First Report of Pythium Root Rot of Rau Ram (Polygonum odoratum)

Polygonum odoratum (= Persicaria odorata), known as rau ram or sang hum, is native to southeastern Asia and is a common herb in Vietnamese cuisine (1). It has been studied most extensively for its aromatic compound content (2). In Florida, rau ram commonly is grown hydroponically in greenhouses using large, cement beds with recirculated water. The plants form dense mats from which new growth is trimmed for market. During January of 2002, a severe dieback was observed in one production house in Saint Lucie County, FL. Plants with less severe symptoms were yellowed and stunted. Roots of symptomatic plants were largely decayed with root symptoms beginning as a tip necrosis. The cortex of severely affected roots slipped off easily, leaving a stringy vascular system. Plating of symptomatic tissue from 20 randomly selected plant samples was performed with multiple general and selective media including potato dextrose agar, corn meal agar with pimaricin, ampicillin, rifampicin, and pentachloronitrobenzene (PARP) (3). All colonies produced were identified as Pythium helicoides Drechsler on the basis of sporangial, oogonial, and antheridial characteristics (4). Isolates had proliferous, obovoid, papillate sporangia, and were homothallic with smooth-walled oogonia and thick-walled, aplerotic oospores. Multiple antheridial attachments per oogonium were common with the antheridium attached along its entire length. Pathogenicity tests were conducted using P. odoratum plants grown from commercial transplants. Two tests were performed. Each test was conducted using eight inoculated and eight control plants. In the first test, plants were maintained in 10-cm pots immersed in sterilized pond water for the duration of the test. Plants were inoculated with five 7- × 70-mm sections of freshly growing mycelial culture per plant using 10-day-old cultures of Pythium helicoides grown on water agar. Chlorosis was observed at approximately 2 months after inoculation. Root necrosis was observed in inoculated plants approximately 5 months after inoculation. This test was performed in the greenhouse with temperatures ranging from 20 to 30°C. The second test was performed in growth chambers at 35 to 40°C. Plants were maintained in 10-cm pots immersed in Hoagland's solution and were inoculated with four 6-mm plugs per plant. Symptoms were observed on inoculated plants at this temperature within 1 week of inoculation. No chlorosis or root decay was observed in noninoculated, immersed plants. The pathogen was reisolated from inoculated, symptomatic tissue. To our knowledge, this is the first report of root rot of P. odoratum caused by Pythium helicoides. References: (1) R. E. Bond. Herbarist 55:34, 1989. (2) N. X. Dung et al. J. Essent. Oil Res. 7:339, 1995. (3) M. E. Kannwischer and D. J. Mitchell. Phytopathology 68:1760, 1978. (4) A. J. van der Plaats-Niterink. Monograph of the Genus Pythium. Vol. 21, Studies in Mycology. Centraalbureau voor Schimmelcutltures, Baarn, The Netherlands, 1981.

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First Report of Hypocotyl and Root Rot Disease Caused by Pythium deliense on Soybean Sprouts in Korea

Plant Disease ◽

10.1094/pdis.2003.87.11.1399b ◽

2003 ◽

Vol 87 (11) ◽

pp. 1399-1399 ◽

Cited By ~ 1

Author(s):

S.-C. Yun ◽

J.-W. Kim

Keyword(s):

Root Rot ◽

Production Systems ◽

Brown Rot ◽

Centraalbureau Voor ◽

First Report ◽

Root Rot Disease ◽

Soybean Sprouts ◽

Pathogenicity Tests ◽

Genus Pythium ◽

Rot Disease

Soybean (Glycine max Merr.) sprouts have been a traditional Korean food for at least 1,000 years. During the summers of 2000 and 2001, severe hypocotyl and root rot occurred on fully grown soybean sprouts, especially in commercial recirculating mass production systems. Brown rot on water-soaked hypocotyls and roots of soybean sprouts caused a 10 to 20% loss in production yield. To investigate the cause, 180 sections of tissue were surface sterilized for 30 s in 75% ethanol and plated on potato dextrose agar (PDA). A fungus with white, aerial mycelia and cultural characteristics of Pythium sp. was isolated consistently. The fungal isolates were identified as Pythium deliense Meurs based on various mycological characteristics (2) on corn meal agar (CMA) and sucrose-asparagine bentgrass leaf culture medium (1). P. deliense oogonia were spherical, smooth, 19 to 23 μm in diameter, and their stalks bent toward the antheridia. The antheridia were the shape of a straw hat, curved club-shaped, terminal or intercalary, monoclinous, occasionally diclinous, 12 to 15 × 8 to 11 μm, and 1 per oogonium (2). In pathogenicity tests, soybean sprouts and the fungus were cultured simultaneously in containers (30 × 30 × 50 cm [W × L × H]) with a daily 3-h showering period at 25°C. There were 8,000 to 10,000 seeds per container inoculated with four plugs of agar inoculum (2 × 2 cm). Inoculum was prepared from 5-day-old fungal cultures grown on PDA. After 6 days, the inoculated soybean sprouts showed the same symptoms as described above, whereas the noninoculated sprouts remained healthy. The fungal pathogen was reisolated from all the inoculated sprouts. P. deliense has never been reported as a pathogen of soybean sprouts. To our knowledge, this is the first report of hypocotyl and root rot disease caused by Pythium deliense on soybean sprout in Korea. References: (1) J.-W. Kim and E.-W. Park. Kor. J. Mycology 25:276, 1997. (2) A. J. Van der Plaatis-Niterink. Monograph of the genus Pythium. Vol. 21, Studies in Mycology. Centraalbureau voor Schimmelcultures, Inst. R. Neth. Acad. Sci. Lett. The Netherlands, 1981.

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First Report of Fusarium stem and root rot of Gerbera jamesonii caused by Fusarium incarnatum in China

Plant Disease ◽

10.1094/pdis-02-21-0440-pdn ◽

2021 ◽

Author(s):

Shuning Chen ◽

Wei Sun ◽

Huizhu Yuan ◽

Xiaojing Yan

Keyword(s):

Root Rot ◽

Vascular System ◽

Elongation Factor ◽

Morphological Observation ◽

Conidial Suspension ◽

Gerbera Jamesonii ◽

Gene Sequences ◽

Plastic Container ◽

First Report ◽

Brown Discoloration

Gerbera (Gerbera jamesonii Bolus) is an important cut flower grown globally. In 2020, gerbera plants (Redaicaoyuan, Baimawangzi, and Hongditan cultivars) with roots, crowns, and stems rot were found in a greenhouse in Nanping, Fujian, China. Approximately 30% of the 60,000 plants showed symptoms. Diseased plants were stunted with chlorotic leaves. The leaves and flower heads were wilted and withered. Brown discoloration with red to black streaks occurred in the vascular system of the crown and stem. The stem pieces (3×3 mm) showing the symptom were surface-disinfected with 1% NaClO for 1 min and washed three times with sterilized water. The stem pieces were then dried and placed on potato dextrose agar (PDA) at 25℃ inside a dark chamber. Ten single-spored isolates were identified as Fusarium incarnatum based on morphological features. White to light brown mycelia were observed among the isolates on PDA medium. Falculate, multicelluar, straight to slightly curved macroconidia produced in monophialide sporodochia without distinctive foot shaped basal cell; and chlamydospores produced in some isolates (Leslie and Summerell). The size of macroconidia was 36.4 ± 5.20 × 4.6 ± 1.3 μm (n = 100) with 3 to 5 septates. Microconidia were mostly 0 to 1 septate measured 14.6 ± 1.9 × 2.6 ± 0.5 μm (n=100). Based on the morphological observation, isolates were further identified by molecular method. The ITS1/4 region combined with partial gene fragments of translation elongation factor (EF-1α, primer EF1/EF2, Geiser et al.) and calmodulin (CAM, primer CL1/CL2A, O’Donnell.) from the isolates were amplified and sequenced. All of the three tested isolates showed identical gene sequences. Sequences amplified from one represented isolate FIN-1 were submitted to Genbank. BLAST searches revealed that ITS1/4 (MW527088), EF-1α (MW556488), and CAM (MW556487) had 99.22%, 99.53%, 99.42% identity compared to F. incarnatum (MN480497, MN233577, and LN901596, respectively) in GenBank. FUSARIUM-ID (Geiser et al. 2004) analysis also showed 99 to 100% similarity with sequences of the F. incarnatum-equiseti species complex (FIESC) (FD_01636 for CAM, FD_01643 for EF-1α). The phylogenetic analysis was conducted using neighbor-joining algorithm based on the ITS, EF-1α, and CAM gene sequences. The isolate was clustered with F. incarnatum clade. Then, the pathogenicity of the fungus was confirmed by performing Koch’s postulates. Pure single-spored cultures were grown on carboxymethyl-cellulose (CMC) medium for sporulation. G. jamesonii plants used for pathogenicity tests were grown on sterilized potting soil in a plastic container to the ten-leaf stage prior to inoculation. Spores harvested from the CMC medium were adjusted to a concentration of 1×105 conidial/ml. Twelve healthy rooted gerbera seedlings were inoculated by drenching 10 ml of the conidial suspension onto roots. Twelve gerbera seedlings treated with 10 ml sterile water served as control treatments. Plants were grown in the glasshouse at temperatures of 23°C, relative humidity >70%, and 16 h light per day. After 10 days, blackening stems and withered leaf edges began to appear on inoculated seedlings, whereas control seedlings remained healthy. F. incarnatum was consistently re-isolated from the symptomatic stems, whereas no isolates were obtained from the control seedlings. The assay was conducted twice. To the best of our knowledge, this is the first report of F. incarnatum causing stem and root rot on G. jamesonii.

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First Report of Stem Blight Caused by Calonectria colhounii (Anamorph Cylindrocladium colhounii) on Greenhouse-Grown Blueberries in the United States

Plant Disease ◽

10.1094/pdis-02-11-0117 ◽

2011 ◽

Vol 95 (9) ◽

pp. 1187-1187

Author(s):

J. J. Sadowsky ◽

T. D. Miles ◽

A. M. C. Schilder

Keyword(s):

United States ◽

North Carolina ◽

Root Rot ◽

The United States ◽

Vaccinium Corymbosum ◽

Conidial Suspension ◽

Centraalbureau Voor ◽

First Report ◽

Stem Lesions ◽

Β Tubulin

Necrotic stems and leaves were observed on 2- to 4-month-old, rooted microshoot plants (Vaccinium corymbosum L. ‘Liberty’ and ‘Bluecrop’, V. angustifolium Aiton ‘Putte’, and V. corymbosum × V. angustifolium ‘Polaris’) in a Michigan greenhouse in 2008 and 2009. As the disease progressed, leaves fell off and 80 to 100% of the plants died in some cases. Root rot symptoms were also observed. A fungus was isolated from stem lesions. On potato dextrose agar (PDA), cultures first appeared light tan to orange, then rusty brown and zonate with irregular margins. Chains of orange-brown chlamydospores were abundant in the medium. Macroconidiophores were penicillately branched and had a stipe extension of 220 to 275 × 2.5 μm with a narrowly clavate vesicle, 3 to 4 μm wide at the tip. Conidia were hyaline and cylindrical with rounded ends, (1-)3-septate, 48 to 73 × 5 to 7 (average 60 × 5.5) μm and were held together in parallel clusters. Perithecia were globose to subglobose, yellow, 290 to 320 μm high, and 255 to 295 μm in diameter. Ascospores were hyaline, 2- to 3-septate, guttulate, fusoid with rounded ends, slightly curved, and 30 to 88 × 5 to 7.5 (average 57 × 5.3) μm. On the basis of morphology, the fungus was identified as Calonectria colhounii Peerally (anamorph Cylindrocladium colhounii Peerally) (1,2). The internal transcribed spacer region (ITS1 and ITS2) of the ribosomal DNA and the β-tubulin gene were sequenced (GenBank Accession Nos. HQ909028 and JF826867, respectively) and compared with existing sequences using BLASTn. The ITS sequence shared 99% maximum identity with that of Ca. colhounii CBS 293.79 (GQ280565) from Java, Indonesia, and the β-tubulin sequence shared 97% maximum identity with that of Ca. colhounii CBS 114036 (DQ190560) isolated from leaf spots on Rhododendron sp. in North Carolina. The isolate was submitted to the Centraalbureau voor Schimmelcultures in the Netherlands (CBS 129628). To confirm pathogenicity, 5 ml of a conidial suspension (1 × 105/ml) were applied as a foliar spray or soil drench to four healthy ‘Bluecrop’ plants each in 10-cm plastic pots. Two water-sprayed and two water-drenched plants served as controls. Plants were misted intermittently for 2 days after inoculation. After 7 days at 25 ± 3°C, drench-inoculated plants developed necrotic, sporulating stem lesions at the soil line, while spray-inoculated plants showed reddish brown leaf and stem lesions. At 28 days, three drench-inoculated and one spray-inoculated plant had died, while others showed stem necrosis and wilting. No symptoms were observed on control plants. Fungal colonies reisolated from surface-disinfested symptomatic stem, leaf, and root segments appeared identical to the original isolate. Cy. colhounii was reported to cause a leaf spot on blueberry plants in nurseries in China (3), while Ca. crotalariae (Loos) D.K. Bell & Sobers (= Ca. ilicicola Boedijn & Reitsma) causes stem and root rot of blueberries in North Carolina (4). To our knowledge, this is the first report of Ca. colhounii causing a disease of blueberry in Michigan or the United States. Because of its destructive potential, this pathogen may pose a significant threat in blueberry nurseries. References: (1) P. W. Crous. Taxonomy and Pathology of Cylindrocladium (Calonectria) and Allied Genera. The American Phytopathological Society, St. Paul, MN, 2002. (2) L. Lombard et al. Stud. Mycol. 66:31, 2010. (3) Y. S. Luan et al. Plant Dis. 90:1553, 2006. (4) R. D. Milholland. Phytopathology 64:831, 1974.

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First Report of Root Rot of Soybeans Caused by Corynespora cassiicola in Wisconsin

Plant Disease ◽

10.1094/pdis.1999.83.7.696b ◽

1999 ◽

Vol 83 (7) ◽

pp. 696-696 ◽

Cited By ~ 5

Author(s):

S. J. Raffel ◽

E. R. Kazmar ◽

R. Winberg ◽

E. S. Oplinger ◽

J. Handelsman ◽

...

Keyword(s):

Root Rot ◽

Growth Stage ◽

Lateral Roots ◽

Seedling Emergence ◽

Fluorescent Light ◽

Corynespora Cassiicola ◽

First Report ◽

Seedling Roots ◽

Symptomatic Tissue ◽

Soybean Plants

Corynespora cassiicola (Berk. & M. A. Curtis) C. T. Wei was isolated from diseased soybean plants (Glycine max) collected in two fields near Racine and Arlington, WI. Plants sampled at seedling emergence (VC), late vegetative (V5), and mid-reproductive (R5) stages exhibited reddish to dark brown longitudinal lesions on the exterior of the tap root extending vertically on the hypocotyl to the soil line, and extensive necrosis of lateral roots. Sample size at each growth stage was 144 plants per site. Roots were surface sterilized in 0.5% sodium hypochlorite for 2 min and sections of symptomatic tissue placed on water agar (12 g/liter) containing 100 μg of streptomycin per ml. Sporulation occurred on lesions and on mycelium that had grown out from the plant tissue onto the water agar following a 2-week incubation at 24°C under fluorescent light (280 μmol s-1 m-2). Incidence of isolation of C. cassiicola at both sites was 40% of plants sampled at growth stage VC, 67% at V5, and 78% at R5. Conidia characteristic of C. cassiicola were particularly abundant on the surface of necrotic lateral root tissue. Elongated conidia produced on water agar were 151 ± 5 μm × 15 ± 0.5 μm with an average of 13 ± 0.4 cells separated by hyaline pseudosepta (1). To confirm pathogenicity, a 1-cm lateral slice into each of four 5-day-old soybean seedling roots was made and a plug of agar taken from the margin of a colony of C. cassiicola grown on potato dextrose agar was placed in each wound and incubated for 14 days at 24°C in a growth chamber. Symptoms similar to those of diseased field plants were observed and C. cassiicola was reisolated from all plants inoculated with C. cassiicola; all controls treated with agar alone had no symptoms and C. cassiicola was recovered from none of the noninoculated controls. This is the first report of root rot caused by C. cassiicola on soybean in Wisconsin. Reference: (1) W. L. Seaman and R. A. Shoemaker. Can. J. Bot. 43:1461, 1965.

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First Report of Crown and Root Rot Caused by Rhizoctonia solani AG-4 on Banana Passionflower (Passiflora mollissima) in Italy

Plant Disease ◽

10.1094/pdis-05-11-0411 ◽

2011 ◽

Vol 95 (9) ◽

pp. 1194-1194 ◽

Cited By ~ 2

Author(s):

G. Polizzi ◽

D. Aiello ◽

V. Guarnaccia ◽

A. Panebianco ◽

P. T. Formica

Keyword(s):

Rhizoctonia Solani ◽

Root Rot ◽

Disease Incidence ◽

Morphological Characteristics ◽

Fluorescent Light ◽

Disease Symptoms ◽

First Report ◽

Pathogenicity Tests ◽

Crown And Root Rot ◽

Safranin O

The genus Passiflora (Passifloraceae family) contains more than 500 species and several hybrids. In Italy, some of these species and hybrids are grown as ornamental evergreen vines or shrubs. During August and September 2010, a crown and root rot was observed in a stock of approximately 6,000 potted 2-year-old plants of Passiflora mollissima (Kunth) Bailey, commonly known as the banana passionflower, in a nursery located in eastern Sicily (southern Italy). Disease incidence was approximately 20%. Disease symptoms consisted of water-soaked lesions at the crown and a root rot. Successively, older crown lesions turned light brown to brown and expanded to girdle the stem. As crown and root rot progressed, basal leaves turned yellow and gradually became necrotic and infected plants wilted and died. A fungus with mycelial and morphological characteristics of Rhizoctonia solani Kühn was consistently isolated from crown lesions and brown decaying roots 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 with a slight constriction at the branch base. Hyphal cells removed from 10 representative 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 on 2% water agar in petri plates (4). Pairings were made with tester strains of AG-1, AG-2, AG-3, AG-4, AG-5, AG-6, and AG-11. Anastomosis was observed only with tester isolates of AG-4 (3). Pathogenicity tests were performed on container-grown, healthy, 3-month-old cuttings. Twenty plants of P. mollissima were inoculated near the base of the stem with five 1-cm2 PDA plugs from 5-day-old mycelial plugs obtained from two representative cultures. The same number of plants served as uninoculated controls. Plants were maintained at 25°C and 95% relative humidity with a 12-h fluorescent light/dark regimen. Wilt symptoms due to crown and root rot, identical to ones observed in the nursery, appeared 7 to 8 days after inoculation with either of the two isolates and all plants died within 20 days. No disease was observed on control plants. R. solani AG-4 was reisolated from symptomatic tissues and identified as previously described, confirming its pathogenicity. Damping-off or crown and root rot due to R. solani were previously detected on P. edulis in Brazil, Africa, India, Oceania, and Australia (2). To our knowledge, this is the first report of R. solani causing crown and root rot on P. mollissima. References: (1) R. J. Bandoni. Mycologia 71:873, 1979. (2) J. L. Bezerra and M. L. Oliveira. Fitopathol. Brasil. 9:273, 1984. (3) D. E. Carling. Page 37 in: Grouping in Rhizoctonia solani by Hyphal Anastomosis Reactions. Kluwer Academic Publishers, the Netherlands, 1996. (4) C. C. Tu and J. W. Kimbrough. Mycologia 65:941, 1973.

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First Report of Rhizoctonia solani Causing a Disease of Sunflower in India

Plant Disease ◽

10.1094/pdis-94-4-0488c ◽

2010 ◽

Vol 94 (4) ◽

pp. 488-488 ◽

Cited By ~ 5

Author(s):

K. Srinivasan ◽

S. Visalakchi

Keyword(s):

Rhizoctonia Solani ◽

Root Rot ◽

Crown Rot ◽

Pathogenicity Test ◽

American Phytopathological Society ◽

First Report ◽

Leaf Yellowing ◽

Crown Tissue ◽

Symptomatic Tissue ◽

White Mycelium

During the spring of 2009, symptoms including leaf yellowing and wilting, root rot, and death of plants were noted in sunflower (Helianthus annuus L.) crops in Dharmapuri District, Tamilnadu, India. In some fields, approximately 30% of the plants were affected. The disease began when plants were approximately 10 weeks old and occurred on scattered or adjacent plants. The presence of white mycelium was observed on necrotic crowns. Symptomatic tissue was surface disinfested in 70% alcohol for 30 s and 0.5% sodium hypochlorite for 1 min and plated onto potato dextrose agar (PDA) (1). One isolate (coded SV001) had near right-angle branching with basal constriction and adjacent septa and sclerotia typical of Rhizoctonia spp. (2). Cream-colored colonies produced irregular, light brown sclerotia that were 3.0 to 7.3 mm (average 3.8 mm) in diameter. Hyphae were 6.8 to 7.0 μm (average 6.9 μm) wide and multinucleate (8 to 15 nuclei per cell). On the basis of hyphal anastomosis with several known AG testers, the fungus was characterized as Rhizoctonia solani Kühn AG-IV (3). One culture was deposited at the Madras University Botany Laboratory, Center for Advanced Studies in Botany, University of Madras, Chennai, India. In a pathogenicity test, R. solani SV001 was grown on PDA for 5 days at 24°C in the dark. Five-millimeter-diameter disks were placed at the base of sunflower plants (cv. Mordan). Four sunflower plants in each of three pots were inoculated; noninoculated plants served as controls. Plants were placed in a glasshouse maintained at 25 to 27°C. Inoculated plants developed yellow foliage and crown rot and root rot symptoms after 7 to 12 days and died in 17 to 20 days. No symptoms were observed on noninoculated plants. The pathogen was reisolated from fragments of necrotic crown tissue of inoculated plants. To our knowledge, this is the first report of R. solani AG-IV causing a disease of sunflower plants in India. References: (1). R. C. Fenille et al. Plant Pathol. 54:325, 2005. (2). J. R. Parmeter et al. Phytopathology 59:1270, 1969. (3) B. Sneh et al. Identification of Rhizoctonia Species. The American Phytopathological Society, St Paul, MN, 1991.

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First Report of Damping-Off and Leaf Spot Caused by Cylindrocladium scoparium on Different Accessions of Bottlebrush Cuttings in Italy

Plant Disease ◽

10.1094/pdis-91-6-0769b ◽

2007 ◽

Vol 91 (6) ◽

pp. 769-769 ◽

Cited By ~ 6

Author(s):

G. Polizzi ◽

A. Vitale ◽

D. Aiello ◽

M. A. Dimartino ◽

G. Parlavecchio

Keyword(s):

South African ◽

Root Rot ◽

Severe Disease ◽

Damping Off ◽

Single Spore ◽

Centraalbureau Voor ◽

First Report ◽

Leaf Spots ◽

Plastic Bags ◽

Collar And Root Rot

In May of 2006, approximately 10,000 cuttings of bottlebrushes (Callistemon cvs. Laevis, Hannah Ray, Kings Park Special, Masotti Mini Red, and Rose Opal with either C. viminalis (Soland. ex Gaertn.) Cheel. [excluded] or C. citrinus (Curtis) Skeels as one parent) grown in a nursery in eastern Sicily (Italy) exhibited severe disease symptoms including damping-off, leaf spots, and collar and root rot. Initially, the infections were detected on approximately 30% of the cuttings, but by late September 2006, 70% of the plants had symptoms. A Cylindrocladium sp. was consistently isolated from the diseased portions of plants onto potato dextrose agar. To determine the species, single-conidial isolates of the fungus were cultured on carnation leaf agar (CLA) for 7 days at 25°C with 12 h of light/dark conditions. Only the mycelia and spores growing on the carnation leaves were examined with a light microscope, and the isolates were identified as Cylindrocladium scoparium Morgan (teleomorph Calonectria morganii Crous, Alfenas & M.J. Wingf.) on the basis of their pyriform to broadly ellipsoidal terminal vesicles, conidiophore branching pattern, and conidia (1). In addition, the ability of the colonies to mate with South African tester strains of C. scoparium (2,3) confirmed the identification. Koch's postulates were fulfilled by inoculating 10 cuttings for each bottlebrush accession with a spore suspension (105 conidia per ml) of one isolate of the pathogen (DISTEF-GCs7) obtained from 14-day-old single-spore colonies grown on CLA at 24°C under fluorescent cool white lights with 12 h of light/dark. Following inoculation, all plants were maintained in plastic bags in a growth chamber at 25 ± 1°C and 90 to 95% relative humidity. The same number of cuttings was used as a control. Damping-off, crown root rot, and leaf spots symptoms identical to those observed in the nursery appeared within 5 to 20 days. No symptoms were detected on the control plants. C. scoparium was reisolated from the artificially infected tissues. The isolate, used in the pathogenicity proof, was deposited at the Fungal Biodiversity Centre, Centraalbureau voor Schimmelcultures (Accession No. CBS 120930). The presence of C. scoparium was detected for the first time in Italy on mastic tree in 2005 (3). To our knowledge, this is the first report of C. scoparium on bottlebrush in Italy and it represents the first information about the susceptibility of these Callistemon cultivar accessions to the fungus and confirms the spread of the pathogen in Sicilian ornamental nurseries. References: (1) P. W. Crous. Taxonomy and Pathology of Cylindrocladium (Calonectria) and Allied Genera. The American Phytopathological Society, St. Paul MN, 2002. (2) P. W. Crous and M. J. Wingfield. Mycotaxon 51:341, 1994. (3) G. Polizzi et al. Plant Dis. 90:1110, 2006.

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First Report of Phytophthora cinnamomi Root Rot, Stem, and Leaf Blight on Ivy

Plant Disease ◽

10.1094/pdis.1997.81.8.960c ◽

1997 ◽

Vol 81 (8) ◽

pp. 960-960 ◽

Cited By ~ 3

Author(s):

K. Thinggaard ◽

B. Toppe

Keyword(s):

Nutrient Solution ◽

Root Rot ◽

Phytophthora Cinnamomi ◽

Pond Water ◽

Pathogenicity Test ◽

Hedera Helix ◽

Cedrus Deodara ◽

First Report ◽

Stems And Leaves ◽

Pot Plants

Phytophthora cinnamomi was isolated from varieties of Hedera helix pot plants in 1989 in two Danish greenhouse nurseries. The symptoms were brown, rotten roots and stems, and brown areas developing from the base of the leaves. The fungus was isolated directly from roots, stems, leaves, and soil, and by baiting the nutrient solutions of the watering systems with needles of Cedrus deodara. The fungus was isolated on Phytophthora selective agar medium containing hymexazol and identified with the keys of Kröber (1) and Stamps et al. (2). The fungus was characterized by coralloid hyphal swellings, chlamydospores, lack of oogonia in single culture, and production of numerous, ovoid sporangia with a nonpapillate, wide pore. The sporangia produced many zoospores after 2 days flooding with autoclaved pond water on V8 juice agar, followed by internal proliferation. The fungus was also isolated in Norway in 1993 from ivy pot plants. The fungus was widespread in Danish and Norwegian pot plant nurseries in 1997 and caused losses in most varieties, especially at temperatures above 23°C. Effective fungicides are not available for use in Denmark and the disease is easily spread with cuttings, and through the watering system with recirculation of the nutrient solution. A Danish isolate of P. cinnamomi originating from roots of H. helix was used in a pathogenicity test. Five-week-old cuttings were inoculated by adding zoospores (5 per ml) to the recirculating nutrient solution. Control plants were on a separate bench with nutrient solution without the fungus. After 1 week, symptoms of root rot were observed, and 2 weeks after inoculation, 75% of plants expressed severe symptoms on roots, stems, and leaves. P. cinnamomi was reisolated from roots, stems, and leaves of diseased plants, but was not isolated from the control plants. The reisolate was morphologically identical to the original isolate. This is the first report of P. cinnamomi from ivy in Europe. References: (1) H. Kröber. Mitt. Biol. Bundesanst. Land Forstwirtsch. Berlin-Dahlem 225:73, 1985. (2) D. J. Stamps et al. 1990. Mycol. Pap. No. 162. CAB Int. Mycol. Inst., Kew, England.

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First Report of Cucumber Black Root Rot Caused by Phomopsis sclerotioides in Italy

Plant Disease ◽

10.1094/pdis.2004.88.4.425a ◽

2004 ◽

Vol 88 (4) ◽

pp. 425-425 ◽

Cited By ~ 6

Author(s):

C. Cappelli ◽

V. M. Stravato ◽

G. Carannante ◽

R. Parisella

Keyword(s):

Root Rot ◽

Management Practices ◽

Central Italy ◽

Economic Losses ◽

Test Plant ◽

Infested Soil ◽

Centraalbureau Voor ◽

Black Root Rot ◽

First Report ◽

Phomopsis Sclerotioides

During April 2002 to September 2003 in unheated plastic greenhouses located in Fondi and Sperlonga (Latium Region of central Italy), in which more than 100 ha of cucumber (Cucumis sativus L.) were cultivated, an unusual disease causing decay of roots and plant wilting was observed. Many of the most common cultivars showed susceptibility, and in some farms, severe economic losses occurred. Disease symptoms observed on young plants included stunting, wilting, black root rot, and marked reduction of root development where pseudosclerotial structures were produced. The degree of root symptoms was proportional to the wilting. During periods of high evapotranspiration, wilting was severe in plants at the early stages of disease development, and even lightly infected plants wilted rapidly. Symptoms resembled those caused by vascular wilt fungi and were generally more severe in greenhouses with poorly drained soils. Samples from each of four greenhouses were collected during different periods of the growing season. Each sampling unit consisted of five to eight root pieces that were surface disinfected in 0.1% HgCl2 for 30 s, rinsed in sterile water, placed on petri dishes containing potato dextrose agar (pH 5.5), and incubated for 7 days at 25°C. Phomopsis sclerotioides van Kesteren (1,2) (identification confirmed by R. A. Samson, Centraalbureau voor Schimmelcultures of Utrecht, the Netherlands) was consistently recovered from affected tissues. Subcultures of three isolates were prepared and evaluated for pathogenicity. The experiments were conducted in a greenhouse with a 12-h photoperiod at 25 to 32°C. Seven-week-old seedlings (20 representatives per isolate) of a susceptible hybrid were dipped for 2 min in an agar slurry suspension of the pathogen and then returned to pots. Within 4 to 5 weeks after inoculation, all plants inoculated with each P. sclerotioides isolate showed the same symptoms observed in the field and caused wilting and death of approximately 80% of the inoculated plants. P. sclerotioides was consistently reisolated from the symptomatic test plant, whereas the fungus was never isolated from control plants. Another experiment using naturally infested soil in comparison with sterilized soil confirmed the soilborne nature of the fungus and its pathogenicity. To our knowledge, this is the first report of P. sclerotioides on cucumber in Italy. According to the experience of farmers and agricultural consultants, the disease was first observed in the last 3 to 4 years in unheated plastic greenhouses. However, we cannot exclude the possibility that the disease may have been present in central Italy prior to our observations, since it can be misdiagnosed and the symptoms can be masked by symptoms of other diseases. For these reasons, an accurate monitoring of the pathogen is necessary to determine the magnitude of the problem and its impact on the industry. Management practices that include long-term crop rotation with nonsusceptible hosts, removal and destruction of infected crop debris, and steam soil sterilization are suggested to reduce the economic losses. References: (1) E. Punithalingam et al. No. 461 in: Descriptions of Pathogenic Fungi and Bacteria. CMI, Kew, Surrey, U.K., 1975. (2) H. A. Van Kesteren. Neth. J. Plant Pathol. 73:112, 1967.

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First Report of Root Rot Caused by Pythium spiculum Affecting Cork Oaks at Doñana Biological Reserve in Spain

Plant Disease ◽

10.1094/pdis-10-12-0952-pdn ◽

2013 ◽

Vol 97 (7) ◽

pp. 991-991 ◽

Cited By ~ 1

Author(s):

P. De Vita ◽

M. S. Serrano ◽

C. Ramo ◽

C. Aponte ◽

L. V. García ◽

...

Keyword(s):

Root Rot ◽

Phytophthora Cinnamomi ◽

Quercus Suber ◽

First Report ◽

Root Necrosis ◽

Pathogenicity Tests ◽

Branch Dieback ◽

The University ◽

Virulence Group ◽

Biological Reserve

Cork oaks (Quercus suber L.) are key tree species at Doñana Biological Reserve (DBR), Huelva, Spain. Sampling was conducted on a total of 13 trees exhibiting symptoms of decline (foliar wilting and defoliation, branch dieback, and root necrosis). In 2008. Phytophthora cinnamomi was isolated from feeder roots of one tree and Pythium spiculum from two additional oaks. In 2011, both pathogens were isolated from six oaks, only P. cinnamomi from three oaks, and only Py. spiculum from one oak. This expansion was associated with high winter rainfall levels since 2009 that led to long periods of soil flooding. While P. cinnamomi is well known to cause a root disease on Q. suber (2), P. spiculum is a newly described species isolated from Quercus, Vitis, Prunus, Castanea, and Celtis species, but its pathogenicity was demonstrated only on Q. ilex (syn. Q. rotundifolia) (1). Pathogenicity tests were conducted on 4-year-old Q. suber plants. Inocula consisted of two isolates of Py. spiculum from DBR (DO8 and DO36 from Q. suber). For comparison with these, three isolates previously tested on Q. ilex (1) were included: two isolates of Py. spiculum, PA54 (from Q. suber) and PE156 (from Q. ilex); and one isolate of P. cinnamomi, PE90 (from Q. ilex). All these isolates came from the Andalucía region, stored at the oomycete collection of the University of Córdoba, and showed a 99 to 100% homology with their expected ITS sequences in GenBank (DQ196131 for Py. spiculum and AY943301 for P. cinnamomi). Inoculum was prepared by shaking and mixing propagule-bearing mycelium produced in carrot broth petri dishes (20°C, 4 weeks) in sterile water, to produce a concentration of 3 × 104 oospores × ml−1 (Py. spiculum) or 3 × 104 chlamydospores × ml−1 (P. cinnamomi). One hundred milliliters of inoculum was applied to each root (1). There were 10 inoculated plants per isolate and 10 non-inoculated control plants. All plants were waterlogged 2 days per week to favor root infection and maintained in an acclimatised greenhouse (12–28°C). Three months later, the inoculated plants showed symptoms of root necrosis that resulted in foliar wilting followed occasionally by defoliation. Control plants did not develop foliar symptoms nor root necrosis. Root damage severity assessed on a 0 to 4 scale (3) exhibited significant differences (P < 0.05) in relation to the control plants for all the isolates tested, with isolate PE90 (P. cinnamomi) and isolates PA54, DO8, and DO36 (P. spiculum) all averaging a root necrosis value of 2.5. Isolate PE156 of P. spiculum produced values of root necrosis (1.6 in average) significantly lower (P < 0.05) than the rest. This isolate belongs to the low virulence group of P. spiculum described on Q. ilex (1). The inoculated oomycete was always reisolated from necrotic roots and never from roots of control plants. To the best of our knowledge, this is the first report of P. spiculum as the cause of root rot of Q. suber. References: (1) Romero et al. J. Phytopathol. 155:289, 2007. (2) Sánchez et al. For. Pathol. 32:5, 2002. (3) Sánchez et al. For. Pathol. 35:115, 2005.

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