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Fusarium, Alternaria and Rhizoctonia: A Spotlight on Fungal Pathogens

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A special issue of Journal of Fungi (ISSN 2309-608X). This special issue belongs to the section "Fungal Genomics, Genetics and Molecular Biology".

Deadline for manuscript submissions: closed (20 February 2024) | Viewed by 14660

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Special Issue Editors

Prof. Dr. Xuehong Wu

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Guest Editor

College of Plant Protection, China Agricultural University, Beijing 100193, China
Interests: species identification of Alternaria, Rhizoctonia, and Fusarium; molecular mechanism of resistance to fungicides; mycoviruses associated with fungi
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Lihua Guo

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Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, China
Interests: Fusarium; Fusarium mycovirus
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Shimin Zuo

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Guest Editor

Department of Crop Genetics and Breeding, Agricultural College of Yangzhou University, Yangzhou, China
Interests: rice sheath blight; host disease resistance; host pathogen; breeding
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Alternaria, Rhizoctonia, and Fusarium are very important phytopathogens causing devastating diseases on many important crops all over the world. Accurate species identification of plant pathogens will provide the theoretical basis for controlling diseases effectively. To date, the management of crop diseases caused by these three genera has mainly relied on the timely application of fungicides. However, the resistance of Alternaria, Rhizoctonia, and Fusarium to fungicides had been reported due to their long-term use. In addition, many biocontrol agents have been recorded for use to protect crops from infection by pathogens belonging to the three genera. Mycoviruses are viruses that replicate in fungi and are widespread in all major taxonomic groups of fungi, including Alternaria, Rhizoctonia, and Fusarium. Some mycoviruses are reported to confer hypovirulence or hypervirulence to their host fungi, and mycoviruses that confer hypovirulence are considered potential biological agents for controlling fungal diseases. This Special Issue plans to give an overview of the most recent advances in the field of Alternaria, Rhizoctonia, and Fusarium. This Special Issue aims to provide contributions on advances in the species identification, molecular mechanism of resistance, pathogenic mechanism, resistant mechanism of plants, mycoviruses, and biocontrol agents used to control diseases with regard to Alternaria, Rhizoctonia, and Fusarium.

Potential topics include but are not limited to species identification of Alternaria, Rhizoctonia, and Fusarium; molecular mechanism of resistance of Alternaria, Rhizoctonia, and Fusarium to fungicides; pathogenic mechanism of Alternaria, Rhizoctonia, and Fusarium; resistant mechanism of plants to Alternaria, Rhizoctonia, and Fusarium; mycoviruses associated with Alternaria, Rhizoctonia, and Fusarium; and biocontrol agents used to control diseases caused by Alternaria, Rhizoctonia, and Fusarium.

Prof. Dr. Xuehong Wu
Prof. Dr. Lihua Guo
Prof. Dr. Shimin Zuo
Guest Editors

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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. Journal of Fungi 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 2600 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

species identification
molecular mechanism of resistance
pathogenic mechanism
resistant mechanism of plants
mycoviruses
biocontrol agents

Related Special Issue

Fusarium, Alternaria and Rhizoctonia: A Spotlight on Fungal Pathogens, 2nd Edition in Journal of Fungi (1 article)

Published Papers (12 papers)

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Research

18 pages, 1900 KiB

Open AccessArticle

Bio-Priming with Bacillus Isolates Suppresses Seed Infection and Improves the Germination of Garden Peas in the Presence of Fusarium Strains

by Dragana Miljaković, Jelena Marinković, Gordana Tamindžić, Dragana Milošević, Maja Ignjatov, Vasiljka Karačić and Snežana Jakšić

J. Fungi 2024, 10(5), 358; https://doi.org/10.3390/jof10050358 - 17 May 2024

Viewed by 448

Abstract

Seed infection caused by Fusarium spp. is one of the major threats to the seed quality and yield of agricultural crops, including garden peas. The use of Bacillus spp. with multiple antagonistic and plant growth-promoting (PGP) abilities represents a potential disease control strategy. This study was performed to evaluate the biocontrol potential of new Bacillus spp. rhizosphere isolates against two Fusarium strains affecting garden peas. Six Bacillus isolates identified by 16S rDNA sequencing as B. velezensis (B42), B. subtilis (B43), B. mojavensis (B44, B46), B. amyloliquefaciens (B50), and B. halotolerans (B66) showed the highest in vitro inhibition of F. proliferatum PS1 and F. equiseti PS18 growth (over 40%). The selected Bacillus isolates possessed biosynthetic genes for endoglucanase (B42, B43, B50), surfactin (B43, B44, B46), fengycin (B44, B46), bacillomycin D (B42, B50), and iturin (B42), and were able to produce indole-3-acetic acid (IAA), siderophores, and cellulase. Two isolates, B. subtilis B43 and B. amyloliquefaciens B50, had the highest effect on final germination, shoot length, root length, shoot dry weight, root dry weight, and seedling vigor index of garden peas as compared to the control. Their individual or combined application reduced seed infection and increased seed germination in the presence of F. proliferatum PS1 and F. equiseti PS18, both after seed inoculation and seed bio-priming. The most promising results were obtained in the cases of the bacterial consortium, seed bio-priming, and the more pathogenic strain PS18. The novel Bacillus isolates may be potential biocontrol agents intended for the management of Fusarium seed-borne diseases. Full article

(This article belongs to the Special Issue Fusarium, Alternaria and Rhizoctonia: A Spotlight on Fungal Pathogens)

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13 pages, 2899 KiB

Open AccessArticle

Molecular Characterization of the First Partitivirus from a Causal Agent of Salvia miltiorrhiza Dry Rot

by Luyang Song, Rongrong Zhong, Zhengzhe Guan, Lina Huang, Ganlin Wang, Zhimin Yang, Ke Shao, Yanhong Qin, Caiyi Wen, Ying Zhao and Fei Wang

J. Fungi 2024, 10(3), 179; https://doi.org/10.3390/jof10030179 - 27 Feb 2024

Viewed by 1222

Abstract

Root rot as a result of Salvia miltiorrhiza is a common root disease caused by Fusarium spp., which has become one of the main diseases affecting the production of S. miltiorrhiza. Currently, several hypovirulence-related mycoviruses have been identified in many phytopathogenic fungi, including Fusarium spp., which show potential as biological controls. In this study, we report a new mycovirus, Fusarium oxysporum partitivirus 1 (FoPV1), isolated from F. oxysporum strain FCR51, which is a causal agent of S. miltiorrhiza dry rot. The FoPV1 genome contains two double-stranded RNA segments (dsRNA1 and dsRNA2). The size of dsRNA1 is 1773 bp, and it encodes a putative RNA-dependent RNA polymerase (RdRp). The dsRNA2 is 1570 bp in length, encoding a putative capsid protein (CP). Multiple sequence alignments and phylogenetic analyses based on the amino acid sequences of the RdRp and the CP proteins indicated that FoPV1 appears to be a new member of the family Partitiviridae that is related to members of the genus Gammapartitivirus. Pathogenicity assay showed that FoPV1 confers hypervirulence to its host, F. oxysporum. This is the first report of a partitivirus infecting F. oxysporum and the first hypovirulence-related mycovirus from the causal agent of S. miltiorrhiza dry rot. Full article

(This article belongs to the Special Issue Fusarium, Alternaria and Rhizoctonia: A Spotlight on Fungal Pathogens)

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16 pages, 2536 KiB

Open AccessArticle

Isolation and Identification of Alternaria alternata from Potato Plants Affected by Leaf Spot Disease in Korea: Selection of Effective Fungicides

by Jiyoon Park, Seoyeon Kim, Miju Jo, Sunmin An, Youngjun Kim, Jonghan Yoon, Min-Hye Jeong, Eun Young Kim, Jaehyuk Choi, Yangseon Kim and Sook-Young Park

J. Fungi 2024, 10(1), 53; https://doi.org/10.3390/jof10010053 - 7 Jan 2024

Viewed by 1875

Abstract

Brown leaf spot disease caused by Alternaria spp. is among the most common diseases of potato crops. Typical brown spot symptoms were observed in commercial potato-cultivation areas of northern Korea from June to August 2020–2021. In total, 68 isolates were collected, and based on sequence analysis of the internal transcribed spacer (ITS) region, the collected isolates were identified as Alternaria spp. (80.9%). Phylogenetic analysis revealed that a majority of these isolates clustered within a clade that included A. alternata. Additionally, the ITS region and rpb2 yielded the most informative sequences for the identification of A. alternata. Pathogenicity tests confirmed that the collected pathogens elicited symptoms identical to those observed in the field. In pathogenicity tests performed on seven commercial cultivars, the pathogens exhibited strong virulence in both wound and non-wound inoculations. Among the cultivars tested, Arirang-1ho, Arirang-2ho, and Golden Ball were resistant to the pathogens. Furthermore, among the fungicides tested in vitro, mancozeb and difenoconazole were found to be effective for inhibiting mycelial growth. In summary, our findings suggest that A. alternata plays a critical role in leaf disease in potato-growing regions and emphasise the necessity of continuous monitoring and management to protect against this disease in Korea. Full article

(This article belongs to the Special Issue Fusarium, Alternaria and Rhizoctonia: A Spotlight on Fungal Pathogens)

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16 pages, 4581 KiB

Open AccessArticle

Ectopic Expression of Gastrodia Antifungal Protein in Rice Enhances Resistance to Rice Sheath Blight Disease

by Junkai Zhu, Xiang Xue, Ran Ju, Jianhua Zhao, Fen Liu, Xian Han, Yu Yan, Yu Wang, Zhiming Feng, Dongmei Lin, Zongxiang Chen, Yiqin Wang, Xijun Chen, Chengcai Chu, Shimin Zuo and Yafang Zhang

J. Fungi 2024, 10(1), 33; https://doi.org/10.3390/jof10010033 - 31 Dec 2023

Viewed by 1177

Abstract

Sheath blight (ShB) disease, caused by Rhizoctonia solani Kühn, is one of the most serious rice diseases. Rice breeding against ShB has been severely hindered because no major resistance genes or germplasms are available in rice. Here, we report that introduction of Gastrodia antifungal protein (GAFP) genes from Gastrodia elata B1 into rice significantly enhances resistance to rice ShB. Four GAFP genes were cloned from G. elata B1, and all displayed a strong ability to inhibit R. solani growth in plate assays. Two versions, with or without a signal peptide, for each of the four GAFP genes were introduced into XD3 and R6547 rice cultivars, and all transgenic lines displayed stronger ShB resistance than the corresponding wild-type control in both greenhouse and field conditions. Importantly, GAFP2 showed the highest ShB resistance; GAFPs with and without its signal peptide showed no significant differences in enhancing ShB resistance. We also evaluated the agronomic traits of these transgenic rice and found that ectopic expression of GAFPs in rice at appropriate levels did not affect agronomic traits other than enhancing ShB resistance. Together, these results indicate that GAFP genes, especially GAFP2, have great potential in rice breeding against ShB disease. Full article

(This article belongs to the Special Issue Fusarium, Alternaria and Rhizoctonia: A Spotlight on Fungal Pathogens)

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22 pages, 4404 KiB

Open AccessArticle

Sixteen Novel Mycoviruses Containing Positive Single-Stranded RNA, Double-Stranded RNA, and Negative Single-Stranded RNA Genomes Co-Infect a Single Strain of Rhizoctonia zeae

by Siwei Li, Zhihao Ma, Xinyi Zhang, Yibo Cai, Chenggui Han and Xuehong Wu

J. Fungi 2024, 10(1), 30; https://doi.org/10.3390/jof10010030 - 31 Dec 2023

Cited by 1 | Viewed by 1084

Abstract

In the present study, sixteen novel RNA mycoviruses co-infecting a single strain of Rhizoctonia zeae (strain D40) were identified and molecularly characterized using metatranscriptome sequencing combined with a method for rapid amplification of cDNA ends. The fungal strain was isolated from diseased seedlings of sugar beet with damping-off symptoms. Based on genome analysis and phylogenetic analysis of amino acid sequences of RNA-dependent RNA polymerase, the sixteen mycoviruses associated with strain D40 contained three genome types with nine distinct lineages, including positive single-stranded RNA (Hypoviridae, Yadokariviridae, Botourmiaviridae, and Gammaflexiviridae), double-stranded RNA (Phlegiviridae, Megabirnaviridae, Megatotiviridae, and Yadonushiviridae), and negative single-stranded RNA (Tulasviridae), suggesting a complex composition of a mycoviral community in this single strain of R. zeae (strain D40). Full genome sequences of six novel mycoviruses and the nearly full-length sequences of the remaining ten novel mycoviruses were obtained. Furthermore, seven of these sixteen mycoviruses were confirmed to assemble virus particles present in the R. zeae strain D40. To the best of our knowledge, this is the first detailed study of mycoviruses infecting R. zeae. Full article

(This article belongs to the Special Issue Fusarium, Alternaria and Rhizoctonia: A Spotlight on Fungal Pathogens)

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15 pages, 9705 KiB

Open AccessArticle

The Wheat Endophyte Epicoccum layuense J4-3 Inhibits Fusarium graminearum and Enhances Plant Growth

by Clement Nzabanita, Lihang Zhang, Yanfei Wang, Shuangchao Wang and Lihua Guo

J. Fungi 2024, 10(1), 10; https://doi.org/10.3390/jof10010010 - 24 Dec 2023

Viewed by 1203

Abstract

Fungal endophytes are well-known for their ability to promote plant growth and hinder fungal diseases, including Fusarium head blight (FHB) caused by Fusarium graminearum. This study aimed to characterize the biocontrol efficacy of strain J4-3 isolated from the stem of symptomless wheat collected from Heilongjiang Province, China. It was identified as Epicoccum layuense using morphological characteristics and phylogenetic analysis of the rDNA internal transcribed spacer (ITS) and beta-tubulin (TUB). In a dual culture assay, strain J4-3 significantly inhibited the mycelial growth of F. graminearum strain PH-1 and other fungal pathogens. In addition, wheat coleoptile tests showed that lesion symptoms caused by F. graminearum were significantly reduced in wheat seedlings treated with hyphal fragment suspensions of strain J4-3 compared to the controls. Under field conditions, applying spore suspensions and culture filtrates of strain J4-3 with conidial suspensions of F. graminearum on wheat spikes resulted in the significant biocontrol efficacy of FHB. In addition, wheat seedlings previously treated with spore suspensions of strain J4-3 before sowing successfully resulted in FHB reduction after the application of conidial suspensions of F. graminearum at anthesis. More importantly, wheat seedlings treated with hyphal fragments and spore suspensions of strain J4-3 showed significant increases in wheat growth compared to the controls under greenhouse and field conditions. Overall, these findings suggest that E. layuense J4-3 could be a promising biocontrol agent (BCA) against F. graminearum, causing FHB and a growth-promoting fungus in wheat. Full article

(This article belongs to the Special Issue Fusarium, Alternaria and Rhizoctonia: A Spotlight on Fungal Pathogens)

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32 pages, 7303 KiB

Open AccessArticle

Coronatine-Induced Maize Defense against Gibberella Stalk Rot by Activating Antioxidants and Phytohormone Signaling

by Mei Liu, Yiping Sui, Chunxin Yu, Xuncheng Wang, Wei Zhang, Baomin Wang, Jiye Yan and Liusheng Duan

J. Fungi 2023, 9(12), 1155; https://doi.org/10.3390/jof9121155 - 30 Nov 2023

Cited by 1 | Viewed by 1204

Abstract

One of the most destructive diseases, Gibberella stalk rot (GSR), caused by Fusarium graminearum, reduces maize yields significantly. An induced resistance response is a potent and cost-effective plant defense against pathogen attack. The functional counterpart of JAs, coronatine (COR), has attracted a lot of interest recently due to its ability to control plant growth and stimulate secondary metabolism. Although several studies have focused on COR as a plant immune elicitor to improve plant resistance to pathogens, the effectiveness and underlying mechanisms of the suppressive ability against COR to F. graminearum in maize have been limited. We investigated the potential physiological and molecular mechanisms of COR in modulating maize resistance to F. graminearum. COR treatment strongly enhanced disease resistance and promoted stomatal closure with H₂O₂ accumulation, and 10 μg/mL was confirmed as the best concentration. COR treatment increased defense-related enzyme activity and decreased the malondialdehyde content with enhanced antioxidant enzyme activity. To identify candidate resistance genes and gain insight into the molecular mechanism of GSR resistance associated with COR, we integrated transcriptomic and metabolomic data to systemically explore the defense mechanisms of COR, and multiple hub genes were pinpointed using weighted gene correlation network analysis (WGCNA). We discovered 6 significant modules containing 10 candidate genes: WRKY transcription factor (LOC100279570), calcium-binding protein (LOC100382070), NBR1-like protein (LOC100275089), amino acid permease (LOC100382244), glutathione S-transferase (LOC541830), HXXXD-type acyl-transferase (LOC100191608), prolin-rich extensin-like receptor protein kinase (LOC100501564), AP2-like ethylene-responsive transcription factor (LOC100384380), basic leucine zipper (LOC100275351), and glycosyltransferase (LOC606486), which are highly correlated with the jasmonic acid–ethylene signaling pathway and antioxidants. In addition, a core set of metabolites, including alpha-linolenic acid metabolism and flavonoids biosynthesis linked to the hub genes, were identified. Taken together, our research revealed differentially expressed key genes and metabolites, as well as co-expression networks, associated with COR treatment of maize stems after F. graminearum infection. In addition, COR-treated maize had higher JA (JA-Ile and Me-JA) levels. We postulated that COR plays a positive role in maize resistance to F. graminearum by regulating antioxidant levels and the JA signaling pathway, and the flavonoid biosynthesis pathway is also involved in the resistance response against GSR. Full article

(This article belongs to the Special Issue Fusarium, Alternaria and Rhizoctonia: A Spotlight on Fungal Pathogens)

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12 pages, 4995 KiB

Open AccessArticle

Comparative Study of the Co-Occurring Alternaria and Colletotrichum Species in the Production of Citrus Leaf Spot

by Mengying Lei, Congyi Zhu, Luoye Li, Jiangshan Liu, Jiashang Liu and Feng Huang

J. Fungi 2023, 9(11), 1089; https://doi.org/10.3390/jof9111089 - 8 Nov 2023

Viewed by 910

Abstract

Both of the two citrus diseases, Alternaria brown spot (ABS) and Anthracnose, caused by Alternaria and Colletotrichum spp., respectively, can produce leaf lesions which are hard to differentiate. These two diseases have been confused as causal agents of brown spot for over a decade in China. In this study, citrus leaves with or without brown spot were collected from Zhaoqing, Guangdong and Wanzhou, Chongqing, and were further used for the taxonomic and functional comparisons between the co-occurring Alternaria and Colletotrichum species. In the amplicon sequencing, the average relative abundance and the composition of Alternaria, but not Colletotrichum, increased (from 0.1 to 9.9, p = 0.059; and to 0.7, p < 0.05) and significantly altered (p < 0.01) with the brown spot in Zhaoqing and Wanzhou, respectively. Two representative isolates Alternaria sp. F12A and Colletotrichum sp. F12C, from the same brown spot, were proved with different virulence and host response activation to citrus leaves. F12A caused typical symptoms of brown spot with the average spot length expanded to 5 and 6.1 cm, and also altered the citrus global gene expression 48 and 72 h after inoculation. In addition, F12A enriched the expression of genes that were most frequently involved in plant defense. In comparison, F12C caused leaf spot limited to the wounded site, and its milder activation of host response recovered 72 h after inoculation. Our study indicates that the incidence of brown spot in China is caused by Alternaria species, and the ABS should be a fungal disease of major concern on citrus. Full article

(This article belongs to the Special Issue Fusarium, Alternaria and Rhizoctonia: A Spotlight on Fungal Pathogens)

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14 pages, 2088 KiB

Open AccessArticle

Exploring the Potential Mechanism of Prothioconazole Resistance in Fusarium graminearum in China

by Feng Zhou, Aohui Han, Yan Jiao, Yifan Cao, Longhe Wang, Haiyan Hu, Runqiang Liu and Chengwei Li

J. Fungi 2023, 9(10), 1001; https://doi.org/10.3390/jof9101001 - 10 Oct 2023

Viewed by 1205

Abstract

The Fusarium head blight (FHB) caused by Fusarium graminearum is one of the most important diseases threatening wheat production in China. However, the triazole sterol 14α-demethylation inhibitor (DMI), prothioconazole, is known to exhibit high activity against F. graminearum. The current study indicated that three highly resistant laboratory mutants exhibited significantly (p < 0.05) altered growth and sporulation, although contrary to expectation, only one of the mutants exhibited reduced growth and sporulation, while the other two exhibited significant (p < 0.05) increases. Despite this, pathogenicity tests revealed that all of the mutants exhibited significantly (p < 0.05) reduced pathogenicity, indicating a substantial cost to fitness. Sequence analysis of the prothioconazole target protein, CYP51, of which F. graminearum has three homologues (FgCYP51A, FgCYP51B, and FgCYP51C), identified three mutations in the FgCYP51B sequence with a high likelihood of being associated with the observed resistance, as well as another three mutations in the FgCYP51B sequence, and two in the FgCYP51A sequence that are worthy of further investigation. Two of the prothioconazole-resistant mutants were also found to have several amino acid substitutions in their FgCYP51C sequences, and it was interesting to note that these two mutants exhibited significantly (p < 0.05) reduced pathogenicity compared to the other mutant. Expression analysis revealed that prothioconazole treatment (0.1 μg/mL) resulted in altered expression of all the FgCYP51 target genes, and that expression was also altered in the prothioconazole-resistant mutants compared to their wild-type parental isolates. Meanwhile, no evidence was found of any cross-resistance between prothioconazole and other commonly used fungicides, including carbendazim, pyraclostrobin, and fluazinam, as well as the triazole tebuconazole and the imidazole DMI prochloraz. Taken together, these results not only provide new insight into potential resistance mechanism in F. graminearum, and the biological characteristics associated with them, but also convincing evidence that prothioconazole can offer effective control of FHB. Full article

(This article belongs to the Special Issue Fusarium, Alternaria and Rhizoctonia: A Spotlight on Fungal Pathogens)

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20 pages, 5896 KiB

Open AccessArticle

Quantitative Acetylome Analysis of Differentially Modified Proteins in Virulence-Differentiated Fusarium oxysporum f. sp. cucumerinum Isolates during Cucumber Colonization

by Ying Zhou, Xiaohong Lu, Jianjun Hao and Shidong Li

J. Fungi 2023, 9(9), 920; https://doi.org/10.3390/jof9090920 - 13 Sep 2023

Cited by 1 | Viewed by 816

Abstract

Fusarium oxysporum f. sp. cucumerinum (Foc) is a prominent pathogen that adversely affects cucumber (Cucumis sativus) production. In the pathogen’s parasitic lifestyle, the pathogenesis and virulence evolution may be regulated by lysine acetylation, as demonstrated in many living organisms. However, its specific function in Foc remains poorly understood. In this study, the acetylome profiles of a mild virulence strain (foc-3b) and its derived virulence-enhanced strain (Ra-4) were analyzed before and post-inoculation on cucumber plants. In total, 10,664 acetylation sites were identified corresponding to 3874 proteins, and 45 conserved acetylation motifs were detected. Through comparison of the acetylomes, numerous differentially lysine-acetylated proteins were enriched in energy metabolism and protein processing processes, indicating the critical role of lysine acetylation during the transition from the saprotrophic lifestyle to the parasitic lifestyle. Comparative acetylome analyses on the two virulence-differentiated strains revealed that several differentially lysine-acetylated proteins were involved in pathways of defense response and energy metabolism. Ra-4 showed enhanced energy metabolism compared to foc-3b. This indicates that robust metabolic activity is required to achieve high virulence and facilitating adaptive evolution. Additionally, faster host responses are supported by an ample energy supply enhancing virulence. Thus, lysine acetylation plays a crucial role in the pathogenesis and virulence evolution of Foc. Full article

(This article belongs to the Special Issue Fusarium, Alternaria and Rhizoctonia: A Spotlight on Fungal Pathogens)

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18 pages, 9484 KiB

Open AccessArticle

Four New Species of Small-Spored Alternaria Isolated from Solanum tuberosum and S. lycopersicum in China

by Yanan Gou, Sein Lai Lai Aung, Zhuanjun Guo, Zhi Li, Shulin Shen and Jianxin Deng

J. Fungi 2023, 9(9), 880; https://doi.org/10.3390/jof9090880 - 27 Aug 2023

Cited by 2 | Viewed by 1151

Abstract

Small-spored Alternaria species have been frequently isolated from diseased leaves of Solanum plants. To clarify the diversity of small-spored Alternaria species, a total of 118 strains were obtained from leaf samples of S. tuberosum and S. lycopersicum in six provinces of China during 2022–2023. Based on morphological characterization and multi-locus phylogenetic analysis of the internal transcribed spacer of the rDNA region (ITS), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), translation elongation factor 1 alpha (TEF1), RNA polymerase second largest subunit (RPB2), Alternaria major allergen gene (Alt a 1), endopolygalacturonase gene (EndoPG) and an anonymous gene region (OPA10-2), seven species were determined, including four novel species and three known species (A. alternata, A. gossypina and A. arborescens). The novel species were described and illustrated as A. longxiensis sp. nov., A. lijiangensis sp. nov., A. lycopersici sp. nov. and A. solanicola sp. nov.. In addition, the pathogenicity of the seven species was evaluated on potato leaves. The species exhibited various aggressiveness, which could help in disease management. Full article

(This article belongs to the Special Issue Fusarium, Alternaria and Rhizoctonia: A Spotlight on Fungal Pathogens)

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12 pages, 8522 KiB

Open AccessArticle

Trehalase Inhibitor Validamycin May Have Additional Mechanisms of Toxicology against Rhizoctonia cerealis

by Xiaoyue Yang, Yan Shu, Shulin Cao, Haiyan Sun, Xin Zhang, Aixiang Zhang, Yan Li, Dongfang Ma, Huaigu Chen and Wei Li

J. Fungi 2023, 9(8), 846; https://doi.org/10.3390/jof9080846 - 14 Aug 2023

Cited by 2 | Viewed by 1315

Abstract

Sharp eyespot is a crucial disease affecting cereal plants, such as bread wheat (Triticum aestivum) and barley (Hordeum vulgare), and is primarily caused by the pathogenic fungus Rhizoctonia cerealis. As disease severity has increased, it has become imperative to find an effective and reasonable control strategy. One such strategy is the use of the trehalose analog, validamycin, which has been shown to have a potent inhibitory effect on several trehalases found in both insects and fungi, and is widely used as a fungicide in agriculture. In this study, we demonstrated that 0.5 μg/mL validamycin on PDA plates had an inhibitory effect on R. cerealis strain R0301, but had no significant impact on Fusarium graminearum strain PH-1. Except for its inhibiting the trehalase activity of pathogenic fungi, little is known about its mechanism of action. Six trehalase genes were identified in the genome of R. cerealis, including one neutral trehalase and five acidic trehalase genes. Enzyme activity assays indicated that treatment with 5 μg/mL validamycin significantly reduces trehalase activity, providing evidence that validamycin treatment does indeed affect trehalase, even though the expression levels of most trehalase genes, except Rc17406, were not obviously affected. Transcriptome analysis revealed that treatment with validamycin downregulated genes involved in metabolic processes, ribosome biogenesis, and pathogenicity in the R. cerealis. KEGG pathway analysis further showed that validamycin affected genes related to the MAPK signaling pathway, with a significant decrease in ribosome synthesis and assembly. In conclusion, our results indicated that validamycin not only inhibits trehalose activity, but also affects the ribosome synthesis and MAPK pathways of R. cerealis, leading to the suppression of fungal growth and pesticidal effects. This study provides novel insights into the mechanism of action of validamycin. Full article

(This article belongs to the Special Issue Fusarium, Alternaria and Rhizoctonia: A Spotlight on Fungal Pathogens)

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