scholarly journals First Report of Late Blight Caused by Phytophthora infestans Clonal Lineage US-22 on Tomato and Potato in Wisconsin

Plant Disease ◽  
2013 ◽  
Vol 97 (3) ◽  
pp. 423-423 ◽  
Author(s):  
A. J. Gevens ◽  
A. C. Seidl
Keyword(s):  
Late Blight ◽  
Phytophthora Infestans ◽  
Average Length ◽  
The State ◽  
Width Ratio ◽  
Clonal Lineage ◽  
First Report ◽  
Hyphal Diameter ◽  
Epidemiological Characteristics

Tomato (Solanum lycopersicum) and potato (S. tuberosum) crops are grown on over 67,000 acres (27,114 hectares) in the state of Wisconsin each year. Late blight, caused by Phytophthora infestans (Mont.) deBary, is a potentially devastating oomycete pathogen that sporadically affects tomato and potato crops in the state. Prevention of this disease through prophylactic application of oomycete-specific fungicides can cost producers millions of dollars per year in additional chemical, fuel, and labor expenses. In 2009, late blight was observed on tomato and potato in over 25 Wisconsin counties. The epidemic initiated on tomato in southern WI in early August and progressed northward in the state with additional reports on tomato primarily from home gardens and small farms. Potato late blight was also identified but with limited incidence in central WI, likely due to routine fungicide programs in commercial production. Clonal lineages of P. infestans documented in Wisconsin in previous epidemics included US-1 in the 1970s and US-8 in the mid-1990s. Populations of P. infestans in the U.S. have recently undergone significant genetic changes, resulting in isolates with unique clonal lineages and epidemiological characteristics (1). Symptoms of late blight observed on tomato and potato included water-soaked to dark brown circular lesions with pale green haloes accompanied by signs of pathogen sporulation typically on leaf undersides during periods of high humidity. Isolates of P. infestans were generated from field infected tomato and potato foliar tissues. Axenic, single zoospore derived cultures were generated and maintained on Rye A agar for further characterization. Mycelium was coenocytic with hyphal diameter of 5 to 8 μm (n = 50). Sporangia were limoniform or ovoid, semi- to fully papillate, caducous, had short pedicels, and were 29.6 (h) × 16.8 μm (w) (n = 50). The average length/width ratio was 1.76. Allozyme banding patterns at the glucose-6-phosphate isomerase (Gpi) locus indicated a 100/122 profile, consistent with the US-22 clonal lineage (3). Mating type assays confirmed the isolates to be A2 and in vitro mefenoxam sensitivity was observed (4). Restriction fragment length polymorphic analysis of a representative isolate from Wisconsin with the multilocus RG57 sequence and EcoRI produced the DNA pattern indicative of US-22 (2). The P. infestans clonal lineage US-22 was predominant in U.S. epidemics on tomato in 2009. To our knowledge, this is the first report of P. infestans clonal lineage US-22 causing late blight on tomato and potato in Wisconsin, USA. References: (1) K. Deahl. (Abstr.) Phytopathology 100(suppl.):S161, 2010. (2) S. B. Goodwin et al. Curr. Genet. 22:107, 1992. (3) C. H. Hu et al. Plant Dis. 96:1323, 2012. (4) A. C. Seidl et al. Phytopathology 101(suppl.):S246, 2011.

scholarly journals First Report of Late Blight Caused by Phytophthora infestans Clonal Lineage US-24 on Potato (Solanum tuberosum) in Wisconsin

Plant Disease ◽  
2013 ◽  
Vol 97 (1) ◽  
pp. 152-152 ◽  
Author(s):  
A. J. Gevens ◽  
A. C. Seidl
Keyword(s):  
Solanum Tuberosum ◽  
Late Blight ◽  
Phytophthora Infestans ◽  
Weather Conditions ◽  
Clonal Lineage ◽  
Banding Patterns ◽  
First Report ◽  
The Us ◽  
Epidemiological Characteristics ◽  
The U.S

Potato (Solanum tuberosum) crops are grown on over 25,090 ha in Wisconsin annually. Late blight, caused by Phytophthora infestans (Mont.) deBary, is a potentially devastating disease that affects tomato and potato crops in Wisconsin every few years when inoculum is introduced and weather conditions favor disease. Incidence and severity of late blight are highly variable in these few years due to differences in pathogen clonal lineages, their timing and means of introduction, and weather conditions. Prevention of this disease through prophylactic fungicide application can cost producers millions of dollars annually in additional chemical, fuel, and labor expenses. Populations of P. infestans in the U.S. have recently undergone significant genetic change, resulting in isolates with unique clonal lineages and epidemiological characteristics (1). In 2010, late blight epidemics were of low severity in discrete portions of a few fields and were seen exclusively on potato in two counties of central Wisconsin. Symptoms included water-soaked to dark brown circular lesions with pale green haloes accompanied by white fuzzy pathogen sporulation typically on leaf undersides in high humidity conditions. Infected plants were collected by professional crop consultants and submitted to the authors at the University of Wisconsin Vegetable Pathology Laboratory in Madison, Wisconsin. Eight isolates of P. infestans were generated from individual leaf samples, representing separate fields, by removing sporangia from sporulating lesions and placing onto Rye A agar amended with rifampicin and ampicillin. Axenic, single zoospore-derived cultures of isolates were generated from parent cultures and maintained on Rye A agar for further characterization. Mycelium was coenocytic with hyphal diameter of 5 to 8 μm (n = 50). Sporangia were limoniform to ovoid, semi- to fully papillate, caducous, had short pedicels, and were 36.22 × 19.11 μm (height × width; n = 50). The average length-width ratio was 1.91. Allozyme banding patterns at the glucose-6-phosphate isomerase (Gpi) locus indicated a 100/100/111 profile, consistent with the US-24 clonal lineage (3,4). Mating type assays confirmed the isolates to be A1 and intermediate insensitivity to mefenoxam was observed in vitro (4). Genomic DNA was extracted with a phenol:chloroform:isoamyl alcohol solution and restriction fragment length polymorphism (RFLP) analysis was performed using the RG-57 probe on a representative isolate and resulted in banding patterns consistent with US-24 (2,3). Clonal lineages of P. infestans documented in Wisconsin in previous epidemics included US-8 in the mid-1990s and US-1 in the 1970s. The US-24 (A1) clonal lineage was very widespread in the U.S. in 2010 and its presence in Wisconsin in the same year as identification of US-22 (A2) posed great concern for potential sexual recombination, oospore production, and soil persistence. Fortunately, the opposite mating types were separated spatiotemporally. To the best of our knowledge, this is the first report of the P. infestans clonal lineage US-24 causing late blight on potato in Wisconsin. References: (1) K. Deahl. (Abstr.) Phytopathology 100:S161, 2010. (2) S. B. Goodwin et al. Curr. Genet. 22:107, 1992. (3) Hu et al. Plant Dis. 96:1323, 2012. (4) A. C. Seidl and A. J. Gevens. (Abstr.) Phytopathology 101:S162, 2011.

scholarly journals First Report of Late Blight Caused by Phytophthora infestans Clonal Lineage US-23 on Tomato and Potato in Wisconsin, United States

Plant Disease ◽  
2013 ◽  
Vol 97 (6) ◽  
pp. 839-839 ◽  
Author(s):  
A. J. Gevens ◽  
A. C. Seidl
Keyword(s):  
United States ◽  
Late Blight ◽  
Phytophthora Infestans ◽  
Weather Conditions ◽  
The United States ◽  
Clonal Lineage ◽  
Banding Patterns ◽  
First Report ◽  
Low Incidence ◽  
Epidemiological Characteristics

Tomato (Solanum lycopersicum) and potato (S. tuberosum) crops are grown on over 67,000 acres (27,114 ha) in Wisconsin annually. Late blight, caused by Phytophthora infestans (Mont.) deBary, is a potentially devastating disease that affects tomato and potato crops in Wisconsin every few years when inoculum is introduced and weather conditions favor disease. Incidence and severity of late blight are highly variable in these few years due to differences in pathogen clonal lineages, their timing and means of introduction, and weather conditions. Prevention of this disease through preventative application of fungicides can cost producers millions of dollars per year in additional chemical, fuel, and labor expenses. In 2009, late blight caused by P. infestans clonal lineage US-23 was observed on potato very late in the season in Vernon County, southwestern Wisconsin, in very low incidence and severity. In 2010, US-23 again appeared but on tomato in two southeastern Wisconsin counties, Waukesha and Ozaukee, again in low incidence and severity. Clonal lineages of P. infestans documented in Wisconsin in previous epidemics included US-8 in the mid-1990s and US-1 in the 1970s. Populations of P. infestans in the United States have recently undergone significant genetic change, resulting in isolates with unique clonal lineages and epidemiological characteristics (1). Foliar symptoms included water-soaked to dark brown circular lesions with pale green haloes accompanied by white pathogen sporulation. On tomato fruit, lesions were firm, sunken, and brown. Isolates of P. infestans were generated from field-infected tomato and potato foliar and fruit tissues collected by the authors and professional crop consultants. In initial pathogen confirmation analysis in 2009, three isolates of P. infestans were generated from one potato plant exhibiting multiple lesions from one of eight fields tested by placing infected leaf excisions onto Rye A agar amended with rifampicin and ampicillin. Axenic, single zoospore-derived cultures of isolates were generated from parent cultures and maintained on Rye A agar for further characterization. In 2010, three US-23 isolates were recovered from three locations (two counties), out of 20 fields tested. Mycelium was coenocytic with hyphal diameter of 5 to 8 μm (n = 50). Sporangia were limoniform or ovoid, semi to fully papillate, caducous, had short pedicels, and were 26.16 μm high × 18.17 μm wide (n = 50). The average length/width ratio was 1.42. Allozyme banding patterns at the glucose-6-phosphate isomerase (Gpi) locus indicated a 100/100 profile, consistent with the US-23 clonal lineage (3) Mating type assays confirmed the isolates to be A1 and in vitro intermediate mefenoxam sensitivity was observed (4). Genomic DNA was extracted with a phenol/chloroform/isoamyl alcohol solution and RFLP analysis was performed using the RG-57 probe on a representative isolate and resulted in banding patterns consistent with US-23 (2,3). The P. infestans clonal lineage US-23 was present in epidemics in 2009 and 2010 in the United States. Disease symptoms associated with US-23 were observed exclusively on potato in 2009 and on tomato in 2010 in Wisconsin. To our knowledge, this is the first report of P. infestans clonal lineage US-23 causing late blight on tomato and potato in Wisconsin and represents a change in the composition of the pathogen population from previous epidemic years. References: (1) K. Deahl. (Abstr.) Phytopathology 100:S161, 2010. (2) S. B. Goodwin et al. Curr. Genet. 22:107, 1992. (3) Hu et al. Plant Dis. 96:1323, 2012. (4) A. C. Seidl and A. J. Gevens. (Abstr.) Phytopathology 101(suppl.):S162, 2011.

scholarly journals First Report of the A2 Mating Type of Phytophthora infestans on Tomato Crops in Taiwan, Republic of China

Plant Disease ◽  
2008 ◽  
Vol 92 (6) ◽  
pp. 978-978 ◽  
Author(s):  
K. L. Deahl ◽  
R. W. Jones ◽  
L. L. Black ◽  
T. C. Wang ◽  
L. R. Cooke
Keyword(s):  
Phytophthora Infestans ◽  
Mating Type ◽  
Morphological Characters ◽  
Mitochondrial Haplotype ◽  
Clonal Lineage ◽  
First Report ◽  
Test Isolate ◽  
The Us ◽  
Differential Hosts

In a study of the Phytophthora infestans population in Taiwan, samples with symptoms typical of late blight were collected from field crops in an important potato- (Solanum tuberosum) and tomato-(Lycopersicon esculentum) production area in the central highlands region. Isolates were obtained by surface disinfecting leaf sections and plating them onto antibiotic-amended rye A agar (1). After subculturing, the pathogen was confirmed as P. infestans on the basis of morphological characters (2). Mating type was determined by co-inoculating unamended rye agar plates with mycelial plugs of the test isolate and a reference P. infestans isolate of either the A1 or A2 mating type (four plates per test isolate, two with different A1, and two with different A2 reference isolates). After incubation (15°C darkness, 7 to 14 days), plates were examined microscopically for the presence of oospores where the colonies interacted. In 2004, one isolate of 200 tested, and in 2006, one isolate of 102 tested, produced oospores only with A1 reference isolates and were concluded to be A2 mating type. In vitro testing showed the two A2 isolates were metalaxyl-resistant (ED50 values >100 mg of metalaxyl per liter on rye grain agar), which is typical of recent P. infestans isolates from potato and tomato in this area (2). Twenty-one single-sporangial isolates from each of the two A2 strains were tested for mating type against two different A1 isolates of P. infestans and confirmed as A2. These isolates were characterized using the techniques described by Deahl et al. (1) and had the allozyme genotype 100/100/111, 100/100 at the loci coding for glucose-6-phosphate isomerase and peptidase, respectively, and were mitochondrial haplotype IIb. This multi-locus genotype is characteristic of recent P. infestans isolates from tomato and potato in Taiwan, but all previous such isolates were A1 mating type and attributed to the US-11 clonal lineage (1). When evaluated on differential hosts, both A2 isolates were tomato race PH-1 and complex potato race R 0,1,2,3,4,7,9,11. RG57 fingerprinting showed that the A2 isolates had fingerprints identical to each other and to A1 P. infestans isolates of the US-11 clonal lineage from tomato in Taiwan (101 011 100 100 110 101 011 001 1). Koch's postulates were completed and the two A2 isolates were found to be highly aggressive on cultivars of potato and tomato. To our knowledge, this is the first report of A2 mating type strains of P. infestans in the field in Taiwan, but currently, their incidence is very low (<1%). One crop from which an A2 isolate was obtained also yielded an A1 isolate, while A1 isolates were obtained from crops in the vicinity of the other. The concurrent presence of the two mating types of P. infestans poses a risk of sexual reproduction and oospore formation in tomato or potato in Taiwan. References: (1) K. L. Deahl et al. Pest Manag. Sci. 58:951, 2002. (2). D. C. Erwin and O. K. Ribeiro, Page 346 in: Phytophthora Diseases Worldwide. The American Phytopathological Society. St. Paul, MN, 1996.

scholarly journals First Report of Late Blight Caused by Phytophthora infestans Clonal Lineage US-23 Variant on Potato in Michigan, USA

Plant Disease ◽  
2016 ◽  
Vol 100 (8) ◽  
pp. 1797-1797
Author(s):  
S. Dangi ◽  
N. Rosenzweig ◽  
L. Steere ◽  
W. W. Kirk
Keyword(s):  
Late Blight ◽  
Phytophthora Infestans ◽  
Clonal Lineage ◽  
First Report

First report of the EU_33_A2 clonal lineage of Phytophthora infestans causing late blight disease of potato in Nigeria

2019 ◽  
Vol 40 ◽  
pp. 20
Author(s):  
N.E. Nnadi ◽  
A.M. Datiri ◽  
D.B. Pam ◽  
A.C. Ngene ◽  
F.O. Okonkwo ◽  
...  
Keyword(s):  
Late Blight ◽  
Phytophthora Infestans ◽  
Clonal Lineage ◽  
First Report ◽  
Late Blight Disease ◽  
Blight Disease

scholarly journals First Report of Phytophthora infestans Genotype US23 Causing Late Blight in Canada

Plant Disease ◽  
2011 ◽  
Vol 95 (7) ◽  
pp. 873-873 ◽  
Author(s):  
L. M. Kawchuk ◽  
R. J. Howard ◽  
R. D. Peters ◽  
K. I. Al-Mughrabi
Keyword(s):  
United States ◽  
Late Blight ◽  
Phytophthora Infestans ◽  
The United States ◽  
Western Canada ◽  
Eastern Canada ◽  
Disease Symptoms ◽  
Metalaxyl Sensitivity ◽  
Epidemiological Characteristics

Late blight is caused by the oomycete Phytophthora infestans (Mont.) de Bary and is one of the most devastating diseases of potato and tomato. Late blight occurs in all major potato- and tomato-growing regions of Canada. Its incidence in North America increased during 2009 and 2010 (2). Foliar disease symptoms appeared earlier than usual (June rather than July) and coincided with the identification of several new P. infestans genotypes in the United States, each with unique characteristics. Prior to 2007, isolates collected from potato and tomato crops were mainly US8 or US11 genotypes (1). However, P. infestans populations in the United States have recently experienced a major genetic evolution, producing isolates with unique genotypes and epidemiological characteristics in Florida and throughout the northeastern states (2). Recent discoveries of tomato transplants with late blight for sale at Canadian retail outlets prompted an examination of the genotypes inadvertently being distributed and causing disease in commercial production areas in Canada. Analysis of isolates of P. infestans from across Canada in 2010 identified the US23 genotype for the first time from each of the four western provinces (Manitoba, Saskatchewan, Alberta, and British Columbia) but not from eastern Canada. Allozyme banding patterns at the glucose phosphate isomerase (Gpi) locus indicated a 100/100 profile consistent with US6 and US23 genotypes (4). Mating type assays confirmed the isolates to be A1 and in vivo metalaxyl sensitivity was observed. Restriction fragment length polymorphic analysis of 50 isolates from western Canada with the multilocus RG57 sequence and EcoRI produced the DNA pattern 1, 2, 5, 6, 10, 13, 14, 17, 20, 21, 24, 24a, 25 that was indicative of US23 (3). The recently described P. infestans genotype US23 appears to be more aggressive on tomato, and although isolates were recovered from both tomato and potato, disease symptoms were often more severe on tomato. Results indicate that movement and evolution of new P. infestans genotypes have contributed to the increased incidence of late blight and that movement of the pathogen on retail plantlets nationally and internationally may provide an additional early season source of inoculum. A major concern is that the introduced new A1 populations in western Canada have established a dichotomy with the endogenous A2 populations in eastern Canada, increasing the potential for sexual recombination producing oospores and additional genotypes should these populations merge. References: (1) Q. Chen et al. Am. J. Potato Res. 80:9, 2003. (2) K. Deahl. (Abstr.) Phytopathology 100(suppl.):S161, 2010. (3) S. B. Goodwin et al. Curr. Genet. 22:107, 1992. (4) S. B. Goodwin et al. Phytopathology 88:939, 2004.

scholarly journals Respuesta de biosurfactantes producidos por Pseudomonas fluorescens para el control de la gota de la papa Phytophthora infestans (Mont) de Bary, bajo condiciones controlada.

2010 ◽  
Vol 11 (1) ◽  
pp. 21
Author(s):  
Hugo F. Rivera ◽  
Erika P. Martínez ◽  
Jairo A. Osorio ◽  
Edgar Martínez
Keyword(s):  
Late Blight ◽  
Phytophthora Infestans ◽  
Pseudomonas Fluorescens ◽  
Negative Impact ◽  
Potato Late Blight ◽  
Pathogen Resistance ◽  
Production Costs ◽  
In Vitro Assays

<p>Phytophthora infestans (Mont.) de Bary, agente causal de la gota de la papa, es considerado la principal limitante de la producción de este cultivo en Colombia. El control habitual del patógeno se realiza con fungicidas de tipo sistémico, que incrementan los costos de producción, pueden inducir la resistencia del patógeno y tiene un impacto negativo en el ambiente. Por tanto, se llevó a cabo este estudio con el propósito de buscar alternativas amigables con el ambiente, que hagan parte de un paquete tecnológico eficaz de control. Dos cepas nativas de Psedomonas fluorescens (039T y 021V), provenientes de cultivos de papa, fueron evaluadas contra P. infestans. Las suspensiones bacterianas y los biosurfactantes parcialmente purificados (BPP), producidos por éstas (obtenidos en medio mínimo de sales con querosén), fueron aplicados sobre foliolos desprendidos en ensayos in vitro y experimentos in vivo en plantas de papa, en condiciones controladas en casa de malla. Los resultados demostraron la capacidad que tienen los biosurfactantes y las suspensiones bacterianas para controlar al patógeno, ya que el BPP 039T logró reducir el nivel de severidad de la enfermedad en 79,9% in vitro y 38,5% in vivo, mientras que el BPP 021V redujo en 78,7% in vitro y 30,2% in vivo. Las suspensiones bacterianas redujeron el nivel de severidad en 72,4% (039T) y 66,1% (021V) en las evaluaciones in vitro y 35% en los experimentos in vivo. Los resultados de esta investigación muestran el potencial que tienen los biosurfactantes para el control de la gota en Colombia.</p><p> </p><p><strong>Evaluation of Biosurfactants Produced by Pseudomonas fluorescens for Potato Late Blight Control (Phytophthora infestans (Mont) de Bary) Under Controlled Conditions</strong></p><p>Phytophthora infestans (Mont.) de Bary, causal agent of potato late blight is considered the main limiting pathogen for the production of this crop in Colombia. The usual control of the disease has been performed with systemic fungicides which increase production costs, can induce pathogen resistance and have a negative impact on the environment. Therefore, this study was carried out in order to find effective and environmentally friendly control alternatives for potato late blight. Two Pseudomonas fluorescens native strains (039T and 021V) isolated from potato crops were evaluated against P. infestans. Bacterial suspensions (obtained from minimal salts medium added with kerosene) and partially purified biosurfactants (BPP) were applied on detached leaflets for in vitro assays and on potato plants in greenhouse, for in vivo assays and the measure of inhibitory effect of the disease was assessed. The results showed the ability of P. fluorescens biosurfactants and bacterial suspensions to control the pathogen. BPP 039T was able to reduce the level of severity disease by 79.9% in vitro and 38.5% in vivo, whereas BPP 021V decreased 78.7% in vitro and 30.2% in vivo. Bacterial suspensions reduced the severity level in 72.4% (039T) and 66.1% (021V) in vitro assessments and 35% in the in vivo experiment. These results show the potential of P. fluorescens biosurfactants to control the potato late blight in Colombia.</p>

scholarly journals Late Blight Caused by Phytophthora infestans on Solanum sarrachoides in Northeastern Maine

Plant Disease ◽  
2005 ◽  
Vol 89 (4) ◽  
pp. 435-435 ◽  
Author(s):  
K. L. Deahl ◽  
R. Jones ◽  
L. A. Wanner ◽  
A. Plant
Keyword(s):  
Late Blight ◽  
Phytophthora Infestans ◽  
Morphological Characteristics ◽  
Dna Fingerprint ◽  
Penicillin G ◽  
Mitochondrial Haplotype ◽  
Clonal Lineage ◽  
Growth Responses ◽  
Hairy Nightshade ◽  
Solanum Sarrachoides

The area bordering three 110-ha (270-acre) fields of blighted potatoes (Solanum tuberosum L.) in three northeastern Maine locations was surveyed during the summer of 2004 for the occurrence of late blight on cultivated and noncultivated host plants. Special attention was directed to solanaceous weed species. Hundreds of Solanum sarrachoides Sendt. ex. Mart. (hairy nightshade) plants with numerous leaf lesions and moderate defoliation were seen. The frequency of blighted hairy nightshade approximated the frequency of late blight in the adjoining potato fields. Lesions typically contained extensive, white, superficial mycelia colonizing the abaxial and adaxial leaf surfaces. Samples placed in a moist chamber produced lemon-shaped sporangia. On the basis of morphological characteristics, the pathogen was tentatively identified as Phytophthora infestans (Mont.) de Bary. Isolates were obtained by surface-disinfecting leaf sections collected from two locations for 2 to 3 min in 0.5% NaOCl and placing the sections on rye grain medium amended with antibiotics (100 ppm each of penicillin G, pimaricin, and polymyxin). P. infestans was confirmed after reisolating onto rye-lima bean medium. Pathogenicity was tested on detached potato, tomato, and hairy nightshade leaves; the undersides of all leaflets from replicate plants were inoculated with droplets of swimming zoospores (≥500 zoospores per droplet), the leaves were kept at 17°C and 100% humidity, and the extent of sporulation was evaluated after 4, 6, and 7 days. With eight isolates obtained from S. sarrachoides, Koch's postulates were completed on potato and hairy nightshade. Radial growth responses of these strains on rye grain agar amended with 1, 10, or 100 μg per ml of metalaxyl (Ridomil 2E) yielded 50% effective dose values greater than 100 μg per ml, since percentage growth at the highest fungicide concentration exceeded 50% of the no metalaxyl control. These resistance levels are typical of the metalaxyl-insensitive strains of P. infestans isolated from potatoes in this area in recent years, which were previously found to correlate with metalaxyl resistance in bioassays using potato tissues (1). Eight single-sporangial isolates were homozygous for glucose-6-phosphate isomerase and peptidase (Gpi 100/111/122, Pep 100/100). All eight were A2-mating type and mitochondrial haplotype Ia, characteristics common to the US-8 clonal lineage of P. infestans from potato (2), which may infect a wider host range than the old US-1 clonal lineage. When evaluated on differential hosts, three isolates were tomato race PH-1 and complex potato race R 0,1,2,3,4,9,11. DNA fingerprint analysis with probe RG57 further established that the eight hairy nightshade isolates were identical to each other and to local P. infestans isolates from potato. To our knowledge, this is the first report of infection of S. sarrachoides by P. infestans in Maine. The pathogen was previously isolated from this host during field surveys in southern California in the 1980s in connection with late blight of tomato (4). Hairy nightshade has been shown to be a host for US-1, US-8, and US-11 isolates of P. infestans in a laboratory setting (3). The epidemiological significance of S. sarrachoides as an alternative or overwintering host of P. infestans is currently being assessed. References: (1) K. L. Deahl et al. Am. Potato J. 70:779, 1993. (2) S. B. Goodwin et al. Phytopathology 88:939, 1998. (3) H. W. Platt. Can. J. Plant Pathol. 21:301, 1999. (4) V. G. Vartanian and R. M. Endo Plant Dis. 69:516, 1985.

scholarly journals Did a novel virus contribute to late blight epidemics?

2018 ◽  
Author(s):  
Guohong Cai ◽  
Kevin Myers ◽  
William E. Fry ◽  
Bradley I. Hillman
Keyword(s):  
North America ◽  
Late Blight ◽  
Phytophthora Infestans ◽  
Molecular Mechanisms ◽  
Rna Virus ◽  
Causal Agent ◽  
Clonal Lineage ◽  
Significant Similarity ◽  
Tomato Production ◽  
The Us

AbstractPhytophthora infestansis the causal agent of potato and tomato late blight. In this study, we characterized a novel RNA virus, Phytophthora infestans RNA virus 2 (PiRV-2). The PiRV-2 genome is 11,170 nt and lacks a polyA tail. It contains a single large open reading frame (ORF) with short 5’- and 3’-untranslated regions. The ORF is predicted to encode a polyprotein of 3710 aa (calculated molecular weight 410.94 kDa). This virus lacks significant similarity to any other known viruses, even in the conserved RNA-dependent RNA polymerase region. Comparing isogenic strains with or without the virus demonstrated that the virus stimulated sporangia production inP. infestansand appeared to enhance its virulence. Transcriptome analysis revealed that it achieved sporulation stimulation likely through down-regulation of ammonium and amino acid intake inP. infestans. This virus was faithfully transmitted through asexual reproduction. Survey of PiRV-2 presence in aP. infestanscollection found it in most strains in the US-8 lineage, a very successful clonal lineage ofP. infestansin North America. We suggest that PiRV-2 may have contributed to its success, raising the intriguing possibility that a potentially hypervirulent virus may contribute to late blight epidemics.Author SummaryPotato late blight, the notorious plant disease behind the Irish Potato Famine, continues to pose a serious threat to potato and tomato production worldwide. While most studies on late blight epidemics focuses on pathogen virulence, host resistance, environmental factors and fungicide resistance, we present evidence in this study that a virus infecting the causal agent,Phytophthora infestans, may have played a role. We characterized a novel RNA virus, Phytophthora infestans RNA virus 2 (PiRV-2) and examined its effects on its host. By comparing identicalP. infestansstrains except with or without the virus, we found that PiRV-2 stimulated sporulation ofP. infestans(a critical factor in late blight epidemics) and increased its virulence. We also profiled gene expression in these strains and identified potential molecular mechanisms through which PiRV-2 asserted its sporulation stimulation effect. In a survey of PiRV-2 presence in aP. infestanscollection, we found PiRV-2 in most isolates of the US-8 clonal lineage, a very successfull ineage that dominated potato fields in North America for several decades. We suggest that PiRV-2 may have contributed to its success. Our findings raise the intriguing possibility that a potentially hypervirulent virus may contribute to late blight epidemics.

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