Search Results (66)

Clubroot, caused by the obligate parasite Plasmodiophora brassicae, is a soilborne disease affecting canola (Brassica napus) and other crucifers. Although planting resistant cultivars remains the primary strategy for managing clubroot, the emergence of resistance-breaking P. brassicae pathotypes continues to threaten canola production. In this context, soil and root microorganisms may play a role in suppressing the disease. This study investigated the impact of P. brassicae infection on the microbial communities of soil, seeds, roots, and the rhizosphere in susceptible and resistant canola lines, with the aim of analyzing host–pathogen–microbiome interactions and identifying microbial taxa potentially associated with disease resistance. Our findings showed that resistant canola lines inoculated with P. brassicae (pathotype 3A) exhibited reduced disease severity compared to their susceptible counterparts. Diversity analyses of microbial communities revealed that clubroot-resistant canola lines tended to maintain more stable and diverse fungal communities, with a higher Shannon index than susceptible lines. Inoculation with P. brassicae induced more pronounced changes in the root microbiome than in the rhizosphere. Additionally, the seed microbiomes of resistant and susceptible lines displayed distinct bacterial and fungal profiles, suggesting that clubroot susceptibility may influence seed-associated microbial community composition. Differential abundance analysis of root and rhizosphere microbiomes indicated that certain microbial taxa, including bacterial genera such as Acidovorax, Bacillus, Cupriavidus, Cytophaga, Duganella, Flavobacterium, Fluviicola, Luteimonas, Methylotenera, Pedobacter, and Peredibacter, as well as fungal genera such as Aspergillus, Candida, Fusicolla, Paecilomyces, and Rhizophlyctis, may be recruited or enriched in resistant canola lines following P. brassicae inoculation, potentially contributing to reduced clubroot severity. Full article

This paper provides data on non-native fungus-like organisms (Oomycota, kingdom Stramenopila), their diversity, and distribution in Lithuania and is an addition to a previously published checklist of alien true fungi (Chytridiomycota, Ascomycota, and Basidiomycota; kingdom Fungi). All available published data were summarized, and the analysis showed that approximately 25% of recorded Lithuania stramenopilous fungus-like organism species are alien. The compiled list represented herein includes 54 species of alien terrestrial and aquatic stramenopilous fungus-like organisms (Oomycota). Most alien Oomycota are obligate pathogens of terrestrial plants. Aquatic organisms are represented by one alien dangerous crayfish pathogen, Aphanomyces astaci, which is currently noted as extinct in Lithuania. The taxonomy of the listed alien species of Oomycota has been revised, and the species names have been adjusted to reflect current nomenclature changes. The taxonomical and ecological analysis demonstrated the prevalence of terrestrial parasitic Peronosporales reported in Lithuania Oomycota and the highest diversity of alien species belonging to the Peronospora genus. The chronology of appearance, distribution within the country, and current status of these non-native organisms were assessed, and some of the most economically or ecologically important harmful invasive species were discussed. Full article

This review summarizes the mechanisms and historical development of fungicides registered for grape downy mildew control in Japan, with a particular focus on their diverse molecular targets, including cell division and mitochondrial respiration. Grapevine downy mildew is one of the most important pathogens in Japanese grapevine cultivation. Grapevine downy mildew tends to be fungicide-resistant, and in recent years, a quinone outside inhibitor (QoI) fungicide-resistant strain of downy mildew has caused extensive damage in Yamanashi Prefecture, making headlines in newspapers. Although approximately 60 fungicides have been registered for downy mildew management in Japan, many have been withdrawn due to the emergence of resistant pathogen populations. Recent challenges with resistance to quinone outside inhibitors, carboxylic acid amides, and oxysterol-binding protein inhibitors underscore the ongoing importance of resistance management in Japanese viticulture and grape downy mildew control strategies. Full article

Considerable losses are inflicted by plant-parasitic nematodes (PPNs) due to their obligate parasitism; serious damage occurs in many susceptible crops, and the parasites have a broad distribution worldwide. As most PPNs have a subterranean nature, the complexity of soils in the plant rhizosphere and the structures and functions of the soil food webs necessitate a grasp of the relevant biotic/abiotic factors in order to ensure their effective control. Such factors frequently lead to the inconsistent performance and untapped activity of applied bionematicides, hindering efforts to develop reliable ones. Research efforts that take these factors into account to back the usage of these bionematicides by combining the disease-suppressive activities of two or more agricultural inputs are highlighted herein. These combinations should be designed to boost useful colonization in the rhizosphere, persistent expression of desirable traits under a wide range of soil settings, and/or antagonism to a larger number of plant pests/pathogens relative to individual applications. Relevant ecological/biological bases with specific settings for effective PPN management are exemplified. Determining the relative sensitivity or incompatibility of some biologicals entails studying their combinations and reactions. Such studies, as suggested herein, should be conducted on a case-by-case basis to avoid unsatisfactory outputs. These studies will enable us to accurately define certain outputs, namely, the synergistic, additive, neutral, and antagonistic interactions among the inputs. In optimizing the efficiencies of these inputs, researchers should consider their multi-functionality and metabolic complementarity. Despite previous research, the market currently lacks these types of safe and effective products. Hence, further explorations of novel integrated pest management plans that boost synergy and coverage to control multiple pathogens/pests on a single crop are required. Also, setting economic incentives and utilizing a standardized regulation that examines the authentic risks of biopesticides are still called for in order to ease cost-effective formulation, registration, farmer awareness, and usage worldwide. On the other hand, tank mixing that ensures legality and avoids physical and chemical agro-input-based incompatibilities can also provide superior merits. The end in view is the unraveling of the complexities of interactions engaged with in applying multiple inputs to develop soundly formulated, safe, and effective pesticides. Sophisticated techniques should be incorporated to overcome such complexities/limitations. These techniques would engage microencapsulation, nanopesticides, volatile organic compounds as signals for soil inhabitants, bioinformatics, and RNA-Seq in pesticide development. Full article

Tar spot is a prevalent fungal disease characterized by shiny black spots on the leaves, stems, and fruits of various plants. It is typically caused by members of the family Phyllachoraceae, which consists of biotrophic and obligate plant parasitic fungi. During field investigations of tar spot fungi in Sichuan Province, China, 70 fungal samples associated with tar spots belonging to the family Poaceae were collected from 13 different locations. Through morphological studies and multi-locus phylogenetic analysis of combined ITS, SSU, and LSU datasets, the collected samples were classified into eight Phyllachora species. Among these, five were identified as new species (Phyllachora cylindricae, P. festucae, P. luzhouensis, P. palmifoliae, and P. wenchuanensis), and two represented new host records (P. chongzhouensis, P. panicicola). The new species are accompanied by descriptions and illustrations, while their characteristics are discussed in relation to comparable taxa. Additionally, P. yuanjiangensis is synonymized under P. xinpingensis. These findings enhance our understanding of tar spot fungi in Sichuan and, given that Phyllachora species are important pathogens of plants in the Poaceae family, establish a foundation for further research to better understand their potential impacts on agriculture and the local ecology. Full article

Viroids represent obligate plant pathogens composed exclusively of non-protein coding small single-stranded RNAs that cause high economic losses worldwide. A field survey was carried out to assess the incidence of the peach latent mosaic viroid (PLMVd) in southeastern Kazakhstan, the region of the country where fruit trees are mainly grown. Of 246 stone fruit trees, 20 (8.13%) were infected with the PLMVd. The incidence of the PLMVd in the peach (19.23%; 15/78) was significantly higher than that in the apricot (6.76%; 5/74; p = 0.0234). Eight of the detected viroids were cloned and used for full-genome sequencing. The nucleotide sequence similarity of the selected isolates found in Kazakhstan was 83.9–100%. A phylogenetic analysis indicated three clusters for the Kazakhstani isolates of the PLMVd. Three groups of Kazakhstani viroids differed in their predicted secondary structure. During the survey, the PLMVd was detected and genetically characterized for the first time in Kazakhstan. The obtained results indicate the need to develop state control measures for the PLMVd, including regular monitoring surveys. We identified several SNPs of the PLMVd that had not been previously described. The results may be useful in optimizing diagnostic approaches for detecting stone fruit viroids and preventing their spread through propagation material. Full article

Chlamydia are obligate intracellular bacterial pathogens affecting humans and animals, causing miscarriage, stillbirth, or weak fetuses in the late stages of pregnancy of goats and sheep. Because there is no commercial vaccine for chlamydia in animals, drug treatment has become the most effective curative method. Natural products, also known as secondary metabolites, are becoming one of the main sources used in new drug development because of their structural diversity and biodiversity. In natural products, plant sources play a major role in the development process of new drugs. In this study, five undescribed highly oxygenated bisabolane sesquiterpenes (Pararubin W, Pararubin X, Pararubin Y., Pararubin Z, and Pararubin AA) were isolated from whole plants of Ligularia narynensis. Their chemical structures were determined via analyses of HRESIMS, IR, 1D, and 2D NMR data, along with the assignment of their relative configurations. These compounds were tested for their anti-chlamydial activity. The results show that compounds 1 and 5 inhibited the growth of Chlamydia abortus in host cells in a dose-dependent manner. Full article

The exocyst complex in eukaryotic cells modulates secretory vesicle transportation to promote exocytosis. The exocyst is also required for the hyphal growth and pathogenic development of several filamentous phytopathogens. Obligate biotrophic powdery mildew fungi cause considerable damage to many cash crops; however, the exocyst’s roles in this group of fungi is not well studied. To verify the functions of the exocyst in powdery mildew fungus, we identified two exocyst subunits, EqSec5 and EqSec6, from Erysiphe quercicola, a powdery mildew fungus that infects the rubber tree Hevea brasiliensis. When GFP-fused EqSec5 and EqSec6 were introduced into E. quercicola and another phytopathogenic fungus, Magnaporthe oryzae, they primarily localized to the hyphal tip region. Inducing gene silencing of EqSec5 or EqSec6 caused growth and infection defects, and those defects could not be fully restored under the NADPH oxidase inhibitor treatment to the plant. The silenced strains also induced the host defense response including reactive oxygen species accumulation and callose deposition. The silencing of EqSec5 or EqSec6 also inhibited the secretion of the effector protein EqIsc1, interrupting plant salicylic acid biosynthesis. Yeast two-hybrid and gene overexpression assays suggested that EqSec5 and EqSec6 interact with each other and can complement each other’s function during host infection. Overall, our study provides evidence that the exocyst in this powdery mildew fungus facilitates effector secretion, hyphal growth, and infection. Full article

Southern corn rust (SCR) caused by Puccinia polysora Underw. has recently emerged as a focal point of study because of its extensive distribution, significant damage, and high prevalence in maize growing areas such as the United States, Canada, and China. P. polysora is an obligate biotrophic fungal pathogen that cannot be cultured in vitro or genetically modified, thus complicating the study of the molecular bases of its pathogenicity. High temperatures and humid environmental conditions favor SCR development. In severe cases, SCR may inhibit photosynthesis and cause early desiccation of maize, a decrease in kernel weight, and yield loss. Consequently, an expedited and accurate detection approach for SCR is essential for plant protection and disease management. Significant progress has been made in elucidating the pathogenic mechanisms of P. polysora, identifying resistance genes and developing SCR-resistant cultivars. A detailed understanding of the molecular interactions between maize and P. polysora will facilitate the development of novel and effective approaches for controlling SCR. This review gives a concise overview of the biological characteristics and symptoms of SCR, its life cycle, the molecular basis of interactions between maize and P. polysora, the genetic resistance of maize to SCR, the network of maize resistance to P. polysora infection, SCR management, and future perspectives. Full article

Branched broomrape (Phelipanche ramosa (L.) Pomel), an obligate parasitic weed with a wide host range, is known for its devasting effects on many crops worldwide. Soil fungi, notably Fusarium sp., are described as pathogenic to broomrape, while the hypothesis of the phytotoxicity of fusaric acid produced by F. verticillioides for parasitic weeds of the genus Orobanche has been proposed. Using image analysis and untargeted metabolomics, this study investigated fungal metabolites phytotoxic for P. ramosa and produced by the F. venenatum MIAE02836 strain, isolated from symptomatic broomrapes and identified as a promising candidate for broomrape biocontrol. Phytotoxicity tests of crude extracts from the fungus alone or in interaction with broomrape on P. ramosa microcalli and quantification of necrosis by image analysis confirmed the phytotoxic potential of F. venenatum MIAE02836 metabolites towards the early developmental stages of P. ramosa. Data analysis of a non-targeted metabolomics approach revealed numerous metabolites produced by F. venenatum MIAE02836. Four of them, accumulated during interaction with the parasitic plant, are known for their phytotoxic potential: maculosin, cyclo(Leu-Phe), phenylalanyl-D-histidine and anguidine. These results suggest that combining image acquisition of the microcalli screening test and untargeted metabolomic approach is an interesting and relevant method to characterize phytotoxic fungal metabolites. Full article

Sugarcane white leaf (SCWL) disease, caused by Candidatus Phytoplasma sacchari, poses a significant threat to sugarcane cultivation. An obligate parasite, phytoplasma is difficult to culture in laboratory conditions, making the isolation of its DNA from the massive amount of plant host DNA extremely challenging. Yet, the appropriate amount and quality of plant microbiome-derived DNA are key for high-quality DNA sequencing data. Here, a simple, cost-effective, alternative method for DNA isolation was applied using a guanidine-HCl-hydroxylated silica (GuHCl-Silica)-based method and microbiome DNA enrichment based on size-selective low-molecular-weight (LMW) DNA by PEG/NaCl precipitation. qPCR analysis revealed a significant enrichment of phytoplasma DNA in the LMW fraction. Additionally, the NEBNext Microbiome DNA enrichment kit was utilized to further enrich microbial DNA, demonstrating a remarkable increase in the relative abundance of phytoplasma DNA to host DNA. Shotgun sequencing of the isolated DNA gave high-quality data on the metagenome assembly genome (MAG) of Ca. Phytoplasma sacchari SCWL with completeness at 95.85 and 215× coverage. The results indicate that this combined approach of PEG/NaCl size selection and microbiome enrichment is effective for obtaining high-quality genomic data from phytoplasma, surpassing previous methods in efficiency and resource utilization. This low-cost method not only enhances the recovery of microbiome DNA from plant hosts but also provides a robust framework for studying plant pathogens in complex plant models. Full article

Ticks are obligate hematophagous ectoparasites that affect animals, and some of them transmit a wide range of pathogens including viruses, bacteria, and protozoa to both animals and humans. Several vaccines have shown immunogenicity and protective efficacy against ticks in animal models and definitive hosts. After several decades on anti-tick vaccine research, only a commercial vaccine based on a recombinant antigen is currently available. In this context, plants offer three decades of research and development on recombinant vaccine production to immunize hosts and as a delivery vehicle platform. Despite the experimental advances in plant-made vaccines to control several parasitosis and infectious diseases, no vaccine prototype has been developed against ticks. This review examines a panorama of ticks of veterinary importance, recombinant vaccine experimental developments, plant-made vaccine platforms, and perspectives on using this technology as well as the opportunities and limitations in the field of tick vaccine research. Full article

Phytoplasmas are obligate intracellular pathogens that profoundly modify the development, physiology and behavior of their hosts by secreting effector proteins that disturb signal pathways and interactions both in plant and insect hosts. The characterization of effectors and their host-cell targets was performed for only a few phytoplasma species where it was shown that the SAP11 effector alters plant morphology by destabilizing plant transcription factors: TEOSINTE BRANCHED 1-CYCLOIDEA-PROLIFERATING CELL FACTOR (TCPs). To explore the possible role of the SAP11-like effector from ‘Ca. P. solani’, we used Arabidopsis thaliana as a model plant. The SAP11-like effector gene from ‘Ca. P. solani’ was introduced into arabidopsis by floral dip and transgenic lines were regenerated. In planta bimolecular fluorescence complementation (BIFC) assays in agroinfiltrated Nicotiana benthamiana leaf cells were conducted to detect interactions between SAP11-like and AtTCP2 and AtTCP4 using confocal microscopy. SAP11-like from ‘Ca. P. solani’ induced significant phenotypic changes in arabidopsis, including crinkled leaves with reduced size, lower biomass, more axillary branches, changes in root morphology, and crinkled and smaller siliques. The BIFC assays proved in planta interaction of SAP11-like effector with AtTCP2 and AtTCP4. To our knowledge, this is the first characterization of the interaction between the ‘Ca. P. solani’ effector and plant transcription factors, suggesting a potential mechanism of modulating plant development and induction of characteristic symptoms in ‘Ca. P. solani’-infected plants. Full article

Plant parasitic nematodes (PPNs), such as Meloidogyne spp., Heterodera spp. and Pratylenchus spp., are obligate parasites on a wide range of crops, causing significant agricultural production losses worldwide. These PPNs mainly feed on and within roots, impairing both the below-ground and the above-ground parts, resulting in reduced plant performance. Plants have developed a multi-component defence mechanism against diverse pathogens, including PPNs. Several natural molecules, ranging from cell wall components to secondary metabolites, have been found to protect plants from PPN attack by conferring nematode-specific resistance. Recent advances in omics analytical tools have encouraged researchers to shed light on nematode detection and the biochemical defence mechanisms of plants during nematode infection. Here, we discuss the recent progress on revealing the nematode-associated molecular patterns (NAMPs) and their receptors in plants. The biochemical defence responses of plants, comprising cell wall reinforcement; reactive oxygen species burst; receptor-like cytoplasmic kinases; mitogen-activated protein kinases; antioxidant activities; phytohormone biosynthesis and signalling; transcription factor activation; and the production of anti-PPN phytochemicals are also described. Finally, we also examine the role of epigenetics in regulating the transcriptional response to nematode attack. Understanding the plant defence mechanism against PPN attack is of paramount importance in developing new, effective and sustainable control strategies. Full article

Wheat leaf rust fungus is an obligate parasitic fungus that can absorb nutrients from its host plant through haustoria and secrete effector proteins into host cells. The effector proteins are crucial factors for pathogenesis as well as targets for host disease resistance protein recognition. Exploring the role of effector proteins in the pathogenic process of Puccinia triticina Eriks. (Pt) is of great significance for unraveling its pathogenic mechanisms. We previously found that a cysteine-rich effector protein, Pt1641, is highly expressed during the interaction between wheat and Pt, but its specific role in pathogenesis remains unclear. Therefore, this study employed techniques such as heterologous expression, qRT-PCR analysis, and host-induced gene silencing (HIGS) to investigate the role of Pt1641 in the pathogenic process of Pt. The results indicate that Pt1641 is an effector protein with a secretory function and can inhibit BAX-induced programmed cell death in Nicotiana benthamiana. qRT-PCR analyses showed that expression levels of Pt1641 were different during the interaction between the high-virulence strain THTT and low-virulence strains FGD and Thatcher, respectively. The highest expression level in the low-virulence strain FGD was four times that of the high-virulence strain THTT. The overexpression of Pt1641 in wheat near-isogenic line TcLr1 induced callose deposition and H₂O₂ production on TcLr1. After silencing Pt1641 in the Pt low-virulence strain FGD on wheat near-isogenic line TcLr1, the pathogenic phenotype of Pt physiological race FGD on TcLr1 changed from “;” to “3”, indicating that Pt1641 plays a non-toxic function in the pathogenicity of FGD to TcLr1. This study helps to reveal the pathogenic mechanism of wheat leaf rust and provides important guidance for the mining and application of Pt avirulent genes. Full article