scholarly journals Molecular Characterization and Diagnosis of QoI Resistance in Cucumber and Eggplant Fungal Pathogens

2007 ◽  
Vol 97 (11) ◽  
pp. 1458-1466 ◽  
Author(s):  
H. Ishii ◽  
K. Yano ◽  
H. Date ◽  
A. Furuta ◽  
Y. Sagehashi ◽  
...  
Keyword(s):  
Cytochrome B ◽  
Fungal Pathogens ◽  
Protective Efficacy ◽  
Resistant Mutant ◽  
Amino Acid Position ◽  
Cytochrome B Gene ◽  
Detection Sensitivity ◽  
Wild Type ◽  
Mutant Type ◽  
Qoi Resistance

The molecular mechanism of QoI fungicide resistance was studied using isolates of cucumber Corynespora leaf spot fungus (Corynespora cassiicola) and the eggplant leaf mold (Mycovellosiella nattrassii). In both pathogens, a mutation at position 143 from glycine to alanine (G143A) was detected in the cytochrome b gene that encodes for the fungicide-targeted protein. Moreover, the nucleotide sequence at amino acid position 143 was converted from GGT or GGA in sensitive (wild-type) to GCT or GCA in resistant (mutant-type) isolates. The methods of polymerase chain reaction restriction fragment length polymorphism commonly used for QoI resistance monitoring were employed successfully, leading to the amplified gene fragment from resistant isolates being cut with the restriction enzyme ItaI. However, heteroplasmy (the coexistence of wild-type and mutated alleles) was found when the resistant isolates of C. cassiicola, M. nattrassii, and Colletotrichum gloeosporioides (strawberry anthracnose fungus) were subcultured in the presence or absence of QoI fungicides. QoI resistance of cucumber powdery and downy mildew isolates persisted for a few years following the removal of the selection pressure imposed by the fungicide under both laboratory and commercial greenhouse conditions. The proportion of mutated sequences in cytochrome b gene decreased over time in the pathogen population. The protective efficacy of the full dose of azoxystrobin decreased when the populations of powdery and downy mildews contained resistant isolates at 10%. Using FMBIO, a fluorescence bio-imaging analyzer, the mutant allele from the QoI-resistant isolates could be detected at the level of 1%, whereas the detection sensitivity of ethidium-bromide-stained gels was ≈10 times lower.

scholarly journals Characterization of Colletotrichum graminicola Isolates Resistant to Strobilurin-Related QoI Fungicides

Plant Disease ◽  
2003 ◽  
Vol 87 (12) ◽  
pp. 1426-1432 ◽  
Author(s):  
Cruz Avila-Adame ◽  
Gilberto Olaya ◽  
Wolfram Köller
Keyword(s):  
Cytochrome B ◽  
Cytochrome B Gene ◽  
In Vitro Test ◽  
Colletotrichum Graminicola ◽  
Wild Type ◽  
Qoi Fungicides ◽  
Test Conditions ◽  
Vitro Test ◽  
Qoi Resistance

Isolates of Colletotrichum graminicola were collected from annual bluegrass or bent grass turf in Japan and the United States, and their sensitivities to QoI fungicides (QoIs) as well as their cytochrome b sequences were characterized. Five isolates sampled from turf treated repeatedly with azoxystrobin were highly QoI resistant under both in vivo and in vitro test conditions. The nucleotide sequences of a large cytochrome b gene segment involving the binding site of QoIs were fully homologous for all resistant isolates and contained the G143A target site mutation known to confer QoI resistance in other pathogens. QoI-sensitive isolates collected prior to treatments with QoIs were more diverse with regard to their cytochrome b gene sequences and their phenotype responses to QoIs. All wild-type isolates retained a glycine in position 143 of cytochrome b. Three of the four QoI-sensitive isolates were, in addition, distinguished by leucines in positions 95, 130, and 141, which were exchanged to threonine in all resistant but also in one of the sensitive isolates. In addition to a more pronounced divergence of cytochrome b sequences, the sensitive wild-type isolates also were diverse with regard to the induction of alternative respiration in response to QoI action, as indicated by comparisons of QoI sensitivities displayed in the absence or presence of the alternative oxidase inhibitor salicylhydroxamic acid. These different phenotype responses expressed under in vitro test conditions had no or only a slight impact on anthracnose control in protective applications of azoxystrobin. Isolate responses in vitro were very similar for trifloxystrobin, indicating cross-resistance among the class of QoIs. Our results imply that C. graminicola falls into the class of pathogens with a potential for rapid selection of highly QoI-resistant phenotypes. Frequent monitoring of population sensitivities will be required to determine the status of population responses toward practical QoI resistance.

Occurrence of quinone outside inhibitor (QoI) resistance in Virginia populations of Parastagonospora nodorum infecting wheat

Plant Disease ◽  
2020 ◽  
Author(s):  
Navjot Kaur ◽  
Chase Mullins ◽  
Nathan Michael Kleczewski ◽  
Hillary Laureen Mehl
Keyword(s):  
Cytochrome B ◽  
Management Practices ◽  
Cultural Practices ◽  
Resistance Management ◽  
Cytochrome B Gene ◽  
Target Site ◽  
Quinone Outside Inhibitor ◽  
Parastagonospora Nodorum ◽  
The U.S ◽  
Qoi Resistance

Stagonospora nodorum blotch (SNB) of wheat, caused by Parastagonospora nodorum, is managed using cultural practices, resistant varieties, and foliar fungicides. Frequent fungicide use can select for fungicide resistance, making certain chemistries less effective; this may in part explain increasing severity of SNB in the mid-Atlantic U.S. Quinone outside inhibitor (QoI) resistance has been documented for a diversity of fungi, but it has not been reported for P. nodorum in the U.S. The objectives of this study were to 1) evaluate QoI sensitivity of P. nodorum from Virginia wheat fields, 2) screen P. nodorum for QoI target site mutations in the cytochrome b gene, and 3) develop a molecular assay to detect target site mutations associated with QoI resistance. Sensitivity of 16 isolates to pyraclostrobin and azoxystrobin was evaluated with radial growth assays, and the cytochrome b gene was sequenced. One isolate was insensitive to both fungicides, and it had the G143A mutation in the cytochrome b gene. For azoxystrobin, 10 isolates without target site mutations had reduced sensitivity. Additional isolates (N=74) were sequenced, and seven had the G143A mutation; all seven isolates with the mutation had reduced sensitivity to pyraclostrobin and azoxystrobin compared to a sensitive control isolate without the mutation. A pyrosequencing assay targeting G143A was developed as a rapid method to screen P. nodorum for the QoI resistance-conferring mutation. To our knowledge, this is the first report of QoI resistant P. nodorum in the U.S. Overall resistance frequency was low, but resistance management practices are needed to maintain the efficacy of fungicides for SNB control.

scholarly journals QoI Resistance in Fusicladium carpophilum Populations from Almond in California and Evaluation of Molecular Resistance Mechanisms

Plant Disease ◽  
2013 ◽  
Vol 97 (10) ◽  
pp. 1322-1330 ◽  
Author(s):  
Y. Luo ◽  
L. Hou ◽  
H. Förster ◽  
J. E. Adaskaveg
Keyword(s):  
Cytochrome B ◽  
High Resistance ◽  
Quantitative Polymerase Chain Reaction ◽  
Resistance Mechanisms ◽  
Cytochrome B Gene ◽  
Analysis Of Covariance ◽  
Mitochondrial Cytochrome B ◽  
Moderately Resistant ◽  
Qoi Resistance

Disease management failures have been reported in California for almond scab caused by Fusicladium carpophilum following quinone outside inhibitor (QoI) applications. Resistance in the pathogen populations was found to be common and at high incidence in the major almond-growing regions beginning in 2003, 4 years after registration of azoxystrobin on this crop. Two levels of azoxystrobin resistance, moderate and high, were identified with 50% effective concentration (EC50) values between 0.15 and 10 μg/ml or >40 μg/ml, respectively. Reference isolates collected before resistance was detected had EC50 values <0.05 μg/ml. High-resistance was associated with a G143A mutation in the mitochondrial cytochrome b gene. For the less commonly found moderately resistant isolates, no mutations in the gene were detected between codons 122 and 212. Using primers targeting the G143A mutation or the cytochrome b gene of all F. carpophilum isolates in quantitative polymerase chain reaction (qPCR) analyses, the frequency of highly resistant isolates was accurately determined in mixtures of conidia with selected ratios of sensitive and resistant isolates. The frequency of high resistance in bulked samples of scab lesions, however, was generally underestimated compared with in vitro testing of fungicide sensitivity of fungal isolates from the same lesions. Competition experiments using conidial suspensions demonstrated stability of the highly resistant genotype in the presence of different amounts of sensitive and moderately resistant genotypes. Analysis of covariance of linear regressions of cycle threshold values on DNA concentrations derived from qPCR amplifications using two primer pairs for cytochrome b alleles with and without the G143 mutation showed that several isolates differed in their slopes and midpoints. Thus, heteroplasmy of mitochondrial-inherited QoI resistance is suggested as a likely cause for incongruence in estimating resistance frequencies using the two methods.

Identification of the G143A Mutation in Cytochrome b Associated with QoI Resistance in Cercospora beticola Isolates from the Red River Valley

2013 ◽  
Vol 14 (1) ◽  
pp. 14 ◽  
Author(s):  
Melvin D. Bolton ◽  
Viviana Rivera-Varas ◽  
Gary A. Secor ◽  
Allan W. Cattanach ◽  
Michael S. Metzger
Keyword(s):  
Cytochrome B ◽  
Amino Acid Position ◽  
Pathogen Resistance ◽  
River Valley ◽  
Red River ◽  
Cercospora Beticola ◽  
Cercospora Leaf Spot ◽  
Red River Valley ◽  
Quinone Outside Inhibitor ◽  
Qoi Resistance

Cercospora leaf spot (CLS), caused by the fungal pathogen Cercospora beticola, is the most important foliar disease of sugarbeet. The disease is managed in part by timely applications of quinone outside inhibitor (QoI) fungicides. However, pathogen resistance to QoI fungicides is associated with the exchange of glycine to alanine at amino acid position 143 (G143A) in the C. beticola cytochrome b gene. To assess whether QoI resistance has developed in C. beticola in the Red River Valley (RRV) of Minnesota and North Dakota, a real-time PCR procedure was used to determine whether the G143A mutation could be identified in samples harvested from 922 fields across the RRV. In total, 12 fields located in diverse locations within the RRV contained the G143A mutation, suggesting that QoI resistance arose independently at each location and in several genetic backgrounds. This is the first report of QoI resistance in the RRV. Careful monitoring of the G143A mutation will be necessary to ensure that QoI fungicides remain efficacious for CLS management in the RRV region. Accepted for publication 31 May 2013. Published 12 August 2013.

scholarly journals Distribution and Stability of Quinone Outside Inhibitor Fungicide Resistance in Populations of Potato Pathogenic Alternaria spp. in Wisconsin

Plant Disease ◽  
2019 ◽  
Vol 103 (8) ◽  
pp. 2033-2040 ◽  
Author(s):  
Shunping Ding ◽  
Dennis A. Halterman ◽  
Kiana Meinholz ◽  
Amanda J. Gevens
Keyword(s):  
Cytochrome B ◽  
Point Mutations ◽  
Alternaria Solani ◽  
Cytochrome B Gene ◽  
Brown Spot ◽  
Qoi Fungicides ◽  
Quinone Outside Inhibitor ◽  
Before And After ◽  
Pathogen Populations ◽  
Qoi Resistance

Quinone outside inhibitor (QoI) fungicides have been an important class in managing potato early blight caused by Alternaria solani and brown spot caused by A. alternata. Because of the single-site mode of action character of QoI fungicides, which are relied on for management of diseases in Wisconsin, and the abundant asexual conidia production of the Alternaria species, pathogen isolates with QoI resistance have been detected after just a few years of QoI fungicide usage in commercial production fields. Resistance to QoIs has been attributed to amino acid substitutions F129L and G143A in cytochrome b of A. solani and A. alternata, respectively, as a result of point mutations. The aim of this study was to assess Alternaria populations in Wisconsin for QoI resistance before and after fungicide applications in order to evaluate resistance stability. A TaqMan single nucleotide polymorphism genotyping assay was designed based on the sequences of the cytochrome b gene from Alternaria isolates collected in Wisconsin to profile QoI resistance in Alternaria populations as well as to explore factors that may influence frequency of QoI resistance in the pathogen populations. This assay successfully identified the mutations conferring QoI resistance in isolates collected from four locations each year from 2015 to 2017. During the course of this study, the frequency of A. solani isolates with the F129L mutation was consistently high and showed primarily the TTA mutation type. The frequency of A. alternata isolates with the G143A mutation started relatively low and increased at the end of the production season in each year (P = 0.0109, P = 0.2083, and P = 0.0159). A potato field managed without use of QoI fungicides showed a significantly lower (P < 0.05) frequency of A. alternata isolates carrying G143A than conventionally managed potato fields. The overall frequency of A. alternata isolates carrying G143A in the four locations was similar over the 3 years (P = 0.2971). The QoI resistance characteristics of the isolates were stable even when QoI selection pressure was removed for at least five subculture transfers, and the mutation types of codons 129 and 143 in the cytochrome b gene in A. solani and A. alternata, respectively, remained the same. This indicated that the application of QoIs in the field is not the sole factor responsible for the variation of the frequency of QoI resistance in the pathogen populations.

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