Genetic Relatedness of African and United States Populations of Cercospora zeae-maydis

Two taxonomically identical but genetically distinct sibling species, designated groups I and II, of Cercospora zeae-maydis cause gray leaf spot of maize in the United States. Isolates of the gray leaf spot pathogen from Africa were compared with isolates from the United States by amplified fragment length polymorphism (AFLP) analysis and restriction digests of internal transcribed spacer (ITS) regions and 5.8S ribosomal DNA (rDNA), as well as by morphological and cultural characteristics. The isolates from Africa were morphologically indistinguishable from the U.S. isolates in both groups, but like isolates of group II, they grew more slowly and failed to produce detectable amounts of cercosporin in culture. Analysis of restriction fragments from the ITS and rDNA regions digested with five endonucleases indicated that all of the African isolates shared the profile of the C. zeae-maydis group II population from the eastern United States and, thus, are distinct from the group I population, which is more prevalent in the United States and other parts of the world. Cluster analysis of 85 AFLP loci confirmed that the African and U.S. group II populations were conspecific (greater than 97% average similarity) with limited variability. Among all group II isolates, only 8 of 57 AFLP loci were polymorphic, and none was specific to either population. Thus, although gray leaf spot was reported in the United States several decades prior to the first record in Africa, the relative age of the two populations on their respective continents could not be ascertained with confidence. The absence of C. zeae-maydis group I in our samples from four countries in the major maize-producing region of Africa as well as the greater AFLP haplotype diversity found in the African group II population, however, suggest that Africa was the source of C. zeae-maydis group II in the United States. The overall paucity of AFLP variation in this sibling species further suggests that its origin is recent or that the ancestral population experienced a severe bottleneck prior to secondary migration.

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Sibling Species of Cercospora Associated with Gray Leaf Spot of Maize

Phytopathology ◽

10.1094/phyto.1998.88.12.1269 ◽

1998 ◽

Vol 88 (12) ◽

pp. 1269-1275 ◽

Cited By ~ 46

Author(s):

Juan Wang ◽

Morris Levy ◽

Larry D. Dunkle

Keyword(s):

United States ◽

Genetic Distance ◽

Sibling Species ◽

Fragment Length ◽

Leaf Spot ◽

The United States ◽

Nucleotide Sequences ◽

Gray Leaf Spot ◽

5.8S Rdna ◽

Its Regions

Monoconidial isolates of the fungus causing gray leaf spot of maize were obtained from diseased leaves collected throughout the United States and analyzed for genetic variability at 111 amplified fragment length polymorphism (AFLP) loci. Cluster analysis revealed two very distinct groups of Cercospora zeae-maydis isolates. Both groups were found to be relatively uniform internally with an average genetic similarity among isolates of approximately 93 and 94%, respectively. The groups were separated from each other by a genetic distance of approximately 80%, a distance greater than that separating each group from the sorghum pathogen, C. sorghi (67 to 70%). Characteristics and dimensions of conidia and conid-iophores produced on infected plants or nutrient media were unreliable criteria for taxonomic differentiation of isolates composing the two groups of C. zeae-maydis. Nucleotide sequences of 5.8S ribosomal DNA (rDNA) and the internal transcribed spacer (ITS) regions were identical within each group but different between the two groups and different from C. sorghi. Restriction fragment length polymorphisms generated by digestion of the 5.8S rDNA and ITS regions with TaqI readily distinguished each group and C. sorghi. Isolates in one group were generally distributed throughout maize-producing regions of the United States; isolates in the other group were localized in the eastern third of the country. Both types were present in the same fields at some locations. The genetic distance based on AFLP profiles and different ITS nucleotide sequences between the two morphologically indistinguishable groups indicate that they are sibling species. Although it is unlikely that breeding for resistance to gray leaf spot will be confounded by local or regional variation in the pathogen, a vigilant approach is warranted, because two pathogenic species exist with unknown abilities to evolve new pathotypes.

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

Plant Disease ◽

10.1094/pdis-05-10-0356 ◽

2011 ◽

Vol 95 (2) ◽

pp. 189-194 ◽

Cited By ~ 17

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.

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Nonpathogenic Isolates of the Citrus Black Spot Fungus, Guignardia citricarpa, Identified as a Cosmopolitan Endophyte of Woody Plants, G. mangiferae (Phyllosticta capitalensis)

Phytopathology ◽

10.1094/phyto.2002.92.5.464 ◽

2002 ◽

Vol 92 (5) ◽

pp. 464-477 ◽

Cited By ~ 127

Author(s):

R. P. Baayen ◽

P. J. M. Bonants ◽

G. Verkley ◽

G. C. Carroll ◽

H. A. van der Aa ◽

...

Keyword(s):

United States ◽

European Union ◽

Woody Plants ◽

Black Spot ◽

The United States ◽

The European Union ◽

Citrus Fruits ◽

Citrus Black Spot ◽

Group I ◽

Group Ii

The population structure of Guignardia citricarpa sensu lato (anamorph: Phyllosticta citricarpa), a fungus of which strains pathogenic to citrus are subject to phytosanitary legislation in the European Union and the United States, was investigated. Internal transcribed spacer sequences revealed two phylogenetically distinct groups in G. citricarpa. This distinction was supported by amplified fragment length polymorphism analysis that also supported the exclusion of two isolates that had apparently been misclassified as G. citricarpa. On cherry decoction agar, but not on other media, growth rates of group I isolates were lower than those of group II isolates. Conidial dimensions were similar, but group I isolates formed conidia with barely visible mucoid sheaths, whereas those of group II formed conidia with thick sheaths. Cultures of isolates belonging to group I produced rare infertile perithecia, whereas fertile perithecia were formed by most isolates of group II. Colonies of isolates belonging to group I were less dark than those of group II, with a wider translucent outer zone and a lobate rather than entire margin. On oatmeal agar, exclusively group I isolates formed a yellow pigment. Group I harbored strains from citrus fruits with classical black spot lesions (1 to 10 mm in diameter) usually containing pycnidia. Group II harbored endophytic strains from a wide range of host species, as well as strains from symptomless citrus fruits or fruits with minute spots (<2-mm diameter) without pycnidia. These observations support the historic distinction between slowly growing pathogenic isolates and morphologically similar fast-growing, nonpathogenic isolates of G. citricarpa. The latter proved to belong to G. mangiferae (P. capitalensis), a ubiquitous endophyte of woody plants with numerous probable synonyms including G. endophyllicola, G. psidii, P. anacardiacearum, and P. theacearum. G. mangiferae occurs in the European Union and the United States on many host species including citrus, and does not cause symptoms of citrus black spot, justifying its exclusion from quarantine measures.

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Comparative Genetic Analysis of Magnaporthe oryzae Isolates Causing Gray Leaf Spot of Perennial Ryegrass Turf in the United States and Japan

Plant Disease ◽

10.1094/pdis-91-5-0517 ◽

2007 ◽

Vol 91 (5) ◽

pp. 517-524 ◽

Cited By ~ 15

Author(s):

Y. Tosa ◽

W. Uddin ◽

G. Viji ◽

S. Kang ◽

S. Mayama

Keyword(s):

United States ◽

Perennial Ryegrass ◽

Magnaporthe Oryzae ◽

Leaf Spot ◽

Genetic Relationships ◽

The United States ◽

Gray Leaf Spot ◽

Genetic Lineage ◽

Type I ◽

Type Ii

Gray leaf spot caused by Magnaporthe oryzae is a serious disease of perennial ryegrass (Lolium perenne) turf in golf course fairways in the United States and Japan. Genetic relationships among M. oryzae isolates from perennial ryegrass (prg) isolates within and between the two countries were examined using the repetitive DNA elements MGR586, Pot2, and MAGGY as DNA fingerprinting probes. In all, 82 isolates of M. oryzae, including 57 prg isolates from the United States collected from 1995 to 2001, 1 annual ryegrass (Lolium multiflorum) isolate from the United States collected in 1972, and 24 prg isolates from Japan collected from 1996 to 1999 were analyzed in this study. Hybridization with the MGR586 probe resulted in approximately 30 DNA fragments in 75 isolates (designated major MGR586 group) and less than 15 fragments in the remaining 7 isolates (designated minor MGR586 group). Both groups were represented among the 24 isolates from Japan. All isolates from the United States, with the exception of one isolate from Maryland, belonged to the major MGR586 group. Some isolates from Japan exhibited MGR586 fingerprints that were identical to several isolates collected in Pennsylvania. Similarly, fingerprinting analysis with the Pot2 probe also indicated the presence of two distinct groups: isolates in the major MGR586 group showed fingerprinting profiles comprising 20 to 25 bands, whereas the isolates in the minor MGR586 group had less than 10 fragments. When MAGGY was used as a probe, two distinct fingerprint types, one exhibiting more than 30 hybridizing bands (type I) and the other with only 2 to 4 bands (type II), were identified. Although isolates of both types were present in the major MGR586 group, only the type II isolates were identified in the minor MGR586 group. The parsimony tree obtained from combined MGR586 and Pot2 data showed that 71 of the 82 isolates belonged to a single lineage, 5 isolates formed four different lineages, and the remaining 6 (from Japan) formed a separate lineage. This study indicates that the predominant groups of M. oryzae associated with the recent outbreaks of gray leaf spot in Japan and the United States belong to the same genetic lineage.

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Pyricularia grisea Causing Gray Leaf Spot of Perennial Ryegrass Turf: Population Structure and Host Specificity

Plant Disease ◽

10.1094/pdis.2001.85.8.817 ◽

2001 ◽

Vol 85 (8) ◽

pp. 817-826 ◽

Cited By ~ 38

Author(s):

G. Viji ◽

B. Wu ◽

S. Kang ◽

W. Uddin ◽

D. R. Huff

Keyword(s):

United States ◽

Population Structure ◽

Winter Wheat ◽

Perennial Ryegrass ◽

Leaf Spot ◽

Genetic Relationships ◽

The United States ◽

Gray Leaf Spot ◽

Pyricularia Grisea ◽

Highly Virulent

Gray leaf spot is a serious disease of perennial ryegrass (Lolium perenne) turf in the United States. Isolates of Pyricularia grisea causing the disease in perennial ryegrass were characterized using molecular markers and pathogenicity assays on various gramineous hosts. Genetic relationships among perennial ryegrass isolates were determined using different types of trans-posons as probes. Phylogenetic analysis using Pot2 and MGR586 probes, analyzed with AMOVA (analysis of molecular variance), showed that these isolates from perennial ryegrass consist of three closely related lineages. All the isolates belonged to a single mating type, MAT1-2. Among 20 isolates from 16 host species other than perennial ryegrass, only the isolates from wheat (Triticum aestivum) and triticale (× Triticosecale), showed notable similarity to the perennial ryegrass isolates based on their Pot2 fingerprints. The copy number and fingerprints of Pot2 and MGR586 in isolates of P. grisea from perennial ryegrass indicate that they are genetically distinct from the isolates derived from rice (Oryza sativa) in the United States. The perennial ryegrass isolates also had the same sequence in the internal transcribed spacer (ITS) region of the genes encoding ribosomal RNA as that of the wheat and triticale isolates, and exhibited rice isolate sequence polymorphisms. In pathogenicity assays, all the isolates of P. grisea from Legacy II perennial ryegrass caused characteristic blast symptoms on Marilee soft white winter wheat, Bennett hard red winter wheat, Era soft white spring wheat, and Presto triticale, and they were highly virulent on these hosts. An isolate from wheat and one from triticale (from Brazil) were also highly virulent on perennial ryegrass and Rebel III tall fescue (Festuca arundinacea). None of the isolates from perennial ryegrass caused the disease on Lagrue rice, and vice versa. Understanding the population structure of P. grisea isolates infecting perennial ryegrass and their relatedness to isolates from other gramineous hosts may aid in identifying alternate hosts for this pathogen.

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Assessing Late Vegetative and Tasseling Fungicide Application Timings on Foliar Disease and Yield in Indiana Corn

Plant Health Progress ◽

10.1094/php-03-20-0022-rs ◽

2020 ◽

Vol 21 (4) ◽

pp. 224-229

Author(s):

Darcy E. P. Telenko ◽

Jeffrey D. Ravellette ◽

Kiersten A. Wise

Keyword(s):

Leaf Spot ◽

The United States ◽

Field Trials ◽

Gray Leaf Spot ◽

Corn Production ◽

Foliar Disease ◽

Application Timing ◽

Cercospora Zeae Maydis ◽

Foliar Fungicide ◽

Disease Pressure

Gray leaf spot (Cercospora zeae-maydis) is a foliar disease of corn (Zea mays) that consistently reduces yields across the United States and is an annual concern in Indiana corn production. Field trials were conducted in West Lafayette, IN, over 3 years (2016 to 2018) to evaluate the effectiveness of 12-leaf collar stage (V12) foliar fungicide applications compared with tasseling (VT) applications for gray leaf spot management and yield. Results indicated that during years in which foliar disease severity was less than 4%, there was no effect of application timing on gray leaf spot severity. In 2018, when gray leaf spot levels exceeded 5%, significantly less disease was observed in treatments receiving VT applications compared with V12 applications. Application timing did not affect yield in any year of the experiment. In 2016, benzovindiflupyr + azoxystrobin + propiconazole resulted in greater yields compared with the nontreated control, and in 2018, pyraclostrobin + metconazole and benzovindiflupyr + azoxystrobin + propiconazole resulted in greater yields compared with the nontreated control. This research indicates that in high disease pressure environments and years, Indiana farmers may want to continue to apply fungicides at VT rather than apply prior to tassel.

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First Report of Gray Leaf Spot on Perennial Ryegrass Turf in California

Plant Disease ◽

10.1094/pdis.2002.86.1.75c ◽

2002 ◽

Vol 86 (1) ◽

pp. 75-75 ◽

Cited By ~ 19

Author(s):

W. Uddin ◽

G. Viji ◽

L. Stowell

Keyword(s):

United States ◽

Perennial Ryegrass ◽

Leaf Spot ◽

Disease Incidence ◽

The United States ◽

Gray Leaf Spot ◽

Water Soluble ◽

Distilled Water ◽

First Report ◽

Polyethylene Bags

Gray leaf spot of perennial ryegrass (Lolium perenne L.) turf was first reported in the United States in 1991. The disease epidemic was primarily confined to golf course fairways in southeastern Pennsylvania (1). Subsequently, moderate to severe outbreaks of gray leaf spot occurred in perennial ryegrass fairways and roughs in numerous locations throughout the eastern and midwestern United States. In August 2001, a serious decline of perennial ryegrass turf was observed in a bermudagrass (Cynodon dactylon (L.) Pers) baseball field in Dodger Stadium in Los Angeles, CA, that had been overseeded with perennial ryegrass. The bermudagrass turf was not affected. The perennial ryegrass turf developed necrotic lesions that resulted in blighting of leaf blades. In laboratory assays, Pyricularia grisea (Cooke) Sacc., was consistently isolated from symptomatic ryegrass blades from turf samples collected from the site. Of the 12 P. grisea isolates collected from the assayed leaf blades, five isolates were selected for a pathogenicity assay. Twenty-five ‘Legacy II’ perennial ryegrass plants were grown from seeds in 4 × 4 in.-plastic pots, (10 × 10 cm) which were filled to 1 cm below the rim with granular calcine clay medium (Turface MVP, Allied Industrial Material Corp., Buffalo Grove, IL). Three weeks after seeding, plants were fertilized with a water-soluble 20-20-20 N-P-K fertilizer (1.3 g/liter of water) once per week. Treatments (isolates of P. grisea and a control) were arranged as a randomized complete block design with five replications. Five-week-old plants were sprayed with an aqueous suspension of P. grisea conidia (≈5 × 104 conidia per ml of sterilized distilled water with 0.1% Tween 20) using an atomizer until the leaves were completely wet. Plants sprayed with sterilized distilled water served as the control. After inoculation, individual pots were covered with clear polyethylene bags and placed in a controlled environment chamber maintained at 28°C and continuous fluorescent light (88 μE m-2 s-1). Four days after inoculation, necrotic lesions (<2 mm diameter) developed on ryegrass blades inoculated with each isolate of P. grisea. Lesions did not develop on leaves of control plants. Seven days after inoculation, the polyethylene bags were removed, and 50 symptomatic blades from each pot were collected, and disease incidence (percent infected leaves) and severity (index 0 to 10; 0 = none, 10 = >90% of the leaf blade necrotic ) were assessed. P. grisea was isolated from symptomatic leaves of plants inoculated with the fungus. Disease incidence and severity on inoculated plants were 92 to 96% and 8.8 to 10, respectively. There were no significant differences in disease incidence and severity (P = 0.05) among the isolates of P. grisea included in the test. To our knowledge, this is the first report of gray leaf spot of perennial ryegrass turf in California. Reference: (1) P. J. Landschoot and B. F. Hoyland. Plant Dis. 76:1280, 1992.

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Pyricularia grisea Isolates Causing Gray Leaf Spot on Perennial Ryegrass (Lolium perenne) in the United States: Relationship to P. grisea Isolates from Other Host Plants

Phytopathology ◽

10.1094/phyto.2002.92.3.245 ◽

2002 ◽

Vol 92 (3) ◽

pp. 245-254 ◽

Cited By ~ 49

Author(s):

Mark L. Farman

Keyword(s):

United States ◽

Molecular Markers ◽

Lolium Perenne ◽

Perennial Ryegrass ◽

Tall Fescue ◽

Leaf Spot ◽

The United States ◽

Gray Leaf Spot ◽

Group Method ◽

Pyricularia Grisea

Gray leaf spot of perennial ryegrass (prg) (Lolium perenne), caused by the fungus Pyricularia grisea (teleomorph = Magnaporthe grisea), has rapidly become the most destructive of all turf grass diseases in the United States. Fungal isolates from infected prg were analyzed with several molecular markers to investigate their relationship to P. grisea strains found on other hosts. All of the molecular markers used in this study revealed that isolates from prg are very distantly related to those found on crabgrass. Fingerprinting with MGR586 (Pot3) revealed zero to three copies of this transposon in the prg pathogens, distinguishing them from isolates pathogenic to rice, which typically have more than 50 copies of this element. RETRO5, a newly identified retroelement in P. grisea, was present at a copy number of >50 in isolates from rice and Setaria spp. but only six to eight copies were found in the isolates from prg. The MAGGY retrotransposon was unevenly distributed in the prg pathogens, with some isolates lacking this element, some possessing six to eight copies, and others having 10 to 30 copies. These results indicated that the P. grisea isolates causing gray leaf spot are distinct from those found on crabgrass, rice, or Setaria spp. This conclusion was supported by an unweighted pair-group method with arithmetic average cluster analysis of single-copy restriction fragment length polymorphism haplo-types. Fingerprints obtained with probes from the Pot2 and MGR583 transposons revealed that the prg pathogens are very closely related to isolates from tall fescue, and that they share similarity with isolates from wheat. However, the wheat pathogens had fewer copies of these elements than those found on prg. Therefore, I conclude that P. grisea isolates commonly found on other host plant species did not cause gray leaf spot epidemics on prg. Instead, the disease appears to be caused by a P. grisea population that is specific to prg and tall fescue.

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Corn Yield Loss Estimates Due to Diseases in the United States and Ontario, Canada, from 2016 to 2019

Plant Health Progress ◽

10.1094/php-05-20-0038-rs ◽

2020 ◽

Vol 21 (4) ◽

pp. 238-247

Author(s):

Daren S. Mueller ◽

Kiersten A. Wise ◽

Adam J. Sisson ◽

Tom W. Allen ◽

Gary C. Bergstrom ◽

...

Keyword(s):

United States ◽

Leaf Spot ◽

Yield Loss ◽

Research Policy ◽

Economic Loss ◽

The United States ◽

Gray Leaf Spot ◽

Corn Yield ◽

Puccinia Polysora ◽

Northern United States

Annual reductions in corn (Zea mays L.) yield caused by diseases were estimated by university Extension-affiliated plant pathologists in 26 corn-producing states in the United States and in Ontario, Canada, from 2016 through 2019. Estimated loss from each disease varied greatly by state or province and year. Gray leaf spot (caused by Cercospora zeae-maydis Tehon & E.Y. Daniels) caused the greatest estimated yield loss in parts of the northern United States and Ontario in all years except 2019, and Fusarium stalk rot (caused by Fusarium spp.) also greatly reduced yield. Tar spot (caused by Phyllachora maydis Maubl.), a relatively new disease in the United States, was estimated to cause substantial yield loss in 2018 and 2019 in several northern states. Gray leaf spot and southern rust (caused by Puccinia polysora Underw.) caused the most estimated yield losses in the southern United States. Unfavorable wet and delayed harvest conditions in 2018 resulted in an estimated 2.5 billion bushels (63.5 million metric tons) of grain contaminated with mycotoxins. The estimated mean economic loss due to reduced yield caused by corn diseases in the United States and Ontario from 2016 to 2019 was US$55.90 per acre (US$138.13 per hectare). Results from this survey provide scientists, corn breeders, government agencies, and educators with data to help inform and prioritize research, policy, and educational efforts in corn pathology and disease management.

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Staphylococcus aureus Isolates with Reduced Susceptibility to Glycopeptides Belong to Accessory Gene Regulator Group I or II

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.48.3.1024-1027.2004 ◽

2004 ◽

Vol 48 (3) ◽

pp. 1024-1027 ◽

Cited By ~ 28

Author(s):

Isabelle Verdier ◽

Marie-Elisabeth Reverdy ◽

Jerome Etienne ◽

Gérard Lina ◽

Michèle Bes ◽

...

Keyword(s):

United States ◽

Staphylococcus Aureus ◽

Multiplex Pcr ◽

Group Membership ◽

The United States ◽

Accessory Gene ◽

Accessory Gene Regulator ◽

Group I ◽

Group Ii

ABSTRACT We used multiplex PCR to determine the agr group membership of 18 European glycopeptide heterointermediate and intermediate-resistant Staphylococcus aureus strains. Of the 15 agr group I strains, 13 were resistant and 2 were susceptible to methicillin. The remaining three strains, like the United States and Japanese control strains, belonged to agr group II.

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