Special Issue "Plant Pathogenic Microorganisms: State-of-the-Art Research in Spain"

A special issue of Microorganisms (ISSN 2076-2607). This special issue belongs to the section "Plant Microbe Interactions".

Deadline for manuscript submissions: closed (31 October 2022) | Viewed by 9912

Special Issue Editors

Dr. Elvira Fiallo-Olivé
E-Mail Website
Guest Editor
Instituto de Hortofruticultura Subtropical y Mediterránea “La Mayora” (IHSM-UMA-CSIC), Consejo Superior de Investigaciones Científicas. Avenida Dr. Wienberg s/n, 29750 Algarrobo-Costa, Málaga, Spain
Interests: plant virology; emergent plant diseases; virus taxonomy; plant–pathogen interactions; insect vectors
Special Issues, Collections and Topics in MDPI journals
Dr. Soledad Sacristán
E-Mail Website
Guest Editor
Centro de Biotecnología y Genómica de Plantas (CBGP) and Departamento de Biotecnología-Biología Vegetal, Escuela Técnica Superior de Ingeniería Agronómica, Alimentaria y de Biosistemas, Universidad Politécnica de Madrid (UPM), Madrid, Spain
Interests: plant-fungus interaction; fungal phytopathogens; fungal endophytes; plant immunity; genomics; transcriptomics
Dr. Ana Palacio-Bielsa
E-Mail Website
Guest Editor
Centro de Investigación y Tecnología Agroalimentaria de Aragón, Instituto Agroalimentario de Aragón – IA2 (CITA-Universidad de Zaragoza), Unidad de Protección Vegetal, 50059 Zaragoza, Spain
Interests: phytopathogenic bacteria; molecular biology; detection; epidemiology; control

Special Issue Information

Dear Colleagues,

Pathogenic microorganisms, including fungi, oomycetes, bacteria, viruses, and viroids, constitute a serious threat to agriculture worldwide. In Spain, one of the countries with the highest proportion of agricultural gross domestic product in Europe, agri-food industry is the country's main manufacturing activity. Consequently, the presence and emergence of microorganisms causing serious plant diseases to economically important crops are especially relevant. In line with this, Spain has an important number of research groups interested on plant pathology, with scientists working on many aspects of the pathogenic microorganism-plant interactions, from basic aspects to more applied studies. In recent years, numerous important advancements have been achieved by scientists working in Spain in the biological and molecular characterization of plant pathogenic microorganisms, in elucidating mechanisms of microbe pathogenesis, plant resistance to microbe infection, and plant-microbe-vector interactions. All these new achievements have provided essential knowledge for agricultural researchers worldwide.

The aim of this Special Issue is to provide a platform for Spanish researchers interested in plant pathogenic microorganisms to share their recent results. To achieve this, we are inviting you to submit research articles, short communications, and reviews related to the various aspects of plant pathogenic microorganisms: microbe–plant host interactions, microbe–vector interactions, microbe–microbe interactions, ecology, and control strategies.

We look forward to assembling an issue that highlights the state-of-the-art on plant pathogenic microorganism research in Spain.

Dr. Elvira Fiallo-Olivé
Dr. Soledad Sacristán
Dr. Ana Palacio-Bielsa
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Microorganisms is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2200 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • plant pathogenic microorganisms
  • microbe–plant interactions
  • microbe–vector interactions
  • microbe–microbe interactions
  • genetic resistance
  • control
  • epidemiology

Published Papers (10 papers)

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Research

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Article
Improvement of Alternaria Leaf Blotch and Fruit Spot of Apple Control through the Management of Primary Inoculum
Microorganisms 2023, 11(1), 101; https://doi.org/10.3390/microorganisms11010101 - 30 Dec 2022
Viewed by 447
Abstract
Alternaria spp. is the causal agent of apple leaf blotch and fruit spot, diseases of recent appearance in Spain. The overwinter inoculum of Alternaria spp. is the source of primary infections in apple, thus the aim of this work was to optimize the [...] Read more.
Alternaria spp. is the causal agent of apple leaf blotch and fruit spot, diseases of recent appearance in Spain. The overwinter inoculum of Alternaria spp. is the source of primary infections in apple, thus the aim of this work was to optimize the control of infection through two environmentally friendly inoculum-management strategies, the removal of winter fallen leaves and the treatment of leaves with the biological agent Trichoderma asperellum to inhibit or prevent inoculum development in commercial orchards. The results of commercial orchard trials showed that leaf aspiration and application of T. asperellum on the ground have efficacy to reduce fruit spot between 50 and 80% and leaf blotch of between 30 and 40% depending on the year. The efficacies on the reduction of leaf blotch were slightly lower than of fruit spot. Disease reduction has been related to a reduction of total spores released during the season. Results of dynamics of spore release indicate that factors influencing spore release were rainfall and temperature. In conclusion, the use of environmentally friendly strategies combined with standard fungicides, and with monitoring environmental conditions, might allow a reduction in the number of phytosanitary applications, thus achieving the goal of reducing their use. Full article
(This article belongs to the Special Issue Plant Pathogenic Microorganisms: State-of-the-Art Research in Spain)
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Article
Chemotactic Responses of Xanthomonas with Different Host Ranges
Microorganisms 2023, 11(1), 43; https://doi.org/10.3390/microorganisms11010043 - 22 Dec 2022
Viewed by 436
Abstract
Xanthomonas citri pv. citri (Xcc) (X. citri subsp. citri) type A is the causal agent of citrus bacterial canker (CBC) on most Citrus spp. and close relatives. Two narrow-host-range strains of Xcc, Aw and A*, from Florida [...] Read more.
Xanthomonas citri pv. citri (Xcc) (X. citri subsp. citri) type A is the causal agent of citrus bacterial canker (CBC) on most Citrus spp. and close relatives. Two narrow-host-range strains of Xcc, Aw and A*, from Florida and Southwest Asia, respectively, infect only Mexican lime (Citrus aurantifolia) and alemow (C. macrophylla). In the initial stage of infection, these xanthomonads enter via stomata to reach the apoplast. Herein, we investigated the differences in chemotactic responses for wide and narrow-host-range strains of Xcc A, X. euvesicatoria pv. citrumelonis (X. alfalfae subsp. citrumelonis), the causal agent of citrus bacterial spot, and X. campestris pv. campestris, the crucifer black rot pathogen. These strains of Xanthomonas were compared for carbon source use, the chemotactic responses toward carbon compounds, chemotaxis sensor content, and responses to apoplastic fluids from Citrus spp. and Chinese cabbage (Brassica pekinensis). Different chemotactic responses occurred for carbon sources and apoplastic fluids, depending on the Xanthomonas strain and the host plant from which the apoplastic fluid was derived. Differential chemotactic responses to carbon sources and citrus apoplasts suggest that these Xanthomonas strains sense host-specific signals that facilitate their location and entry of stomatal openings or wounds. Full article
(This article belongs to the Special Issue Plant Pathogenic Microorganisms: State-of-the-Art Research in Spain)
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Article
Ralstonia solanacearum Facing Spread-Determining Climatic Temperatures, Sustained Starvation, and Naturally Induced Resuscitation of Viable but Non-Culturable Cells in Environmental Water
Microorganisms 2022, 10(12), 2503; https://doi.org/10.3390/microorganisms10122503 - 16 Dec 2022
Viewed by 964
Abstract
Ralstonia solanacearum is a bacterial phytopathogen affecting staple crops, originally from tropical and subtropical areas, whose ability to survive in temperate environments is of concern under global warming. In this study, two R. solanacearum strains from either cold or warm habitats were stressed [...] Read more.
Ralstonia solanacearum is a bacterial phytopathogen affecting staple crops, originally from tropical and subtropical areas, whose ability to survive in temperate environments is of concern under global warming. In this study, two R. solanacearum strains from either cold or warm habitats were stressed by simultaneous exposure to natural oligotrophy at low (4 °C), temperate (14 °C), or warm (24 °C) temperatures in environmental water. At 4 °C, the effect of temperature was higher than that of oligotrophy, since R. solanacearum went into a viable but non-culturable (VBNC) state, which proved to be dependent on water nutrient contents. Resuscitation was demonstrated in vitro and in planta. At 14 °C and 24 °C, the effect of oligotrophy was higher than that of temperature on R. solanacearum populations, displaying starvation-survival responses and morphological changes which were stronger at 24 °C. In tomato plants, starved, cold-induced VBNC, and/or resuscitated cells maintained virulence. The strains behaved similarly regardless of their cold or warm areas of origin. This work firstly describes the natural nutrient availability of environmental water favoring R. solanacearum survival, adaptations, and resuscitation in conditions that can be found in natural settings. These findings will contribute to anticipate the ability of R. solanacearum to spread, establish, and induce disease in new geographical and climatic areas. Full article
(This article belongs to the Special Issue Plant Pathogenic Microorganisms: State-of-the-Art Research in Spain)
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Article
Sweet Potato Symptomless Virus 1: First Detection in Europe and Generation of an Infectious Clone
Microorganisms 2022, 10(9), 1736; https://doi.org/10.3390/microorganisms10091736 - 28 Aug 2022
Viewed by 805
Abstract
Sweet potato (Ipomoea batatas), a staple food for people in many of the least developed countries, is affected by many viral diseases. In 2017, complete genome sequences of sweet potato symptomless virus 1 (SPSMV-1, genus Mastrevirus, family Geminiviridae) isolates [...] Read more.
Sweet potato (Ipomoea batatas), a staple food for people in many of the least developed countries, is affected by many viral diseases. In 2017, complete genome sequences of sweet potato symptomless virus 1 (SPSMV-1, genus Mastrevirus, family Geminiviridae) isolates were reported, although a partial SPSMV-1 genome sequence had previously been identified by deep sequencing. To assess the presence of this virus in Spain, sweet potato leaf samples collected in Málaga (southern continental Spain) and the Spanish Canary Islands of Tenerife and Gran Canaria were analyzed. SPSMV-1 was detected in samples from all the geographical areas studied, as well as in plants of several entries obtained from a germplasm collection supposed to be virus-free. Sequence analysis of full-length genomes of isolates from Spain showed novel molecular features, i.e., a novel nonanucleotide in the intergenic region, TCTTATTAC, and a 24-nucleotide deletion in the V2 open reading frame. Additionally, an agroinfectious clone was developed and infectivity assays showed that the virus was able to asymptomatically infect Nicotiana benthamiana, Ipomoea nil, I. setosa, and sweet potato, thus confirming previous suggestions derived from observational studies. To our knowledge, this is the first report of the presence of SPSMV-1 in Spain and Europe and the first agroinfectious clone developed for this virus. Full article
(This article belongs to the Special Issue Plant Pathogenic Microorganisms: State-of-the-Art Research in Spain)
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Article
Biochemical Diversity, Pathogenicity and Phylogenetic Analysis of Pseudomonas viridiflava from Bean and Weeds in Northern Spain
Microorganisms 2022, 10(8), 1542; https://doi.org/10.3390/microorganisms10081542 - 29 Jul 2022
Viewed by 751
Abstract
Pseudomonas viridiflava was originally reported as a bean pathogen, and subsequently as a wide-host range pathogen affecting numerous plants species. In addition, several authors have reported the epiphytic presence of this bacterium in “non-host plants”, which may act as reservoir of P. viridiflava [...] Read more.
Pseudomonas viridiflava was originally reported as a bean pathogen, and subsequently as a wide-host range pathogen affecting numerous plants species. In addition, several authors have reported the epiphytic presence of this bacterium in “non-host plants”, which may act as reservoir of P. viridiflava and source of inoculum for crops. A new biotype of this bacterium, showing an atypical LOPAT profile, was found in Asturias, a Northern region of Spain, causing significant damage in beans, kiwifruit, lettuce, and Hebe. In order to investigate the involvement of weeds in bean disease, samples were collected from beans and weeds growing in the same fields. A total of 48 isolates of P. viridiflava were obtained, 39 from weeds and 9 from beans. 48% and 52% of them showed typical (L− O− P+ A− T+) and atypical (L+ O− P v A− T+) LOPAT profiles, and they displayed high biochemical diversity. Regarding virulence factors, the T-PAI and S-PAI pathogenicity islands were found in 29% and 70.8% of the isolates, 81.2% displayed pectinolytic activity on potato slices, and 59% of the weed isolates produced symptoms after inoculation on bean pods. A phylogenetic tree based on concatenated rpoD, gyrB, and gltA sequences separated the strains carrying S-PAI and T-PAI into different clusters, both containing isolates from beans and weeds, and pathogenic as well as non-pathogenic strains. Closely related strains were found in the two hosts, and more than half of the weed isolates proved to be pathogenic in beans. This is consistent with the role of weeds as a reservoir and source of inoculum for bean infection. Detection of P. viridiflava in weeds throughout the year further supports these roles. Full article
(This article belongs to the Special Issue Plant Pathogenic Microorganisms: State-of-the-Art Research in Spain)
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Article
Assessment of Psyllid Handling and DNA Extraction Methods in the Detection of ‘Candidatus Liberibacter Solanacearum’ by qPCR
Microorganisms 2022, 10(6), 1104; https://doi.org/10.3390/microorganisms10061104 - 26 May 2022
Viewed by 1019
Abstract
Candidatus Liberibacter solanacearum’ (CaLsol) is an uncultured bacterium, transmitted by psyllids and associated with several diseases in Solanaceae and Apiaceae crops. CaLsol detection in psyllids often requires insect destruction, preventing a subsequent morphological identification. In this work, we have assessed the influence [...] Read more.
Candidatus Liberibacter solanacearum’ (CaLsol) is an uncultured bacterium, transmitted by psyllids and associated with several diseases in Solanaceae and Apiaceae crops. CaLsol detection in psyllids often requires insect destruction, preventing a subsequent morphological identification. In this work, we have assessed the influence on the detection of CaLsol by PCR in Bactericera trigonica (Hemiptera: Psyllidae), of four specimen preparations (entire body, ground, cut-off head, and punctured abdomen) and seven DNA extraction methods (PBS suspension, squashing on membrane, CTAB, Chelex, TRIsureTM, HotSHOT, and DNeasy®). DNA yield and purity ratios, time consumption, cost, and residues generated were also evaluated. Optimum results were obtained through grinding, but it is suggested that destructive procedures are not essential in order to detect CaLsol. Although CaLsol was detected by qPCR with DNA obtained by the different procedures, HotSHOT was the most sensitive method. In terms of time consumption and cost, squashed on membrane, HotSHOT, and PBS were the fastest, while HotSHOT and PBS were the cheapest. In summary, HotSHOT was accurate, fast, simple, and sufficiently sensitive to detect this bacterium within the vector. Additionally, cross-contamination with CaLsol was assessed in the ethanol solutions where B. trigonica specimens were usually collected and preserved. CaLsol-free psyllids were CaLsol-positive after incubation with CaLsol-positive specimens. This work provides a valuable guide when choosing a method to detect CaLsol in vectors according to the purpose of the study. Full article
(This article belongs to the Special Issue Plant Pathogenic Microorganisms: State-of-the-Art Research in Spain)
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Article
Gene Overlapping as a Modulator of Begomovirus Evolution
Microorganisms 2022, 10(2), 366; https://doi.org/10.3390/microorganisms10020366 - 04 Feb 2022
Cited by 1 | Viewed by 1012
Abstract
In RNA viruses, which have high mutation—and fast evolutionary— rates, gene overlapping (i.e., genomic regions that encode more than one protein) is a major factor controlling mutational load and therefore the virus evolvability. Although DNA viruses use host high-fidelity polymerases for their replication, [...] Read more.
In RNA viruses, which have high mutation—and fast evolutionary— rates, gene overlapping (i.e., genomic regions that encode more than one protein) is a major factor controlling mutational load and therefore the virus evolvability. Although DNA viruses use host high-fidelity polymerases for their replication, and therefore should have lower mutation rates, it has been shown that some of them have evolutionary rates comparable to those of RNA viruses. Notably, these viruses have large proportions of their genes with at least one overlapping instance. Hence, gene overlapping could be a modulator of virus evolution beyond the RNA world. To test this hypothesis, we use the genus Begomovirus of plant viruses as a model. Through comparative genomic approaches, we show that terminal gene overlapping decreases the rate of virus evolution, which is associated with lower frequency of both synonymous and nonsynonymous mutations. In contrast, terminal overlapping has little effect on the pace of virus evolution. Overall, our analyses support a role for gene overlapping in the evolution of begomoviruses and provide novel information on the factors that shape their genetic diversity. Full article
(This article belongs to the Special Issue Plant Pathogenic Microorganisms: State-of-the-Art Research in Spain)
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Review

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Review
Evaluation of Control Strategies for Xylella fastidiosa in the Balearic Islands
Microorganisms 2022, 10(12), 2393; https://doi.org/10.3390/microorganisms10122393 - 02 Dec 2022
Viewed by 1043
Abstract
The emergence of Xylella fastidiosa (Xf) in the Balearic Islands in October 2016 was a major phytosanitary challenge with international implications. Immediately after its detection, eradication and containment measures included in Decision 2015/789 were implemented. Surveys intensified during 2017, which soon revealed that [...] Read more.
The emergence of Xylella fastidiosa (Xf) in the Balearic Islands in October 2016 was a major phytosanitary challenge with international implications. Immediately after its detection, eradication and containment measures included in Decision 2015/789 were implemented. Surveys intensified during 2017, which soon revealed that the pathogen was widely distributed on the islands and eradication measures were no longer feasible. In this review, we analyzed the control measures carried out by the Balearic Government in compliance with European legislation, as well as the implementation of its control action plan. At the same time, we contrasted them with the results of scientific research accumulated since 2017 on the epidemiological situation. The case of Xf in the Balearic Islands is paradigmatic since it concentrates on a small territory with one of the widest genetic diversities of Xf affecting crops and forest ecosystems. We also outline the difficulties of anticipating unexpected epidemiological situations in the legislation on harmful exotic organisms on which little biological information is available. Because Xf has become naturalized in the islands, coexistence alternatives based on scientific knowledge are proposed to reorient control strategies towards the main goal of minimizing damage to crops and the landscape. Full article
(This article belongs to the Special Issue Plant Pathogenic Microorganisms: State-of-the-Art Research in Spain)
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Review
Synthetic Peptides against Plant Pathogenic Bacteria
Microorganisms 2022, 10(9), 1784; https://doi.org/10.3390/microorganisms10091784 - 03 Sep 2022
Cited by 2 | Viewed by 941
Abstract
The control of plant diseases caused by bacteria that seriously compromise crop productivity around the world is still one of the most important challenges in food security. Integrated approaches for disease control generally lack plant protection products with high efficacy and low environmental [...] Read more.
The control of plant diseases caused by bacteria that seriously compromise crop productivity around the world is still one of the most important challenges in food security. Integrated approaches for disease control generally lack plant protection products with high efficacy and low environmental and health adverse effects. Functional peptides, either from natural sources or synthetic, are considered as novel candidates to develop biopesticides. Synthetic peptides can be obtained based on the structure of natural compounds or de novo designed, considering the features of antimicrobial peptides. The advantage of this approach is that analogues can be conveniently prepared, enabling the identification of sequences with improved biological properties. Several peptide libraries have been designed and synthetized, and the best sequences showed strong bactericidal activity against important plant pathogenic bacteria, with a good profile of biodegradability and low toxicity. Among these sequences, there are bacteriolytic or antibiofilm peptides that work against the target bacteria, plant defense elicitor peptides, and multifunctional peptides that display several of these properties. Here, we report the research performed by our groups during the last twenty years, as well as our ongoing work. We also highlight those peptides that can be used as candidates to develop novel biopesticides, and the main challenges and prospects. Full article
(This article belongs to the Special Issue Plant Pathogenic Microorganisms: State-of-the-Art Research in Spain)
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Review
Bacteria as Biological Control Agents of Plant Diseases
Microorganisms 2022, 10(9), 1759; https://doi.org/10.3390/microorganisms10091759 - 31 Aug 2022
Cited by 5 | Viewed by 1462
Abstract
Biological control is an effective and sustainable alternative or complement to conventional pesticides for fungal and bacterial plant disease management. Some of the most intensively studied biological control agents are bacteria that can use multiple mechanisms implicated in the limitation of plant disease [...] Read more.
Biological control is an effective and sustainable alternative or complement to conventional pesticides for fungal and bacterial plant disease management. Some of the most intensively studied biological control agents are bacteria that can use multiple mechanisms implicated in the limitation of plant disease development, and several bacterial-based products have been already registered and marketed as biopesticides. However, efforts are still required to increase the commercially available microbial biopesticides. The inconsistency in the performance of bacterial biocontrol agents in the biological control has limited their extensive use in commercial agriculture. Pathosystem factors and environmental conditions have been shown to be key factors involved in the final levels of disease control achieved by bacteria. Several biotic and abiotic factors can influence the performance of the biocontrol agents, affecting their mechanisms of action or the multitrophic interaction between the plant, the pathogen, and the bacteria. This review shows some relevant examples of known bacterial biocontrol agents, with especial emphasis on research carried out by Spanish groups. In addition, the importance of the screening process and of the key steps in the development of bacterial biocontrol agents is highlighted. Besides, some improvement approaches and future trends are considered. Full article
(This article belongs to the Special Issue Plant Pathogenic Microorganisms: State-of-the-Art Research in Spain)
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