First report of Globisporangium ultimum causing damping-off of wild rocket seedlings

Mediterranean fan palm (Chamaerops humilis L.), one of just two autochthonous European palms, is native to the western Mediterranean Region in southwestern Europe and northwestern Africa. It can be found growing wild in the Mediterranean area. In Europe, this species is very popular as an ornamental plant. In March 2009, a widespread damping-off was observed in a stock of approximately 30,000 potted 1-month-old plants of C. humilis cv. Vulcano in a nursery in eastern Sicily. Disease incidence was approximately 20%. Disease symptoms consisted of lesions at the seedling shoot (plumule). Stem lesions were initially orange, turned brown, and followed by death of the entire plumule or eophyll. A fungus with mycelial and morphological characteristics of Rhizoctonia solani Kühn was consistently isolated from lesions when plated on potato dextrose agar (PDA) amended with streptomycin sulfate at 100 μg/ml. Fungal colonies were initially white, turned brown with age, and produced irregularly shaped, brown sclerotia. Mycelium was branched at right angles with a septum near the branch and a slight constriction at the branch base. Hyphal cells removed from cultures grown at 25°C on 2% water agar were determined to be multinucleate when stained with 1% safranin O and 3% KOH solution (1) and examined at ×400. Anastomosis groups were determined by pairing isolates with tester strains AG-1 IA, AG-2-2-1, AG-2-2IIIB, AG-2-2IV, AG-3, AG-4, AG-5, AG-6, and AG-11 on 2% water agar in petri plates (3). Anastomosis was observed only with tester isolates of AG-4, giving both C2 and C3 reactions (2). One representative isolate obtained from symptomatic tissues was deposited at the Fungal Biodiversity Centre, Centraalbureau voor Schimmelcultures (CBS No. 125095). Pathogenicity tests were performed on container-grown, healthy, 1-month-old seedlings. Twenty plants of C. humilis cv. Vulcano were inoculated near the base of the stem with two 1-cm2 PDA plugs from 5-day-old mycelial cultures. The same number of plants served as uninoculated controls. Plants were incubated in a growth chamber and maintained at 25°C and 95% relative humidity on a 12-h fluorescent light/dark regimen. Symptoms identical to those observed in the nursery appeared 5 days after inoculation and all plants died within 20 days. No disease was observed on control plants. A fungus identical in culture morphology to R. solani AG-4 was consistently reisolated from symptomatic tissues, confirming its pathogenicity. To our knowledge, this is the first report in the world of R. solani causing damping-off on Mediterranean fan palm. References: (1) R. J. Bandoni. Mycologia 71:873, 1979. (2) D. E. Carling. Page 37 in: Grouping in Rhizoctonia solani by Hyphal Anastomosis Reactions. Kluwer Academic Publishers, the Netherlands, 1996. (3) C. C. Tu and J. W. Kimbrough. Mycologia 65:941, 1973.

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First report ofRhizoctonia solaniAG 4 HG-II attacking castor bean plants (Ricinus communis) in Brazil and evaluation of two castor bean cultivars for resistance to damping-off

Australasian Plant Disease Notes ◽

10.1071/dn08048 ◽

2008 ◽

Vol 3 (1) ◽

pp. 121 ◽

Cited By ~ 1

Author(s):

M. A. Basseto ◽

H. A. Chagas ◽

D. D. Rosa ◽

M. D. Zanotto ◽

E. L. Furtado

Keyword(s):

Castor Bean ◽

Ricinus Communis ◽

Damping Off ◽

First Report ◽

Bean Plants

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First Report of Damping-Off on Cucumis melo Caused by Pythium irregulare in South Korea

Plant Disease ◽

10.1094/pdis-03-20-0507-pdn ◽

2020 ◽

Vol 104 (11) ◽

pp. 3060-3060

Author(s):

Mi-Jeong Park ◽

Chang-Gi Back ◽

Jong-Han Park

Keyword(s):

South Korea ◽

Cucumis Melo ◽

Damping Off ◽

Pythium Irregulare ◽

First Report

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First Report of Damping-Off Caused by Rhizoctonia solani AG-4 on Lagunaria patersonii in Italy

Plant Disease ◽

10.1094/pdis-92-5-0836a ◽

2008 ◽

Vol 92 (5) ◽

pp. 836-836 ◽

Cited By ~ 3

Author(s):

D. Aiello ◽

G. Parlavecchio ◽

A. Vitale ◽

E. Lahoz ◽

R. Nicoletti ◽

...

Keyword(s):

Rhizoctonia Solani ◽

Morphological Characteristics ◽

Ruthenium Red ◽

Fluorescent Light ◽

Damping Off ◽

First Report ◽

Pectic Enzymes ◽

Electrophoretic Patterns ◽

Blue Solution ◽

Hyphal Diameter

Lagunaria patersonii (Adr.) G. Don (cow itch tree) is native to Australia and tolerates salted winds. During July 2007, damping-off of cow itch tree was observed on 4-month-old seedlings growing in a commercial nursery in eastern Sicily, Italy. More than 20% of the seedlings showed disease symptoms. First symptoms consisting of water-soaked lesions at the seedling base that expand rapidly girdle the stem and collapse the seedling in a few days. Diseased tissues were disinfested for 1 min in 1% NaOCl, rinsed in sterile water, plated on potato dextrose agar (PDA) amended with streptomycin sulphate at 100 mg/l, and then incubated at 25°C. A fungus with mycelial and morphological characteristics of Rhizoctonia solani Kühn was consistently yielded. Fungal colonies were initially white, turned brown with age, and produced irregularly shaped, brown sclerotia. Microscopic examination revealed that hyphae had a right-angle branching pattern, were constricted at the base of the branch near the union with main hyphae, and septate near the constriction. Basidia were not observed in the greenhouses or on the plates. Hyphal cells were determined to be multinucleate when stained with 0.5% aniline blue solution and examined at ×400 magnification with a microscope. Anastomosis groups were determined by pairing isolates on 2% water agar in petri plates (3). Pairings were made with tester strains of AG-1 IA, AG-2-2-1, AG-2-2IIIB, AG-2-2IV, AG-3, AG-4, AG-5, AG-6, AG-11. Anastomosis was observed only with tester isolates of AG-4 producing both C2 and C3 reactions. The hyphal diameter at the point of anastomosis was reduced, the anastomosis point was obvious, and cell death of adjacent cells was observed. These results were consistent with other reports on anastomosis reactions (1). The identification of group AG-4 within R. solani has been confirmed by electrophoretic patterns of pectic enzymes (polygalacturonases) in vertical pectin-acrylamide gel stained with ruthenium red (2). Pathogenicity tests were conducted on potted, healthy, 3-month-old seedlings of cow itch tree. Twenty plants were inoculated by placing plugs of PDA from 5-day-old mycelial cultures near the base of the stem. The same number of plants was treated with 1 cm2 PDA plugs as control. Plants were kept at 25°C and 95% relative humidity on a 12-h fluorescent light/dark regimen. Wilt symptoms due to basal stem rot, identical to ones observed in the nursery, appeared 10 days after inoculation and all inoculated plants showed symptoms within 1 month. Control plants remained healthy. The pathogen was reisolated from symptomatic tissues, completing Koch's postulates. To our knowledge, this is the first report in the world of R. solani causing disease on L. patersonii. References: (1) D. E. Carling. Page 37 in: Grouping in Rhizoctonia solani by Hyphal Anastomosis Reactions. Kluwer Academic Publishers, the Netherlands, 1996. (2) R. H. Cruickshank and G. C. Wade. Anal. Biochem. 107:177, 1980. (3) C. C. Tu and J. W. Kimbrough. Mycologia 65:941, 1973.

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First Report on Ovate-leaf Atractylodes Damping-off Caused by Fusarium oxysporum species Complex in South Korea

Plant Disease ◽

10.1094/pdis-05-21-1107-pdn ◽

2021 ◽

Author(s):

Oliul Hassan ◽

Taehyun Chang

Keyword(s):

South Korea ◽

Fusarium Oxysporum ◽

Species Complex ◽

Disease Incidence ◽

Fusarium Species ◽

Morphological Characteristics ◽

Conidial Suspension ◽

Sterile Water ◽

Damping Off ◽

First Report

In South Korea, ovate-leaf atractylodes (OLA) (Atractylodes ovata) is cultivated for herbal medicine. During May to June 2019, a disease with damping off symptoms on OLA seedlings were observed at three farmer fields in Mungyeong, South Korea. Disease incidence was estimated as approximately 20% based on calculating the proportion of symptomatic seedlings in three randomly selected fields. Six randomly selected seedlings (two from each field) showing damping off symptoms were collected. Small pieces (1 cm2) were cut from infected roots, surface-sterilized (1 minute in 0.5% sodium hypochlorite), rinsed twice with sterile water, air-dried and then plated on potato dextrose agar (PDA, Difco, and Becton Dickinson). Hyphal tips were excised and transferred to fresh PDA. Six morphologically similar isolates were obtained from six samples. Seven-day-old colonies, incubated at 25 °C in the dark on PDA, were whitish with light purple mycelia on the upper side and white with light purple at the center on the reverse side. Macroconidia were 3–5 septate, curved, both ends were pointed, and were 19.8–36.62 × 3.3–4.7 µm (n= 30). Microconidia were cylindrical or ellipsoid and 5.5–11.6 × 2.5–3.8 µm (n=30). Chlamydospores were globose and 9.6 –16.3 × 9.4 – 15.0 µm (n=30). The morphological characteristics of present isolates were comparable with that of Fusarium species (Maryani et al. 2019). Genomic DNA was extracted from 4 days old cultures of each isolate of SRRM 4.2, SRRH3, and SRRH5, EF-1α and rpb2 region were amplified using EF792 + EF829, and RPB2-5f2 + RPB2-7cr primer sets, respectively (Carbone and Kohn, 1999; O'Donnell et al. 2010) and sequenced (GenBank accession number: LC569791- LC569793 and LC600806- LC600808). BLAST query against Fusarium loci sampled and multilocus sequence typing database revealed that 99–100% identity to corresponding sequences of the F. oxysporum species complex (strain NRRL 28395 and 26379). Maximum likelihood phylogenetic analysis with MEGA v. 6.0 using the concatenated sequencing data for EF-1α and rpb2 showed that the isolates belonged to F. oxysporum species complex. Each three healthy seedlings with similar sized (big flower sabju) were grown for 20 days in a plastic pot containing autoclaved peat soil was used for pathogenicity tests. Conidial suspensions (106 conidia mL−1) of 20 days old colonies per isolate (two isolates) were prepared in sterile water. Three pots per strain were inoculated either by pouring 50 ml of the conidial suspension or by the same quantity of sterile distilled water as control. After inoculation, all pots were incubated at 25 °C with a 16-hour light/8-hour dark cycle in a growth chamber. This experiment repeated twice. Inoculated seedlings were watered twice a week. Approximately 60% of the inoculated seedlings per strain wilted after 15 days of inoculation and control seedlings remained asymptomatic. Fusarium oxysporum was successfully isolated from infected seedling and identified based on morphology and EF-1α sequences data to confirm Koch’s postulates. Fusarium oxysporum is responsible for damping-off of many plant species, including larch, tomato, melon, bean, banana, cotton, chickpea, and Arabidopsis thaliana (Fourie et al. 2011; Hassan et al.2019). To the best of our knowledge, this is the first report on damping-off of ovate-leaf atractylodes caused by F. oxysporum in South Korea. This finding provides a basis for studying the epidemic and management of the disease.

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First Report of Damping-Off on African Daisy Caused by Rhizoctonia solani AG-4 in Italy

Plant Disease ◽

10.1094/pdis-92-9-1367b ◽

2008 ◽

Vol 92 (9) ◽

pp. 1367-1367 ◽

Cited By ~ 2

Author(s):

D. Aiello ◽

I. Castello ◽

A. Vitale ◽

E. Lahoz ◽

R. Nicoletti ◽

...

Keyword(s):

Rhizoctonia Solani ◽

Morphological Characteristics ◽

Aerial Mycelium ◽

Ruthenium Red ◽

Fluorescent Light ◽

Damping Off ◽

First Report ◽

Perennial Plant ◽

Pectic Enzymes ◽

Electrophoretic Patterns

Osteospermum (African Daisy or Cape Daisy) is a genus belonging to the Calendulae with a large number of perennial plant species. In February of 2007, a severe damping-off occurred on 3- to 4-month-old potted cuttings of Osteospermum ‘Impassion Rose Purple’, ‘Impassion White’, ‘Impassion Purple’, and ‘Impassion White Rose’ cultivated in a nursery in eastern Sicily. More than 30% of the plants were infected. Disease symptoms consisted of extensive water-soaked lesions at the base of the stem followed by wilt and collapse of the plant. Isolations from diseased tissues on potato dextrose agar (PDA) amended with streptomycin sulfate at 100 mg/l consistently recovered a fungus with morphological characteristics of Rhizoctonia solani. Fungal colonies were initially white, turned brown after 2 to 3 days, and produced irregularly shaped, brown sclerotia after 1 week. Microscopic examination revealed that hyphae had right angle branching patterns, were constricted at the base of the branch near the union with main hyphae, and septate near the constriction. The number of nuclei per hyphal cell was determined on cultures grown at 25°C on 2% water agar in petri plates. Mycelium was stained with 0.5% aniline blue solution (4) and examined with a microscope at ×400. The hyphal cells were all multinucleate. Anastomosis groups were determined by pairing isolates (3) with tester isolates of AG-1 IA, AG-2-2-1, AG-2-2IIIB, AG-2-2IV, AG-3, AG-4, AG-5, AG-6, and AG-11. Anastomosis was observed only with tester isolates of AG-4, giving C2 reactions (1) at a high frequency. The identification of group AG-4 within R. solani had been obtained by electrophoretic patterns of pectic enzymes (polygalacturonases) in vertical pectin-acrylamide gel stained with ruthenium red (2). All isolates of R. solani collected from infected plants were paired in all combinations on PDA plus 1% activated charcoal and examined for somatic interaction. All paired colonies merged without producing visible tufts of aerial mycelium. Absence of tufts and the lack of formation of heterokaryon at the hyphal interaction zone indicated that all isolates belonged to the same mating type with the same mating alleles (3). Pathogenicity tests were performed by placing plugs of PDA from 5-day-old mycelial cultures in the soil near the base of the stem on 20 potted, healthy, 2-month-old cuttings of Osteospermum cv. Impassion Rose Purple. The same number of plants treated with 1/cm2 PDA plugs served as controls. Following inoculation, all plants were maintained in a growth chamber at 25°C and 95% relative humidity on a 12-h fluorescent light/dark regimen. Wilt symptoms and lesions at the base of stem identical to those observed in the nursery developed 7 days after inoculation, and all inoculated plants died within 20 days. Control plants remained symptomless. R. solani AG-4 was consistently reisolated from symptomatic tissues, completing Koch's postulates. To our knowledge, this is the first report of damping-off on the genus Osteospermum caused by R. solani. References: (1) D. E. Carling. Page 37 in: Grouping in Rhizoctonia solani by Hyphal Anastomosis Reactions. Kluwer Academic Publishers, the Netherlands, 1996. (2) R. H. Cruickshank and G. C. Wade. Anal. Biochem. 107:177, 1980. (3) M. C. Juliàn et al. Phytopathology 86:566, 1996. (4) C. C. Tu and J. W. Kimbrough. Mycologia 65:941, 1973.

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First Report of Mefenoxam Sensitivity and Pathogenicity of Phytophthora citricola Isolated from American Ginseng (Panax quinquefolium)

Plant Disease ◽

10.1094/pdis-92-12-1706a ◽

2008 ◽

Vol 92 (12) ◽

pp. 1706-1706

Author(s):

S. N. Hill ◽

O. P. Hurtado-Gonzales ◽

K. H. Lamour ◽

M. K. Hausbeck

Keyword(s):

Block Design ◽

Silica Sand ◽

Distilled Water ◽

Panax Quinquefolium ◽

Damping Off ◽

Tissue Samples ◽

First Report ◽

Zoospore Release ◽

Fluorescent Lighting

In March of 2004, stratified ginseng seeds from commercial Wisconsin gardens were planted in sterilized silica sand in a research greenhouse at Michigan State University. Following emergence, seedlings exhibiting wilting, damping off, and black stem lesions were observed. In the laboratory, symptomatic seedlings were rinsed with distilled water. Tissue samples were excised and embedded in water agar amended with ampicillin (100 mg/liter) and incubated at 25°C. In addition to the isolation of Phytophthora cactorum, a known pathogen of ginseng, P. citricola, (five isolates) also was identified from single-zoospore cultures based on morphology (2). One-week-old, dilute V8 agar cultures were used to obtain single zoospores. Cultures were flooded with 20 ml of sterilized distilled water chilled to 10°C and incubated at 25°C for 25 min to induce zoospore release. Zoospore suspensions were spread onto water agar plates, and after 24 h at 25°C, single germinating zoospores were selected at random and transferred to benomyl, ampicillin, rifampicin, and pentachloronitrobenzene (BARP)-amended V8 agar plates. Sequence analysis of the internal transcribed spacer (ITS) region 1 and 2 of the rDNA was also used to distinguish P. citricola from P. cactorum. A representative sequence for the isolates of P. citricola (NCBI Accession No. FJ217388) matched (100% similarity) a P. citricola isolate deposited in GenBank (Accession No. DQ486661). To screen P. citricola for in vitro response to mefenoxam, agar plugs (7-mm diameter) from 1-week-old V8 agar cultures incubated at 25°C under fluorescent lighting were placed in the center of each of two V8 agar plates amended with 0 and 100 ppm of mefenoxam (Ridomil Gold EC, 48% a.i., suspended in sterile distilled water and added to V8 agar cooled to 49°C). The plates were incubated at 25°C for 3 days under fluorescent lighting. Isolates were assigned a mefenoxam sensitivity rating based on the percentage of radial mycelial growth on the amended V8 agar when compared with the unamended control. Each of the five isolates was scored as mefenoxam resistant with growth on 100-ppm plates >30% of the controls. Koch's postulates were conducted for the isolates of P. citricola recovered from ginseng seedlings to confirm pathogenicity. Previously, P. citricola was reported as nonpathogenic to ginseng (1). Three-week-old, healthy ginseng seedlings were planted into 89- × 64-mm pots filled with autoclaved medium-particle vermiculite and maintained in the greenhouse under 63% shade cloth with temperatures between 18 and 26°C. Pots were arranged in a completely randomized block design with eight seedlings per isolate as replicates and watered as needed. A 2-ml inoculum suspension (approximately 104 zoospores) was injected into the potting medium at the stem base of each seedling. All of the isolates were pathogenic to ginseng seedlings with 60% of inoculated seedlings per isolate exhibiting wilting, damping off, and blackened stems within 3 weeks after inoculation. P. citricola was reisolated from all inoculated plants. To our knowledge, this is the first report of P. citricola pathogenic on ginseng. References: (1) T. W. Darmono et al. Plant Dis. 75:610, 1991. (2) D. C. Erwin and O. K. Ribeiro. Page 96 in: Phytophthora Diseases Worldwide. The American Phytopathological Society, St. Paul, MN. 1996.

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First Report of Damping-Off Caused by Pythium arrhenomanes on Rice in China

Plant Disease ◽

10.1094/pdis-01-18-0113-pdn ◽

2018 ◽

Vol 102 (11) ◽

pp. 2382 ◽

Cited By ~ 1

Author(s):

Y. Ling ◽

J. Xia ◽

K. Koji ◽

X. Zhang ◽

Z. Li

Keyword(s):

Damping Off ◽

First Report ◽

Pythium Arrhenomanes

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First Report of Seedling Blight Caused by Sclerotium rolfsii on Wheat in Oklahoma

Plant Disease ◽

10.1094/pd-90-0686b ◽

2006 ◽

Vol 90 (5) ◽

pp. 686-686 ◽

Cited By ~ 1

Author(s):

V. Choppakatla ◽

R. M. Hunger ◽

H. A. Melouk

Keyword(s):

Filter Paper ◽

Sclerotium Rolfsii ◽

Significant Risk ◽

Triticum Aestivum L ◽

The United States ◽

Damping Off ◽

Wheat Seedlings ◽

First Report ◽

Significant Difference ◽

Pure Cultures

Wheat (Triticum aestivum L.) is an important crop in Oklahoma and throughout the Central Plains of the United States. The soilborne fungus, Sclerotium rolfsii, is a major pathogen on peanut (Arachis hypogaea L.) but is not known to cause major damage on wheat. During September of 1998, damping-off and rotting of young wheat seedlings were observed in breeder plots in Payne County, OK. The occurrence of symptoms was sporadic with an estimated stand reduction of 10 to 15%. Symptomatic plants were collected from the field and brought to the laboratory. Sclerotia-like bodies from the symptomatic plants were surface disinfested in aqueous 1% NaOCl for 2 min and allowed to germinate at 25 ± 2°C on sterile filter paper moistened with a 1% aqueous solution of methanol. Aerial mycelia from germinating sclerotia were transferred to potato dextrose agar amended with 100 ppm of streptomycin (SPDA) to obtain pure cultures. Pure cultures had coarse, white mycelium distinctive of S. rolfsii and produced very small (0.05 to 0.1 mm), abundant, round, brown sclerotia on the surface of the medium after 15 days of incubation. Pathogenicity was tested on three hard red winter wheat cultivars commonly grown in Oklahoma (Jagger, 2137, and 2174). Four plants of each cultivar were inoculated at the two-leaf stage (Feekes' scale stage 1) by placing a 0.5-cm agar disk removed from a 3-day-old culture onto a 1-cm diameter filter paper that was then pressed to the base of the shoot. Noninoculated plants were used as a control. After inoculation, pots were covered with polyethylene sheets to maintain 95 to 100% relative humidity and incubated at 25 ± 2°C in the greenhouse. Lesions were initially superficial, yellowish, and water soaked. Lesions expanded and resulted in damping-off of seedlings. Noninoculated plants were free of disease and remained healthy. No significant difference (P ≤ 0.05) in disease severity was observed among the cultivars. To fulfill Koch's postulates, the fungus was reisolated onto SPDA where it had the same characteristics as the initial culture. To our knowledge, this is the first report of S. rolfsii on wheat in Oklahoma. Even though S. rolfsii is not expected to pose a significant risk to wheat production, infection of wheat may enhance survival of S. rolfsii and facilitate infection and losses in a following peanut crop. This is especially important in certain areas of Oklahoma where a wheat-peanut rotation is occasionally practiced.

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First Report of Pythium debaryanum Causing Chili Damping Off in Pakistan

Plant Disease ◽

10.1094/pdis-08-16-1209-pdn ◽

2017 ◽

Vol 101 (2) ◽

pp. 391-391

Author(s):

A. A. Shahid ◽

M. Ali ◽

S. Ali

Keyword(s):

Damping Off ◽

First Report

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