Diagnosis of Plant Pathogenic Fungi and Oomycetes and Plant Breeding for Disease Resistance 2.0

A special issue of Journal of Fungi (ISSN 2309-608X). This special issue belongs to the section "Fungal Pathogenesis and Disease Control".

Deadline for manuscript submissions: closed (1 February 2023) | Viewed by 18395

Special Issue Editors

Consiglio per la Ricerca in Agricoltura e L’analisi Dell’economia Agraria - Centro di Ricerca Cerealicoltura e Colture Industriali (CREA-CI), Acireale, Italy
Interests: cereal; pulse and industrial crops pathology and disease management strategies; diagnosis and tolerances/resistances to pathogenic fungi of durum and bread wheat genotypes; breeding for cereal and pulse resistance; postharvest management of durum and bread wheat
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Special Issue Information

Dear Colleagues,

DNA sequencing technology has revolutionized the taxonomy and diagnostics of true fungi and oomycetes, here referred to as fungi in a broad sense. Whole-genome sequencing of plant pathogens made the targeted design of primers for molecular diagnosis possible, next-generation sequencing proved to be a powerful tool to study the plant-associated microbiomes and the multi-locus sequence phylogeny resulted in a substantial taxonomic and nomenclatural revision of families and genera, including those of important plant pathogens. However, defining species boundaries is still challenging, and plant pathologists feel the need for a more stable molecular taxonomy. Moreover, not all fungi associated with plants are pathogens, and many shift to an aggressive pathogenic lifestyle when environmental conditions are favorable or the host plant is stressed. A promising aspect of a molecular taxonomy that also takes functional aspects into consideration is the search for genetic markers predicting the pathogenetic potential of fungi.

The aim of this Special Issue is to stimulate the debate on the implications of molecular taxonomy for both plant pathology and crop breeding for disease resistance. This Special Issue welcomes reviews addressing these general topics and scientific contributions demonstrating the usefulness of molecular techniques in identifying fungi associated with agricultural and forestry plants.

Dr. Santa Olga Cacciola
Dr. Alfio Spina
Guest Editors

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Published Papers (8 papers)

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Research

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19 pages, 2180 KiB  
Article
Molecular Variability of the Fusarium solani Species Complex Associated with Fusarium Wilt of Melon in Iran
by Fatemeh Sabahi, Zia Banihashemi, Maryam Mirtalebi, Martijn Rep and Santa Olga Cacciola
J. Fungi 2023, 9(4), 486; https://doi.org/10.3390/jof9040486 - 18 Apr 2023
Cited by 1 | Viewed by 1900
Abstract
Species of the Fusarium solani species complex (FSSC) are responsible for the Fusarium wilt disease of melon (Cucumis melo), a major disease of this crop in Iran. According to a recent taxonomic revision of Fusarium based primarily on multilocus phylogenetic analysis, [...] Read more.
Species of the Fusarium solani species complex (FSSC) are responsible for the Fusarium wilt disease of melon (Cucumis melo), a major disease of this crop in Iran. According to a recent taxonomic revision of Fusarium based primarily on multilocus phylogenetic analysis, Neocosmospora, a genus distinct from Fusarium sensu stricto, has been proposed to accommodate the FSSC. This study characterized 25 representative FSSC isolates from melon collected in 2009–2011 during a field survey carried out in five provinces of Iran. Pathogenicity assays showed the isolates were pathogenic on different varieties of melon and other cucurbits, including cucumber, watermelon, zucchini, pumpkin, and bottle gourd. Based on morphological characteristics and phylogenetic analysis of three genetic regions, including nrDNA internal transcribed spacer (ITS), 28S nrDNA large subunit (LSU) and translation elongation factor 1-alpha (tef1), Neocosmospora falciformis (syn. F. falciforme), N. keratoplastica (syn. F. keratoplasticum), N. pisi (syn. F. vanettenii), and Neocosmospora sp. were identified among the Iranian FSSC isolates. The N. falciformis isolates were the most numerous. This is the first report of N. pisi causing wilt and root rot disease in melon. Iranian FSSC isolates from different regions in the country shared the same multilocus haplotypes suggesting a long-distance dispersal of FSSC, probably through seeds. Full article
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12 pages, 1121 KiB  
Article
Genetic Variation of Puccinia triticina Populations in Iran from 2010 to 2017 as Revealed by SSR and ISSR Markers
by Zahra Nemati, Ali Dadkhodaie, Reza Mostowfizadeh-Ghalamfarsa, Rahim Mehrabi and Santa Olga Cacciola
J. Fungi 2023, 9(3), 388; https://doi.org/10.3390/jof9030388 - 22 Mar 2023
Viewed by 1240
Abstract
Puccinia triticina is a major wheat pathogen worldwide. Although Iran is within the Fertile Crescent, which is supposed to be the center of origin of both wheat and P. triticina, the knowledge of the genetic variability of local populations of this basidiomycete [...] Read more.
Puccinia triticina is a major wheat pathogen worldwide. Although Iran is within the Fertile Crescent, which is supposed to be the center of origin of both wheat and P. triticina, the knowledge of the genetic variability of local populations of this basidiomycete is limited. We analyzed 12 inter simple sequence repeats (ISSRs) and 18 simple sequence repeats (SSRs) of 175 P. triticina isolates sampled between 2010 and 2017 from wheat and other Poaceae in 14 provinces of Iran. SSRs revealed more polymorphisms than ISSRs, indicating they were more effective in differentiating P. triticina populations. Based on a dissimilarity matrix with a variable mutation rate for SSRs and a Dice coefficient for ISSRs, the isolates were separated into three large groups, each including isolates from diverse geographic origins and hosts. The grouping of SSR genotypes in UPGMA dendrograms was consistent with the grouping inferred from the Bayesian approach. However, isolates with a common origin clustered into separate subgroups within each group. The high proportion of heterozygous alleles suggests that in Iran clonal reproduction prevails over sexual reproduction of the pathogen. A significant correlation was found between SSR and ISSR genotypes and the virulence phenotypes of the isolates, as determined in a previous study. Full article
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20 pages, 3656 KiB  
Article
Benzimidazole Derivatives Suppress Fusarium Wilt Disease via Interaction with ERG6 of Fusarium equiseti and Activation of the Antioxidant Defense System of Pepper Plants
by Asmaa El-Nagar, Abdelnaser A. Elzaawely, Hassan M. El-Zahaby, Tran Dang Xuan, Tran Dang Khanh, Mohamed Gaber, Nadia El-Wakeil, Yusif El-Sayed and Yasser Nehela
J. Fungi 2023, 9(2), 244; https://doi.org/10.3390/jof9020244 - 12 Feb 2023
Cited by 2 | Viewed by 1766
Abstract
Sweet pepper (Capsicum annuum L.), also known as bell pepper, is one of the most widely grown vegetable crops worldwide. It is attacked by numerous phytopathogenic fungi, such as Fusarium equiseti, the causal agent of Fusarium wilt disease. In the current [...] Read more.
Sweet pepper (Capsicum annuum L.), also known as bell pepper, is one of the most widely grown vegetable crops worldwide. It is attacked by numerous phytopathogenic fungi, such as Fusarium equiseti, the causal agent of Fusarium wilt disease. In the current study, we proposed two benzimidazole derivatives, including 2-(2-hydroxyphenyl)-1-H benzimidazole (HPBI) and its aluminum complex (Al−HPBI complex), as potential control alternatives to F. equiseti. Our findings showed that both compounds demonstrated dose-dependent antifungal activity against F. equiseti in vitro and significantly suppressed disease development in pepper plants under greenhouse conditions. According to in silico analysis, the F. equiseti genome possesses a predicted Sterol 24-C-methyltransferase (FeEGR6) protein that shares a high degree of homology with EGR6 from F. oxysporum (FoEGR6). It is worth mentioning that molecular docking analysis confirmed that both compounds can interact with FeEGR6 from F. equiseti as well as FoEGR6 from F. oxysporum. Moreover, root application of HPBI and its aluminum complex significantly enhanced the enzymatic activities of guaiacol-dependent peroxidases (POX), polyphenol oxidase (PPO), and upregulated four antioxidant-related enzymes, including superoxide dismutase [Cu-Zn] (CaSOD-Cu), L-ascorbate peroxidase 1, cytosolic (CaAPX), glutathione reductase, chloroplastic (CaGR), and monodehydroascorbate reductase (CaMDHAR). Additionally, both benzimidazole derivatives induced the accumulation of total soluble phenolics and total soluble flavonoids. Collectively, these findings suggest that the application of HPBI and Al−HPBI complex induce both enzymatic and nonenzymatic antioxidant defense machinery. Full article
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12 pages, 4212 KiB  
Article
A New Species of Neoscytalidium hylocereum sp. nov. Causing Canker on Red-Fleshed Dragon Fruit (Hylocereus polyrhizus) in Southern Thailand
by Prisana Wonglom, Chaninun Pornsuriya and Anurag Sunpapao
J. Fungi 2023, 9(2), 197; https://doi.org/10.3390/jof9020197 - 03 Feb 2023
Cited by 7 | Viewed by 3211
Abstract
During 2020–2021, cultivated red-fleshed dragon fruit (Hylocereus polyrhizus) in Phatthalung province, southern Thailand, was infected with canker disease in all stages of growth. Small, circular, sunken, orange cankers first developed on the cladodes of H. polyrhizus and later expanded and became [...] Read more.
During 2020–2021, cultivated red-fleshed dragon fruit (Hylocereus polyrhizus) in Phatthalung province, southern Thailand, was infected with canker disease in all stages of growth. Small, circular, sunken, orange cankers first developed on the cladodes of H. polyrhizus and later expanded and became gray scabs with masses of pycnidia. The fungi were isolated using the tissue transplanting method and identified based on the growth of the fungal colony, and the dimensions of the conidia were measured. Their species level was confirmed with the molecular study of multiple DNA sequences, and their pathogenicity was tested using the agar plug method. Morphological characterization and molecular identification of the internal transcribed spacer (ITS), translation elongation factor 1-α (tef1-α) and β-tubulin (tub) sequences revealed the fungal pathogen to be a new species. It was named Neoscytalidium hylocereum sp. nov. The biota of the new species, N. hylocereum, was deposited in Mycobank, and the species was assigned accession number 838004. The pathogenicity test was performed to fulfil Koch’s postulates. N. hylocereum showed sunken orange cankers with a mass of conidia similar to those observed in the field. To our knowledge, this is the first report of H. polyrhizus as a host of the new species N. hylocereum causing stem cankers in Thailand. Full article
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15 pages, 904 KiB  
Article
Fungal Pathogens Associated with Crown and Root Rot in Wheat-Growing Areas of Northern Kyrgyzstan
by Göksel Özer, İsmail Erper, Şenol Yıldız, Tuğba Bozoğlu, Sezim Zholdoshbekova, Mehtap Alkan, Fatih Tekin, Tair Esenali Uulu, Mustafa İmren, Abdelfattah A. Dababat and Sibel Derviş
J. Fungi 2023, 9(1), 124; https://doi.org/10.3390/jof9010124 - 16 Jan 2023
Cited by 3 | Viewed by 2164
Abstract
Fungal species associated with crown and root rot diseases in wheat have been extensively studied in many parts of the world. However, no reports on the relative importance and distribution of pathogens associated with wheat crown and root rot in Kyrgyzstan have been [...] Read more.
Fungal species associated with crown and root rot diseases in wheat have been extensively studied in many parts of the world. However, no reports on the relative importance and distribution of pathogens associated with wheat crown and root rot in Kyrgyzstan have been published. Hence, fungal species associated with wheat crown/root rot were surveyed in three main wheat production regions in northern Kyrgyzstan. Fungal species were isolated on 1/5 strength potato-dextrose agar amended with streptomycin (0.1 g/L) and chloramphenicol (0.05 g/L). A total of 598 fungal isolates from symptomatic tissues were identified using morphological features of the cultures and conidia, as well as sequence analysis of the nuclear ribosomal internal transcribed spacer (ITS) region, the translation elongation factor 1α (TEF1), and the RNA polymerase II beta subunit (RPB2) genes. The percentage of fields from which each fungus was isolated and their relative percentage isolation levels were determined. Bipolaris sorokiniana, the causal agent of common root rot, was the most prevalent pathogenic species isolated, being isolated from 86.67% of the fields surveyed at a frequency of isolation of 40.64%. Fusarium spp. accounted for 53.01% of all isolates and consisted of 12 different species. The most common Fusarium species identified was Fusarium acuminatum, which was isolated from 70% of the sites surveyed with an isolation frequency of 21.57%, followed by Fusarium culmorum, Fusarium nygamai, Fusarium oxysporum, and Fusarium equiseti, all of which had a field incidence of more than 23%. Inoculation tests with 44 isolates representing 17 species on the susceptible Triticum aestivum cv. Seri 82 revealed that Fusarium pseudograminearum and F. culmorum isolates were equally the most virulent pathogens. The widespread distribution of moderately virulent B. sorokiniana appears to be a serious threat to wheat culture, limiting yield and quality. With the exception of F. culmorum, the remaining Fusarium species did not pose a significant threat to wheat production in the surveyed areas because common species, such as F. acuminatum, F. nygamai, F. oxysporum, and F. equiseti, were non-pathogenic but infrequent species, such as Fusarium redolens, Fusarium algeriense, and F. pseudograminearum, were highly or moderately virulent. Curvularia inaequalis, which was found in three different fields, was mildly virulent. The remaining Fusarium species, Fusarium solani, Fusarium proliferatum, Fusarium burgessii, and Fusarium tricinctum, as well as Microdochium bolleyi, Microdochium nivale, and Macrophomina phaseolina, were non-pathogenic and considered to be secondary colonizers. The implications of these findings are discussed. Full article
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19 pages, 3106 KiB  
Article
A Melanin-Deficient Isolate of Venturia inaequalis Reveals Various Roles of Melanin in Pathogen Life Cycle and Fitness
by Ulrike Steiner and Erich-Christian Oerke
J. Fungi 2023, 9(1), 35; https://doi.org/10.3390/jof9010035 - 25 Dec 2022
Cited by 3 | Viewed by 1805
Abstract
Venturia inaequalis is the ascomycetous pathogen causing apple scabs and forms dark-pigmented spores and partially melanised infection structures. Although melanin is considered to be essential for the infection of host tissue, a spontaneously occurring melanin-deficient mutant was isolated from an abaxial side of [...] Read more.
Venturia inaequalis is the ascomycetous pathogen causing apple scabs and forms dark-pigmented spores and partially melanised infection structures. Although melanin is considered to be essential for the infection of host tissue, a spontaneously occurring melanin-deficient mutant was isolated from an abaxial side of an apple leaf and can be cultivated in vitro as well as in vivo. The morphology and development of the melanin-deficient-isolate SW01 on leaves of susceptible apple plants were compared to that of the corresponding wild-type isolate HS1. White conidia of SW01 were often wrinkled when dry and significantly increased their volume in suspension. Germination and formation of germtubes and appressoria were not impaired; however, the lack of melanisation of the appressorial ring structure at the interface with the plant cuticle significantly reduced the infection success of SW01. The colonisation of leaf tissue by non-melanised subcuticular hyphae was not affected until the initiation of conidiogenesis. Non-melanised conidiophores penetrated the plant cuticle from inside less successfully than the wild type, and the release of white conidia from less solid conidiophores above the cuticle was less frequent. Melanin in the outer cell wall of V. inaequalis was not required for the survival of conidia under ambient temperature or at −20 °C storage conditions, however, promoted the tolerance of the pathogen to copper and synthetic fungicides affecting the stability and function of the fungal cell wall, plasma membrane, respiration (QoIs) and enzyme secretion, but had no effect on the sensitivity to sulphur and SDHIs. The roles of melanin in different steps of the V. inaequalis life cycle and the epidemiology of apple scabs are discussed. Full article
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16 pages, 3381 KiB  
Article
Phytophthora × cambivora as a Major Factor Inciting the Decline of European Beech in a Stand within the Southernmost Limit of Its Natural Range in Europe
by Mario Riolo, Francesco Aloi, Sebastiano Conti Taguali, Antonella Pane, Massimo Franco and Santa Olga Cacciola
J. Fungi 2022, 8(9), 973; https://doi.org/10.3390/jof8090973 - 18 Sep 2022
Cited by 3 | Viewed by 1975
Abstract
The objective of this study was to investigate the role of the oomycete Phytophthora× cambivora in the decline affecting European beech (Fagus sylvatica) in the Nebrodi Regional Park (Sicily, southern Italy). In a survey of a beech forest stand in [...] Read more.
The objective of this study was to investigate the role of the oomycete Phytophthora× cambivora in the decline affecting European beech (Fagus sylvatica) in the Nebrodi Regional Park (Sicily, southern Italy). In a survey of a beech forest stand in the heart of the park, Phytophthora× cambivora was the sole Phytophthora species recovered from the rhizosphere soil and fine roots of trees. Both A1 and A2 mating type isolates were found. Direct isolation from the stem bark of trees showing severe decline symptoms and bleeding stem cankers yielded exclusively P. gonapodyides, usually considered as an opportunistic pathogen. The mean inoculum density of P.× cambivora in the rhizosphere soil, as determined using the soil dilution plating method and expressed in terms of colony forming units (cfus) per gm of soil, the isolation frequency using leaf baiting, and the percentage of infected fibrous roots from 20 randomly selected beech trees with severe decline symptoms (50 to 100 foliage transparency classes) were 31.7 cfus, 80%, and 48.6%, respectively. These were significantly higher than the corresponding mean values of 20 asymptomatic or slightly declining trees, suggesting P.× cambivora is a major factor responsible for the decline in the surveyed stand. Full article
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Review

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35 pages, 7034 KiB  
Review
Diagnosis of Soybean Diseases Caused by Fungal and Oomycete Pathogens: Existing Methods and New Developments
by Behnoush Hosseini, Ralf Thomas Voegele and Tobias Immanuel Link
J. Fungi 2023, 9(5), 587; https://doi.org/10.3390/jof9050587 - 18 May 2023
Cited by 3 | Viewed by 3517
Abstract
Soybean (Glycine max) acreage is increasing dramatically, together with the use of soybean as a source of vegetable protein and oil. However, soybean production is affected by several diseases, especially diseases caused by fungal seed-borne pathogens. As infected seeds often appear [...] Read more.
Soybean (Glycine max) acreage is increasing dramatically, together with the use of soybean as a source of vegetable protein and oil. However, soybean production is affected by several diseases, especially diseases caused by fungal seed-borne pathogens. As infected seeds often appear symptomless, diagnosis by applying accurate detection techniques is essential to prevent propagation of pathogens. Seed incubation on culture media is the traditional method to detect such pathogens. This method is simple, but fungi have to develop axenically and expert mycologists are required for species identification. Even experts may not be able to provide reliable type level identification because of close similarities between species. Other pathogens are soil-borne. Here, traditional methods for detection and identification pose even greater problems. Recently, molecular methods, based on analyzing DNA, have been developed for sensitive and specific identification. Here, we provide an overview of available molecular assays to identify species of the genera Diaporthe, Sclerotinia, Colletotrichum, Fusarium, Cercospora, Septoria, Macrophomina, Phialophora, Rhizoctonia, Phakopsora, Phytophthora, and Pythium, causing soybean diseases. We also describe the basic steps in establishing PCR-based detection methods, and we discuss potentials and challenges in using such assays. Full article
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