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Mao X, Wu Z, Zhao F, Yang X, Zhou M, Hou Y. Bioactivity and Resistance Risk of Fluxapyroxad, a Novel SDHI Fungicide, in Didymella bryoniae. Plant Dis 2024; 108:658-665. [PMID: 37773329 DOI: 10.1094/pdis-07-23-1374-re] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/01/2023]
Abstract
Gummy stem blight, caused by Didymella bryoniae, is an important disease in watermelon in China. Fluxapyroxad, a new succinate dehydrogenase inhibitor fungicide, shows strong inhibition of the mycelia growth of D. bryoniae. However, its resistance risk in D. bryoniae is unclear. In this research, the sensitivities of 60 D. bryoniae strains to fluxapyroxad were investigated. The average EC50 value and MIC values of 60 D. bryoniae strains against fluxapyroxad were 0.022 ± 0.003 μg/ml and ≤0.1 μg/ml for mycelial growth, respectively. Eight fluxapyroxad-resistant mutants with medium resistance levels were acquired from three wild-type parental strains. The mycelial growth and dry weight of mycelia of most mutants were significantly lower than those of their parental strains. However, four resistant mutants showed a similar phenotype in pathogenicity compared with their parental strains. The above results demonstrated that there was a medium resistance risk for fluxapyroxad in D. bryoniae. The cross-resistance assay showed that there was positive cross-resistance between fluxapyroxad and pydiflumetofen, thifluzamide, and boscalid, but there was no cross-resistance between fluxapyroxad and tebuconazole and mepronil. These results will contribute to evaluating the resistance risk of fluxapyroxad for managing diseases caused by D. bryoniae and further increase our understanding about the mode of action of fluxapyroxad.
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Affiliation(s)
- Xuewei Mao
- College of Plant Protection, Nanjing Agricultural University, Nanjing, Jiangsu, China
- College of Plant Protection, Henan Agricultural University, Zhengzhou, Henan, China
| | - Zhiwen Wu
- College of Plant Protection, Nanjing Agricultural University, Nanjing, Jiangsu, China
| | - Feifei Zhao
- College of Plant Protection, Nanjing Agricultural University, Nanjing, Jiangsu, China
| | - Xin Yang
- College of Plant Protection, Nanjing Agricultural University, Nanjing, Jiangsu, China
| | - Mingguo Zhou
- College of Plant Protection, Nanjing Agricultural University, Nanjing, Jiangsu, China
| | - Yiping Hou
- College of Plant Protection, Nanjing Agricultural University, Nanjing, Jiangsu, China
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Mao X, Wu Z, Bi C, Wang J, Zhao F, Gao J, Hou Y, Zhou M. Molecular and Biochemical Characterization of Pydiflumetofen-Resistant Mutants of Didymella bryoniae. J Agric Food Chem 2020; 68:9120-9130. [PMID: 32806116 DOI: 10.1021/acs.jafc.0c03690] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Gummy stem blight (GSB), caused by Didymella bryoniae, is a devastating disease on watermelon. Pydiflumetofen belongs to succinate dehydrogenase inhibitor (SDHI) fungicide, which is effective in controlling many plant diseases. The EC50 values of 69 D. bryoniae isolates to pydiflumetofen ranged from 0.0018 to 0.0071 μg/mL, and the minimal inhibitory concentration (MIC) value of all strains to pydiflumetofen was <0.05 μg/mL. Eight pydiflumetofen-resistant mutants were obtained, and the level of resistance was stable. The mycelial growth, dry weight of mycelia, hyphal morphology, and pathogenicity of most resistant mutants did not change significantly compared with their parental strains, which indicated that the resistance risk of D. bryoniae to pydiflumetofen would be medium to high. Sequencing alignment showed that five resistant mutants presented a mutation at codon 277 (H277Y) in the SdhB gene. The point mutants FgSdhBH248Y/R exhibited decreased sensitivity to pydiflumetofen in Fusarium graminearum, which indicated that the point mutants of SdhB could reduce sensitivity to pydiflumetofen. These results further increase our understanding about the mode of action and the resistance mechanism of pydiflumetofen.
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Affiliation(s)
- Xuewei Mao
- College of Plant Protection, Nanjing Agricultural University, Nanjing, Jiangsu Province 210095, China
| | - Zhiwen Wu
- College of Plant Protection, Nanjing Agricultural University, Nanjing, Jiangsu Province 210095, China
| | - Chaowei Bi
- College of Plant Protection, Southwest University, Chongqing 400715, China
| | - Jianxin Wang
- College of Plant Protection, Nanjing Agricultural University, Nanjing, Jiangsu Province 210095, China
| | - Feifei Zhao
- College of Plant Protection, Nanjing Agricultural University, Nanjing, Jiangsu Province 210095, China
| | - Jing Gao
- College of Plant Protection, Nanjing Agricultural University, Nanjing, Jiangsu Province 210095, China
| | - Yiping Hou
- College of Plant Protection, Nanjing Agricultural University, Nanjing, Jiangsu Province 210095, China
| | - Mingguo Zhou
- College of Plant Protection, Nanjing Agricultural University, Nanjing, Jiangsu Province 210095, China
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Li HX, Nuckols TA, Harris D, Stevenson KL, Brewer MT. Differences in fungicide resistance profiles and multiple resistance to a quinone-outside inhibitor (QoI), two succinate dehydrogenase inhibitors (SDHI), and a demethylation inhibitor (DMI) for two Stagonosporopsis species causing gummy stem blight of cucurbits. Pest Manag Sci 2019; 75:3093-3101. [PMID: 30924240 DOI: 10.1002/ps.5426] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2018] [Revised: 02/08/2019] [Accepted: 03/28/2019] [Indexed: 06/09/2023]
Abstract
BACKGROUND Gummy stem blight (GSB) is a devastating disease of cucurbits that has been effectively managed with fungicide applications. However, the Stagonosporopsis spp. that cause GSB have rapidly evolved resistance to multiple classes of fungicides. To better understand the evolution and persistence of fungicide resistance in field populations, resistance profiles of unique and clonal genotypes of 113 Stagonosporopsis citrulli and 19 S. caricae isolates to four different fungicides were determined based on in vitro mycelial growth assays and molecular markers based on genes encoding fungicide targets. RESULTS All 19 S. caricae isolates screened were resistant to tebuconazole and azoxystrobin, and sensitive to boscalid and fluopyram. All 113 S. citrulli isolates were sensitive to tebuconazole and sensitive to fluopyram, with one exception that was fluopyram-resistant. All isolates of S. citrulli except two were resistant to azoxystrobin. Phenotypic differences in response to boscalid were detected among S. citrulli isolates, but the phenotypes were not associated with multilocus genotypes (MLG) determined by 16 microsatellite loci. Additionally, isolates sharing the same MLG varied by SdhB genotype. A unique mutation of I229V in SdhB, a target of succinate dehydrogenase inhibitor fungicides, was detected for the fluopyram-resistant isolate of S. citrulli. CONCLUSION Both the lack of association of fungicide resistance profiles with genetic similarity of isolates based on microsatellite loci and the finding that widely distributed MLG varied in fungicide resistance profiles suggest that independent evolutionary events for resistance to boscalid have likely occurred. Frequent genetic recombination within populations may be responsible for resistance to multiple fungicides. This study provides useful information for effectively managing both species of GSB fungi present in the southeastern USA and understanding the evolution of fungicide resistance within populations of plant-pathogenic fungi. © 2019 Society of Chemical Industry.
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Affiliation(s)
- Hao-Xi Li
- Department of Plant Pathology, University of Georgia, Athens, GA, USA
| | - Thomas A Nuckols
- Department of Plant Pathology, University of Georgia, Athens, GA, USA
| | - Devon Harris
- Department of Plant Pathology, University of Georgia, Athens, GA, USA
| | | | - Marin T Brewer
- Department of Plant Pathology, University of Georgia, Athens, GA, USA
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Li HX, Gottilla TM, Brewer MT. Organization and evolution of mating-type genes in three Stagonosporopsis species causing gummy stem blight of cucurbits and leaf spot and dry rot of papaya. Fungal Biol 2017; 121:849-857. [PMID: 28889909 DOI: 10.1016/j.funbio.2017.06.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Revised: 06/12/2017] [Accepted: 06/13/2017] [Indexed: 11/25/2022]
Abstract
Population divergence and speciation of closely related lineages can result from reproductive differences leading to genetic isolation. An increasing number of fungal diseases of plants and animals have been determined to be caused by morphologically indistinguishable species that are genetically distinct, thereby representing cryptic species. We were interested in identifying if mating systems among three Stagonosporopsis species (S. citrulli, S. cucurbitacearum, and S. caricae) causing gummy stem blight (GSB) of cucurbits or leaf spot and dry rot of papaya differed, possibly underlying species divergence. Additionally, we were interested in identifying evolutionary pressures acting on the genes controlling mating in these fungi. The mating-type loci (MAT1) of three isolates from each of the three species were identified in draft genome sequences. For the three species, MAT1 was structurally identical and contained both mating-type genes necessary for sexual reproduction, which suggests that all three species are homothallic. However, both MAT1-1-1 and MAT1-2-1 were divergent among species showing rapid evolution with a much greater number of amino acid-changing substitutions detected for the reproductive genes compared with genes flanking MAT1. Positive selection was detected in MAT1-2-1, especially in the highly conserved high mobility group (MATA_HMG-box) domain. Thus, the mating-type genes are rapidly evolving in GSB fungi, but a difference in mating systems among the three species does not underlie their divergence.
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Affiliation(s)
- Hao-Xi Li
- Department of Plant Pathology, University of Georgia, Athens 30602, USA
| | - Thomas M Gottilla
- Department of Plant Pathology, University of Georgia, Athens 30602, USA
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Yao X, Li P, Xu J, Zhang M, Ren R, Liu G, Yang X. Rapid and Sensitive Detection of Didymella bryoniae by Visual Loop-Mediated Isothermal Amplification Assay. Front Microbiol 2016; 7:1372. [PMID: 27625648 PMCID: PMC5003822 DOI: 10.3389/fmicb.2016.01372] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Accepted: 08/18/2016] [Indexed: 11/14/2022] Open
Abstract
Didymella bryoniae is a pathogenic fungus that causes gummy stem blight (GSB) in Cucurbitaceae crops (e.g., cantaloupe, muskmelon, cucumber, and watermelon). GSB produces lesions on the stems and leaves, and can also be spread by seeds. Here, we developed a rapid, visual, and sensitive loop-mediated amplification (LAMP) assay for D. bryoniae detection based on sequence-characterized amplified regions (GenBank accession nos GQ872461 and GQ872462) common to the two random amplification of polymorphic DNA group genotypes (RGI and RGII) of D. bryoniae; ideal conditions for detection were optimized for completion in 45 min at 63°C. The sensitivity and specificity of the LAMP assay were further analyzed in comparison with those of a conventional polymerase chain reaction (PCR). The sensitivity of the LAMP assay was 1000-fold higher than that of conventional PCR with a detection limit of 0.1 fg μL(-1) of targeted DNA. The LAMP assay could be accomplished in about 45 min, with the results visible to the naked eye. The assay showed high specificity in discriminating all D. bryoniae isolates from seven other fungal pathogens that occur in Cucurbitaceae crops. The LAMP assay also detected D. bryoniae infection in young muskmelon leaves with suspected early symptoms of GSB disease. Hence, the technique has great potential for developing rapid and sensitive visual detection methods for the D. bryoniae pathogen in crops and seeds. This method has potential application in early prediction of disease and reducing the risk of epidemics.
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Affiliation(s)
| | | | | | | | | | | | - Xingping Yang
- Institute of Vegetable Crops, Jiangsu Academy of Agricultural Sciences/Jiangsu Key Laboratory for Horticultural Crop Genetic ImprovementNanjing, China
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Stewart JE, Turner AN, Brewer MT. Evolutionary history and variation in host range of three Stagonosporopsis species causing gummy stem blight of cucurbits. Fungal Biol 2015; 119:370-82. [PMID: 25937065 DOI: 10.1016/j.funbio.2014.12.008] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Revised: 12/03/2014] [Accepted: 12/18/2014] [Indexed: 11/28/2022]
Abstract
Recently diverged species may form complexes of morphologically similar, yet genetically distinct lineages that occur in overlapping geographic ranges and niches. Using a multilocus sequencing approach we discovered that gummy stem blight of cucurbits is caused by three genetically distinct species: Stagonosporopsis cucurbitacearum (syn. Didymella bryoniae), Stagonosporopsis citrulli, and Stagonosporopsis caricae, which had previously been considered only a pathogen of papaya. Experiments showed that all three species are pathogenic to cucurbits in the genera Cucurbita, Cucumis, and Citrullus, but only S. caricae is aggressive to papaya. Species tree estimates show that S. citrulli and S. cucurbitacearum are phylogenetically distinct sister species, and that S. caricae is the ancestral lineage. The time estimate for divergence of S. caricae from the ancestor of S. cucurbitacearum and S. citrulli at 72 900 YBP pre-dates domestication of papaya and Cucurbita species in the American tropics. The divergence estimate observed for S. cucurbitacearum and S. citrulli at 10 900 YBP suggests that diversification of Cucurbita species and domestication of gourds and squashes could have driven their divergence. This work highlights the use of molecular systematics and population genetics to elucidate genetic identity among previously unassociated fungi and to understand the patterns of pathogen diversification.
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Affiliation(s)
- Jane E Stewart
- Department of Plant Pathology, University of Georgia, Athens, GA 30602, USA
| | - Ashley N Turner
- Department of Plant Pathology, University of Georgia, Athens, GA 30602, USA
| | - Marin T Brewer
- Department of Plant Pathology, University of Georgia, Athens, GA 30602, USA.
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Choi IY, Choi JN, Choi DC, Sharma PK, Lee WH. Identification and Characterization of the Causal Organism of Gummy Stem Blight in the Muskmelon (Cucumis melo L.). Mycobiology 2010; 38:166-70. [PMID: 23956648 PMCID: PMC3741540 DOI: 10.4489/myco.2010.38.3.166] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2010] [Accepted: 06/04/2010] [Indexed: 05/20/2023]
Abstract
Gummy stem blight is a major foliar disease of muskmelon (Cucumis melo L.). In this study, morphological characteristics and rDNA internal transcribed spacer (ITS) sequences were analyzed to identify the causal organism of this disease. Morphological examination of the Jeonbuk isolate revealed that the percentage of monoseptal conidia ranged from 0% to 10%, and the average length × width of the conidia was 70 (± 0.96) × 32.0 (± 0.15) µm on potato dextrose agar. The BLAST analysis showed nucleotide gaps of 1/494, 2/492, and 1/478 with identities of 485/492 (98%), 492/494 (99%), 491/494 (99%), and 476/478 (99%). The similarity in sequence identity between the rDNA ITS region of the Jeonbuk isolate and other Didymella bryoniae from BLAST searches of GenBank was 100% and was 95.0% within the group. Nucleotide sequences of the rDNA ITS region from pure culture ranged from 98.2% to 99.8%. Phylogenetic analysis with related species of D. bryoniae revealed that D. bryoniae is a monophyletic group distinguishable from other Didymella spp., including Ascochyta pinodes, Mycosphaerella pinodes, M. zeae-maydis, D. pinodes, D. applanata, D. exigua, D. rabiei, D. lentis, D. fabae, and D. vitalbina. Phylogenetic analysis, based on rDNA ITS sequence, clearly distinguished D. bryoniae and Didymella spp. from the 10 other species studied. This study identified the Jeonbuk isolate to be D. bryoniae.
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Affiliation(s)
- In Young Choi
- Jeollabuk-do Agricultural Research and Extension Services, Iksan 570-704, Korea
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