scholarly journals Outbreaks of Soybean Frogeye Leaf Spot in Iowa

Plant Disease ◽  
2001 ◽  
Vol 85 (4) ◽  
pp. 443-443 ◽  
Author(s):  
X. B. Yang ◽  
M. D. Uphoff ◽  
S. Sanogo
Keyword(s):  
Disease Severity ◽  
Leaf Spot ◽  
Performance Test ◽  
Disease Incidence ◽  
Central City ◽  
Cercospora Sojina ◽  
East Central ◽  
Production Region ◽  
Frogeye Leaf Spot ◽  
Winter Temperatures

Frogeye leaf spot of soybean, caused by Cercospora sojina, is typically a disease of warm and humid regions (2). Although the disease was reported in the Midwest in the 1920s (1), no outbreaks have been recorded in Iowa. Outbreaks of frogeye leaf spot occurred during 1999 in soybean fields in Ames and Grand Junction in central Iowa. During the 2000 growing season, the disease occurred in southwestern, southcentral, central, southeastern, and east-central Iowa. Occurrences of the disease with severity (reduction of green leaf area) greater than 50% were observed in production soybean fields at Grand Junction in central Iowa and Central City in eastern Iowa. In a 12-ha no-till field planted with cv. Asgrow 2501, the disease was noticeable and uniformly distributed in the entire field in mid July. Disease severity in this field was greater than 70% by the end of August. Disease incidence, however, was less than 10% in three adjacent soybean fields. In a soybean performance test at a central Iowa location where the disease occurred in 1999 and 2000, the disease was observed on all 80 varieties, with four having a severity equal to or greater than 40%. Fourteen entries had less than a 10% disease severity and 19 entries had a disease severity equal to or greater than 30%. Infected leaves in these locations had typical lesions of frogeye leaf spot, which appeared as reddish brown margins surrounding light brown or ash gray centers. On the infected tissues, hyaline, straight, and multiseptate conidia from clustered conidiophores were found, isolated, and identified to C. sojina. The relatively warm winter temperatures in 1998 to 1999 and 1999 to 2000 were associated with frogeye leaf spot epidemics. Because of the seedborne nature of C. sojina, efforts are warranted to monitor and survey the occurrence of frogeye leaf spot in Iowa, an important seed production state in the northern soybean production region. References: (1) K. Athow and A. H. Probst. Phytopathology 42:660–662, 1952. (2) D. V. Phillips. 1999. Pages 20–21 in: Soybean Disease Compendium. Hartman et al. eds, American Phytopathological Society. St. Paul, MN.

scholarly journals First Report of Frogeye Leaf Spot (Cercospora sojina) in Wisconsin

Plant Disease ◽  
2002 ◽  
Vol 86 (11) ◽  
pp. 1272-1272 ◽  
Author(s):  
Alemu Mengistu ◽  
N. C. Kurtzweil ◽  
C. R. Grau
Keyword(s):  
Leaf Spot ◽  
Disease Incidence ◽  
Light Output ◽  
Growth Chamber ◽  
Growth Stages ◽  
Cercospora Sojina ◽  
First Report ◽  
Frogeye Leaf Spot ◽  
Pathogenicity Tests ◽  
Leaf Symptoms

Frogeye leaf spot, caused by Cercospora sojina, is an economically important foliar disease of soybean (Glycine max (L.) Merr.) in areas where growing conditions are warm and humid. During a survey conducted in 2000 and 2001 in soybean fields in Wisconsin, reddish brown, circular to angular spots varying in diameter from 1 to 5 mm were observed on soybean leaves in four fields in Dane and Iowa counties, and in five and six fields in Lafayette and Green counties, respectively. Soybean plants were in growth stages between R3 and R5 during sampling. Disease incidence ranged from 30 to 100% with 5 to 10% of leaf area covered with leaf spot in 2000. In 2001, trace levels of the disease were detected in Dane County, but no symptomatic plants were present in the other counties. Symptomatic leaves were collected from all locations in 2000 and Dane county in 2001. Ten leaves were randomly picked from all samples for each year, placed in a 100 × 15 mm petri dish dampened with Whatman No.1 filter paper, and incubated overnight at 24°C. Fungal sporulation developed after 24 h. Fifteen spores were removed from the 10 leaves, placed on acidified potato dextrose agar (APDA), and incubated in the dark at 24°C. Cultures with dark pigmentation and associated conidia and conidiophores were observed after 3 weeks. The conidiophore, spore type, and leaf symptoms correspond to the description of C. sojina (1). Conidiophores were light-to-dark brown, one to four septate, and fasciculate. The conidiophores were also geniculate and measured 52 to 120 x 4 to 6 μm. Conidia were 0 to 10 septate, hyaline, elongate to fusiform, and measured 40 to 60 x 6 to 8 μm. Cultures were maintained on APDA, and spores for inoculations were produced on this medium. Spores from the 2000 cultures were harvested, bulked together, and used for pathogenicity tests. Pathogenicity tests were conducted in a growth chamber using a known susceptible soybean cultivar, Blackhawk. Ten-cm-diameter pots each containing 4 plants was used. Twenty plants were inoculated and 20 served as noninoculated controls. Ten-day-old plants were inoculated with a spore suspension of 3 × 105 spores/ml by spraying inoculum over the entire leaf surfaces with a spray atomizer. Control plants were sprayed similarly with sterile distilled water. Plants were incubated in an enclosed, transparent fiberglass box with a humidifier that provided 95 to 100% humidity. Lighting in the growth chamber was adjusted to 18-h light and 6-h dark during the inoculation period. Plants were removed from the box after 48 h and placed in a growth chamber with a 12-h photoperiod. The light output in the growth chamber was 300 μmol·m-2·s-1 and the temperature was maintained at 24 ± 3°C. The experiment was repeated once. Typical field symptoms appeared on each of the inoculated plant 8 days after inoculation, while the controls expressed no leaf symptoms. C. sojina was reisolated from all symptomatic plants. To our knowledge, this is the first report of C. sojina from soybean in Wisconsin. Reference: (1) D. V. Phillips. Frogeye leaf spot. Page 20 in: Compendium of Soybean Diseases. 4th ed. G. L. Hartman, J. B. Sinclair, and J. C. Rupe, eds. American Phytopathological Society, St. Paul, MN, 1999.

scholarly journals Frogeye Leaf Spot of Soybean Caused by Cercospora sojina in Northwestern Argentina

Plant Disease ◽  
2001 ◽  
Vol 85 (7) ◽  
pp. 801-801 ◽  
Author(s):  
L. D. Ploper ◽  
V. González ◽  
M. R. Gálvez ◽  
M. R. Devani ◽  
F. Ledesma ◽  
...  
Keyword(s):  
Leaf Area ◽  
Leaf Spot ◽  
Leaf Surface ◽  
Disease Incidence ◽  
Growing Season ◽  
Conidial Suspension ◽  
Cercospora Sojina ◽  
Northwestern Argentina ◽  
Resistant Cultivars ◽  
Frogeye Leaf Spot

Frogeye leaf spot of soybean (Glycine max (L.) Merr.), caused by Cercospora sojina Hara, was first detected during the 1997-98 growing season at low incidence and severity (<1% of the leaf diseased) levels in the provinces of Tucumán, Salta, Jujuy, Catamarca, and Santiago del Estero in northwestern Argentina. During the 1998-1999 growing season, disease incidence increased and disease severity grew to 10% of the leaf surface diseased on highly susceptible cultivars in a few locations. An outbreak of frogeye leaf spot occurred throughout northwestern Argentina during the 1999-2000 growing season. Frogeye leaf spot was severe on susceptible cultivars in the provinces of Salta, Santiago del Estero and Catamarca with the greatest intensity in the northeastern part of the Province of Tucumán. Symptoms on leaves were circular lesions that ranged in size from 1 to 5 mm, were reddish-brown to gray or tan, and were bordered by a narrow, reddish-brown to purple margin. Conidiophores and conidia of C. sojina developed on the abaxial leaf surface (1,2). Severely diseased leaves were desiccated and dropped during the R6 stage of growth. Lesions also developed on stems, pods, and seeds. Field surveys indicated that this disease reduced the yields of the highly susceptible cultivars Anta 82 RR, Coker 6738, and A 6445 RG by 48, 34, and 25%, respectively. C. sojina was cultured from diseased tissue on PDA acidified with 0.2% lactic acid and maintained on V-8 juice agar amended with streptomycin sulfate (100 mg/l). Conidia were elongated, dark, 38 to 62 × 5 to 9 μm, with 2 to 6 septa, and borne on dark conidiophores with 1 to 4 septa. Pathogenicity tests were conducted on seedlings of the susceptible cultivars A 6445 RG and Coker 6738 and on the resistant cultivars A 8000 RG and Shulka. Seedlings were inoculated at the V3 growth stage by spraying the leaves with a conidial suspension (4 × 104 conidia/ml) using a hand-held atomizer. Control plants were sprayed with sterile distilled water. Plants were placed in a moist chamber at 26°C for 2 days and then transferred to a greenhouse bench where they were kept at 25 to 30°C. Symptoms identical to those observed in the field became visible after 7 to 10 days. Ratings were made 14 days after inoculation by estimating the percentage of leaf area affected using a standard area diagram. Lesions covered 60 to 65% of the leaf area of susceptible cultivars, but less than 2% on resistant cultivars. Control plants remained healthy. C. sojina was reisolated from lesions on leaves of susceptible plants. Above-average rainfall and high relative humidity in northwestern Argentina during the first three months of 2000 may have encouraged the severe outbreak of frogeye leaf spot of soybean. The outbreak was aggravated by the widespread use of notillage systems in the region and the large hectarage planted with susceptible cultivars. References: (1) S.G. Lehman J. Agric. Res. 36:811–833, 1928. (2) D. V. Philips and J. T. Yorinori. 1989. Frogeye leaf spot. Pages 19–21 in: Compendium of Soybean Diseases, 3rd ed. APS Press, St. Paul, MN.

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.

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.

Quantifying the Effects of Fungicides and Tillage on Cercospora sojina Severity and Yield of Soybean

2018 ◽  
Vol 19 (3) ◽  
pp. 226-232
Author(s):  
Alemu Mengistu ◽  
Heather M. Kelly ◽  
Prakash R. Arelli ◽  
Nacer Bellaloui ◽  
Binbin Lin
Keyword(s):  
Disease Severity ◽  
Environmental Conditions ◽  
Leaf Spot ◽  
Cercospora Sojina ◽  
University Of Tennessee ◽  
No Till ◽  
Untreated Check ◽  
Severity Of The Disease ◽  
Research And Education ◽  
The University

A field study was conducted in 2014 through 2016 at the University of Tennessee Research and Education Center, Milan, TN, to determine fungicide effects on frogeye leaf spot (FLS) caused by Cercospora sojina and to determine disease severity and yield under no-till and tillage. Each plot was visually rated for FLS severity based on the percent leaf area covered from 0 to 100%. The result showed that tillage did not affect severity of the disease or yield. However, there were significant effects from fungicide, year-to-year effects, and fungicide × year interactions. Among the three years, disease severity in 2016 was greater than in 2014 and 2015. Among the six fungicides, Topsin, Topguard, Quadris TOP SBX, and Priaxor significantly (P ≤ 0.05) reduced maximum disease severity in 2016. All fungicide applications improved yield relative to the untreated check. Topsin and Quadris TOP SBX, however, had consistently the highest percent yield increases. These results suggest that not all fungicides that reduced FLS severity equally protected yield, indicating that yield and environmental conditions need to be considered when making appropriate fungicide recommendations in tilled and no-till systems.

CERCOSPORA SOJINA LESIONS ON SOYBEAN

1966 ◽  
Vol 46 (5) ◽  
pp. 567-568 ◽  
Author(s):  
W. G. Benedict ◽  
L. Fucikovsky
Keyword(s):  
Leaf Spot ◽  
Leaf Tissue ◽  
Cercospora Sojina ◽  
Frogeye Leaf Spot ◽  
Soybean Leaf

Soybean leaf tissue infected by Cercospora sojina Hara showed cellular disorganization and accumulation of chlorophyll, starch, and phosphorus-32 in advance of the mycelium in a distinct plesionecrotic ring around the holonecrotic area constituting the "frogeye" leaf-spot.

scholarly journals Severe Outbreaks of Soybean Frogeye Leaf Spot Caused by Cercospora sojina in the Pampean Region, Argentina

Plant Disease ◽  
2009 ◽  
Vol 93 (9) ◽  
pp. 966-966 ◽  
Author(s):  
M. A. Carmona ◽  
M. Scandiani ◽  
A. Luque
Keyword(s):  
Leaf Spot ◽  
Buenos Aires ◽  
Buenos Aires Province ◽  
Santa Fe ◽  
Cercospora Sojina ◽  
Northwest Argentina ◽  
Pampean Region ◽  
Frogeye Leaf Spot ◽  
Plastic Bags ◽  
Severity Levels

Frogeye leaf spot of soybean (Glycine max (L.) Merr.) caused by Cercospora sojina Hara was reported to be severe from 1998 to 1999 in northwest Argentina (2). Although the disease was detected at low prevalence (5 to 25%), incidence, and severity in the Pampean Region from 2005 to 2008, no severe outbreaks have been recorded in the provinces of Córdoba, Santa Fe, and Buenos Aires. During the 2008–2009 growing season, disease spread rapidly throughout most soybean-growing areas of the Pampean Region. Disease was observed on almost all varieties of maturity group (MG) III, IV, and V. Symptoms on leaves were circular, reddish brown-to-gray spots (1 to 6 mm) and bordered by typical, narrow, reddish purple margins. Morphology of the fungi was examined on infected tissues. Conidiophores were light-to-dark brown, fasciculate, geniculate, and measured 110 to 203 μm long. Conidia were 1 to 9 septate, hyaline, elongate to fusiform, and measured 26 to 111 (47.3 ± 14.7) × 5.2 to 7.4 μm (6.1 ± 0.7). Pathogenicity tests were conducted on seedlings of a susceptible cultivar by spraying leaves of each of 80 plants at the V3 growth stage with 18 ml of a conidial suspension (3 × 104 conidia/ml) with a hand-held atomizer. Plants were covered with plastic bags and placed in a greenhouse at 28 to 30°C for 48 h. The plastic bags were removed and plants were maintained in high humidity at the same temperature. The same number of noninoculated plants was used as controls. After 10 to 12 days, all inoculated plants showed typical symptoms. Koch's postulates were fulfilled by isolating C. sojina from inoculated plants. Control plants remained healthy. Foliar lesions and morphological characteristics of the pathogen were consistent with C. sojina (1). Disease assessments were made for the middle and upper canopy from 15 arbitrarily collected plants. Soybean plants were in growth stages between R3 and R5 during the survey. Incidence (percentage of plants affected) and severity (percentage of leaf area affected with lesions) were visually estimated from each of the 30 soybean-production fields located in Monte Cristo, Alta Gracia, Jesús María, W. Escalante, Monte Buey, (10 fields, Córdoba Province), Venado Tuerto, Villa Cañás, Cristophersen, María Teresa, (12 fields, Santa Fe Province), Pergamino, Rojas, and Salto (8 fields, Buenos Aires Province). Incidence was 100% in all fields from Córdoba and Santa Fe. Incidence in Buenos Aires was 0 to 100%. Highest severity levels were quantified from fields in Córdoba (severity of 30 to 60%). Lesions also developed on stems and pods. In samples from Buenos Aires, severity levels were ≤10% in the eight soybean fields. Number of lesions per leaflet was recorded from central leaflets in samples from Monte Cristo, Alta Gracia, Venado Tuerto, and María Teresa with 20 to 55 typical lesions per leaflet. Since the disease was always more important in northwest Argentina, genetic resistance is more commonly available in varieties of MG VII to VIII, so most of the varieties of MG III, IV, and V frequently planted in Pampean Region are susceptible. This fact in combination with rainfall, warm temperatures, and high relative humidity in no-till fields during this summer have encouraged the severe outbreak of frogeye leaf spot, especially in the province of Córdoba and in some regions of Santa Fe. References: (1) D. V. Phillips. Page 20 in: Compendium of Soybean Diseases. 4th ed. The American Phytopathological Society. St. Paul, MN, 1999. (2) D. L. Ploper et al. Plant Dis. 85:801, 2001.

Resistance to Frogeye Leaf Spot in Selected Soybean Accessions in MG I through MG VI

2012 ◽  
Vol 13 (1) ◽  
pp. 13 ◽  
Author(s):  
Alemu Mengistu ◽  
Jason Bond ◽  
Rouf Mian ◽  
Randall Nelson ◽  
Grover Shannon ◽  
...  
Keyword(s):  
Molecular Markers ◽  
Glycine Max ◽  
Seed Yield ◽  
Leaf Spot ◽  
Yield Loss ◽  
Field Trials ◽  
Maturity Group ◽  
Cercospora Sojina ◽  
Frogeye Leaf Spot ◽  
Glycine Max L

Frogeye leaf spot (FLS) caused by Cercospora sojina Hara is a disease of soybean [Glycine max (L.) Merr.] that causes significant seed yield loss in warm, humid environments worldwide. The Rcs3 gene in soybean has been reported to condition resistance to all known races of C. sojina. The objectives of this study were to: (i) identify maturity group (MG) I to VI accessions resistant to C. sojina race 11 by field screening at two locations; and (ii) determine if the FLS resistance of the symptomless soybean accessions is likely to be conditioned by the Rcs3 allele. A total of 260 accessions including 12 differentials were evaluated for reaction to race 11 in field trials in Missouri and Illinois during 2009, and 20 accessions that did not develop symptoms were retested in 2010 to validate their resistance. The 20 accessions remained resistant and were tested for the potential presence of Rcs3 allele using molecular markers; and none was predicted to carry the Rcs3 allele. These accessions may contain novel loci for FLS resistance and may be used to broaden the base for developing soybean cultivars with frogeye leaf spot resistance. Accepted for publication 16 April 2012. Published 21 May 2012.

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.

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