Widespread Occurrence of Quinone Outside Inhibitor Fungicide-Resistant Isolates of Cercospora sojina, Causal Agent of Frogeye Leaf Spot of Soybean, in the United States

2018 ◽  
Vol 19 (4) ◽  
pp. 295-302 ◽  
Author(s):  
Guirong Zhang ◽  
Tom W. Allen ◽  
Jason P. Bond ◽  
Ahmad M. Fakhoury ◽  
Anne E. Dorrance ◽  
...  
Keyword(s):  
United States ◽  
Leaf Spot ◽  
Management Practices ◽  
Integrated Management ◽  
The United States ◽  
Causal Agent ◽  
Cercospora Sojina ◽  
Widespread Occurrence ◽  
Quinone Outside Inhibitor ◽  
Frogeye Leaf Spot

Isolates of Cercospora sojina, causal agent of frogeye leaf spot of soybean (Glycine max), were collected across Alabama, Arkansas, Delaware, Illinois, Indiana, Iowa, Kentucky, Louisiana, Mississippi, Missouri, North Carolina, Ohio, Tennessee, and Virginia and were evaluated for quinone outside inhibitor (QoI) fungicide resistance. Collection of these isolates from these 14 states occurred between 2010 and 2017. QoI fungicide-resistant C. sojina isolates were detected in all 14 states surveyed and represent a total of 240 counties or parishes. In 2017, these 240 counties and parishes represented approximately 13% of the harvested soybean hectares in the United States. In light of this widespread occurrence of QoI fungicide-resistant C. sojina isolates, management of frogeye leaf spot should focus on integrated management practices such as planting resistant soybean cultivars, rotating with nonhost crops, and tilling to speed up decomposition of infested soybean residue. When foliar fungicide application is warranted, fungicide products that contain active ingredients from chemistry classes other than the QoI class should be applied for frogeye leaf spot management.

Resistance to Quinone Outside Inhibitor Fungicides Conferred by the G143A Mutation in Cercospora sojina (Causal Agent of Frogeye Leaf Spot) Isolates from Michigan, Minnesota, and Nebraska Soybean Fields

2020 ◽  
Vol 21 (4) ◽  
pp. 230-231 ◽  
Author(s):  
Danilo L. Neves ◽  
Martin I. Chilvers ◽  
Tamra A. Jackson-Ziems ◽  
Dean K. Malvick ◽  
Carl A. Bradley
Keyword(s):  
United States ◽  
Leaf Spot ◽  
Fungicide Resistance ◽  
The United States ◽  
Pcr Assay ◽  
Cercospora Sojina ◽  
Qoi Fungicides ◽  
Quinone Outside Inhibitor ◽  
Frogeye Leaf Spot ◽  
Important Disease

Frogeye leaf spot, caused by Cercospora sojina, is an important disease of soybean (Glycine max) in the United States. An important tactic to manage frogeye leaf spot is to apply foliar fungicides. Isolates of C. sojina were collected from soybean fields in one county in Michigan, three counties in Minnesota, and 10 counties in Nebraska in 2019, and they were tested for resistance to quinone outside inhibitor (QoI) fungicides using a discriminatory dose assay, a PCR assay, and DNA sequencing. Results of the testing indicated that QoI fungicide-resistant isolates were detected in isolates from all counties. Testing results also indicated that the G143A mutation was responsible for the QoI fungicide resistance. This is the first report of QoI fungicide-resistant C. sojina isolates in Michigan, Minnesota, and Nebraska and expands the geographical distribution of QoI fungicide-resistant C. sojina isolates to 18 states in total.

scholarly journals First Report of the Soybean Frogeye Leaf Spot Fungus (Cercospora sojina) Resistant to Quinone Outside Inhibitor Fungicides in North America

Plant Disease ◽  
2012 ◽  
Vol 96 (5) ◽  
pp. 767-767 ◽  
Author(s):  
G. R. Zhang ◽  
M. A. Newman ◽  
C. A. Bradley
Keyword(s):  
Leaf Spot ◽  
Management Practices ◽  
The United States ◽  
Conidial Germination ◽  
Cercospora Sojina ◽  
Soybean Field ◽  
Qoi Fungicides ◽  
First Report ◽  
Quinone Outside Inhibitor ◽  
Frogeye Leaf Spot

Quinone outside inhibitor (QoI; also known as strobilurin) fungicides sometimes are applied to soybean (Glycine max) fields to help manage frogeye leaf spot of soybean (caused by Cercospora sojina) in the United States. In August 2010, soybean leaflets exhibiting severe frogeye leaf spot symptoms were collected from a field in Lauderdale County, TN that had been treated twice with pyraclostrobin during that growing season. The field had been planted into soybean annually since at least 2008, and a QoI fungicide had been applied to the field in each of those years. Fifteen single-spore isolates of C. sojina were recovered from the affected soybean leaflets. These isolates were identified as C. sojina based on the observed symptoms on the soybean leaflets and the morphology and size of conidiophores and conidia (3). In addition, DNA was extracted from the cultures, PCR amplification of the small subunit rDNA and internal transcribed spacer (ITS) region was conducted (2), and the resulting PCR product was sequenced at the Keck Biotechnology Center at the University of Illinois, Urbana. The resulting nucleotide sequences were compared with sequences deposited in the nucleotide database ( http://www.ncbi.nlm.nih.gov ) and showed highest homology to sequences of C. sojina. The isolates were tested for their sensitivity to technical-grade formulations of the QoI fungicides azoxystrobin, pyraclostrobin, and trifloxystrobin with an in vitro conidial germination assay with fungicide + salicylhydroxamic acid (SHAM)-amended potato dextrose agar as described by Bradley and Pedersen (1). The effective concentration at which 50% conidial germination was inhibited (EC50) was determined for all 15 C. sojina isolates, with mean values of 3.1644 (2.7826 to 4.5409), 0.3297 (0.2818 to 0.6404), and 0.8573 (0.3665 to 2.5119) μg/ml for azoxystrobin, pyraclostrobin, and trifloxystrobin, respectively. When compared with previously established mean EC50 values of C. sojina baseline isolates (4), EC50 values of the C. sojina isolates collected from the Lauderdale County, TN soybean field were approximately 249- to 7,144-fold greater than the EC50 values of the baseline isolates. These results indicate that all isolates recovered from the Lauderdale County, TN soybean field were highly resistant to QoI fungicides. To our knowledge, this is the first report of QoI fungicide resistance occurring in C. sojina, and surveys for additional QoI fungicide-resistant C. sojina isolates are needed to determine their prevalence and geographic distribution. In light of these findings, soybean growers in Tennessee and adjacent states should consider utilizing alternative frogeye leaf spot management practices such as planting resistant cultivars, rotating to nonhost crops, and tilling affected soybean residue (3). References: (1) C. A. Bradley and D. K. Pedersen. Plant Dis. 95:189, 2011. (2) N. S. Lord et al. FEMS Microbiol. Ecol. 42:327, 2002. (3) D. V. Phillips. Page 20 in: Compendium of Soybean Diseases. 4th ed. G. L. Hartman et al., eds. The American Phytopathological Society, St. Paul, MN, 1999. (4) G. Zhang et al. Phytopathology (Abstr.) 100(suppl.):S145, 2010.

scholarly journals Resistance to Quinone Outside Inhibitor Fungicides Conferred by the G143A Mutation in Cercospora sojina (Causal Agent of Frogeye Leaf Spot) Isolates from South Dakota Soybean Fields

2019 ◽  
Vol 20 (2) ◽  
pp. 104-105 ◽  
Author(s):  
Febina M. Mathew ◽  
Emmanuel Byamukama ◽  
Danilo L. Neves ◽  
Carl A. Bradley
Keyword(s):  
South Dakota ◽  
Leaf Spot ◽  
Causal Agent ◽  
Chain Reaction ◽  
Cercospora Sojina ◽  
Qoi Fungicides ◽  
Quinone Outside Inhibitor ◽  
Frogeye Leaf Spot ◽  
Polymerase Chain

Resistance to quinone outside inhibitor (QoI) fungicides was detected in Cercospora sojina (causal agent of frogeye leaf spot) isolates collected from soybean (Glycine max) fields in four South Dakota counties during the 2018 growing season. A discriminatory dose assay was used to detect QoI-resistant isolates, and a follow-up polymerase chain reaction assay was used to determine the presence of the G143A mutation in QoI-resistant isolates. This is the first report of resistance to QoI fungicides in C. sojina isolates from South Dakota.

Assessment of quinone outside inhibitor sensitivity and frogeye leaf spot race of Cercospora sojina in Georgia soybean

Plant Disease ◽  
2021 ◽  
Author(s):  
Bennett Harrelson ◽  
Bikash Ghimire ◽  
Robert Kemerait ◽  
Albert Culbreath ◽  
Zenglu Li ◽  
...  
Keyword(s):  
Leaf Spot ◽  
Fungicide Resistance ◽  
Mycelial Growth ◽  
The United States ◽  
In Vitro Assays ◽  
Cercospora Sojina ◽  
Quinone Outside Inhibitor ◽  
Frogeye Leaf Spot ◽  
Differential Cultivars

Frogeye leaf spot (FLS), caused by the fungal pathogen Cercospora sojina K. Hara, is a foliar disease of soybean (Glycine max L. (Merr.)) responsible for yield reductions throughout the major soybean producing regions in the world. In the United States, management of FLS relies heavily on the use of resistant cultivars and in-season fungicide applications, specifically within the class of quinone outside inhibitors (QoIs), which has resulted in the development of fungicide resistance in many states. In 2018 and 2019, 80 isolates of C. sojina were collected from six counties in Georgia and screened for QoI fungicide resistance using molecular and in vitro assays, with resistant isolates being confirmed from three counties. Additionally, 50 isolates, including a “baseline isolate” with no prior fungicide exposure, were used to determine the percent reduction of mycelial growth to two fungicides, azoxystrobin and pyraclostrobin, at six concentrations: 0.0001, 0.001, 0.01, 0.1, 1, and 10 g ml-1. Mycelial growth observed for resistant isolates varied significantly from both the sensitive isolates and the baseline isolate for azoxystrobin concentrations of 10, 1, 0.1, and 0.01 g ml-1 and for pyraclostrobin concentrations of 10, 1, 0.1, 0.01 and 0.001 g ml-1. Moreover, 40 isolates were used to evaluate pathogen race on six soybean differential cultivars by assessing susceptible or resistant reactions. Isolate reactions suggested 12 races of C. sojina present in Georgia, four of which have not been previously described. Species richness indicators (rarefaction and abundance-based coverage estimator - ACE) indicated that within-county C. sojina race numbers were undersampled in the present study, suggesting the potential for the presence of either additional undescribed races or known but unaccounted for races in Georgia. However, no isolates were pathogenic on differential cultivar ‘Davis’, carrying the Rcs3 resistance allele, suggesting the gene is still an effective source of resistance in Georgia.

scholarly journals Characterization of Quinone Outside Inhibitor Fungicide Resistance in Cercospora sojina and Development of Diagnostic Tools for its Identification

Plant Disease ◽  
2015 ◽  
Vol 99 (4) ◽  
pp. 544-550 ◽  
Author(s):  
F. Zeng ◽  
E. Arnao ◽  
G. Zhang ◽  
G. Olaya ◽  
J. Wullschleger ◽  
...  
Keyword(s):  
Cytochrome B ◽  
Leaf Spot ◽  
Fungicide Resistance ◽  
Cytochrome B Gene ◽  
Diagnostic Tools ◽  
Polymerase Chain Reaction Primer ◽  
Cercospora Sojina ◽  
Qoi Fungicides ◽  
Quinone Outside Inhibitor ◽  
Frogeye Leaf Spot

Frogeye leaf spot of soybean, caused by the fungus Cercospora sojina, reduces soybean yields in most of the top-producing countries around the world. Control strategies for frogeye leaf spot can rely heavily on quinone outside inhibitor (QoI) fungicides. In 2010, QoI fungicide-resistant C. sojina isolates were identified in Tennessee for the first time. As the target of QoI fungicides, the cytochrome b gene present in fungal mitochondria has played a key role in the development of resistance to this fungicide class. The cytochrome b genes from three QoI-sensitive and three QoI-resistant C. sojina isolates were cloned and sequenced. The complete coding sequence of the cytochrome b gene was identified and found to encode 396 amino acids. The QoI-resistant C. sojina isolates contained the G143A mutation in the cytochrome b gene, a guanidine to cytosine transversion at the second position in codon 143 that causes an amino acid substitution of alanine for glycine. C. sojina-specific polymerase chain reaction primer sets and TaqMan probes were developed to efficiently discriminate QoI-resistant and -sensitive isolates. The molecular basis of QoI fungicide resistance in field isolates of C. sojina was identified as the G143A mutation, and specific molecular approaches were developed to discriminate and to track QoI-resistant and -sensitive isolates of C. sojina.

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.

scholarly journals First Report of Colletotrichum karstii Causing Glomerella Leaf Spot on Apple in Santa Catarina State, Brazil

Plant Disease ◽  
2014 ◽  
Vol 98 (1) ◽  
pp. 157-157 ◽  
Author(s):  
A. C. Velho ◽  
M. J. Stadnik ◽  
L. Casanova ◽  
P. Mondino ◽  
S. Alaniz
Keyword(s):  
United States ◽  
Leaf Spot ◽  
Management Practices ◽  
Eastern China ◽  
The United States ◽  
Subtropical Climate ◽  
Santa Catarina ◽  
First Report ◽  
Glomerella Leaf Spot ◽  
Santa Catarina State

Glomerella leaf spot (GLS) is an emerging disease of apple (Malus domestica Borkh.) that has been reported in regions with a humid subtropical climate, such as southern Brazil, the southeastern United States, and more recently eastern China. GLS is favored by high humidity and temperatures between 23 and 28°C and can result in extensive defoliation when the severity is high. The disease was first reported 1988 in Brazil on cvs. Gala and Golden Delicious in orchards in Paraná State (3), but now is widespread in the country's producing areas. Two Colletotrichum species of different complexes have been associated with GLS, C. gloeosporioides (Penz.) Penz. & Sacc. and its sexual stage Glomerella cingulata (Stoneman) Spaulding & Scherenk, and C. acutatum J. H. Simmonds, although GLS is more commonly associated with the former. In the summer of 2012, necrotic spots were observed on apple leaves (cv. Gala) in Santa Catarina state, Brazil. The first symptoms were reddish-brown spots, evolving to small necrotic lesions 1 to 10 mm long at 7 to 10 days after symptoms were first noted. Pure cultures were obtained by monosporic isolation and grown on PDA at 25°C and with a 12-h photoperiod under fluorescent light. The color of the upper surface of the colony varied from white to gray and the reverse was pink. The conidia length and width ranged from 9.1 to 17.1 μm ([Formula: see text] = 12.8) and from 2.9 to 6.8 μm ([Formula: see text] = 4.9), respectively, and were cylindrical, hyaline, and straight. After germination, conidia formed oval or circular appressoria measuring between 4.0 and 10.0 ([Formula: see text] = 6.3) × 3.0 and 9.0 ([Formula: see text] = 5.7). To confirm pathogenicity, susceptible apple seedlings (cv. Gala) were inoculated with a suspension of 1 × 106 conidia.mL–1. Seedlings sprayed with sterile distilled water served as controls. Seedlings were incubated in a moist chamber at 25°C and 100% RH for 48 h. First symptoms appeared 4 days after inoculation and were similar to those observed in the field. The control treatment remained symptomless. The pathogen was reisolated from lesions, confirming Koch's postulates. Fungus was molecularly characterized by sequencing the internal transcribed spacer (ITS) rDNA and glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and the nucleotide sequence was deposited in the GenBank database (KC876638 and KC875408). C. karstii, considered as part of the C. boninense species complex (1), was identified with 100% sequence homology. This species was previously reported in China (4), Thailand, and the United States, affecting Orchidaceae plants (2), and in Brazil it has been reported affecting Carica papaya, Eugenia uniflora, and Bombax aquaticum (1). To our knowledge, this is the first report of C. karstii causing GLS on apple in Brazil. The development of pre-harvest management practices may be warranted to manage this disease. References: (1) U. Damm et al. Stud. Mycol. 73:1, 2012. (2) I. Jadrane. Plant Dis. 96:1227, 2012. (3) T. B. Sutton. Plant Dis. 82:267, 1998. (4) Y. Yang. Cryptogamie Mycologie 32:229, 2011.

scholarly journals Seedborne Cladosporium variabile and Stemphylium botryosum in Spinach

Plant Disease ◽  
2006 ◽  
Vol 90 (2) ◽  
pp. 137-145 ◽  
Author(s):  
Pablo Hernandez-Perez ◽  
Lindsey J. du Toit
Keyword(s):  
United States ◽  
Relative Humidity ◽  
Leaf Spot ◽  
Spinacia Oleracea ◽  
The United States ◽  
Causal Agent ◽  
Similar Species ◽  
Stemphylium Botryosum ◽  
Aerial Hyphae ◽  
Potential Difficulty

Assays of 77 spinach (Spinacia oleracea) seed lots produced in the United States, Denmark, the Netherlands, or New Zealand in 2000 to 2003 showed that Stemphylium botryosum, causal agent of Stemphylium leaf spot, was present in every lot, at a mean incidence of 29.1% per lot. Either Cladosporium variabile, causal agent of Cladosporium leaf spot, or the morphologically similar species C. macrocarpum, was present in 37 of the 77 lots, at a mean incidence of 1.8% per lot. Some seed isolates of S. botryosum and C. variabile proved pathogenic on spinach. Nonpathogenic isolates resembling C. variabile were identified as C. macrocarpum by the absence of torulose aerial hyphae. Pathogenic isolates of S. botryosum were also detected in each of 12 seed lots stored for up to 11 years at 4.4°C and 60% relative humidity. C. variabile or C. macrocarpum was detected in only 2 of the 11 lots, which had been stored for 3 and 8 years. Component seed assays demonstrated that S. botryosum and C. variabile (or C. macrocarpum) were internal and external in spinach seed. S. botryosum was detected in 5 to 76% of the embryos of five seed lots, but the two Cladosporium species were detected in only 0 to 1% of the embryos of these lots. This suggests greater potential difficulty at eradicating S. botryosum than C. variabile from infected spinach seed using seed treatments.

scholarly journals Differential Responses of Soybean Cultivars to Cercospora sojina Isolates, the Causal Agent of Frogeye Leaf Spot in Korea

2011 ◽  
Vol 27 (2) ◽  
pp. 183-186 ◽  
Author(s):  
Ji-Seong Kim ◽  
Young-Su Lee ◽  
Sung-Kee Kim ◽  
Ki-Deok Kim ◽  
Jin-Won Kim
Keyword(s):  
Leaf Spot ◽  
Causal Agent ◽  
Cercospora Sojina ◽  
Soybean Cultivars ◽  
Frogeye Leaf Spot ◽  
Differential Responses

scholarly journals Assessing Missouri soybean fields for azoxystrobin resistant cercospora sojina

2021 ◽  
Author(s):  
◽  
Bruna MacGregor
Keyword(s):  
Leaf Spot ◽  
Successful Management ◽  
Technical Grade ◽  
Fungicide Sensitivity ◽  
Cercospora Sojina ◽  
Quinone Outside Inhibitor ◽  
Frogeye Leaf Spot ◽  
Resistant Varieties ◽  
Insight Into ◽  
The U.S

Successful management of Cercospora sojina, the causal agent of frogeye leaf spot, can be achieved through utilizing resistant varieties and fungicide applications. Fungicides in the quinone outside inhibitor (QoI) class are most effective in controlling C. sojina in the field. Unfortunately, azoxystrobin fungicide-resistant isolates of C. sojina have been recovered in many soybean growing areas of the U.S. Fungicide-resistant isolates of C. sojina were first detected in 2011 and 2012 in two counties in southeast Missouri, but no further assessment was conducted. In this study, 121 isolates were collected from 15 surveyed counties between 2019 and 2020 in an effort to understand the geographical distribution of fungicide-resistant C. sojina. Isolates were collected from fields based on the presence of frogeye leaf spot symptoms. Samples were brought to the laboratory and isolates were recovered from individual lesions. A fungicide sensitivity bioassay was conducted to determine which isolates were resistant to the QoI class of fungicides. The fungicide sensitivity bioassay consisted of full-strength PDA amended with technical grade azoxystrobin at five different concentrations and a no fungicide control. Out of 121 isolates, 81 were fungicide-resistant representing 13 of the 15 Missouri counties included in the survey. Notably, the northwest corner of Missouri had the highest concentration of fungicide-resistant isolates, consistent with the recent recovery of fungicide-resistant C. sojina isolates in Iowa and Nebraska. The widespread recovery of fungicide-resistant C. sojina in multiple counties throughout Missouri provides new insight into disease management in the state.

Sign in / Sign up

Export Citation Format

Share Document