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

Plant Disease ◽  
2007 ◽  
Vol 91 (5) ◽  
pp. 517-524 ◽  
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.

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

Plant Disease ◽  
2001 ◽  
Vol 85 (8) ◽  
pp. 817-826 ◽  
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.

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

Plant Disease ◽  
2002 ◽  
Vol 86 (1) ◽  
pp. 75-75 ◽  
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.

scholarly journals 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

2002 ◽  
Vol 92 (3) ◽  
pp. 245-254 ◽  
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.

scholarly journals Sibling Species of Cercospora Associated with Gray Leaf Spot of Maize

1998 ◽  
Vol 88 (12) ◽  
pp. 1269-1275 ◽  
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.

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

2000 ◽  
Vol 90 (5) ◽  
pp. 486-490 ◽  
Author(s):  
Larry D. Dunkle ◽  
Morris Levy
Keyword(s):  
United States ◽  
Sibling Species ◽  
Leaf Spot ◽  
The United States ◽  
Gray Leaf Spot ◽  
Ancestral Population ◽  
Aflp Analysis ◽  
Group I ◽  
Cercospora Zeae Maydis ◽  
Group Ii

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.

scholarly journals Fitness and Competitive Ability of an Azoxystrobin-Resistant G143A Mutant of Magnaporthe oryzae from Perennial Ryegrass

Plant Disease ◽  
2009 ◽  
Vol 93 (10) ◽  
pp. 1044-1049 ◽  
Author(s):  
B. Ma ◽  
W. Uddin
Keyword(s):  
Perennial Ryegrass ◽  
Magnaporthe Oryzae ◽  
Type Strain ◽  
Competitive Ability ◽  
Wild Type Strain ◽  
The United States ◽  
Gray Leaf Spot ◽  
Relative Fitness ◽  
Wild Type ◽  
Development Of Resistance

Development of azoxystrobin resistance in Magnaporthe oryzae from perennial ryegrass has been reported in certain locations in the United States, and possible development of resistance in additional areas is a major concern in the golf course industry. The study was undertaken to evaluate the relative fitness and competitive ability of a field-collected azoxystrobin-resistant G143A mutant by comparing it with a wild-type strain using detached perennial ryegrass blades. A fitness comparison experiment indicated that the disease severity of the wild-type strain was significantly higher than that of the mutant; however, the mutant produced greater secondary inoculum. When inoculated with three mixed populations of resistant and wild-type strains at different ratios, the production of conidia by the wild-type strain increased and that of the mutant decreased after infection occurred in all three populations tested. In an experiment on the effect of various fungicides on the population initially containing 5% of the mutant, preventive application of azoxystrobin allowed 5% of the mutant to dominate the population after the infection. However, other non-quinone outside inhibitor fungicides and mixtures of azoxystrobin with contact fungicides eliminated the entire mutant. This study demonstrates that the wild-type strain of M. oryzae has a competitive advantage over the mutant within the environment tested. Mixtures and alternations of fungicides with different modes of actions may prevent rapid build-up of resistance in the gray leaf spot pathosystem.

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 Detection of Pyricularia grisea Causing Gray Leaf Spot of Perennial Ryegrass Turf by a Rapid Immuno-Recognition Assay

Plant Disease ◽  
2003 ◽  
Vol 87 (7) ◽  
pp. 772-778 ◽  
Author(s):  
W. Uddin ◽  
G. Viji ◽  
G. L. Schumann ◽  
S. H. Boyd
Keyword(s):  
Monoclonal Antibody ◽  
Rhode Island ◽  
Perennial Ryegrass ◽  
Leaf Spot ◽  
The United States ◽  
Gray Leaf Spot ◽  
In Vitro Assays ◽  
Pyricularia Grisea ◽  
Curvularia Lunata ◽  
Colletotrichum Graminicola

An immuno-recognition assay using a monoclonal antibody was developed to detect Pyricularia grisea, the causal agent of gray leaf spot of perennial ryegrass (Lolium perenne). In vitro assays with isolates of P. grisea from perennial ryegrass, tall fescue (Festuca arundinacea), St. Augustinegrass (Stenotaphrum secundatum), crabgrass (Digitaria sanguinalis), finger millet (Eleusine coracana), wheat (Triticum aestivum), triticale (× Triticosecale rimpaui), and rice (Oryza sativa) showed positive reactions; however, the strength of the reactions differed among isolates. Reactions were more intense with isolates from perennial ryegrass, wheat, and triticale. All P. grisea isolates from perennial ryegrass collected from various regions of the United States showed positive reactions. P. grisea was detected at antigen dilution rates of 0.5×, 0.25×, 0.13×, 0.06×, and 0.03×. Dot-blot assays with Bipolaris sorokiniana, Colletotrichum graminicola, Curvularia lunata, Microdochium nivale, Pythium aphanidermatum, Rhizoctonia solani, or Sclerotinia homoeocarpa isolated from turfgrasses were negative. In vivo assays of symptomatic leaves of perennial ryegrass plants inoculated with P. grisea also showed positive reactions, and those inoculated with B. sorokiniana, P. aphanidermatum, R. solani, or S. homoeocarpa were negative. Intensity of reaction between the monoclonal antibody and P. grisea was proportional to disease severity in perennial ryegrass inoculated with P. grisea; however, there was no reaction in dot blots of leaf tissue collected during the latent period. P. grisea was detected in perennial ryegrass samples from golf course fairways affected by gray leaf spot in Connecticut, Massachusetts, Maine, New Jersey, Pennsylvania, and Rhode Island using this procedure. The monoclonal antibody recognition system is highly sensitive to P. grisea and can be used effectively for the rapid diagnosis of gray leaf spot of perennial ryegrass turf.

Genotyping Dickeya dianthicola causing potato blackleg and soft rot outbreak associated with inoculum geography in the United States

Plant Disease ◽  
2020 ◽  
Author(s):  
Tongling Ge ◽  
He Jiang ◽  
Steven B Johnson ◽  
Robert Larkin ◽  
Amy O Charkowski ◽  
...  
Keyword(s):  
United States ◽  
Bacterial Pathogen ◽  
Soft Rot ◽  
The United States ◽  
Lower Percentage ◽  
Economic Losses ◽  
Type I ◽  
Type Ii ◽  
Northeastern United States ◽  
Type Iii

An outbreak of blackleg and soft rot of potato, caused primarily by the bacterial pathogen Dickeya dianthicola, has resulted in significant economic losses in the Northeastern United States since 2015. The spread of this seedborne disease is highly associated with seed distribution, therefore the pathogen likely spread with seed tubers. To describe the blackleg epidemic and track inoculum origins, a total of 1183 potato samples were collected from 11 states associated with blackleg outbreak from 2015 to 2019. Of these samples, 39.8% tested positive for D. dianthicola. Seventeen isolates of Dickeya dianthicola were recovered from these samples and the genetic diversity of these isolates was examined. Fingerprinting with BOX-PCR and phylogenetic analysis based on sequences of the 16S rRNA and gapA genes indicated that D. dianthicola isolates were divided into three genotypes, denoted Type I, II, and III. Ninety five percent of samples from Maine were Type I. Type II was found in Maine only in 2015 and 2018. Type II was present throughout the five years in some states at a lower percentage than Type I. Type III was found in Pennsylvania, New Jersey and Massachusetts, but not in Maine. Therefore, Type I appears to be associated with Maine, but Type II appeared to be endemic to the Northeastern United States. The Type II and rarer Type III strain were closer to the D. dianthicola type strain isolated from the United Kingdom. This work provides evidence that the outbreak of blackleg of potato in the Northeastern United States was caused by multiple strains of D. dianthicola. The geographic origins of these strains remain unknown.

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