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 First Report of Leaf Spot Disease Caused by Epicoccum nigrum on Lablab purpureus in India

Plant Disease ◽  
2014 ◽  
Vol 98 (2) ◽  
pp. 284-284 ◽  
Author(s):  
S. Mahadevakumar ◽  
K. M. Jayaramaiah ◽  
G. R. Janardhana
Keyword(s):  
Leaf Spot ◽  
Leaf Surface ◽  
Disease Incidence ◽  
Leaf Spot Disease ◽  
Post Inoculation ◽  
Conidial Suspension ◽  
Lablab Purpureus ◽  
First Report ◽  
Spot Disease ◽  
Epicoccum Nigrum

Lablab purpureus (L.) Sweet (Indian bean) is an important pulse crop grown in arid and semi-arid regions of India. It is one of the most widely cultivated legume species and has multiple uses. During a September 2010 survey, we recorded a new leaf spot disease on L. purpureus in and around Mysore district (Karnataka state) with 40 to 80% disease incidence in 130 ha of field crop studied, which accounted for 20 to 35% estimated yield loss. The symptoms appeared as small necrotic spots on the upper leaf surface. The leaf spots were persistent under mild infection throughout the season with production of conidia in clusters on abaxial leaf surface. A Dueteromyceteous fungus was isolated from affected leaf tissues that were surface sterilized with 2% NaOCl2 solution then washed thrice, dried, inoculated on potato dextrose agar (PDA) medium, and incubated at 28 ± 2°C at 12 h alternate light and dark period for 7 days. The fungal colony with aerial mycelia interspersed with dark cushion-shaped sporodochia consists of short, compact conidiophores bearing large isodiametric, solitary, muricate, brown, globular to pear shaped conidia (29.43 to 23.92 μm). Fungal isolate was identified as Epicoccum sp. based on micro-morphological and cultural features (1). Further authenticity of the fungus was confirmed by PCR amplification of the internal transcribed spacer (ITS) region using ITS1/ITS4 universal primer. The amplified PCR product was purified, sequenced directly, and BLASTn search revealed 100% homology to Epicoccum nigrum Link. (DQ093668.1 and JX914480.1). A representative sequence of E. nigrum was deposited in GenBank (Accession No. KC568289.1). The isolated fungus was further tested for its pathogenicity on 30-day-old healthy L. purpureus plants under greenhouse conditions. A conidial suspension (106 conidia/ml) was applied as foliar spray (three replicates of 15 plants each) along with suitable controls. The plants were kept under high humidity (80%) for 5 days and at ambient temperature (28 ± 2°C). The appearance of leaf spot symptoms were observed after 25 days post inoculation. Further, the pathogen was re-isolated and confirmed by micro-morphological characteristics. E. nigrum has been reported to cause post-harvest decay of cantaloupe in Oklahoma (2). It has also been reported as an endophyte (3). Occurrence as a pathogen on lablab bean has not been previously reported. To our knowledge, this is the first report of the occurrence of E. nigrum on L. purpureus in India causing leaf spot disease. References: (1) H. L. Barnet and B. B. Hunter. Page 150 in: Illustrated Genera of Imperfect Fungi, 1972. (2) B. D. Bruten et al. Plant Dis. 77:1060, 1993. (3) L. C. Fávaro et al. PLoS One 7(6):e36826, 2012.

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 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 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 First Report of Alternaria Leaf Spot Caused by Alternaria sp. on Highbush Blueberry (Vaccinium corymbosum) in South Korea

Plant Disease ◽  
2014 ◽  
Vol 98 (10) ◽  
pp. 1434-1434
Author(s):  
J.-H. Kwon ◽  
D.-W. Kang ◽  
M.-G. Cheon ◽  
J. Kim
Keyword(s):  
South Korea ◽  
Leaf Spot ◽  
Disease Incidence ◽  
Vaccinium Corymbosum ◽  
Its Rdna ◽  
Universal Primers ◽  
Conidial Suspension ◽  
First Report ◽  
Representative Isolate ◽  
Alternaria Sp

In South Korea, the culture, production, and consumption of blueberry (Vaccinium corymbosum) have increased rapidly over the past 10 years. In June and July 2012, blueberry plants with leaf spots (~10% of disease incidence) were sampled from a blueberry orchard in Jinju, South Korea. Leaf symptoms included small (1 to 5 mm in diameter) brown spots that were circular to irregular in shape. The spots expanded and fused into irregularly shaped, large lesions with distinct dark, brownish-red borders. The leaves with severe infection dropped early. A fungus was recovered consistently from sections of surface-disinfested (1% NaOCl) symptomatic leaf tissue after transfer onto water agar and sub-culture on PDA at 25°C. Fungal colonies were dark olive and produced loose, aerial hyphae on the culture surfaces. Conidia, which had 3 to 6 transverse septa, 1 to 2 longitudinal septa, and sometimes also a few oblique septa, were pale brown to golden brown, ellipsoid to ovoid, obclavate to obpyriform, and 16 to 42 × 7 to 16 μm (n = 50). Conidiophores were pale to mid-brown, solitary or fasciculate, and 28 to 116 × 3 to 5 μm (n = 50). The species was placed in the Alternaria alternata group (1). To confirm the identity of the fungus, the complete internal transcribed spacer (ITS) rDNA region of a representative isolate, AAVC-01, was amplified using ITS1 and ITS4 primers (2). The DNA products were cloned into the pGEM-T Easy vector (Promega, Madison, WI) and the resulting pOR13 plasmid was sequenced using universal primers. The resulting 570-bp sequence was deposited in GenBank (Accession No. KJ636460). Comparison of ITS rDNA sequences with other Alternaria spp. using ClustalX showed ≥99% similarity with the sequences of A. alternata causing blight on Jatropha curcas (JQ660842) from Mexico and Cajannus cajan (JQ074093) from India, citrus black rot (AF404664) from South Africa, and other Alternaria species, including A. tenuissima (WAC13639) (3), A. lini (Y17071), and A. longipes (AF267137). Two base substitutions, C to T at positions 345 and 426, were found in the 570-bp amplicon. Phylogenetic analysis revealed that the present Alternaria sp. infecting blueberry grouped separately from A. tenuissima and A. alternata reported from other hosts. A representative isolate of the pathogen was used to inoculate V. corymbosum Northland leaves for pathogenicity testing. A conidial suspension (2 × 104 conidia/ml) from a single spore culture and 0.025% Tween was spot inoculated onto 30 leaves, ranging from recently emerged to oldest, of 2-year-old V. corymbosum Northland plants. Ten leaves were treated with sterilized distilled water and 0.025% Tween as a control. The plants were kept in a moist chamber with >90% relative humidity at 25°C for 48 h and then moved to a greenhouse. After 15 days, leaf spot symptoms similar to those observed in the field developed on the inoculated leaves, whereas the control plants remained asymptomatic. The causal fungus was re-isolated from the lesions of the inoculated plants to fulfill Koch's postulates. To our knowledge, this is the first report of Alternaria sp. on V. corymbosum in South Korea. References: (1) E. G. Simmons. Page 1797 in: Alternaria: An Identification Manual. CBS Fungal Biodiversity Centre, Utrecht, The Netherlands, 2007. (2) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, 1990. (3) M. P. You et al. Plant Dis. 98:423, 2014.

scholarly journals First report of banana (Musa acuminate L. AAA Cavendish, cv. Formosana) leaf spot disease caused by Curvularia geniculata in China

Plant Disease ◽  
2021 ◽  
Author(s):  
Yanxiang Qi ◽  
Yanping Fu ◽  
Jun Peng ◽  
Fanyun Zeng ◽  
Yanwei Wang ◽  
...  
Keyword(s):  
Leaf Spot ◽  
Disease Incidence ◽  
Morphological Characteristics ◽  
Universal Primers ◽  
Leaf Spot Disease ◽  
Leaf Margin ◽  
Conidial Suspension ◽  
Tropical Fruit ◽  
First Report ◽  
Spot Disease

Banana (Musa acuminate L.) is an important tropical fruit in China. During 2019-2020, a new leaf spot disease was observed on banana (M. acuminate L. AAA Cavendish, cv. Formosana) at two orchards of Chengmai county (19°48ʹ41.79″ N, 109°58ʹ44.95″ E), Hainan province, China. In total, the disease incidence was about 5% of banana trees (6 000 trees). The leaf spots occurred sporadically and were mostly confined to the leaf margin, and the percentage of the leaf area covered by lesions was less than 1%. Symptoms on the leaves were initially reddish brown spots that gradually expanded to ovoid-shaped lesions and eventually become necrotic, dry, and gray with a yellow halo. The conidia obtained from leaf lesions were brown, erect or curved, fusiform or elliptical, 3 to 4 septa with dimensions of 13.75 to 31.39 µm × 5.91 to 13.35 µm (avg. 22.39 × 8.83 µm). The cells of both ends were small and hyaline while the middle cells were larger and darker (Zhang et al. 2010). Morphological characteristics of the conidia matched the description of Curvularia geniculata (Tracy & Earle) Boedijn. To acquire the pathogen, tissue pieces (15 mm2) of symptomatic leaves were surface disinfected in 70% ethanol (10 s) and 0.8% NaClO (2 min), rinsed in sterile water three times, and transferred to potato dextrose agar (PDA) for three days at 28°C. Grayish green fungal colonies appeared, and then turned fluffy with grey and white aerial mycelium with age. Two representative isolates (CATAS-CG01 and CATAS-CG92) of single-spore cultures were selected for molecular identification. Genomic DNA was extracted from the two isolates, the internal transcribed spacer (ITS), large subunit ribosomal DNA (LSU rDNA), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), translation elongation factor 1-alpha (TEF1-α) and RNA polymerase II second largest subunit (RPB2) were amplified and sequenced with universal primers ITS1/ITS4, LROR/LR5, GPD1/GPD2, EF1-983F/EF1-2218R and 5F2/7cR, respectively (Huang et al. 2017; Raza et al. 2019). The sequences were deposited in GenBank (MW186196, MW186197, OK091651, OK721009 and OK491081 for CATAS-CG01; MZ734453, MZ734465, OK091652, OK721100 and OK642748 for CATAS-CG92, respectively). For phylogenetic analysis, MEGA7.0 (Kumar et al. 2016) was used to construct a Maximum Likelihood (ML) tree with 1 000 bootstrap replicates, based on a concatenation alignment of five gene sequences of the two isolates in this study as well as sequences of other Curvularia species obtained from GenBank. The cluster analysis revealed that isolates CATAS-CG01 and CATAS-CG92 were C. geniculata. Pathogenicity assays were conducted on 7-leaf-old banana seedlings. Two leaves from potted plants were stab inoculated by puncturing into 1-mm using a sterilized needle and placing 10 μl conidial suspension (2×106 conidia/ml) on the surface of wounded leaves and equal number of leaves were inoculated with sterile distilled water serving as control (three replicates). Inoculated plants were grown in the greenhouse (12 h/12 h light/dark, 28°C, 90% relative humidity). Necrotic lesions on inoculated leaves appeared seven days after inoculation, whereas control leaves remained healthy. The fungus was recovered from inoculated leaves, and its taxonomy was confirmed morphologically and molecularly, fulfilling Koch’s postulates. C. geniculata has been reported to cause leaf spot on banana in Jamaica (Meredith, 1963). To our knowledge, this is the first report of C. geniculata on banana in China.

scholarly journals First Report of a Leaf Spot Disease of Bells-of-Ireland (Moluccella laevis) Caused by Cercospora apii in California

Plant Disease ◽  
2003 ◽  
Vol 87 (2) ◽  
pp. 203-203
Author(s):  
S. T. Koike ◽  
S. A. Tjosvold ◽  
J. Z. Groenewald ◽  
P. W. Crous
Keyword(s):  
Leaf Spot ◽  
Sequence Data ◽  
Disease Incidence ◽  
Leaf Spot Disease ◽  
Conidial Suspension ◽  
Internal Transcribed Spacer Region ◽  
First Report ◽  
Spot Disease ◽  
Leaf Spots ◽  
Initial Symptoms

Bells-of-Ireland (Moluccella laevis) (Lamiaceae) is an annual plant that is field planted in coastal California (Santa Cruz County) for commercial cutflower production. In 2001, a new leaf spot disease was found in these commercially grown cutflowers. The disease was most serious in the winter-grown crops in 2001 and 2002, with a few plantings having as much as 100% disease incidence. All other plantings that were surveyed during this time had at least 50% disease. Initial symptoms consisted of gray-green leaf spots. Spots were generally oval in shape, often delimited by the major leaf veins, and later turned tan. Lesions were apparent on both adaxial and abaxial sides of the leaves. A cercosporoid fungus having fasciculate conidiophores, which formed primarily on the abaxial leaf surface, was consistently associated with the spots. Based on morphology and its host, this fungus was initially considered to be Cercospora molucellae Bremer & Petr., which was previously reported on leaves of M. laevis in Turkey (1). However, sequence data obtained from the internal transcribed spacer region (ITS1, ITS2) and the 5.8S gene (STE-U 5110, 5111; GenBank Accession Nos. AY156918 and AY156919) indicated there were no base pair differences between the bells-of-Ireland isolates from California, our own reference isolates of C. apii, as well as GenBank sequences deposited as C. apii. Based on these data, the fungus was subsequently identified as C. apii sensu lato. Pathogenicity was confirmed by spraying a conidial suspension (1.0 × 105 conidia/ml) on leaves of potted bells-of-Ireland plants, incubating the plants in a dew chamber for 24 h, and maintaining them in a greenhouse (23 to 25°C). After 2 weeks, all inoculated plants developed leaf spots that were identical to those observed in the field. C. apii was again associated with all leaf spots. Control plants, which were treated with water, did not develop any symptoms. The test was repeated and the results were similar. To our knowledge this is the first report of C. apii as a pathogen of bells-of-Ireland in California. Reference: (1) C. Chupp. A Monograph of the Fungus Genus Cercospora. Cornell University Press, Ithaca, New York, 1954.

scholarly journals First Report of Curvularia aeria on Etlingera linguiformis from Nagaland, India

Plant Disease ◽  
2014 ◽  
Vol 98 (11) ◽  
pp. 1580-1580 ◽  
Author(s):  
C. Kithan ◽  
L. Daiho
Keyword(s):  
Leaf Surface ◽  
Agricultural Research ◽  
Disease Incidence ◽  
Indian Agricultural Research Institute ◽  
Mountain Range ◽  
Pathogenicity Test ◽  
Distilled Water ◽  
Conidial Suspension ◽  
First Report ◽  
Initial Symptoms

Etlingera linguiformis (Roxb.) R.M.Sm. of Zingiberaceae family is an important indigenous medicinal and aromatic plant of Nagaland, India, that grows well in warm climates with loamy soil rich in humus (1). The plant rhizome has medicinal benefits in treating sore throats, stomachache, rheumatism, and respiratory complaints, while its essential oil is used in perfumery. A severe disease incidence of leaf blight was observed on the foliar portion of E. linguiformis at the Patkai mountain range of northeast India in September 2012. Initial symptoms of the disease are small brown water soaked flecks appearing on the upper leaf surface with diameter ranging from 0.5 to 3 cm, which later coalesced to form dark brown lesions with a well-defined border. Lesions often merged to form large necrotic areas, covering more than 90% of the leaf surface, which contributed to plant death. The disease significantly reduces the number of functional leaves. As disease progresses, stems and rhizomes were also affected, reducing quality and yield. The diseased leaf tissues were surface sterilized with 0.2% sodium hypochlorite for 2 min followed by rinsing in sterile distilled water and transferred into potato dextrose agar (PDA) medium. After 3 days, the growing tips of the mycelium were transferred to PDA slants and incubated at 25 ± 2°C until conidia formation. Fungal colonies on PDA were dark gray to dark brown, usually zonate; stromata regularly and abundantly formed in culture. Conidia were straight to curved, ellipsoidal, 3-septate, rarely 4-septate, middle cells broad and darker than other two end cells, middle septum not median, smooth, 18 to 32 × 8 to 16 μm (mean 25.15 × 12.10 μm). Conidiophores were terminal and lateral on hyphae and stromata, simple or branched, straight or flexuous, often geniculate, septate, pale brown to brown, smooth, and up to 800 μm thick (2,3). Pathogen identification was performed by the Indian Type Culture Collection, Division of Plant Pathology, Indian Agricultural Research Institute, New Delhi (ITCC Accession No. 7895.10). Further molecular identity of the pathogen was confirmed as Curvularia aeria by PCR amplification and sequencing of the internal transcribed spacer (ITS) regions of the ribosomal DNA by using primers ITS4 and ITS5 (4). The sequence was submitted to GenBank (Accession No. MTCC11875). BLAST analysis of the fungal sequence showed 100% nucleotide similarity with Cochliobolus lunatus and Curvularia aeria. Pathogenicity tests were performed by spraying with an aqueous conidial suspension (1 × 106 conidia /ml) on leaves of three healthy Etlingera plants. Three plants sprayed with sterile distilled water served as controls. The first foliar lesions developed on leaves 7 days after inoculation and after 10 to 12 days, 80% of the leaves were severely infected. Control plants remained healthy. The inoculated leaves developed similar blight symptoms to those observed on naturally infected leaves. C. aeria was re-isolated from the inoculated leaves, thus fulfilling Koch's postulates. The pathogenicity test was repeated twice. To our knowledge, this is the first report of the presence of C. aeria on E. linguiformis. References: (1) M. H. Arafat et al. Pharm. J. 16:33, 2013. (2) M. B. Ellis. Dematiaceous Hyphomycetes. CMI, Kew, Surrey, UK, 1971. (3) K. J. Martin and P. T. Rygiewicz. BMC Microbiol. 5:28, 2005. (4) C. V. Suberamanian. Proc. Indian Acad. Sci. 38:27, 1955.

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.

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