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

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 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 Wilt Caused by Verticillium dahliae on Cosmos (Cosmos bipinnatus) in Italy

Plant Disease ◽

10.1094/pdis-93-8-0846b ◽

2009 ◽

Vol 93 (8) ◽

pp. 846-846 ◽

Cited By ~ 1

Author(s):

A. Carlucci ◽

F. Lops ◽

S. Frisullo

Keyword(s):

Verticillium Wilt ◽

Verticillium Dahliae ◽

Vascular Tissue ◽

Sequence Similarity ◽

Morphological Characteristics ◽

Herbaceous Plant ◽

Conidial Suspension ◽

Internal Transcribed Spacer Region ◽

First Report ◽

Cosmos Bipinnatus

Cosmos (Cosmos bipinnatus Cav., Asteraceae) is an herbaceous plant that is grown for landscape use. During August and September of 2008 in five public and three private gardens located in Monopoli (Apulia, southern Italy), 3 to 8% of the plants showed severe symptoms of vine decline, stunting, gradual yellowing and wilting of the leaves, and final collapse of the whole plant. External symptoms were associated with brown or black streaking of the vascular tissue of roots, collar, and stem. Dead plants had numerous microsclerotia embedded in the xylem of plant tissues. Stem, collar, and root sections (0.5 cm long) from symptomatic plants collected in five gardens were surface disinfested in 5% NaOCl for 1 min and transferred to petri dishes containing potato dextrose agar (PDA) amended with 100 μg ml–1 of streptomycin sulfate and 10 μg ml–1 of neomycin. After 10 days of incubation, at 25°C in the dark, hyaline hyphae with dark microsclerotia (37 to 112 μm) and verticillate conidiophores were produced. Conidia were single celled and hyaline with dimensions of 3.3 to 7.8 × 1.8 to 3.3 μm (mean dimensions 4.2 × 2.5 μm). According to morphological characteristics, the fungus was identified as Verticillium dahliae Kleb. (1) (isolates no. Vd1818, Vd1819, and Vd1820 stored in a collection at the Department DiSACD, University of Foggia). Molecular analyses were performed on the basis of nucleotide sequences of the internal transcribed spacer region (ITS1-5.8S-ITS2) of ribosomal DNA. ITS sequences of this fungus, compared with sequences found in GenBank and attributed to V. dahliae (no. GQ130129, GQ130130, GQ130131), showed 98 to 99% sequence similarity. Healthy 40-day-old plants of C. bipinnatus (garden cosmos) cv. Sonata Pink Blusk and C. sulphurous (yellow cosmos) cv. Bilbo, obtained from seeds previously disinfested for 1 min in 3% NaOCl and ascertained to be healthy by isolation on PDA medium, were used for pathogenicity tests. Plants were grown in 3-liter pots in a steam-disinfested peat, sand, and soil mixture (2:1:1) in the greenhouse at 23 to 26°C. Ten plants of each cultivar were inoculated by root dipping into a conidial suspension of each fungal isolate (1.5 × 106 CFU ml–1). Six noninoculated cosmos plants of each cultivar served as controls. The experiment was repeated three times. First symptoms of wilting were observed on all inoculated plants of each cultivar 20 days after the inoculation; at 40 days, symptom severity ratings on plants were taken, in which 1 = asymptomatic, 2 = stunted, 3 = wilting, and 4 = dead. All three isolates caused vascular discoloration, stunting, wilting, and plant death. The mean disease rating was 3.2 and did not differ significantly among isolates. The pathogen was consistently reisolated from infected plants, fulfilling Koch's postulates. Noninoculated plants remained healthy. To our knowledge, this is the first report of Verticillium wilt on cosmos in Italy. The finding is important since other ornamental plants that are susceptible to Verticillium wilt are also grown in landscapes in the region. The disease was previously reported in Turkey (2). References: (1) G. F. Pegg and B. L. Brandy. Verticillium Wilts. CABI Publishing, Wallingford, UK, 2002. (2) E. Sezgin et al. Turk. Phytopathol. 14:43, 1985.

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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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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 Figmarigold in Italy

Plant Disease ◽

10.1094/pdis-94-1-0129b ◽

2010 ◽

Vol 94 (1) ◽

pp. 129-129

Author(s):

A. Garibaldi ◽

D. Bertetti ◽

P. Pensa ◽

M. L. Gullino

Keyword(s):

Verticillium Wilt ◽

Cross Sections ◽

Vascular Tissue ◽

Morphological Characteristics ◽

Ground Cover ◽

Its Region ◽

Peat Moss ◽

Conidial Suspension ◽

First Report ◽

Initial Symptoms

Lampranthus spp. N.B. Brown (figmarigold) belongs to the Aizoaceae family and is grown as a ground cover in gardens or as a potted plant. In January 2009, severe outbreaks of a previously unknown wilt were observed at a commercial farm in Liguria (northern Italy) where 7-month-old potted plants were grown outdoors in a mix of peat/clay/pumice at pH 6.5. In cultivars with pink flowers, 12% of plants were affected, while only a few cultivars with red flowers were diseased. Initial symptoms were yellowing of external leaves and brown or black streaks in the vascular tissue of roots, crown, and leaves. Subsequently, infected tissues wilted and stopped growing, stems and leaves appeared desiccated, and infected plants died. Stems of 10 pink-flowered plants were severed with a knife, cut ends sealed with wax, and surfaces disinfected with 1% sodium hypochlorite. Cross-sections (1 mm long) through symptomatic vascular tissue were plated onto potato dextrose agar. After 10 days at 22°C, 90% of the stems tested positive for Verticillium. Irregular, dark microsclerotia, 22 to 128 × 13 to 66 (average 51 × 29) μm, developed in hyaline hyphae after 10 days of growth at 22 ± 1°C (12-h photoperiod). Hyaline, elliptical, single-celled conidia, 2.9 to 4.8 × 1.3 to 2.4 (average 4.1 × 1.7) μm, developed on verticillate conidiophores. On the basis of these morphological characteristics, the fungus was identified as V. dahliae (3). The internal transcribed spacer (ITS) region of rDNA was amplified using primers ITS4/ITS6 (2) and sequenced. BLASTn analysis (1) of the 476-bp segment showed a 100% homology with the sequence of V. dahliae. The nucleotide sequence has been assigned GenBank Accession No. GQ 149479. Pathogenicity tests were performed twice using five 40-day-old plants of a pink-flower cultivar of a Lampranthus sp. grown in 1-liter pots containing a 50:20:20:10 mix of peat moss/pumice/pine bark cortex/clay. The substrate was infested with a conidial suspension (1.0 × 107/ml) of one isolate of V. dahliae recovered from infected plants. Inoculum (50 ml) were added to each pot, drenching the top of the soil. Noninoculated plants served as controls. Plants (five per treatment) were maintained in a glasshouse at daily average temperatures between 20 and 26°C and at 50 to 70% relative humidity. The first wilt symptoms and a vascular discoloration in the roots, crown, and veins developed 30 days after inoculation. V. dahliae was consistently reisolated. Noninoculated plants remained healthy. In a second test, the susceptibility of purple-, white-, yellow-, red-, and orange-flowered cultivars was tested. Ten rooted cuttings of each cultivar were inoculated as described above. The severity of Verticillium wilt was evaluated and each cultivar was classified as resistant, partially resistant, average susceptible, susceptible, or highly susceptible. All tested cultivars were susceptible or highly susceptible to Verticillium. Only the purple cultivar showed an average susceptibility. To our knowledge, this is the first report of Verticillium wilt on Lampranthus spp. in Italy as well as worldwide. Today, the economic importance of Verticillium wilt on figmarigold in Italy is still limited. References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997. (2) M. A. Innis et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, CA, 1990. (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 Pistachio Caused by Verticillium dahliae in Spain

Plant Disease ◽

10.1094/pdis-94-3-0382b ◽

2010 ◽

Vol 94 (3) ◽

pp. 382-382

Author(s):

J. Moral ◽

F. J. López-Escudero ◽

L. F. Roca ◽

M. A. Blanco-López ◽

A. Trapero

Keyword(s):

Verticillium Wilt ◽

Verticillium Dahliae ◽

Vascular Tissue ◽

Agar Medium ◽

Tap Water ◽

Conidial Suspension ◽

First Report ◽

Soil P ◽

La Mancha ◽

Dahliae Isolate

Pistachio (Pistacia vera L.) trees in the Castilla La Mancha and Andalusia regions of central and southern Spain are grown close to olive orchards, which are often severely affected by Verticillium dahliae. During the last decade, wilt and death of one or several branches have been observed on pistachio (cv. Kerman) scions grafted on rootstock (P. terebinthus). Discoloration of vascular tissue was occasionally observed. In five surveyed orchards, incidence of affected trees was less than 2%. Wood chips with the bark removed from symptomatic trees were washed in running tap water, surface disinfested in 0.5% sodium hypochlorite for 1 min, and placed onto potato dextrose agar plates incubated at 25°C in the dark. Isolates were identified as V. dahliae on the basis of the characteristics of microsclerotia, conidiophores, and conidia. V. dahliae isolate V117 from olive was used as reference (1). The fungus was also isolated from soil in pistachio orchards using wet sieving and a modified sodium polypectate agar medium (1). Inoculum density varied from 0 to 4.73 microsclerotia per gram of soil. P. terebinthus seedlings were inoculated with two isolates of V. dahliae from pistachio trees by injecting the stems with 50 μl of a conidial suspension (107 conidia per ml) (2). Wilt symptoms of varying severity developed in 12 and 15 seedlings of the 20 pistachio seedlings inoculated with each of two isolates. No symptoms developed on the control seedlings. The pathogen was recovered from stem tissues of inoculated plants. To our knowledge, this is the first report of Verticillium wilt of pistachio in Spain. This study demonstrates the susceptibility of certain rootstocks to V. dahliae and the importance of using resistant rootstocks, such as UCBI (2), in pistachio plantations established on soils infested by V. dahliae. References: (1) F. J. López-Escudero and M. A. Blanco-López. Plant Dis. 91:1372, 2007. (2) D. P. Morgan et al. Plant Dis. 76:310, 1992.

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First Report of Tuber Rot Disease of Kala Zeera Caused by a Member of the Fusarium solani Species Complex in India

Plant Disease ◽

10.1094/pdis-02-12-0148-pdn ◽

2012 ◽

Vol 96 (7) ◽

pp. 1067-1067 ◽

Cited By ~ 1

Author(s):

V. Gupta ◽

D. John ◽

V. K. Razdan ◽

S. K. Gupta

Keyword(s):

Fusarium Solani ◽

Species Complex ◽

Morphological Characteristics ◽

Distilled Water ◽

Conidial Suspension ◽

Potato Dextrose Broth ◽

First Report ◽

Fusarium Solani Species Complex ◽

Rot Disease ◽

Tuber Rot

Bunium persicum (Kala zeera, also black cumin) is an economically important culinary crop that is cultivated for its seed pods and its tuberlike roots. In India, high-altitude regions of Himachal Pradesh, including the Padder valley and the Gurez area of Jammu and Kashmir, are areas of kalazeera production (3). In 2008 to 2009, tuber rot disease of kala zeera was observed during the late spring season in the Padder valley. Symptomatic plants were distributed in localized areas in the field and the symptoms included drying of foliage and rotting of tubers. White mycelia were found on the tubers at the late stages of disease development. Incidence of infection in the surveyed area was 80 to 90%. Yield losses were 50 to 60%. To isolate the causal pathogen, we cultured tissues from symptomatic tubers. Small bits of the infected tissue were surface disinfested in 0.1% mercuric chloride, followed by rinsing three times in sterile distilled water. The surface disinfested tissues were plated on potato dextrose agar (PDA) and incubated at 27°C for 4 days. Pure cultures of the mycelium from the diseased tissues were transferred to a second set of PDA for species identification. The fungus produced three types of spores: small, one-celled, oval microconidia; large, slightly curved, septate macroconidia; and rounded, thick-walled chlamydospores. Microconidia were mostly non-septate and 8.91 to 15.73 × 2.3 to 3.5 μm, whereas macroconidia were three- to five-septate and were 35.55 to 54.74 × 3.91 to 6.5 μm. On the basis of morphological characteristics (1), the fungus was identified and deposited as a member of the Fusarium solani species complex in the Indian Type Culture Collection, New Delhi (ID No. 8422.11). To confirm pathogenicity, healthy tubers were submerged for 20 min in a conidial suspension of the isolated fungus (1 × 105 cfu/ml), which was prepared in potato dextrose broth, incubated for 10 days at 27°C, and centrifuged at 140 rpm. Noninoculated controls were submerged in distilled water. Inoculated and control tubers were then planted in separate pots filled with sterilized soil and kept in a shade house. Symptoms appeared on inoculated tubers 9 to 10 days after planting. Signs of the pathogen in the form of mycelia were present. The tubers rotted and died 12 to 15 days after inoculation. Control tubers did not display any symptoms. F. solani species complex was reisolated from inoculated tubers, fulfilling Koch's postulates. F. solani has been reported to cause corm rot on gladiolus and saffron (2). To our knowledge, this is the first report of the F. solani species complex as pathogenic to tubers of kalazeera in India. References: (1) C. Booth. The Genus Fusarium. 47, 1971. (2) L. Z. Chen et al. J. Shanghai Agric. College 12:240, 1994. (3) K. S. Panwar et al. Agriculture Situation in India. 48:151, 1993.

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First Report of Verticillium Wilt of Watermelon Caused by Verticillium dahliae in China

Plant Disease ◽

10.1094/pdis-01-21-0045-pdn ◽

2021 ◽

Author(s):

Xiuyun Lu ◽

Junyan Shang ◽

Luxin Niu ◽

Xiangrui Sun ◽

Zhenhe Su ◽

...

Keyword(s):

Verticillium Wilt ◽

Verticillium Dahliae ◽

Its Region ◽

Sequence Information ◽

Post Inoculation ◽

Continuous Cropping ◽

Conidial Suspension ◽

First Report ◽

Fungal Isolates ◽

Pathogenicity Tests

Watermelon (Citrullus lanatus T.) is one of the most important economic crops in China. Soil-borne diseases are becoming more and more serious with longer growing seasons and continuous cropping of watermelon in greenhouses. In May 2020, symptoms were observed on plants in greenhouses located at Xingtai, Hebei province of China and included wilted leaves, chlorosis and plant death. Among the 26 greenhouses examined, symptomatic plants were observed in 17 greenhouses. The incidences of infected plants ranged from 1% to 35%, and caused an average 10% yield loss. Symptoms began on lower part of the plants and progressed upward to the vines and leaves. At the early stage of infection, the edge of watermelon leaves changed from green to yellow, and became soft. As the disease progressed, infected leaves wilted and desicated. The vascular tissue of the stem exhibited a uniform brown discoloration that often extended throughout the vine. To identify the causal agent, small pieces approximate 3.0×3.0 mm size of infected stem tissues were collected and sterilized with 0.5% sodium hypochlorite solution for 1 min, rinsed three times with sterile water and transferred onto potato dextrose agar (PDA) medium amended with 100 μg·mL-1 of chloramphenicol. The plates were incubated at 25°C for 3 days in the dark and fungal isolates were purified using the single-spore isolation method. A total of 22 fungal isolates with identical colony morphology were collected from diseased plants. The color of the fungal colonies on PDA medium was creamy-white with an abundance of mycelia that darken after 5 days growth due to the formation of microsclerotia. Fungal colonies consisted of fine, hyaline hyphae with verticillate conidiophores producing hyaline, ellipsoidal to oval conidia with an average size of 5.12×3.41 μm (n=50). The morphological characters of the fungal isolates were identical to those of Verticillium dahliae Kleb. described by Hawksworth and Talboys (Hawksworth, D. and Talboys, P, 1970). Pathogenicity tests were performed by soaking 30 watermelon seedlings with wounded root tips in the fungal conidial suspension (1x107 conidium/mL) for 30 min (Ma, et al, 2004). The same number of non-inoculated watermelon seedlings was used as a control. All plants were kept in a greenhouse at 25°C and 90%-95% relative humidity. Seven days post-inoculation (dpi), leaves of treated plants began to show symptoms of wilt. At 10-dpi, lower leaves wilted and dry and by 15-dpi, whole plants were dead. Pathogenicity tests were repeated three times with consistent results. The pathogen was re-isolated from the diseased plants and displayed identical morphological characteristics to the original isolates. To further identity the pathogens, the ribosomal DNA Internal Transcribed Spacer (rDNA-ITS) region was amplified by PCR (White et al., 1990; Liu et al., 1999; Bellemain et al.. 2010). The amplicon was sequenced and showed 99%-100% identity to the ITS region of the V. dahliae reference strains deposited in the NCBI database (MK093977.1, MK287620.1, MT348570.1 and LC549667.1, respectively). Based on morphological and ITS sequence information, the fungal pathogen was identified as V. dahliae. V. dahliae is an economically important pathogen with a wide host range worldwide. The discovery of Verticillium wilt on watermelons indicates that there might be a risk of Verticillium wilt when watermelons are planted in subsequent crops of the host plants of the disease, such as cotton or eggplant. To our knowledge, this is the first report of V. dahliae causing Verticillium wilt of watermelon in China. Financed: the Special Fund for Agro-scientific Research in the Public Interest, China (201503109) References: Hawksworth, D. and Talboys, P. 1970. Description of Pathogenic Fungi and Bacteria, CMI, Surrey. Ma, P., et al. 2004. A New Inoculation Method for Verticillium Wilt on Cotton and Its Application in Evaluating Pathogenesis and Host Resistance. Acta Phytopathologica Sinica, 34(6): 536-541. White, T. J., et al. 1990. Amplification and Direct Sequencing of Fungal Ribosomal RNA Genes for Phylogenetics. PCR protocols: a guide to methods and applications, 18(1), 315-322. Bellemain, E., et al. 2010. ITS as an Environmental DNA Barcode for Fungi: an in Silico Approach Reveals Potential PCR Biases. BMC microbiology, 10(1), 1-9. Liu, Y. J., et al. 1999. Phylogenetic Relationships Among Ascomycetes: Evidence from an RNA Polymerse II SubunitMol. Biol. Evol. 16:1799-1808.

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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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