown under controlled conditions. In this study, we carried out a comprehensive farm survey and sampling (2018-2021) on button mushroom (Agaricus bisporus) farms in 15 provinces in Iran to monitor the status of bacterial pathogens infecting the crop. Mycopathogenic bacterial strains were isolated from pins, stems, and caps, as well as the casing layer in 38 mushroom farms. The bacterial strains incited symptoms on mushroom caps ranging from faint discoloration to dark brown and blotch of the inoculated surfaces. Among the bacterial strains inciting disease symptoms on bottom mushroom, 40 strains were identified as Ewingella americana based on biochemical assays and phylogeny of 16S rRNA and gyrB gene. Ewingella americana strains differed in their aggressiveness on mushroom caps and stipes where the corresponding symptoms ranged from deep yellow to dark brown. In the phylogenetic analyses, all E. americana strains isolated in this study were clustered in a monophyletic clade closely related to the non-pathogenic and environmental strains of the species. BOX-PCR-based fingerprinting revealed intraspecific diversity. Using the cutoff level of 73-76% similarity, the strains formed six clusters. A chronological pattern was observed where the strains isolated in 2018 were differentiated from those isolated in 2020 and 2021. Taking together, due to the multifaceted nature of the pathogen, such a widespread occurrence of E. americana in mushroom farms in Iran could be an emerging threat for mushroom industry in the country.
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