First Report of Verticillium Wilt Caused by Verticillium dahliae on Avocado Trees in Greece

Avocado (Persea americana) is an important crop for Chania, Crete, Greece, and is grown on more than 800 ha. In November 2013, 4-year-old trees in a new avocado grove of cv. Hass grafted onto the rootstock ‘Bacon,’ previously planted in citrus trees, showed symptoms of yellowing, leaf fall, twig and branch dieback and vascular tissue discoloration. Disease incidence was estimated at 2.3% (12 out of 530 trees affected). A fungus was consistently and readily isolated from symptomatic vascular tissue, previously surface-disinfested with 95% ethanol, on acidified potato dextrose agar (APDA). After 7 days, slow-growing colonies were transferred to PDA and the growth rate of the fungus was 2.9 mm/day at 24°C in the dark. Microscopic observations revealed hyaline hyphae with many irregular, dark microsclerotia measuring 40 to 200 × 30 to 75 μm (average 94.5 × 50.3 μm) developing after 21 days of growth. Hyaline, elliptical, single-celled conidia measuring 2.8 to 7.5 × 2.5 to 4.3 μm (average 4.8 × 3.1 μm) developed on verticillate conidiophores. For molecular characterization, Verticillium dahliae specific primer pair ITS1-F/ITS2-R that amplifies the rRNA internal transcribed spacer (ITS) region was used (2). Band of expected size was amplified, sequenced, and deposited in GenBank (Accession No. KJ818294). On the basis of morphological characteristics (3) and a BLAST search with 100% identity to the published ITS sequence of a V. dahliae isolate in GenBank (KC834733.1), the fungus was identified as V. dahliae. Five 1-year-old avocado plants of cv. Hass, grafted onto the rootstock ‘Bacon,’ were used for pathogenicity tests. Artificial inoculation was performed by making a 5.0 × 3.5 mm hole in the rootstock trunk, injecting approximately 40 μl of a 2.8 × 107 conidia/ml suspension into the vessels (spores were introduced passively), sealing with Vaseline, and covering with adhesive paper tape. Five control plants were mock inoculated with sterilized distilled water. Disease symptoms that appeared 18 days post artificial inoculation were similar to those observed under natural infection conditions. Thirty-five days post artificial inoculation, disease incidence was 80%, whereas the percentage of positive V. dahliae re-isolations from infected tissues was 95% (96.7 and 93.3% from rootstock and graft, respectively). The extent of vascular tissue discoloration from the point of inoculation ranged from 11 to 62 cm, whereas V. dahliae was successfully re-isolated even from the end of the graft (approximately 60 cm above the initial inoculation point), thus confirming Koch's postulates. Neither symptoms nor positive isolations were observed in control plants. The pathogenicity test was repeated twice with similar results. Verticillium wilt of avocado has been observed in several countries including Argentina, Chile, Ecuador, Israel, Mexico, Morocco, Spain, and the United States (1). To the best of our knowledge, this is the first report of Verticillium wilt on avocado in Greece. This disease could potentially be an increasing problem in areas where young avocado trees are established on land previously planted in vegetable crops. References: (1) J. C. Goud and J. A. Hiemstra. Chapter 3 in: A Compendium of Verticillium Wilt in Trees Species, 1998. (2) E. A. Markakis et al. Eur. J. Plant Pathol. 124:603, 2009. (3) G. F. Pegg and B. L. Brady. Verticillium Wilts. CABI Publishing, Wallingford, UK, 2002.

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First Report of Verticillium Wilt of Grapevine (Vitis vinifera) Caused by Verticillium dahliae in China

Plant Disease ◽

10.1094/pdis-93-8-0841c ◽

2009 ◽

Vol 93 (8) ◽

pp. 841-841 ◽

Cited By ~ 4

Author(s):

L. Zhang ◽

G. L. Zhang ◽

X. Qian ◽

G. Y. Li

Keyword(s):

Vitis Vinifera ◽

Verticillium Wilt ◽

Verticillium Dahliae ◽

Sequential Analysis ◽

Vascular Tissue ◽

Tap Water ◽

The United States ◽

Conidial Suspension ◽

First Report ◽

5.8S Rdna

Verticillium dahliae Kleb. causes Verticillium wilt in large numbers of crops all over the world. Common symptoms caused by the pathogen include yellowing, wilting of leaves, and discoloration in vascular tissue of the stem. In June 2007, symptoms of Verticillium wilt were observed in a grapevine (Vitis vinifera) field in the Shihezi Region of Xinjiang. To isolate the pathogen, stem segments (0.5 cm long) were surface sterilized with 1% HgCl2 for 1 min and then dipped in 70% ethanol for 10 s. The sterilized tissues were rinsed with sterile water and incubated in the dark for 7 days at 25°C on potato dextrose agar (PDA) medium. The fungus growing from the diseased tissue showed dark colonies that produced verticillate conidiophores with two to three layers with colorless, ovoid, unicellular conidia and small, black microsclerotia, which are characteristics of V. dahliae (3). To confirm its identity, ribosomal DNA fragments (regions ITS1, 5.8S rDNA, and ITS4) were PCR amplified with primer pair ITS1/ITS4 (4) and sequenced (GenBank Accession No. FJ475122). Sequential analysis revealed that the rDNA region of the fungus isolated from grapevine was identical to that of a Greek strain of V. dahliae (GenBank Accession No. AF104926). Furthermore, the specific fragment (1,500 bp) of nondefoliating pathotype of V. dahliae (1) was PCR amplified from 24 grapevine isolates of V. dahliae collected in Xinjiang, indicating that the V. dahliae pathogen from Xinjiang is a nondefoliating pathotype. To verify the causal role of the isolated fungus, pathogenicity assays were conducted on 1-year-old seedlings of the Centennial seedless cultivar. Trimmed roots were submerged in a conidial suspension (1 × 106 conidia/ml) for 30 min and sterile tap water was used as a control. The seedlings were transplanted into a pot containing 2:1 sterile mixture of peat/perlite (vol/vol). Plants were grown in a greenhouse at 25°C. Six Verticillium isolates were found to cause the same symptoms as in fields 50 days after inoculation. V. dahliae was successfully reisolated from the stems of inoculated plants. Control seedlings inoculated in sterile tap water remained healthy. Because grapevine (Vitis vinifera) is an economically important crop for fruit and winemaking material in Xinjiang, Verticillium wilt poses a threat. The disease has been previously reported in the United States (2), but to our knowledge, this is the first report from China. References: (1) E. Pérez Artés et al. Eur. J. Plant Pathol. 106:507, 2000. (2) W. C. Schnathorst and A. C. Goheen. Plant Dis. Rep. 61:909, 1977. (3) H. C. Smith. N. Z. J. Agric. Res. 8:450, 1965. (4) T. J. White et al. PCR Protocols. Academic Press, San Diego, CA, 1990.

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First Report of Verticillium Wilt Caused by Verticillium dahliae on Lettuce in Italy

Plant Disease ◽

10.1094/pdis-91-6-0770c ◽

2007 ◽

Vol 91 (6) ◽

pp. 770-770 ◽

Cited By ~ 8

Author(s):

A. Garibaldi ◽

G. Gilardi ◽

M. L. Gullino

Keyword(s):

Verticillium Wilt ◽

Verticillium Dahliae ◽

Vascular Tissue ◽

Morphological Characteristics ◽

The United States ◽

Conidial Suspension ◽

First Report ◽

Lactuca Sativa L ◽

Northeastern Italy ◽

Pathogenicity Tests

Lettuce (Lactuca sativa L.) is an important crop used for fresh and processing markets in Italy and is grown on more than 21,000 ha. During October and November of 2006, wilt symptoms were observed on field-grown lettuce, cv. Estelle, in Forlì, Emila Romagna (northeastern Italy) and on cv. Ballerina grown under plastichouses in Piedmont (northwestern Italy). Both lettuce cultivars were of a butterhead type. Affected plants were stunted and developed yellow leaves with brown or black streaks in the vascular tissue. Yellowing started from the external leaves. Discoloration was observed in the vascular tissue of roots, crown, and leaves. A fungus was consistently and readily isolated from symptomatic vascular tissue, previously disinfested in 1% sodium hypochlorite, when cultured on potato dextrose agar (PDA). Microscopic observations revealed hyaline hyphae with many ovoid, dark microsclerotia measuring 32 to 43 × 16 to 26 μm developing after 15 days of growth at 18°C in the dark. Conidiophores showed two verticils of three elements. Conidia were hyaline, elliptical, single celled, and measured 3.5 to 8.5 × 1.8 to 4.3 μm (average 5.5 × 2.5 μm). According to its morphological characteristics, the fungus was identified as Verticillium dahliae (2). Healthy, 20-day-old lettuce plants, cvs. Principessa and Maxima, both belonging to the butterhead type, were separately inoculated by root dip with a conidial suspension (106/ml) of two isolates of V. dahliae isolated, respectively, at Forlì and Torino. Noninoculated lettuce plants served as control treatments. Plants (10 per treatment) were grown in pots (10-liter vol.) in a steam-disinfested peat/perlite/sand (3:1:1 vol/vol) substrate and were maintained in a glasshouse at temperatures ranging between 17 and 22°C and relative humidity ranging between 60 and 70%. First wilt symptoms and vascular discoloration in the roots, crown, and veins developed 40 days after the artificial inoculation. Forty percent of the plants were affected in the case of cv. Maxima and 30% for cv. Principessa. Noninoculated plants remained healthy. The pathogenicity tests were repeated twice. To our knowledge, this is the first report in Italy of Verticillium wilt on lettuce. The disease has been previously reported in Greece (1) and the United States (3). Currently, Verticillium wilt of lettuce seems restricted in Italy to very few farms in the two locations; moreover, its incidence is very low (0.05%). References: (1) E. K. Ligoxigakis et al. Phytoparasitica 30:141, 2002. (2) G. F. Pegg and B. L. Brady. Verticillium Wilts. CABI Publishing, Wallingford, UK, 2002. (3) G. E. Vallad et al. Plant Dis. 89:317, 2005.

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First Report of Verticillium Wilt Caused by Verticillium dahliae on Rudbeckia fulgida (Orange Coneflower) in Italy

Plant Disease ◽

10.1094/pdis-92-9-1367c ◽

2008 ◽

Vol 92 (9) ◽

pp. 1367-1367 ◽

Cited By ~ 1

Author(s):

A. Garibaldi ◽

D. Bertetti ◽

M. L. Gullino

Keyword(s):

United States ◽

Verticillium Wilt ◽

Verticillium Dahliae ◽

Vascular Tissue ◽

Morphological Characteristics ◽

Its Region ◽

The United States ◽

Conidial Suspension ◽

First Report ◽

Initial Symptoms

Rudbeckia fulgida (common name orange coneflower) is an herbaceous perennial (Asteraceae) grown in full sun in perennial borders in gardens. At the end of the summer of 2007, in a public garden located in Turin (northern Italy), symptoms of vascular wilt and stunting were observed on approximately 80% of the plants grown in a mixed border. Initial symptoms were yellowing of external leaves and brown or black streaks in the vascular tissue of roots, crown, and leaves. A fungus was consistently and readily isolated on potato dextrose agar from symptomatic vascular tissue previously disinfested in 1% sodium hypochloride. Ovoid, dark microsclerotia, 41 to 108 μm, developed in hyaline hyphae after 10 days of growth at 23°C (12 h of light and 12 h of dark). Hyaline, elliptical, single-celled conidia, 3.2 to 7.3 × 2.1 to 3.7 (average 4.7 × 2.8) μm, developed on verticillate conidiophores. On the basis of these morphological characteristics, the fungus was identified as Verticillium dahliae (4). The internal transcribed spacer (ITS) region of rDNA was amplified using primers ITS4/ITS6 and sequenced. BLASTn analysis (1) of the 530 bp showed a 100% homology with the sequence of V. dahliae. The nucleotide sequence has been assigned GenBank Accession No. EU 627007. Healthy, 30-day-old R. fulgida plants were grown in a steam-disinfested mix of sphagnum peat:pomix:pine bark:clay (50:20:20:10) infested with a conidial suspension (1.5 × 106/ml) of three isolates of V. dahliae isolated from infected plants. Noninoculated plants served as controls. Plants (16 per treatment) were grown in pots (3 liter vol) and maintained in a glasshouse at temperatures between 22 and 25°C and relative humidity between 50 and 70%. First wilt symptoms and vascular discoloration in the roots, crown, and veins developed 17 days after inoculation. Noninoculated plants remained healthy. The pathogenicity tests were carried out twice. To our knowledge, this is the first report in Italy of Verticillium wilt on R. fulgida. Wilts caused by V. dahliae on R. laciniata in Poland (3) and V. albo-atrum on R. hirta in the United States (2) were previously reported. The importance and economic impact of this disease is currently limited but may increase because of the popularity of Rudbeckia spp. in private and public parks. References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997. (2) D. F. Farr et al. Fungi on Plants and Their Products in the United States. The American Phytopathological Society, St Paul, MN, 1989. (3) B. Leski. Rocz. Nauk Roln. 253, 1974. (4) G. F. Pegg and B. L. Brady. Verticillium Wilts. CABI Publishing, Wallingford, UK, 2002.

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First Report of Passalora Leaf Spot Caused by Passalora bougainvilleae on Bougainvillea in Mexico

Plant Disease ◽

10.1094/pdis-11-10-0787 ◽

2011 ◽

Vol 95 (6) ◽

pp. 775-775 ◽

Cited By ~ 1

Author(s):

V. Ayala-Escobar ◽

V. Santiago-Santiago ◽

A. Madariaga-Navarrete ◽

A. Castañeda-Vildozola ◽

C. Nava-Diaz

Keyword(s):

Uv Light ◽

Disease Incidence ◽

Morphological Characteristics ◽

The United States ◽

Pathogenicity Test ◽

Commonwealth Mycological Institute ◽

Conidial Suspension ◽

Single Spore ◽

First Report ◽

Bougainvillea Spectabilis

Bougainvillea (Bougainvillea spectabilis Willd) growing in 28 gardens during 2009 showed 100% disease incidence and 3 to 7% disease severity. Bougainvilleas with white flowers were the most affected. Symptoms consisted of light brown spots with dark brown margins visible on adaxial and abaxial sides of the leaves. Spots were circular, 2 to 7 mm in diameter, often surrounded by a chlorotic halo, and delimited by major leaf veins. Single-spore cultures were incubated at 24°C under near UV light for 7 days to obtain conidia. Pathogenicity was confirmed by spraying a conidial suspension (1 × 104 spores/ml) on leaves of potted bougainvillea plants (white, red, yellow, and purple flowers), incubating the plants in a dew chamber for 48 h and maintaining them in a greenhouse (20 to 24°C). Identical symptoms to those observed at the residential gardens appeared on inoculated plants after 45 to 60 days. The fungus was reisolated from inoculated plants that showed typical symptoms. No symptoms developed on control plants treated with sterile distilled water. The fungus produced distinct stromata that were dark brown, spherical to irregular, and 20 to 24 μm in diameter. Conidiophores were simple, born from the stromata, loose to dense fascicles, brown, straight to curved, not branched, zero to two septate, 14 × 2 μm, with two to four conspicuous and darkened scars. The conidia formed singly, were brown, broad, ellipsoid, obclavate, straight to curved with three to four septa, 40 × 4 μm, and finely verrucous with thick hilum at the end. Fungal DNA from the single-spore cultures was obtained using a commercial DNA Extraction Kit (Qiagen, Valencia, CA); ribosomal DNA was amplified with ITS5 and ITS4 primers and sequenced. The sequence was deposited at the National Center for Biotechnology Information Database (GenBank Accession Nos. HQ231216 and HQ231217). The symptoms (4), morphological characteristics (1,2,4), and pathogenicity test confirm the identity of the fungus as Passalora bougainvilleae (Muntañola) Castañeda & Braun (= Cercosporidium bougainvilleae Muntañola). This pathogen has been reported from Argentina, Brazil, Brunei, China, Cuba, El Salvador, India, Indonesia, Jamaica, Japan, Thailand, the United States, and Venezuela (3). To our knowledge, this is the first report of this disease on B. spectabilis Willd in Mexico. P. bougainvilleae may become an important disease of bougainvillea plants in tropical and subtropical areas of Mexico. References: (1) U. Braun and R. R. Castañeda. Cryptogam. Bot. 2/3:289, 1991. (2) M. B. Ellis. More Dematiaceous Hypomycetes. Commonwealth Mycological Institute, Kew, Surrey, UK, 1976. (3) C. Nakashima et al. Fungal Divers. 26:257, 2007. (4) K. L. Nechet and B. A. Halfeld-Vieira. Acta Amazonica 38:585, 2008.

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First Report of Dieback Caused by Verticillium dahliae on Blighia sapida in the United States

Plant Disease ◽

10.1094/pdis.2002.86.1.74c ◽

2002 ◽

Vol 86 (1) ◽

pp. 74-74

Author(s):

R. T. McMillan ◽

W. R. Graves ◽

T. F. Wood ◽

R. M. Leahy

Keyword(s):

United States ◽

Verticillium Dahliae ◽

Vascular Tissue ◽

The United States ◽

South Florida ◽

First Report ◽

Disturbed Soil ◽

Florida Department ◽

Consumer Services ◽

Blighia Sapida

Mature akee trees, Blighia sapida K. Koenig, in a local south Florida commercial orchard had wilt and dieback symptoms during spring 1999. A fungus isolated from the gray xylem root tissue on V8 agar was identified as Verticillium dahliae Klebahn at the Division of Plant Industry of the Florida Department of Agriculture and Consumer Services. Twenty akee seedlings were transplanted into 3.85-liter plastic pots and grown in a greenhouse at a daytime temperature of 28°C and nighttime temperature of 23°C. When plants were approximately 25 cm high, a 15-cm knife was used to sever roots in the four quadrants of each pot. Inoculum was made from a 2-week-old culture of V. dahliae on V8 agar and blended with 160 ml of sterile water, and 15 ml of this slurry was poured into the disturbed soil of each of 10 treated plants. A plate of uninoculated V8 agar was applied, as above, to 10 control plants. Plants were kept in the greenhouse. After 6 weeks, inoculated plants showed symptoms of leaf wilt, dieback and plant death. No symptoms were seen on control plants. V. dahliae was isolated directly from the gray vascular tissue of inoculated plants. The inoculation experiment was repeated three times, fulfilling Koch's postulates. To our knowledge, this is the first report of Verticillium dieback on B. sapida in the United States.

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First Report of Verticillium Wilt caused by Verticillium dahliae Kleb. on New Zealand Spinach (Tetragonia tetragonioides) in Italy

Plant Disease ◽

10.1094/pdis-07-12-0678-pdn ◽

2013 ◽

Vol 97 (1) ◽

pp. 145-145

Author(s):

A. Garibaldi ◽

S. Rapetti ◽

P. Martini ◽

L. Repetto ◽

D. Bertetti ◽

...

Keyword(s):

New Zealand ◽

Verticillium Wilt ◽

Verticillium Dahliae ◽

Vascular Tissue ◽

Spinacia Oleracea ◽

Morphological Characteristics ◽

Conidial Suspension ◽

Potato Dextrose Broth ◽

First Report ◽

Tetragonia Tetragonioides

Tetragonia tetragonioides (New Zealand spinach, Aizoaceae) is an Australasian annual species that occurs naturally in Italy, where it is cultivated for the edible young shoots and succulent leaves. In September 2011, a previously unknown wilt was observed in 10 private gardens, each 0.1 to 0.5 ha, near Castellaro, Northern Italy, on 7-month-old New Zealand spinach plants. Leaves wilted, starting from the collar and moving up the plant, and vascular tissues showed brown streaks in the roots, crowns, and stems. Diseased plants were stunted with small, chlorotic leaves. Infected stems and leaves then wilted, and plants often died. Of about 500 plants, 30% were affected. Stems of 10 diseased plants were disinfected with 1% NaOCl for 1 min. Sections of symptomatic vascular tissue were plated on potato dextrose agar. After 3 days at 23 ± 1°C, colonies developed that were white and turned a grey to dark green color. Irregular, black microsclerotia (32.0) 63.1 ± 16.8 μm (106.1) × (18.7) 39.1 ± 12.3 μm (65.8) developed in hyaline hyphae after 8 days. Hyaline, elliptical, single-celled conidia (2.7) 3.8 ± 0.6 μm (4.8) × (1.9) 2.6 ± 0.5 μm (3.5) developed on verticillate conidiophores with three phialides at each node. Based on these morphological characteristics, the fungus was identified as Verticillium dahliae (1). The internal transcribed spacer (ITS) region of rDNA was amplified for one isolate using the primers ITS1/ITS4 (3) and sequenced (GenBank Accession No. JX308315). BLASTn analysis of the 479-bp segment showed 100% homology with the ITS sequence of a V. dahliae isolate (AB551206). Pathogenicity tests were performed twice using 60-day-old plants of T. tetragonioides. Unwounded roots of eight plants were dipped for 1 min in a conidial suspension (5 × 107 conidia/ml) of one isolate of V. dahliae obtained from the original infected New Zealand spinach plants, and grown in potato dextrose broth. The inoculated plants were transplanted into 2-liter pots (1 plant/pot) containing steamed potting mix (sphagnum peat-perlite-pine bark-clay; 50:20:20:10) and maintained in a growth chamber at 20 to 24°C and 50 to 80% RH. Eight plants immersed in sterile water served as a control treatment. Wilt symptoms were observed 30 days after inoculation, with vascular discoloration in the roots, crowns and stems. V. dahliae was reisolated consistently from infected tissues, but not from the control plants that remained healthy. Pathogenicity was also tested using the same method on plants of four cultivars (five plants/cultivar) of Spinacia oleracea (Matador, Asti, Merlo Nero, and America). Wilt symptoms developed on all cultivars and V. dahliae was reisolated from each inoculated plant. No fungal colonies were reisolated from control plants, which remained healthy. To our knowledge, this is the first report of Verticillium wilt caused by V. dahliae on T. tetragonioides in Italy, as well in Europe. V. dahliae was reported on T. tetragonioides in Canada (2). At this time, the economic impact of Verticillium wilt on New Zealand Spinach in Italy is limited, although the use of this vegetable in Italy is increasing. References: (1) G. F. Pegg and B. L. Brady. Verticillium Wilts. CABI Publishing, Wallingford, UK, 2002. (2) M. J. Richardson. Page 387 in: An Annotated List of Seed-Borne Diseases, Fourth Edition. International Seed Testing Association, Zurich, Switzerland, 1990. (3) T. J. White et al. Page 315 in: PCR Protocols. A Guide to Methods and Applications. Academic Press, San Diego, CA, 1990.

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First Report of Verticillium Wilt of Faba Bean Caused by Verticillium dahliae in Spain

Plant Disease ◽

10.1094/pdis-93-4-0432b ◽

2009 ◽

Vol 93 (4) ◽

pp. 432-432 ◽

Cited By ~ 6

Author(s):

M. Berbegal ◽

J. Armengol

Keyword(s):

Verticillium Wilt ◽

Verticillium Dahliae ◽

Faba Bean ◽

Vascular Tissue ◽

Conidial Suspension ◽

Central Spain ◽

First Report ◽

Severe Stunting ◽

Plant Pathol ◽

Nested Pcr Assays

Faba bean (Vicia faba L.) crops in eastern-central Spain are usually grown in rotation or double cropped with artichoke (Cynara cardunculus L. var. scolymus (L.) Fiori). In this region, artichoke is grown annually and is severely affected by Verticillium dahliae Kleb. (1). During February of 2007, wilt symptoms were observed at harvesting time on faba bean fields located in Castellón Province (eastern-central Spain). Symptoms consisted of leaf yellowing, wilting, and gradual death of the leaves while stems generally remained green except for severely affected plants. The vascular tissue in the stems showed a tan-to-light brown discoloration and plants were stunted. For isolation, crown and stem sections (10 cm long) were surface disinfected for 1 min in 1.5% NaOCl and washed twice with sterile distilled water. The sections were cut longitudinally and small pieces of discolored vascular tissue were plated onto potato dextrose agar (PDA) amended with streptomycin sulfate (0.5 g liter–1). Plates were incubated at 25°C in the dark. V. dahliae was consistently isolated and colonies transferred to PDA were identified on the basis of the presence of microsclerotia and conidiophore morphology. Identity of monoconidial isolates 3H, 4H, 7H, and 8H was confirmed by specific multiplex nested-PCR assays using primers NDf/NDr in the first PCR round and INTND2f/INTND3r/MCR2B in the second round (2). PCR markers amplified with these primers were originally developed for the detection and vegetative compatibility group (VCG) identification of V. dahliae isolates infecting artichoke plants. Isolates 3H, 4H, 7H, and 8H amplified the 688-bp and the 964-bp markers indicating that they belong to VCG2B. Recent studies identified VCG2B as the prevalent group in the population of V. dahliae affecting artichoke in Castellón Province (3). Pathogenicity of two selected isolates, 3H and 7H, was determined on faba bean (cv. Muchamiel) and artichoke seedlings (cv. Madrigal) at the two-true-leaf stage. Seedlings were inoculated by watering the roots with 25 ml of a conidial suspension (106 conidia ml–1) harvested from 3-week-old cultures grown on PDA. Ten replicates (each one in individual pots) for each isolate and plant species were used, with an equal number of control plants. Plants were maintained in a greenhouse at 23 to 25°C. Within 1 month of inoculation, symptoms developed on all inoculated plants as severe stunting, leaf necrosis, and wilting. The fungus was reisolated from vascular tissues of the crown area and the stems of inoculated seedlings, completing Koch's postulates. Symptoms were not visible in the control seedlings and V. dahliae was not isolated from them. To our knowledge, this is the first report of V. dahliae infecting faba bean in Spain. Verticillium wilt had been previously reported on V. faba in Greece (4). Verticillium wilt of faba bean may bear importance in the epidemiology of the disease in artichoke as an alternative host for inoculum increase and survival of V. dahliae under field conditions. References: (1) M. Berbegal et al. Plant Dis. 91:1131, 2007. (2) M. Collado-Romero et al. Online publication. doi:10.1111/j.1365-3059.2008.01981.x. Plant Pathol., 2008. (3) R. M. Jiménez-Díaz et al. Phytopathology 96:288, 2006. (4) E. K. Ligoxigakis and D. J. Vakalounakis. Plant Pathol. 43:755, 1994.

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Verticillium Wilt of African Daisy (Osteospermum sp.) in Italy Caused by Verticillium dahliae

Plant Disease ◽

10.1094/pd-89-0688a ◽

2005 ◽

Vol 89 (6) ◽

pp. 688-688

Author(s):

A. Garibaldi ◽

A. Minuto ◽

M. L. Gullino

Keyword(s):

Verticillium Wilt ◽

Verticillium Dahliae ◽

Plant Disease ◽

Vascular Tissue ◽

Northern Italy ◽

Wilt Disease ◽

Pathogenicity Test ◽

Conidial Suspension ◽

Average Temperature ◽

Food Agric

During the winter of 2004, container-grown African daisy (Osteospermum sp.) plants, cv Seaside, showing symptoms of a wilt disease were observed in an open field in Albenga located in northern Italy. Symptoms were first observed on 120-day-old plants grown in a peat/composted bark/clay/pumice (50:20:10:20) substrate. The vascular tissues of affected plants appeared brown. These plants were stunted and developed yellow leaves with brown or black streaks in the vascular tissue. Verticillium dahliae was consistently and readily isolated from symptomatic vascular tissue when cultured on potato dextrose agar. Healthy rooted plants (40-day-old cv Seaside) were inoculated by root dip with a conidial suspension (5 × 107 CFU/ml) from one of three isolates of V. dahliae isolated from infected plants and transplanted into pots filled with steam-sterilized soil. Noninoculated plants served as control treatments. Plants (10 per treatment) were grown in a glasshouse at an average temperature of 25°C. First wilt symptoms and vascular discoloration in the roots, crown, and veins developed within 15 days on each inoculated plant and become very evident after 50 days. Noninoculated plants remained healthy. V. dahliae was consistently reisolated from inoculated plants. The pathogenicity test was conducted twice. To our knowledge, this is the first report of V. dahliae on Osteospermum sp. in Italy and in Europe. Verticillium wilt has been previously reported on O. fruticosum in California (1). Reference: (1) A. M. French. California Plant Disease Host Index. Calif. Dep. Food Agric. 1989.

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Verticillium Wilt Incited by Verticillium dahliae in Eggplant Grafted on Solanum torvum in Italy

Plant Disease ◽

10.1094/pd-89-0777b ◽

2005 ◽

Vol 89 (7) ◽

pp. 777-777 ◽

Cited By ~ 5

Author(s):

A. Garibaldi ◽

A. Minuto ◽

M. L. Gullino

Keyword(s):

Verticillium Wilt ◽

Verticillium Dahliae ◽

Vascular Tissue ◽

Disease Incidence ◽

Conidial Suspension ◽

Root Knot Nematode ◽

Solanum Torvum ◽

Meloidogyne Spp ◽

Resistant Rootstock ◽

Low Incidence

Eggplant cultivars grafted on rootstocks resistant to root-knot nematodes (Meloidogyne spp.) are increasingly grown in Italy to reduce nematode infection. During the winter of 2003-2004, eggplants (cv Black Bell and Mirabell) grafted on the nematode-resistant rootstock Solanum torvum were observed with symptoms of a wilt disease in several greenhouses in Sicily (southern Italy). The vascular tissue in stems of affected plants appeared brown. These plants were stunted and developed yellow leaves with brown or black streaks in the vascular tissue. The wilt appeared in several greenhouses at a very low incidence (0.01 to 0.05%). Later, during the fall of 2004, disease incidence was approximately ten times greater in the same greenhouses on new crops. Verticillium dahliae was consistently and readily isolated from symptomatic vascular tissue of the rootstock (S. torvum) and the scion (cv Black bell) when cultured on potato dextrose agar (PDA) (1). Healthy, 50-day-old plants of S. torvum and eggplant (cv. Black Bell) were separately inoculated by root dip with a conidial suspension (1 × 107 CFU/ml) of two isolates of V. dahliae obtained from the rootstock and the scion of the infected grafted plants and with a known pathogenic isolate of V. dahliae from nongrafted eggplant. Noninoculated S. torvum and eggplant served as control treatments. Plants (30 per treatment) were grown in a glasshouse at temperatures ranging between 12 and 41°C (weekly average 15 to 36°C) and relative humidity ranging between 36 and 99% (weekly average 54 to 95%). The first wilt symptoms and vascular discoloration in the roots, crowns, and veins developed 26 and 21 days after inoculation on S. torvum and eggplant, respectively. Seventy-two days after inoculation, 20, 26, and 27% of S. torvum plants and 97, 100, and 87% of the eggplants showed symptoms caused by V. dahliae isolates obtained from the scion of diseased grafted plants, the rootstock of diseased grafted plants, and nongrafted eggplants, respectively. Noninoculated plants remained healthy. To our knowledge, this is the first report in Italy of Verticillium wilt on eggplant grafted on S. torvum rootstocks under commercial conditions. Use of eggplant grafted on the nematode-resistant rootstock of S. torvum presents an interesting opportunity to control the root-knot nematode but has to be carefully considered when dealing with soils severely infested by V. dahliae. Reference: (1) G. F. Pegg and B. L. Brady. Verticillium Wilts. CABI Publishing, Wallingford, UK, 2002.

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First Report of Verticillium Wilt Caused by Verticillium dahliae on Coleus verschaffeltii in Italy

Plant Disease ◽

10.1094/pdis-03-11-0247 ◽

2011 ◽

Vol 95 (7) ◽

pp. 878-878 ◽

Cited By ~ 1

Author(s):

A. Garibaldi ◽

D. Bertetti ◽

A. Poli ◽

M. L. Gullino

Keyword(s):

United States ◽

Verticillium Wilt ◽

Verticillium Dahliae ◽

The United States ◽

Peat Moss ◽

Conidial Suspension ◽

First Report ◽

Vascular Tissues ◽

Initial Symptoms ◽

Bedding Plant

Coleus verschaffeltii Lem. (synonym C. blumei Benth., Plectranthus scutellaroides (L.) R. Br., and Solenostemon scutellarioides (L.) Codd), a perennial plant belonging to the Lamiaceae family, is used as a bedding plant for public gardens. The most popular cultivars produce speckled leaves of various colors. In October 2010, severe outbreaks of a previously unknown wilt were observed in a public garden at Torino (northern Italy) on 50 8-month-old plants. Plants were sprinkle irrigated. Initial symptoms were withering of leaves starting from the collar and brown streaks in the vascular tissue of roots, crown, and stem. Subsequently, infected tissues wilted and plants became stunted. Early leaf drop was observed and plants appeared bare, keeping few leaves only at the end of stems. Infected plants did not die but they lost the original ornamental aspect. Seventy percent of the plants were affected. Stems of 10 plants were disinfected with 1% sodium hypochlorite. Cross-sections through symptomatic vascular tissues were plated on potato dextrose agar amended with 25 ppm of streptomycin sulfate. After 10 days at 20 to 23°C, a fungus was consistently recovered from 90% of stems. Irregular, black microsclerotia, 29 to 76 × 14 to 52 (average 49 × 28) μm, developed in hyaline hyphae after 15 days of growth. Hyaline, elliptical, single-celled conidia, 3.9 to 7.2 × 1.7 to 2.8 (average 5.1 × 2.2) μm, developed on verticillate conidiophores with three phialides at each node. On the basis of these morphological characteristics, the fungus was identified as Verticillium dahliae (3). The internal transcribed spacer (ITS) region of rDNA was amplified using the primers ITS1/ITS4 (4) and sequenced. BLASTn analysis (1) of the 491-bp segment showed a 99% homology with the sequence of V. dahliae (Accession No. GU461634). The ITS nucleotide sequence of our isolate has been assigned the GenBank Accession No. JF704205. Pathogenicity tests were performed twice using 45-day-old plants obtained from seeds of C. verschaffeltii grown in 1-liter pots containing a 50:20:20:10 steamed mix of peat moss/pumice/pine bark/clay. Roots of 10 healthy plants were immersed in a conidial suspension (1.7 × 107 ml–1) of one culture of V. dahliae isolated from infected plants. Ten plants immersed in sterile water served as controls. Plants were maintained in a glasshouse at daily average temperatures between 20 and 28°C and relative humidity between 50 and 80%. First wilt symptoms and vascular discoloration in the roots, crown, and stems developed 20 days after inoculation. V. dahliae was consistently reisolated from infected vascular tissues of crown and stems of symptomatic plants. Noninoculated plants remained healthy. To our knowledge, this is the first report of Verticillium wilt on C. verschaffeltii in Italy. Verticillium wilt had been previously reported on S. scutellaroides in the United States (2). At this time, the economic importance of Verticillium wilt on C. verschaffeltii in Italy is limited. References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997. (2) D. Farr et al. Fungi on Plants and Plant Products in the United States. The American Phytopathological Society. St Paul, MN, 1989. (3) G. F. Pegg and B. L. Brady. Verticillium Wilts. CABI Publishing, Wallingford, UK, 2002. (4) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, 1990.

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