The Challenge of Coping with Globally and Locally Emerging Fungal and Oomycetes Plant Pathogens

A special issue of Plants (ISSN 2223-7747). This special issue belongs to the section "Plant Protection and Biotic Interactions".

Deadline for manuscript submissions: closed (30 April 2021) | Viewed by 41565

Special Issue Editors

Centro di Competenza Agroinnova and DISAFA, University of Torino, 10124 Torino, TO, Italy
Interests: plant pathology; plant disease management; plant and food biosecurity; climate change and plant disease
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The General Assembly of United Nations proclaimed 2020 the International Year of Plant Health (IYPH), with the aims of raising awareness of the importance of plant health for a sustainable development and supporting plant health policies and plant protection services as strategic aspects of global food security, economic development, environment protection, and human health. The scope of this Special Issue is to highlight globally or locally emerging and re-emerging diseases of agricultural crops, ornamentals, and landscape and forest plants, addressing the threat they pose to food security, national and international economy, biodiversity, and the stability of natural ecosystems, and evoke sustainable strategies to cope with them. The emergence of new plant diseases caused by fungi and oomycetes as a consequence of different drivers, including globalization and climate change, is a never ending challenge, and new management strategies have to be developed to counteract the reduction of available fungicides due to justified environmental and human health concerns. An aspect to which particular emphasis will be given is the contribution of new sciences and technologies, such as molecular taxonomy, omics, high throughput sequencing, genome editing, biomatematics, epidemiological modeling, nanotechnologies, and remote sensing, as well as new technical tools, such as sentinel-trees, in situ diagnostics, biostimulants, resistance inducers, eco-friendly substances, and fungicides with specific-activity, in the development of innovative disease management strategies that help increase productivity and ensure food security as well as environmental and human health. Reviews and original research articles dealing with new problems posed by well-known diseases and innovative strategies for their management or addressing new diseases for which it is necessary to develop specific protection tools or modify currently applied management strategies fit the scope of this Issue.

Dr. Santa Olga Cacciola
Prof. Dr. Maria Lodovica Gullino
Guest Editors

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Keywords

  • alert pathogens
  • environment protection and human health
  • climate changes
  • driving factors
  • diagnostics

Published Papers (10 papers)

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Research

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18 pages, 5258 KiB  
Article
Loop-Mediated Isothermal Amplification (LAMP) and SYBR Green qPCR for Fast and Reliable Detection of Geosmithia morbida (Kolařik) in Infected Walnut
by Domenico Rizzo, Chiara Aglietti, Alessandra Benigno, Matteo Bracalini, Daniele Da Lio, Linda Bartolini, Giovanni Cappellini, Antonio Aronadio, Cristina Francia, Nicola Luchi, Alberto Santini, Santa Olga Cacciola, Tiziana Panzavolta and Salvatore Moricca
Plants 2022, 11(9), 1239; https://doi.org/10.3390/plants11091239 - 03 May 2022
Cited by 4 | Viewed by 2558
Abstract
Walnut species (Juglans spp.) are multipurpose trees, widely employed in plantation forestry for high-quality timber and nut production, as well as in urban greening as ornamental plants. These species are currently threatened by the thousand cankers disease (TCD) complex, an insect–fungus association [...] Read more.
Walnut species (Juglans spp.) are multipurpose trees, widely employed in plantation forestry for high-quality timber and nut production, as well as in urban greening as ornamental plants. These species are currently threatened by the thousand cankers disease (TCD) complex, an insect–fungus association which involves the ascomycete Geosmithia morbida (GM) and its vector, the bark beetle Pityophthorus juglandis. While TCD has been studied extensively where it originated in North America, little research has been carried out in Europe, where it was more recently introduced. A key step in research to cope with this new phytosanitary emergency is the development of effective molecular detection tools. In this work, we report two accurate molecular methods for the diagnosis of GM, based on LAMP (real-time and visual) and SYBR Green qPCR, which are complimentary to and integrated with similar recently developed assays. Our protocols detected GM DNA from pure mycelium and from infected woody tissue with high accuracy, sensitivity, and specificity, without cross-reactivity to a large panel of taxonomically related species. The precision and robustness of our tests guarantee high diagnostic standards and could be used to support field diagnostic end-users in TCD monitoring and surveillance campaigns. Full article
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16 pages, 4311 KiB  
Article
Rapid Detection of Pityophthorus juglandis (Blackman) (Coleoptera, Curculionidae) with the Loop-Mediated Isothermal Amplification (LAMP) Method
by Domenico Rizzo, Salvatore Moricca, Matteo Bracalini, Alessandra Benigno, Umberto Bernardo, Nicola Luchi, Daniele Da Lio, Francesco Nugnes, Giovanni Cappellini, Chiara Salemi, Santa Olga Cacciola and Tiziana Panzavolta
Plants 2021, 10(6), 1048; https://doi.org/10.3390/plants10061048 - 22 May 2021
Cited by 9 | Viewed by 2904
Abstract
The walnut twig beetle Pityophthorus juglandis is a phloem-boring bark beetle responsible, in association with the ascomycete Geosmithia morbida, for the Thousand Cankers Disease (TCD) of walnut trees. The recent finding of TCD in Europe prompted the development of effective diagnostic protocols [...] Read more.
The walnut twig beetle Pityophthorus juglandis is a phloem-boring bark beetle responsible, in association with the ascomycete Geosmithia morbida, for the Thousand Cankers Disease (TCD) of walnut trees. The recent finding of TCD in Europe prompted the development of effective diagnostic protocols for the early detection of members of this insect/fungus complex. Here we report the development of a highly efficient, low-cost, and rapid method for detecting the beetle, or even just its biological traces, from environmental samples: the loop-mediated isothermal amplification (LAMP) assay. The method, designed on the 28S ribosomal RNA gene, showed high specificity and sensitivity, with no cross reactivity to other bark beetles and wood-boring insects. The test was successful even with very small amounts of the target insect’s nucleic acid, with limit values of 0.64 pg/µL and 3.2 pg/µL for WTB adults and frass, respectively. A comparison of the method (both in real time and visual) with conventional PCR did not display significant differences in terms of LoD. This LAMP protocol will enable quick, low-cost, and early detection of P. juglandis in areas with new infestations and for phytosanitary inspections at vulnerable sites (e.g., seaports, airports, loading stations, storage facilities, and wood processing companies). Full article
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25 pages, 425 KiB  
Article
Screening of Durum Wheat (Triticum turgidum L. subsp. durum (Desf.) Husn.) Italian Cultivars for Susceptibility to Fusarium Head Blight Incited by Fusarium graminearum
by Gaetano Bentivenga, Alfio Spina, Karim Ammar, Maria Allegra and Santa Olga Cacciola
Plants 2021, 10(1), 68; https://doi.org/10.3390/plants10010068 - 31 Dec 2020
Cited by 13 | Viewed by 3671
Abstract
In 2009, a set of 35 cultivars of durum wheat (Triticum turgidum L. subsp. durum (Desf.) Husn.) of Italian origin was screened for fusarium head blight (FHB) susceptibility at CIMMYT (Mexico) and in the 2019–20 cropping season, 16 of these cultivars, which [...] Read more.
In 2009, a set of 35 cultivars of durum wheat (Triticum turgidum L. subsp. durum (Desf.) Husn.) of Italian origin was screened for fusarium head blight (FHB) susceptibility at CIMMYT (Mexico) and in the 2019–20 cropping season, 16 of these cultivars, which had been included in the Italian National Plant Variety Register, were tested again in southern and northern Italy. Wheat cultivars were artificially inoculated during anthesis with a conidial suspension of Fusarium graminearum sensu lato using a standard spray inoculation method. Inoculum was a mixture of mono-conidial isolates sourced in the same areas where the trials were performed. Isolates had been characterized on the basis of morphological characteristics and by DNA PCR amplification using a specific primer set and then selected for their virulence and ability to produce mycotoxins. The susceptibility to FHB was rated on the basis of the disease severity, disease incidence and FHB index. Almost all of the tested cultivars were susceptible or very susceptible to FHB with the only exception of “Duprì”, “Tiziana” and “Dylan” which proved to be moderately susceptible. The susceptibility to FHB was inversely correlated with the plant height and flowering biology, the tall and the late heading cultivars being less susceptible. Full article
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16 pages, 1556 KiB  
Article
Rootstock-Scion Interaction Affects the Composition and Pathogen Inhibitory Activity of Tobacco (Nicotiana tabacum L.) Root Exudates
by Cheng-Sheng Zhang, Yanfen Zheng, Lijuan Peng and Jianmin Cao
Plants 2020, 9(12), 1652; https://doi.org/10.3390/plants9121652 - 26 Nov 2020
Cited by 3 | Viewed by 1849
Abstract
The composition and allelopathy to Phytophthora nicotianae (the causal agent of tobacco black shank disease) of root exudates from a resistant tobacco (Nicotiana tabacum L.) cultivar Gexin 3, a susceptible cultivar Xiaohuangjin 1025 and their reciprocal grafts were investigated. Grafting with disease-resistant [...] Read more.
The composition and allelopathy to Phytophthora nicotianae (the causal agent of tobacco black shank disease) of root exudates from a resistant tobacco (Nicotiana tabacum L.) cultivar Gexin 3, a susceptible cultivar Xiaohuangjin 1025 and their reciprocal grafts were investigated. Grafting with disease-resistant rootstock could improve resistance to black shank; this is closely related to the allelopathy of root exudates. The root exudates from the resistant cultivar inhibited the growth of P. nicotianae, while those from the susceptible cultivar promoted the growth; the grafting varieties had intermediate properties. The root exudate composition differed among cultivars. Gexin 3 was rich in esters and fatty acids, while Xiaohuangjin 1025 contained more hydrocarbons and phenolic acids. The composition of root exudates of grafted cultivars as well as their allelopathy to P. nicotianae were altered, and tended to be close to the composition of cultivar used as rootstock. Eugenol, 4-tert-butylphenol, mono (2-ethylhexyl) phthalate, 4-hydroxybenzoic acid, 2,6-di-tert-butylphenol, dipropyl phthalate, and methyl myristate were identified as the main compounds contributing to inhibitory properties of root exudates. Sorbitol was suggested to play a role in disease induction. Overall, rootstock–scion interaction affected the composition of tobacco root exudates, which may be attributed to the different disease resistance among grafted plants, rootstock and scion. Full article
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13 pages, 2769 KiB  
Article
Fungal Pathogens Affecting the Production and Quality of Medical Cannabis in Israel
by Shachar Jerushalmi, Marcel Maymon, Aviv Dombrovsky and Stanley Freeman
Plants 2020, 9(7), 882; https://doi.org/10.3390/plants9070882 - 13 Jul 2020
Cited by 26 | Viewed by 6926
Abstract
The use of and research on medical cannabis (MC) is becoming more common, yet there are still many challenges regarding plant diseases of this crop. For example, there is a lack of formal and professional knowledge regarding fungi that infect MC plants, and [...] Read more.
The use of and research on medical cannabis (MC) is becoming more common, yet there are still many challenges regarding plant diseases of this crop. For example, there is a lack of formal and professional knowledge regarding fungi that infect MC plants, and practical and effective methods for managing the casual agents of disease are limited. The purpose of this study was to identify foliar, stem, and soilborne pathogens affecting MC under commercial cultivation in Israel. The predominant major foliage pathogens were identified as Alternaria alternata and Botrytis cinerea, while the common stem and soilborne pathogens were identified as Fusarium oxysporum and F. solani. Other important fungi that were isolated from foliage were those producing various mycotoxins that can directly harm patients, such as Aspergillus spp. and Penicillium spp. The sampling and characterization of potential pathogenic fungi were conducted from infected MC plant parts that exhibited various disease symptoms. Koch postulates were conducted by inoculating healthy MC tissues and intact plants with fungi isolated from infected commercially cultivated symptomatic plants. In this study, we report on the major and most common plant pathogens of MC found in Israel, and determine the seasonal outbreak of each fungus. Full article
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16 pages, 3250 KiB  
Article
Characterization of Colletotrichum ocimi Population Associated with Black Spot of Sweet Basil (Ocimum basilicum) in Northern Italy
by Santa Olga Cacciola, Giovanna Gilardi, Roberto Faedda, Leonardo Schena, Antonella Pane, Angelo Garibaldi and Maria Lodovica Gullino
Plants 2020, 9(5), 654; https://doi.org/10.3390/plants9050654 - 22 May 2020
Cited by 18 | Viewed by 5017
Abstract
Black spot is a major foliar disease of sweet basil (Ocimum basilicum) present in a typical cultivation area of northern Italy, including the Liguria and southern Piedmont regions, where this aromatic herb is an economically important crop. In this study, 15 [...] Read more.
Black spot is a major foliar disease of sweet basil (Ocimum basilicum) present in a typical cultivation area of northern Italy, including the Liguria and southern Piedmont regions, where this aromatic herb is an economically important crop. In this study, 15 Colletotrichum isolates obtained from sweet basil plants with symptoms of black spot sampled in this area were characterized morphologically and by nuclear DNA analysis using internal transcribed spacers (ITS) and intervening 5.8S nrDNA as well as part of the β-tubulin gene (TUB2) regions as barcode markers. Analysis revealed all but one isolate belonged to the recently described species C. ocimi of the C. destructivum species complex. Only one isolate was identified as C. destructivum sensu stricto (s.s.). In pathogenicity tests on sweet basil, both C. ocimi and C. destructivum s.s. isolates incited typical symptoms of black spot, showing that although C. ocimi prevails in this basil production area, it is not the sole causal agent of black spot in northern Italy. While no other hosts of C. ocimi are known worldwide, the close related species C. destructivum has a broad host range, suggesting a speciation process of C. ocimi within this species complex driven by adaptation to the host. Full article
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19 pages, 3800 KiB  
Article
Pathological and Epidemiological Characterization of First Outbreak of Daylily Rust in Europe and Evaluation of Puccinia hemerocallidis Resistance in Hemerocallis Cultivars
by Madalena Ramos, Rita Carvalho, Elsa Soares da Silva, Ana Paula Ramos and Pedro Talhinhas
Plants 2020, 9(4), 427; https://doi.org/10.3390/plants9040427 - 31 Mar 2020
Cited by 3 | Viewed by 3075
Abstract
Daylily rust—caused by Puccinia hemerocallidis—was confined to Eastern Asia until the disease was reported in Oceania, Africa, the Americas and Portugal in the 21st century. Although information on rust resistance of American cultivars is available, little is known about the resistance of [...] Read more.
Daylily rust—caused by Puccinia hemerocallidis—was confined to Eastern Asia until the disease was reported in Oceania, Africa, the Americas and Portugal in the 21st century. Although information on rust resistance of American cultivars is available, little is known about the resistance of European bred cultivars, threating the ornamental sector if the fungus spreads to other European countries. Aiming to provide tools to address this, we analyzed the Portuguese pathogens and characterized rust resistance in a selection of cultivars, while optimizing disease rating scales. Morphologic, genetic and cytogenomic characterization of four isolates reveals narrow diversity and raises the question whether the pathogen may have originated in North- or Central America. Daily records of multiple symptomatologic parameters enabled a detailed disease progress analysis, discriminating cultivars according to their resistance levels and revealing susceptibility as the most common state. Among the tested cultivars, 12 out of 17 began to show symptoms between 6–8 dai and were classified as susceptible. Cultivars ‘Stella d’Oro’, ‘Bitsy’ and ‘Cherry Tiger’ behaved as moderately resistant although the occurrence of late sporulation on leaves suggests incomplete resistance and challenges common rating scales. The identification of resistance sources in European breeding lines is crucial for the sustainable future of daylilies. Full article
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16 pages, 6791 KiB  
Article
The Search for Quorum Sensing in Botrytis cinerea: Regulatory Activity of Its Extracts on Its Development
by Esteban D. Rosero-Hernández and Fernando L. Echeverri
Plants 2020, 9(2), 168; https://doi.org/10.3390/plants9020168 - 31 Jan 2020
Cited by 2 | Viewed by 2274
Abstract
Botrytis cinerea is a phytopathogenic fungus that causes large crop and post-harvest losses. Therefore, new and effective strategies are needed to control the disease and to reduce resistance to fungicides. Modulating pathogenicity and virulence by manipulating microbial communication is a promising strategy. This [...] Read more.
Botrytis cinerea is a phytopathogenic fungus that causes large crop and post-harvest losses. Therefore, new and effective strategies are needed to control the disease and to reduce resistance to fungicides. Modulating pathogenicity and virulence by manipulating microbial communication is a promising strategy. This communication mechanism, called Quorum Sensing (QS), has already been reported in bacteria and yeasts; however, it has not yet been studied in B. cinerea. To establish the existence of this biochemical process in B. cinerea, we prepared extracts at different growth times (D1-D12), which were applied to fresh cultures of the same fungi. The chemical analysis of the extracts obtained from several fermentations showed different compositions and biological activities. We confirmed the presence of several phytotoxins, as well as compounds 1-phenylethanol and 3-phenylpropanol. Day five extract (0.1%) inhibited conidia germination and elongation of germ tubes, day seven extract (1%) produced the greatest phytotoxic effect in tomato leaves, and day nine extract (0.1%) was a sporulation inhibitor. In contrast, the extracts from days 7, 9, and 12 of fermentation (0.1% and 0.01%) promoted pellet and biofilm formation. Sporulation was slightly induced at 0.01%, while at 0.1% there was a great inhibition. At the highest extract concentrations, a biocidal effect was detected, but at the lowest, we observed a QS-like effect, regulating processes such as filamentation, morphogenesis, and pathogenesis. These results of the biological activity and composition of extracts suggest the existence of a QS-like mechanism in B. cinerea, which could lead to new non-biocidal alternatives for its control through interference in the pathogenicity and virulence mechanisms of the fungi. Full article
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Review

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20 pages, 1605 KiB  
Review
The Role of Grafting in the Resistance of Tomato to Viruses
by Roberta Spanò, Massimo Ferrara, Donato Gallitelli and Tiziana Mascia
Plants 2020, 9(8), 1042; https://doi.org/10.3390/plants9081042 - 16 Aug 2020
Cited by 21 | Viewed by 6374
Abstract
Grafting is routinely implemented in modern agriculture to manage soilborne pathogens such as fungi, oomycetes, bacteria, and viruses of solanaceous crops in a sustainable and environmentally friendly approach. Some rootstock/scion combinations use specific genetic resistance mechanisms to impact also some foliar and airborne [...] Read more.
Grafting is routinely implemented in modern agriculture to manage soilborne pathogens such as fungi, oomycetes, bacteria, and viruses of solanaceous crops in a sustainable and environmentally friendly approach. Some rootstock/scion combinations use specific genetic resistance mechanisms to impact also some foliar and airborne pathogens, including arthropod or contact-transmitted viruses. These approaches resulted in poor efficiency in the management of plant viruses with superior virulence such as the strains of tomato spotted wilt virus breaking the Sw5 resistance, strains of cucumber mosaic virus carrying necrogenic satellite RNAs, and necrogenic strains of potato virus Y. Three different studies from our lab documented that suitable levels of resistance/tolerance can be obtained by grafting commercial tomato varieties onto the tomato ecotype Manduria (Ma) rescued in the framework of an Apulian (southern Italy) regional program on biodiversity. Here we review the main approaches, methods, and results of the three case studies and propose some mechanisms leading to the tolerance/resistance observed in susceptible tomato varieties grafted onto Ma as well as in self-grafted plants. The proposed mechanisms include virus movement in plants, RNA interference, genes involved in graft wound response, resilience, and tolerance to virus infection. Full article
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Other

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9 pages, 1149 KiB  
Brief Report
First Report of Root Rot Caused by Phytophthora bilorbang on Olea europaea in Italy
by Elena Santilli, Mario Riolo, Federico La Spada, Antonella Pane and Santa Olga Cacciola
Plants 2020, 9(7), 826; https://doi.org/10.3390/plants9070826 - 30 Jun 2020
Cited by 23 | Viewed by 5622
Abstract
Leaf chlorosis, severe defoliation and wilt associated with root rot were observed on mature olive trees cv. Nera di Gonnos in an experimental orchard at Mirto Crosia (Calabria, southern Italy). An oomycete was consistently isolated from rotten roots of symptomatic olive trees. It [...] Read more.
Leaf chlorosis, severe defoliation and wilt associated with root rot were observed on mature olive trees cv. Nera di Gonnos in an experimental orchard at Mirto Crosia (Calabria, southern Italy). An oomycete was consistently isolated from rotten roots of symptomatic olive trees. It was identified as Phytophthora bilorbang by morphological characters and sequencing of Internal Transcribed Spacer (ITS) regions of ribosomal DNA (rDNA). Pathogenicity was verified by inoculating potted two-month-old rooted cuttings of Olea europaea var. Nera di Gonnos in a soil infestation trial. P. bilorbang was re-isolated from roots of symptomatic, artificially inoculated olive cuttings to fulfill Koch’s postulates. This is the first report of P. bilorbang on O. europaea L. and on a species of the Oleaceae family worldwide. Full article
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