Sensitivity of Rhizoctonia solani AG 2-2 isolates from soybean and sugar beet to selected SDHI and QoI fungicides

Plant Disease ◽  
2021 ◽  
Author(s):  
Pratibha Sharma ◽  
Dean Malvick ◽  
Ashok Kumar Chanda
Keyword(s):  
Sugar Beet ◽  
North Dakota ◽  
Rhizoctonia Solani ◽  
Fungal Growth ◽  
Anastomosis Group ◽  
Qoi Fungicides ◽  
Quinone Outside Inhibitor ◽  
Periodic Monitoring ◽  
The Mean

Rhizoctonia solani causes root and stem diseases on soybean and sugar beet, and fungicides are commonly used to manage these diseases. Quinone outside inhibitor (QoI) fungicides (pyraclostrobin and azoxystrobin) have been used for in-furrow and post-emergence application since 2000. Succinate dehydrogenase inhibitor (SDHI) fungicides (sedaxane, penthiopyrad, and fluxapyroxad) became popular seed treatments following their registration in Minnesota and North Dakota between 2012 and 2016. Periodic monitoring of sensitivity to these fungicides in R. solani anastomosis group (AG) 2-2 is important to detect potential shifts in sensitivity over time. R. solani AG 2-2 isolates (n=35) collected from soybean and sugar beet in Minnesota and North Dakota were evaluated in vitro for sensitivity. Isolates were considered as baseline or non-baseline for the above mentioned fungicides based on previous potential exposure. The effective concentration (EC50) required to suppress radial fungal growth by 50% was determined. The mean EC50 values for sedaxane, penthiopyrad, fluxapyroxad and pyraclostrobin were 0.1, 0.15, 0.16, and 0.25 µg ml-1, respectively. The mean EC50 value for azoxystrobin for 22 isolates was 0.76 to 1.56 µg ml-1; and EC50 could not be determined for 13 isolates due to < 50% inhibition at the highest concentrations used. The EC50 values for the QoI fungicides did not differ significantly between baseline and non-baseline isolates. EC50 values for SDHI fungicides were significantly higher for isolates collected from soybean than from sugar beet, and isolates collected from both crops had similar EC50 values for pyraclostrobin. All SDHI fungicides and pyraclostrobin effectively suppressed R. solani isolates from soybean and sugar beet at low concentrations in vitro.

scholarly journals Sensitivity of Rhizoctonia solani AG-2-2 from Sugar Beet to Fungicides

Plant Disease ◽  
2016 ◽  
Vol 100 (12) ◽  
pp. 2427-2433 ◽  
Author(s):  
Sahar Arabiat ◽  
Mohamed F. R. Khan
Keyword(s):  
Sugar Beet ◽  
Rhizoctonia Solani ◽  
Root Rot ◽  
The United States ◽  
Damping Off ◽  
Growth Assay ◽  
The Mean ◽  
Crown And Root Rot ◽  
Mean Concentration

Rhizoctonia damping-off and crown and root rot caused by Rhizoctonia solani are major diseases of sugar beet (Beta vulgaris L.) worldwide, and growers in the United States rely on fungicides for disease management. Sensitivity of R. solani to fungicides was evaluated in vitro using a mycelial radial growth assay and by evaluating disease severity on R. solani AG 2-2 inoculated plants treated with fungicides in the greenhouse. The mean concentration that caused 50% mycelial growth inhibition (EC50) values for baseline isolates (collected before the fungicides were registered for sugar beet) were 49.7, 97.1, 0.3, 0.2, and 0.9 μg ml−1 and for nonbaseline isolates (collected after registration and use of fungicides) were 296.1, 341.7, 0.9, 0.2, and 0.6 μg ml−1 for azoxystrobin, trifloxystrobin, pyraclostrobin, penthiopyrad, and prothioconazole, respectively. The mean EC50 values of azoxystrobin, trifloxystrobin, and pyraclostrobin significantly increased in the nonbaseline isolates compared with baseline isolates, with a resistant factor of 6.0, 3.5, and 3.0, respectively. Frequency of isolates with EC50 values >10 μg ml−1 for azoxystrobin and trifloxystrobin increased from 25% in baseline isolates to 80% in nonbaseline isolates. Although sensitivity of nonbaseline isolates of R. solani to quinone outside inhibitors decreased, these fungicides at labeled rates were still effective at controlling the pathogen under greenhouse conditions.

scholarly journals Differentiation of Three Homogeneous Groups of Rhizoctonia solani Anastomosis Group 4 by Analysis of Fatty Acids

2001 ◽  
Vol 91 (9) ◽  
pp. 821-830 ◽  
Author(s):  
Janell Stevens Johnk ◽  
Roger K. Jones
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Sugar Beet ◽  
North Dakota ◽  
Rhizoctonia Solani ◽  
Acid Methyl Ester ◽  
Anastomosis Group ◽  
Homogeneous Groups ◽  
Fame Analysis ◽  
Group 4

Profiles of fatty acids from 70 isolates of Rhizoctonia solani anastomosis group (AG)-4 clustered into three groups, corresponding to homogeneous group (HG)-I, HG-II, and a newly described HG-III. Isolates from Georgia peanuts exhibiting limb rot were characterized as gas chromatography (GC) subgroup 1 (GC-1) and contained HG-I isolates. Isolates from diseased soybean hypocotyls grown in North Dakota and sugar beet seedlings, taproots, and tare soil in Minnesota and North Dakota were characterized as GC subgroup 2 (GC-2) and contained predominantly HG-II isolates but also included three distinct isolates based on fatty acid methyl ester (FAME) analysis and morphological features. Selected isolates from North Carolina cucumbers clustered into three distinct groups that corresponded to HG-I, HG-II, and the newly described HG-III. Distinct isolates from the soybean and sugar beet populations clustered with HG-III. Fatty acid profiles of AG-4 were compared with FAME library profiles of AG-1, AG-2 type 2, and AG-3, which were developed in previous studies and were sufficiently different that they could be used to support speciation of this group from R. solani. It is suggested that binomial R. practicola may be appropriate for the portion of AG-4 identified as HG-II.

scholarly journals Prevalence of QoI resistance and mtDNA diversity in the Irish Zymoseptoria tritici population

2019 ◽  
Vol 58 (1) ◽  
pp. 27-33
Author(s):  
S. Kildea ◽  
D.E. Bucar ◽  
F. Hutton ◽  
S. de la Rosa ◽  
T.E. Welch ◽  
...  
Keyword(s):  
Septoria Tritici Blotch ◽  
Septoria Tritici ◽  
Entire Group ◽  
Zymoseptoria Tritici ◽  
Qoi Fungicides ◽  
Quinone Outside Inhibitor ◽  
Strain Collection ◽  
Increased Sensitivity ◽  
Mtdna Diversity

Abstract The emergence and spread of Quinone outside Inhibitor (QoI) fungicide resistance in the Irish Zymoseptoria tritici population in the early 2000s had immediate impacts on the efficacy of the entire group of fungicides for the control of septoria tritici blotch. As a result, a dramatic reduction in the quantities applied to winter wheat occurred in the following seasons. Even in the absence of these fungicides, the frequency of the resistance allele, G143A in the pathogens mtDNA has remained exceptionally high (>97%), and as such, it can be anticipated that continued poor efficacy of current QoI fungicides will be observed. Amongst the isolates with G143A, differences in sensitivity to the QoI pyraclostrobin were observed in vitro. The addition of the alternative oxidase (AOX) inhibitor salicylhydroxamic acid increased sensitivity in these isolates, suggesting some continued impairment of respiration by the QoI fungicides, albeit weak. Interestingly, amongst those tested, the strains from a site with a high frequency of inserts in the MFS1 transporter gene known to enhance QoI efflux did not exhibit this increase in sensitivity. A total of 19 mtDNA haplotypes were detected amongst the 2017 strain collection. Phylogenetic analysis confirmed the suggestion of a common ancestry of all the haplotypes, even though three of the haplotypes contained at least one sensitive strain.

scholarly journals Sensitivity of Bipolaris oryzae Isolates Pathogenic on Cultivated Wild Rice to the Quinone Outside Inhibitor Azoxystrobin

Plant Disease ◽  
2019 ◽  
Vol 103 (8) ◽  
pp. 1910-1917 ◽  
Author(s):  
Claudia V. Castell-Miller ◽  
Deborah A. Samac
Keyword(s):  
Cytochrome B ◽  
Fungicide Resistance ◽  
Wild Rice ◽  
Brown Spot ◽  
Bipolaris Oryzae ◽  
Qoi Fungicides ◽  
Quinone Outside Inhibitor ◽  
Group I ◽  
Mitochondrial Cytochrome B

The occurrence of fungal brown spot, caused by Bipolaris oryzae, has increased in cultivated wild rice (Zizania palustris) paddies in spite of the use of azoxystrobin-based fungicides. The active ingredient blocks electron transfer at the quinone outside inhibitor (QoI) site in the mitochondrial cytochrome b within the bc1 complex, thus obstructing respiration. The in vitro averaged EC50 of baseline isolates collected in 2007 before widespread fungicide use was estimated to be 0.394 µg/ml with PROBIT and 0.427 µg/ml with linear regression analyses. Isolates collected during 2008, 2015, and 2016 had a range of sensitivity as measured by relative spore germination (RG) at a discriminatory dose of 0.4 µg/ml azoxystrobin. Isolates with a higher (≥80%) and lower RG (≤40%) had the wild type nucleotides at amino acid positions F129, G137, and G143 of cytochrome b, sites known to be associated with QoI fungicide resistance. Two Group I introns were found in the QoI target area. The splicing site for the second intron was found immediately after the codon for G143. A mutation for fungicide resistance at this location would hinder splicing and severely reduce fitness. B. oryzae expresses an alternative oxidase in vitro, which allows the fungus to survive inhibition of respiration by azoxystrobin. This research indicates that B. oryzae has not developed resistance to QoI fungicides, although monitoring for changes in sensitivity should be continued. Judicious use of QoI fungicides within an integrated disease management system will promote an effective and environmentally sound control of the pathogen in wild rice paddies.

scholarly journals Effects of SHAM on the Sensitivity of Sclerotinia sclerotiorum and Botrytis cinerea to QoI Fungicides

Plant Disease ◽  
2019 ◽  
Vol 103 (8) ◽  
pp. 1884-1888 ◽  
Author(s):  
Hongjie Liang ◽  
Jinli Li ◽  
Chaoxi Luo ◽  
Jianhong Li ◽  
Fu-Xing Zhu
Keyword(s):  
Botrytis Cinerea ◽  
Sclerotinia Sclerotiorum ◽  
Mycelial Growth ◽  
Control Efficacy ◽  
Vitro Assay ◽  
Qoi Fungicides ◽  
Quinone Outside Inhibitor ◽  
Fungal Phytopathogens ◽  
The Ideal

It is a common practice to add salicylhydroxamic acid (SHAM) into artificial medium in the in vitro sensitivity assay of fungal phytopathogens to the quinone outside inhibitor (QoI) fungicides. The rationale for adding SHAM is to inhibit fungal alternative oxidase, which is presumed to be inhibited by secondary metabolites of plants. Therefore, the ideal characteristics of SHAM should be almost nontoxic to phytopathogens and have no significant effect on control efficacy of fungicides. However, this study showed that the average effective concentration for 50% inhibition (EC50) of mycelial growth values of SHAM were 97.5 and 401.4 μg/ml for Sclerotinia sclerotiorum and Botrytis cinerea, respectively. EC50 values of the three QoI fungicides azoxystrobin, kresoxim-methyl, and trifloxystrobin in the presence of SHAM at 20 and 80 μg/ml for S. sclerotiorum and B. cinerea, respectively, declined by 52.7 to 78.1% compared with those without SHAM. For the dicarboximide fungicide dimethachlone, the average EC50 values in the presence of SHAM declined by 18.2% (P = 0.008) for S. sclerotiorum and 35.9% (P = 0.012) for B. cinerea. Pot experiments showed that SHAM increased control efficacy of the three QoI fungicides against the two pathogens by 43 to 83%. For dimethachlone, SHAM increased control efficacy by 134% for S. sclerotiorum and 86% for B. cinerea. Biochemical studies showed that SHAM significantly inhibited peroxidase activity (P = 0.024) of B. cinerea and esterase activity (P = 0.015) of S. sclerotiorum. The strong inhibitions of SHAM per se on mycelial growth of B. cinerea and S. sclerotiorum and significant influences on the sensitivity of the two pathogens to both the QoI fungicides and dimethachlone as well as inhibitions on peroxidase and esterase indicate that SHAM should not be added in the in vitro assay of sensitivity to the QoI fungicides.

scholarly journals Characterization and Pathogenicity of Rhizoctonia solani Isolates Affecting Pisum sativum in North Dakota

Plant Disease ◽  
2012 ◽  
Vol 96 (5) ◽  
pp. 666-672 ◽  
Author(s):  
F. M. Mathew ◽  
R. S. Lamppa ◽  
K. Chittem ◽  
Y. W. Chang ◽  
M. Botschner ◽  
...  
Keyword(s):  
Pisum Sativum ◽  
North Dakota ◽  
Rhizoctonia Solani ◽  
Resistance Breeding ◽  
Its Region ◽  
Anastomosis Group ◽  
Field Pea ◽  
State University ◽  
Dry Bean ◽  
North Dakota State University

Acreage of dry field pea (Pisum sativum) in North Dakota has increased approximately eightfold from the late 1990s to the late 2000s to over 200,000 ha annually. A coincidental increase in losses to root rots has also been observed. Root rot in dry field pea is commonly caused by a complex of pathogens which included Fusarium spp. and Rhizoctonia solani. R. solani isolates were obtained from roots sampled at the three- to five-node growth stage from North Dakota pea fields and from symptomatic samples received at the Plant Diagnostic Lab at North Dakota State University in 2008 and 2009. Using Bayesian inference and maximum likelihood analysis of the internal transcribed spacer (ITS) region of the ribosomal DNA (rDNA), 17 R. solani pea isolates were determined to belong to anastomosis group (AG)-4 homogenous group (HG)-II and two isolates to AG-5. Pathogenicity of select pea isolates was determined on field pea and two rotation hosts, soybean and dry bean. All isolates caused disease on all hosts; however, the median disease ratings were higher on green pea, dry bean, and soybean cultivars when inoculated with pea isolate AG-4 HG-II. Identification of R. solani AGs and subgroups on field pea and determination of relative pathogenicity on rotational hosts is important for effective resistance breeding and appropriate rotation strategies.

scholarly journals Baseline Sensitivity of Cercospora zeae-maydis to Quinone Outside Inhibitor Fungicides

Plant Disease ◽  
2011 ◽  
Vol 95 (2) ◽  
pp. 189-194 ◽  
Author(s):  
C. A. Bradley ◽  
D. K. Pedersen
Keyword(s):  
United States ◽  
Leaf Spot ◽  
The United States ◽  
Gray Leaf Spot ◽  
Alternative Respiration ◽  
Baseline Sensitivity ◽  
Qoi Fungicides ◽  
Quinone Outside Inhibitor ◽  
Cercospora Zeae Maydis

Cercospora zeae-maydis, the causal agent of gray leaf spot on corn (Zea mays), can cause severe yield loss in the United States. Quinone outside inhibitor (QoI) fungicides are effective tools that can be used to manage gray leaf spot, and their use has increased in corn production in the United States. In total, 61 C. zeae-maydis isolates collected from fields in which QoI fungicides had never been applied were tested in vitro using azoxystrobin-, pyraclostrobin-, or trifloxystrobin-amended medium to determine the effective fungicide concentration at which 50% of the conidial germination was inhibited (EC50). The effect of salicylhydroxamic acid (SHAM) also was evaluated for seven isolates to determine whether C. zeae-maydis is capable of using alternative respiration in azoxystrobin-amended medium. All seven C. zeae-maydis isolates tested had significantly greater (P < 0.02) EC50 values when SHAM was not included in medium amended with azoxystrobin, indicating that C. zeae-maydis has the potential to utilize alternative respiration to overcome QoI fungicide inhibition in vitro. Baseline EC50 values of azoxystrobin ranged from 0.003 to 0.031 μg/ml, with mean and median values of 0.018 and 0.019 μg/ml, respectively. Baseline EC50 values of pyraclostrobin ranged from 0.0003 to 0.0025 μg/ml, with mean and median values of 0.0010 and 0.0010 μg/ml, respectively. Baseline EC50 values of trifloxystrobin ranged from 0.0004 to 0.0034 μg/ml, with mean and median values of 0.0023 and 0.0024 μg/ml, respectively. These baseline sensitivity values will be used in a fungicide resistance monitoring program to determine whether shifts in sensitivity to QoI fungicides are occurring in C. zeae-maydis populations.

Typing of anastomosis groups ofRhizoctonia solaniby restriction analysis of ribosomal DNA

2003 ◽  
Vol 49 (9) ◽  
pp. 556-568 ◽  
Author(s):  
Cécile Guillemaut ◽  
Véronique Edel-Hermann ◽  
Pierre Camporota ◽  
Claude Alabouvette ◽  
Marc Richard-Molard ◽  
...  
Keyword(s):  
Sugar Beet ◽  
Rhizoctonia Solani ◽  
Ribosomal Dna ◽  
Restriction Analysis ◽  
Anastomosis Group ◽  
Internal Transcribed Spacers ◽  
Its Sequences ◽  
Typing Method ◽  
Rflp Type ◽  
Pcr Rflp

A method based on restriction analysis of polymerase chain reaction (PCR)-amplified ribosomal DNA was developed for the rapid characterization of large populations of Rhizoctonia solani at the anastomosis group (AG) level. The restriction maps of the internal transcribed spacers (ITS) sequences were compared for 219 isolates of R. solani belonging to AG-1 to AG-12 and AG-BI, representing diverse geographic and host range origins. Four discriminant restriction enzymes (MseI, AvaII, HincII, and MunI) resolved 40 restriction fragment length polymorphism (RFLP) types among the 219 ITS sequences of R. solani. Each RFLP type could be assigned to a single AG except for two RFLP types, which were common to two AG. A fifth enzyme allowed the discrimination of AG-6 and AG-12. In addition, the combination of four enzymes allowed the discrimination of subsets within AG-1, AG-2, AG-3, and AG-4. The efficiency of the typing method was confirmed by analyzing PCR-amplified ITS sequences of 30 reference strains. Furthermore, the PCR–RFLP method was used to characterize at the AG level 307 isolates of R. solani originating from ten sugar beet fields exhibiting patches of diseased plants in France. The PCR-based procedure described in this paper provides a rapid method for AG typing in R. solani.Key words: Rhizoctonia solani, anastomosis group, PCR–RFLP, ITS, identification, sugar beet.

scholarly journals Baseline Sensitivity of Guignardia citricarpa Isolates from Florida to Azoxystrobin and Pyraclostrobin

Plant Disease ◽  
2014 ◽  
Vol 98 (6) ◽  
pp. 780-789 ◽  
Author(s):  
Martha Hincapie ◽  
Nan-Yi Wang ◽  
Natalia A. Peres ◽  
Megan M. Dewdney
Keyword(s):  
Mycelial Growth ◽  
Control Measure ◽  
Black Spot ◽  
Conidial Germination ◽  
Baseline Sensitivity ◽  
Qoi Fungicides ◽  
Resistance Risk ◽  
Guignardia Citricarpa ◽  
The Mean

Citrus black spot (CBS), caused by Guignardia citricarpa, is an emerging disease in Florida. Fungicide applications are the main control measure worldwide. The in vitro activity and baseline sensitivity of G. citricarpa isolates to quinone outside inhibitor (QoI) fungicides (azoxystrobin and pyraclostrobin) were evaluated. The effective concentration needed to reduce mycelial growth or spore germination by 50% (EC50) was determined for 86 isolates obtained from Florida counties where CBS is found. The effect of salicylhydroxamic acid (SHAM) plus azoxystrobin and pyraclostrobin was also assessed for mycelial growth and conidial germination. The mean EC50 for mycelial growth for azoxystrobin was 0.027 μg/ml and that for pyraclostrobin was significantly lower at 0.007 μg/ml (P < 0.0001). Similarly, the mean EC50 for conidial germination for azoxystrobin was 0.016 μg/ml and that for pyraclostrobin was significantly lower at 0.008 μg/ml (P < 0.0001). There was no effect of SHAM on inhibition of mycelial growth or conidial germination by the QoI fungicides but SHAM slightly affected mycelium inhibition by pyraclostrobin. Cytochrome b was partially sequenced and three group 1 introns were found. One intron was immediately post G143, likely inhibiting resistance-conferring mutations at that site. It is surmised that the QoI resistance risk is low in the Florida G. citricarpa population.

scholarly journals Fitness, Competitive Ability, and Mutation Stability of Isolates of Colletotrichum acutatum from Strawberry Resistant to QoI Fungicides

2018 ◽  
Vol 108 (4) ◽  
pp. 462-468 ◽  
Author(s):  
Bruna B. Forcelini ◽  
Carolina S. Rebello ◽  
Nan-Yi Wang ◽  
Natalia A. Peres
Keyword(s):  
Competitive Ability ◽  
The United States ◽  
Fruit Production ◽  
Field Resistance ◽  
Relative Fitness ◽  
Colletotrichum Acutatum ◽  
Qoi Fungicides ◽  
Quinone Outside Inhibitor ◽  
Production Areas

Quinone-outside inhibitor (QoI) fungicides are used to manage anthracnose of strawberry, caused by Colletotrichum acutatum. However, selection for resistance to QoI fungicides was first reported in 2013 in Florida and, subsequently, in strawberry nurseries and production areas across the United States and Canada. C. acutatum resistance to QoIs is associated with the G143A point mutation in the cytochrome b gene. This mutation is known to be associated with field resistance even at high rates of QoI. In this study, we investigated the relative fitness and competitive ability of QoI-resistant and -sensitive C. acutatum isolates. A fitness comparison did not indicate any difference between resistant and sensitive isolates in aggressiveness, spore production, and mycelial growth at different temperatures. Additionally, in the absence of selection pressure, resistant and sensitive isolates were equally competitive. Cultivation of QoI-resistant and QoI-sensitive isolates for four culture cycles in vitro in the absence of azoxystrobin showed that QoI resistance was stable. The observed lack of fitness penalties and stability of the G143A mutation in QoI-resistant C. acutatum populations suggest that the interruption and further reintroduction of QoI fungicides might not be an option for strawberry nurseries and fruit production areas. Further investigation of alternative chemical and nonchemical C. acutatum control practices, in addition to the integration of multisite fungicides, is needed to reduce the occurrence and distribution of QoI-resistant populations in strawberry fields.

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