First Report of Crown Rot Caused by Phytophthora tropicalis on Gloxinia in North Carolina

Heather A. Olson; D. Michael Benson

doi:10.1094/php-2010-0708-03-br

Red Crown Rot of Hop in Oregon Caused by Phomopsis tuberivora

Plant Health Progress ◽

10.1094/php-2013-0624-01-br ◽

2013 ◽

Vol 14 (1) ◽

pp. 52

Author(s):

David H. Gent ◽

George Mueller-Warrant ◽

Joanna L. Woods ◽

Melodie L. Putnam ◽

Megan C. Twomey

Keyword(s):

Crown Rot ◽

Management Implications ◽

Koch’S Postulates ◽

First Report ◽

Red Crown Rot ◽

Weak Growth ◽

Koch's Postulates

During July 2007, symptoms including weak growth and death of plants of cultivar Fuggle were reported by a hop grower in Marion Co., OR. Phomopsis tuberivora H.T. Güssow & W.R. Foster 1932 was consistently recovered from affected plants. Koch's postulates were fulfilled with three isolates of the fungus, establishing the pathogen and the disease red crown rot as the cause of the damage. This is the first report of red crown rot on hop in Oregon, which may have important management implications for affected hop yards and farms. Accepted for publication 19 March 2013. Published 24 June 2013.

Download Full-text

First Report of Pilidiella granati on Pomegranate with Symptoms of Crown Rot in the Prefecture of Xanthi, Greece

Plant Disease ◽

10.1094/pdis-07-10-0514 ◽

2011 ◽

Vol 95 (1) ◽

pp. 79-79 ◽

Cited By ~ 8

Author(s):

T. Thomidis ◽

E. Exadaktylou

Keyword(s):

Potato Dextrose Agar ◽

Crown Rot ◽

Fruit Rot ◽

Adhesive Tape ◽

Petroleum Jelly ◽

Koch’S Postulates ◽

First Report ◽

Agar Plug ◽

Pilidiella Granati ◽

Koch's Postulates

In spring 2010, plants of pomegranate (Punica granatum L.) cv. Wonderful with symptoms of crown rot were observed in the Prefecture of Xanthi, Thrace, Greece. Close examination of these plants revealed distinct symptoms of crown rots. Isolations from the lower margins of the necrotic area were made by plating tissues of approximately 3 mm on acidified (2.5 ml of 85% lactic acid per liter of nutrient medium to create a pH = 3.5 after autoclaving) potato dextrose agar. The plates were incubated at 23°C for 5 to 7 days, and consistent colonies with light yellow, leathery mycelia and abundant, black, solitary pycnidia of various sizes were observed. Hyphae were septate and conidia were hyaline, one-celled, and ellipsoid to fusiform (average 10.1 to 20.2 × 3.2 to 4.3 μm). The pathogen was identified as Pilidiella granati Saccardo (synonym Coniella granati (Saccardo) Petrak & Sydow (3)) based on mycelium and spore morphology and ribosomal ITS1-5.8S-ITS2 sequences, which were identical to GenBank No. FN908875. Koch's postulates were completed in the laboratory by inoculating 20 1-year-old plants of pomegranate cv. Wonderful. With a 7-mm-diameter cork borer, a wound was created in the middle of each collar by removing the bark. A 6-mm-diameter agar plug bearing mycelia and spores from a 15-day-old culture of P. granati was inserted into each wound. The wound was covered with petroleum jelly and wrapped with adhesive tape to prevent desiccation. Ten trees were inoculated with sterile potato dextrose agar plugs to serve as controls. All plants were incubated at 25°C for 10 days, at which time necrosis was observed. Koch's postulates were satisfied after reisolating the fungus from inoculated plants that developed symptoms similar to those observed in the field. Control plants produced no symptoms of disease. To our knowledge, this is the first report of P. granati from pomegranate plants with symptoms of crown rots in Greece. The role of predisposing factors such as herbicides and frost damage to infection by P. granati is unknown. This pathogen has been reported to cause fruit rot of pomegranate in Spain (2) and California (1). References: (1) T. J. Michailides et al. (Abstr.) Phytopathology 100(suppl.):S83, 2010. (2) L. Palou et al. New Dis. Rep. Online publication. doi:10.5197/j.2044-0588.2010.022.021, 2010. (3) G T. Tziros and K. Tzavella-Klonari. Plant Pathol. 57:783, 2007.

Download Full-text

First Report of Pathogenicity of Fusarium sporotrichioides and Fusarium acuminatum on Sunflowers in the United States

Plant Health Progress ◽

10.1094/php-2010-0915-02-br ◽

2010 ◽

Vol 11 (1) ◽

pp. 42 ◽

Cited By ~ 4

Author(s):

F. Mathew ◽

B. Kirkeide ◽

T. Gulya ◽

S. Markell

Keyword(s):

United States ◽

Helianthus Annuus ◽

The United States ◽

Fusarium Sporotrichioides ◽

Charcoal Rot ◽

Koch’S Postulates ◽

First Report ◽

Fusarium Acuminatum ◽

Helianthus Annuus L ◽

Koch's Postulates

Widespread infection of charcoal rot was observed in a commercial sunflower field in Minnesota in September 2009. Based on morphology, isolates were identified as F. sporotrichioides and F. acuminatum. Koch's postulates demonstrated pathogencity of both species. To our knowledge, this is the first report of F. sporotrichoides and F. acuminatum causing disease on Helianthus annuus L. in the United States. Accepted for publication 23 August 2010. Published 15 September 2010.

Download Full-text

First Report of Stemphylium botryosum Causing Leaf Blight of Kiwi in the Province Imathia, Northern Greece

Plant Disease ◽

10.1094/pdis-92-4-0650b ◽

2008 ◽

Vol 92 (4) ◽

pp. 650-650 ◽

Cited By ~ 1

Author(s):

T. Thomidis ◽

T. J. Michailides

Keyword(s):

Apical Cell ◽

Morphological Characteristics ◽

Leaf Blight ◽

Width Ratio ◽

Northern Greece ◽

Cell Width ◽

Koch’S Postulates ◽

First Report ◽

Stemphylium Botryosum ◽

Koch's Postulates

In Greece, kiwi (Actinidia deliciosa) is mostly found in the northern part of the country where approximately 440,000 ha are grown. In the summer of 2006, a Stemphylium sp. was frequently isolated from leaves of kiwi (cv. Hayward) grown in the province of Imathia. Symptomatic leaves were covered with irregular, necrotic, brown areas. Lesions had a distinct margin that, in some cases, covered a wide part of the diseased leaves. Intense symptoms were frequently observed and associated with defoliation. This Stemphylium sp. was consistently isolated from diseased leaves onto potato dextrose agar (PDA) after surface sterilization with 0.1% chlorine solution. On the basis of morphological characteristics of mycelia, dimensions (length 20 to 29 μm and width 14 to 21 μm) and mean length/width ratio (1.42 μm) of conidia, and width and apical cell width of condiophores, the fungus was identified as Stemphylium botryosum (Wallr.) (2,3) Koch's postulates were completed in the laboratory by inoculating leaves of kiwi (cv. Hayward) with an isolate of S. botryosum originated from a symptomatic leaf of a Hayward kiwi. Twenty leaves were surface sterilized by dipping them into 0.1% chlorine solution for 2 to 3 min, washing in sterile distilled water, and allowing them to dry in a laminar flow hood. A leaf was then placed into a petri plate containing a wet, sterilized paper towel. Inoculation was made by transferring a 5-mm-diameter mycelial disc from the margins of a 7-day-old culture onto the center of each leaf surface. Petri plates were closed and incubated at 25°C with 12 h of light for 6 days. Koch's postulates were satisfied when the same S. botryosum was reisolated from 100% of inoculated leaves that developed symptoms similar to those observed in the vineyards. Leaves inoculated with a PDA plug alone (with no S. botryosum) did not develop any symptoms. Previously, Alternaria alternata was reported as the causal agent of a leaf spot pathogen of kiwi (1,4). To our knowledge, this is the first report of the occurrence of S. botryosum causing leaf blight of kiwi in Greece and worldwide. This pathogen can cause a high level of defoliation in diseased plants. References: (1) L. Corazza et al. Plant Dis. 83:487, 1999. (2) M. B. Ellis. Dematiaceous Hyphomycetes. Mycology Institute. London, England, 1971. (3) E. G. Simmons. Mycologia 61:1, 1969. (4) C. Tsahouridou and C. C. Thanassoulopoulos. Plant Dis. 84:371, 2000

Download Full-text

First report of Pestalotiopsis diospyri causing canker on persimmon trees

Revista Brasileira de Fruticultura ◽

10.1590/s0100-29452011005000103 ◽

2011 ◽

Vol 33 (3) ◽

pp. 1019-1022 ◽

Cited By ~ 2

Author(s):

Giselda Alves ◽

Francineia Silva Verbiski ◽

Themis J. Michaelides ◽

Louise Larissa May-de Mio

Keyword(s):

Diospyros Kaki ◽

Southern Brazil ◽

Severe Damage ◽

Santa Catarina ◽

Koch’S Postulates ◽

Canker Disease ◽

First Report ◽

Koch's Postulates

During 2006 to 2009 season symptoms of a canker disease were observed on twigs and branches of young and mature persimmon trees (Diospyros kaki L.) cv. Fuyu in the States of Santa Catarina and Paraná in the Southern Brazil. The cankers result in severe damage and reduced production. Isolations from the margins of these cankers revealed a genus of Pestalotiopsis. Koch's postulates were confirmed using two isolates of the pathogen which was identified as Pestalotiopsis diospyri.

Download Full-text

First Report of Phytophthora ramorum Infecting Grand fir in California

Plant Health Progress ◽

10.1094/php-2011-0401-01-br ◽

2011 ◽

Vol 12 (1) ◽

pp. 37

Author(s):

Kathleen L. Riley ◽

Gary A. Chastagner ◽

Cheryl Blomquist

Keyword(s):

Phytophthora Ramorum ◽

Christmas Tree ◽

Native Range ◽

Tree Plantation ◽

Koch’S Postulates ◽

First Report ◽

Stem Lesions ◽

Koch's Postulates

Phytophthora ramorum was detected on grand fir in 2003 and 2005 in a Christmas tree plantation near Los Gatos, CA, in association with infected California bay laurel. Isolates derived from stem lesions were used to inoculate grand fir seedlings in two tests. Isolations from lesions on inoculated plants were positive for P. ramorum in both tests. This work provides the completion of Koch's postulates to establish grand fir as a host of P. ramorum. The potential for grand fir to be infected within its native range is unknown. Accepted for publication 1 February 2011. Published 1 April 2011.

Download Full-text

First Report of Leaf Spot Disease on Walnut Caused by Colletotrichum fioriniae in China

Plant Disease ◽

10.1094/pdis-09-14-0938-pdn ◽

2015 ◽

Vol 99 (2) ◽

pp. 289-289 ◽

Cited By ~ 9

Author(s):

Y. Z. Zhu ◽

W. J. Liao ◽

D. X. Zou ◽

Y. J. Wu ◽

Y. Zhou

Keyword(s):

Dna Sequences ◽

Leaf Spot ◽

Juglans Regia ◽

Morphological Characteristics ◽

Leaf Spot Disease ◽

Koch’S Postulates ◽

First Report ◽

Spot Disease ◽

Leaf Spots ◽

Koch's Postulates

In May 2014, a severe leaf spot disease was observed on walnut tree (Juglans regia L.) in Hechi, Guangxi, China. Leaf spots were circular to semicircular in shape, water-soaked, later becoming grayish white in the center with a dark brown margin and bordered by a tan halo. Necrotic lesions were approximately 3 to 4 mm in diameter. Diseased leaves were collected from 10 trees in each of five commercial orchards. The diseased leaves were cut into 5 × 5 mm slices, dipped in 75% ethanol for 30 s, washed three times in sterilized water, sterilized with 0.1% (w/v) HgCl2 for 3 min, and then rinsed five times with sterile distilled water. These slices were placed on potato dextrose agar (PDA), followed by incubating at 28°C for about 3 to 4 days. Fungal isolates were obtained from these diseased tissues, transferred onto PDA plates, and incubated at 28°C. These isolates produced gray aerial mycelium and then became pinkish gray with age. Moreover, the reverse of the colony was pink. The growth rate was 8.21 to 8.41 mm per day (average = 8.29 ± 0.11, n = 3) at 28°C. The colonies produced pale orange conidial masses and were fusiform with acute ends, hyaline, sometimes guttulate, 4.02 to 5.25 × 13.71 to 15.72 μm (average = 4.56 ± 0.31 × 14.87 ± 1.14 μm, n = 25). The morphological characteristics and measurements of this fungal isolate matched the previous descriptions of Colletotrichum fioriniae (Marcelino & Gouli) R.G. Shivas & Y.P. Tan (2). Meanwhile, these characterizations were further confirmed by analysis of the partial sequence of five genes: the internal transcribed spacer (ITS) of the ribosomal DNA, beta-tubulin (β-tub) gene, glyceraldehyde 3-phosphate dehydrogenase (GAPDH) gene, chitin synthase 3(CHS-1) gene, and actin (ACT) gene, with universal primers ITS4/ITS5, T1/βt2b, GDF1/GDR1, CHS1-79F/CHS1-354R, and ACT-512F/ACT-783R, respectively (1). BLAST of these DNA sequences using the nucleotide database of GenBank showed a high identify (ITS, 99%; β-tub, 99%; GAPDH, 99%; CHS-1, 99%; and ACT, 100%) with the previously deposited sequences of C. fioriniae (ITS, KF278459.1, NR111747.1; β-tub, AB744079.1, AB690809.1; GAPDH, KF944355.1, KF944354.1; CHS-1, JQ948987.1, JQ949005.1; and ACT, JQ949625.1, JQ949626.1). Koch's postulates were fulfilled by inoculating six healthy 1-year-old walnut trees in July 2014 with maximum and minimum temperatures of 33 and 26°C. The 6-mm mycelial plug, which was cut from the margin of a 5-day-old colony of the fungus on PDA, was placed onto each pin-wounded leaf, ensuring good contact between the mycelium and the wound. Non-colonized PDA plugs were placed onto pin-wounds as negative controls. Following inoculation, both inoculated and control plants were covered with plastic bags. Leaf spots, similar to those on naturally infected plants, were observed on the leaves inoculated with C. fioriniae within 5 days. No symptoms were observed on the negative control leaves. Finally, C. fioriniae was re-isolated from symptomatic leaves; in contrast, no fungus was isolated from the control, which confirmed Koch's postulates. To our knowledge, this is the first report of leaf disease on walnut caused by C. fioriniae. References: (1) L. Cai et al. Fungal Divers. 39:183, 2009. (2) R. G. Shivas and Y. P. Tan. Fungal Divers. 39:111, 2009.

Download Full-text

First Report of Aspergillus niger Causing Postharvest Fruit Rot of Cherry in the Prefectures of Imathia and Pella, Northern Greece

Plant Disease ◽

10.1094/pdis-07-11-0620 ◽

2012 ◽

Vol 96 (3) ◽

pp. 458-458 ◽

Cited By ~ 1

Author(s):

T. Thomidis ◽

E. Exadaktylou

Keyword(s):

Aspergillus Niger ◽

Fungal Spores ◽

Morphological Characteristics ◽

Fruit Rot ◽

Northern Greece ◽

Centraalbureau Voor ◽

Koch’S Postulates ◽

First Report ◽

Postharvest Rot ◽

Koch's Postulates

In June 2011, symptoms of postharvest rot were observed on approximately 3% of all cherries collected from commercial orchards of cultivars Lapen and Ferrovia in the prefectures of Imathia and Pella (northern Greece). Fruit were harvested in a timely manner to avoid overripeness. No wounds or other predisposing injuries were observed on the infected fruits. Lesions enlarged rapidly and separated easily from healthy tissue when pressure was applied. Infected tissues were pale and water soaked and the associated fungal spores were dark and powdery and easily liberated when mature. The fungus grew rapidly and produced black colonies on acidified potato dextrose agar (2.5 ml of 85% lactic acid per liter of nutrient medium) after 5 days at 24°C. Identification of the pathogen was based on morphological characteristics (1). The conidial head was radiate, vesicles were nearly spherical and covered with metulae and phialides (biseriate). Conidia were globose (3 to 5 μm in diameter) and usually very rough with irregular ridges, bars, and verrucae. Koch's postulates were completed in the laboratory by inoculating mature cherry fruits (cv. Lapen). The fruits were surface sterilized by dipping in 10% chloride bleach solution, allowed to dry in a laminar flow hood, and wounded with a sharp glass rod that was 2 mm in diameter. A 40-μl drop of a suspension containing 20,000 conidia per ml of water was placed on each wound. There were 20 inoculated and 20 control fruits (similarly wounded and inoculated with a 40-μl drop of sterile distilled water) in a randomized design and incubated at 24 to 26°C for 6 days. Koch's postulates were satisfied after reisolating the fungus from inoculated fruit that developed symptoms similar to those observed on fruit collected from orchards. Control fruits did not show any symptom of the disease. To our knowledge, this is the first report of the occurrence of Aspergillus niger as the causal agent of postharvest rots of cherries in Greece. Postharvest fruit rots caused by A. niger have been reported in cherry orchards of other countries around the world (2). Because this disease causes postharvest rots of cherry fruits, measures may need to be implemented to manage the pathogen. References: (1) M. A. Klich. Page 12 in: Identification of Common Aspergillus Species. Centraalbureau Voor Schimmelcultures, Utrecht, the Netherlands, 2002. (2) A. Valiuskaite et al. Phytopathol. Pol. 35:197, 2005.

Download Full-text

First Report of a Leaf Spot Disease of Tobacco Caused by Pseudomonas cichorii in China

Plant Disease ◽

10.1094/pdis-10-21-2158-pdn ◽

2021 ◽

Author(s):

Dayu Lan ◽

Fangling Shu ◽

Yanhui Lu ◽

Anfa Shou ◽

Wei Lin ◽

...

Keyword(s):

Pseudomonas Syringae ◽

Leaf Spot ◽

Leaf Spot Disease ◽

Pathogenicity Test ◽

Pseudomonas Cichorii ◽

Koch’S Postulates ◽

First Report ◽

Initial Symptoms ◽

Wide Range ◽

Koch's Postulates

Tobacco (Nicotiana tabacum L.), one of the chief commercial crops, is wildly cultivated worldwide. In June 2020 and 2021, an unknown bacterial leaf spot on tobacco was found in Hezhou and Hechi City, Guangxi, China. 30% of the tobacco were affected and the rate of diseased leaves reached about 10% in the field under high temperature and rainstorm. The disease mainly damaged the middle and top leaves of tobacco plants at vigorous growing stage. The initial symptoms were water-soaked spots on the frontal half of a leaf, and then expanded into circular to irregular spots with a yellow halo at the edge. The spots mostly appeared dark brown at high air humidity, while yellow brown at low humidity and exhibited a concentric pattern. In severe cases, the lesions coalesced and the whole leaf was densely covered with lesions, resulting in the loss of baking value. A bacterium was consistently isolated from diseased leaf tissues on nutrient agar (NA). Growth on NA was predominantly grayish white circular bacterial colonies with smooth margins, and the bacterium is rod-shaped, gram-negative and fluorescent on King’s B medium. Seven isolates (ND04A-ND04C and ZSXF02-ZSXF05) were selected for molecular identification and pathogenicity tests. Genomic DNA of the bacterium was extracted and the housekeeping gene of cts (encoding citrate synthase) was amplified with the primers cts-Fs/cts-Rs (forward primer cts-Fs: 5’-CCCGTCGAGCTGCCAATWCTGA-3’; reverse primer cts-Rs: 5’-ATCTCGCACGGSGTRTTGAACATC-3’) (Berge et al. 2014; Sarkar et al. 2004). 409-bp cts gene sequences were deposited in the GenBank database for seven isolates (accession no. OK105110-OK105116). Sequence of seven isolates shared 100% identity with several Pseudomonas cichorii strains within the GenBank database (accession no. KY940268 and KY940271), and the phylogenetic tree of cts genes of the seven isolates clustered with the phylogroup 11 of Pseudomonas syringae (accession no. KJ877799 and KJ878111), which was classified as P.cichorii. To satisfy Koch’s postulates, a pathogenicity test was tested by using a needle to dip a suspension of the bacterium (108 CFU/ml) and pricking three holes in the tobacco leaf. The control plants leaves were needled with sterile water. Each tobacco plant was inoculated with three leaves, and the test was repeated three times. All plants were placed in transparent plastic boxes and incubated in a greenhouse at 25 ± 3°C. The water-soaked spots appeared 24h after inoculation and quickly expanded through leaf veins. Three days after inoculation, all the inoculated leaves showed symptoms similar to those observed in the field. Control plants remained healthy. Only P. cichorii was successfully re-isolated from the lesions, confirming Koch’s postulates. Pseudomonas cichorii can infect eggplant, lettuce, tomatoand other crops, and has a wide range of hosts (Timilsina et al. 2017; Ullah et al. 2015). To our knowledge, this is the first report of P. cichorii causing leaf spot on tobacco in China.

Download Full-text

First Report of Rhizoctonia solani AG4 HG-II Infecting Potato Stems in Idaho

Plant Disease ◽

10.1094/pdis-06-12-0568-pdn ◽

2012 ◽

Vol 96 (11) ◽

pp. 1701-1701 ◽

Cited By ~ 5

Author(s):

J. W. Woodhall ◽

P. S. Wharton ◽

J. C. Peters

Keyword(s):

Rhizoctonia Solani ◽

Seed Tuber ◽

Its Region ◽

Stem Canker ◽

Potato Production ◽

Koch’S Postulates ◽

First Report ◽

Rdna Its ◽

Plant Pathol ◽

Koch's Postulates

The fungus Rhizoctonia solani is the causal agent of stem canker and black scurf of potato (Solanum tuberosum). R. solani is a species complex consisting of 13 anastomosis groups (AGs) designated AG1 to 13 (2, 3). Stems of potato (cv. Russet Norkotah) with brown lesions were recovered from one field in Kimberley, Idaho, in August 2011. Using previously described methods (3), R. solani was recovered from the symptomatic stems and one representative isolate (J15) was selected for further characterization. Sequencing of the rDNA ITS region of isolate J15 was undertaken as previously described (3) and the resulting rDNA ITS sequence (HE667745) was 99% identical to sequences of other AG4 HG-II isolates in GenBank (AF354072 and AF354074). Pathogenicity of the isolate was determined by conducting the following experiment. Mini-tubers of cv. Santé were planted individually in 1-liter pots containing John Innes Number 3 compost (John Innes Manufacturers Association, Reading, UK). Pots were either inoculated with J15, an isolate of AG3-PT (Rs08), or were not inoculated. Each treatment was replicated four times. Inoculum consisted of five 10-mm-diameter potato dextrose agar plugs, fully colonized by the appropriate isolate, placed in the compost approximately 40 mm above each seed tuber. Pots were held in a controlled environment room at 21°C with 50% relative humidity and watered as required. After 21 days, plants were assessed for disease. No symptoms of the disease were present in non-inoculated plants. In the Rs08 (AG3-PT) inoculated plants, all stems displayed large brown lesions and 20% of the stems had been killed. No stem death was observed in J15 (AG4 HG-II) inoculated plants. However, brown lesions were observed in three of the four J15 (AG4 HG-II) inoculated plants. These lesions were less severe than in plants inoculated with the Rs08(AG3-PT) inoculated plants and were present in 40% of the main stems. In the J15 (AG4 HG-II) inoculated pots, R. solani AG4 HG-II was reisolated from the five symptomatic stems, thereby satisfying Koch's postulates. To our knowledge, this is the first report of AG4 HG-II causing disease on potatoes in Idaho. AG4 has been isolated from potato previously from North Dakota, although the subgroup was not identified (1). The only previous report where AG4 HG-II was specifically determined to cause disease on potato was in Finland, but the isolate could not be maintained and Koch's postulates were not completed (3). The present study shows that AG4 HG-II can cause stem disease in potatoes, although disease does not develop as severely or as consistently as for AG3-PT. However, as demonstrated with isolates of AG2-1 and AG5, even mild stem infection can reduce tuber yield by as much as 12% (4). AG4 HG-II is a pathogen of sugar beet in Idaho, which was grown previously in this field. This history may have contributed to high levels of soilborne inoculum required to produce disease on potato. References: (1) N. C. Gudmestad et al. Page 247 in: J. Vos et al. eds. Effects of Crop Rotation on Potato Production in the Temperate Zones. Kluwer, Dordrecht, Netherlands, 1989. (2) M. J. Lehtonen et al. Agric. Food Sci. 18:223, 2009. (3) J. W. Woodhall et al. Plant Pathol. 56:286, 2007. (4) J. W. Woodhall et al. Plant Pathol. 57:897, 2008.

Download Full-text