First Report of Fusarium oxysporum on Lettuce in Europe

In spring 2001, plants of the lettuce cv. Salad Bowl showing symptoms of a wilt disease were observed in several commercial plastic greenhouses near Bergamo, in northern Italy. Wilted plants were first observed during the spring and summer of 2001 when temperatures were between 26 and 35°C. Symptoms were observed in the same area and the same farms in March 2002, in concomitance with a period of high temperatures. Although the distribution of the disease was generally uniform, symptoms were more severe in the central part of the greenhouses where temperatures were warmest. Symptoms were first observed at thinning, when seedlings (30 days old) appeared wilted. Vascular tissues of affected seedlings appeared red or brown. Affected plants were stunted and developed yellow leaves and brown or black streaks in the vascular system. The vascular streaks in the yellow leaves extended from the crown and were continuous with a red-brown discoloration in the vascular system of the crown and upper taproot. Symptoms were typically not visible on the outside of the crowns or roots. Fusarium oxysporum was consistently and readily isolated from symptomatic vascular tissues on a Fusarium-selective medium (2). Seeds of cv. Salad Bowl were planted in steam-sterilized soil artificially infested with 1 × 104 CFU/g soil of each of two isolates of F. oxysporum obtained from infected plants. Plants grown in noninfested soil served as noninoculated control treatments. Plants (25 per treatment) were grown at 25 to 28°C in growth chambers. Wilt symptoms and vascular discoloration of the roots, crown, and veins developed 20 days after seeding for all plants grown in the infested soil, and F. oxysporum was consistently reisolated from infected plants. The pathogenicity test was conducted twice. To our knowledge, this is the first report of F. oxysporum on lettuce in Europe. A wilt of lettuce attributed to F. oxysporum f. sp. lactucae was reported in Japan in 1967 (3) and in the United States in 1993 (1), in the latter case the incitant organism was described as F. oxysporum f. sp. lactucum. References: (1) J. C. Hubbard and J. S. Gerik. Plant Dis. 77:750, 1993. (2) H. Komada. Rev. Plant Prot. Res. 8:114, 1975. (3) T. Matuo and S. Motohashi. Trans. Mycol. Soc. Jpn. 8:13, 1967.

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First Report of Fusarium oxysporum on Eruca vesicaria and Diplotaxis spp. in Europe

Plant Disease ◽

10.1094/pdis.2003.87.2.201a ◽

2003 ◽

Vol 87 (2) ◽

pp. 201-201 ◽

Cited By ~ 9

Author(s):

A. Garibaldi ◽

G. Gilardi ◽

M. L. Gullino

Keyword(s):

Fusarium Oxysporum ◽

Vascular System ◽

Selective Medium ◽

Wild Plants ◽

Pathogenicity Test ◽

First Report ◽

Vascular Tissues ◽

Brown Discoloration ◽

Diplotaxis Erucoides ◽

Wild Rocket

Two types of rocket are available on the market in Italy: (i) Eruca vesicaria (synonym E. sativa) known as ruchetta or cultivated garden rocket; and (ii) several species of Diplotaxis (Diplotaxis erucoides, D. muralis, and D. tenuifolia), which are wild plants now widely cultivated. Rocket is increasingly used in the mediterranean cuisine as salad and or to decorate dishes. In spring 2002, plants of the cultivated (E. vesicaria) and wild (Diplotaxis spp.) rocket showing symptoms of a wilt disease were observed in several commercial plastic greenhouses near Bergamo, in northern Italy. Wilted plants were first observed during the spring and summer of 2001 when temperatures were between 26 and 35°C. In May 2002, symptoms were again observed in the same area, on the same farm as well as other farms. Although the distribution of the disease was generally uniform, symptoms were more severe in the central part of the greenhouses where temperatures were warmest (30 to 60% of plants were affected). Diseased plants were stunted and chlorotic with brown or black streaks in the vascular system. Vascular tissues of affected plants appeared red or brown. Vascular streaks in the chlorotic leaves extended from the crown and were continuous with a red-brown discoloration in the vascular system of the crown and upper taproot. Fusarium oxysporum was consistently and readily isolated from symptomatic vascular tissues when plated on a Fusarium-selective medium (2). Microconidia measured 8.8 × 3.0 µm. E. vesicaria and Diplotaxis spp. were grown in steam-sterilized soil, and 10 days after emergence they were artificially inoculated by root dipping in a spore suspension (1 × 105 CFU/ml) of three F. oxysporum strains collected from infected plants. Uninoculated plants served as control. Plants (60 per treatment) were grown at 25 to 28°C in growth chambers. Wilt symptoms developed on all plants 20 days after inoculation, and F. oxysporum was consistently reisolated from infected plants. The pathogenicity test was conducted twice. To our knowledge, this is the first report of F. oxysporum on cultivated rocket in Europe and the first on wild rocket (Diplotaxis spp.) in the world. A wilt of E. sativa attributed to F. oxysporum f. sp. erucae was previously reported in India in 1973 (1). Studies are being carried out to determine if the Italian isolates of F. oxysporum belong to the same formae speciales. References: (1) C. Chatterjee and J. N. Rai. Indian Phytopathol 28:309, 1973. (2) H. Komada. Rev. Plant Prot. Res. 8:114, 1975.

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Fusarium Wilt of African Daisy (Osteospermum sp.) Caused by Fusarium oxysporum in Italy

Plant Disease ◽

10.1094/pdis.2004.88.3.309a ◽

2004 ◽

Vol 88 (3) ◽

pp. 309-309 ◽

Cited By ~ 4

Author(s):

A. Garibaldi ◽

A. Minuto ◽

M. L. Gullino

Keyword(s):

Fusarium Oxysporum ◽

Vascular Tissue ◽

Vascular System ◽

Selective Medium ◽

Northern Italy ◽

Wilt Disease ◽

Pathogenicity Test ◽

Conidial Suspension ◽

Average Temperature ◽

Brown Discoloration

During the fall of 2002, African daisy (Osteospermum sp.) plants showing symptoms of a wilt disease were observed in a commercial, nonheated glasshouse in Albenga in northern Italy. Wilted plants were first observed when outside temperatures were between 15 and 28°C. Symptoms were first observed on seedlings 40 days after they had been transplanted into pots. The vascular tissues of affected plants appeared brown. These plants were stunted and developed yellowed leaves with brown or black streaks in the vascular system. The vascular streaks in the yellow leaves extended from the crown and were continuous with a brown discoloration in the vascular system of the crown and upper taproot. Fusarium oxysporum was consistently and readily isolated from symptomatic vascular tissue onto a Fusarium-selective medium (1). Healthy, rooted, 40-day-old plants were inoculated by root-dip with a conidial suspension (1 × 107 CFU/ml) of three isolates of F. oxysporum obtained 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 (minimum of 12°C and maximum of 39°C). Wilt symptoms and vascular discoloration in the roots, crown, and veins developed within 20 days on each inoculated plant, while noninoculated plants remained healthy. F. oxysporum was consistently reisolated from infected plants. The pathogenicity test was conducted twice. To our knowledge, this is the first report of F. oxysporum on Osteospermum sp. in Italy or elsewhere in the world. Reference: (1) H. Komada. Rev. Plant Prot. Res. 8:114, 1975.

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First Report of Fusarium Wilt of Chicory (Cichorium intybus) Caused by Fusarium oxysporum in Italy

Plant Disease ◽

10.1094/pdis-12-10-0872 ◽

2011 ◽

Vol 95 (4) ◽

pp. 496-496 ◽

Cited By ~ 4

Author(s):

A. Garibaldi ◽

G. Gilardi ◽

A. Poli ◽

M. L. Gullino

Keyword(s):

Fusarium Oxysporum ◽

Vascular Tissue ◽

Vascular System ◽

Fusarium Species ◽

Apical Cell ◽

Selective Medium ◽

Cichorium Intybus ◽

Pathogenicity Test ◽

First Report ◽

Sequence Identity

In the summer of 2009, a wilt of chicory was observed on 25 to 30% of 30-day-old Cichorium intybus L. cv. Clio plants grown outdoors on a commercial farm in Piedmont (northern Italy). Affected plants were chlorotic and stunted with poorly developed root systems compared with healthy plants. Black streaks were observed in the stem and proximal part of the leaf vascular system in wilted plants. Fusarium oxysporum Schltdl. was isolated from symptomatic vascular tissue on a Fusarium-selective medium (1) from 80% of samples. Grown on potato dextrose agar (PDA) for 4 days at 23°C, the colonies, initially white and later pale pink, produced hyaline microconidia that were oval-elliptical and cylindrical in shape measuring 5.6 to 14.9 (average 10.2) × 2.1 to 4.5 (3.0) μm, borne on short monophialides measuring 8.2 to 16.1 (average 13.2) × 2.1 to 4.2 (3.3) μm. Macroconidia were slightly curved, three-septate, with a slightly hooked apical cell and a foot-shaped basal cell measuring 24.9 to 41.6 (average 32.2) × 3.2 to 5.2 (4.3) μm. Chlamydospores were both terminally and intercalary, solitary but also in short chains (2 to 4 elements) measuring 21.1 to 41.0 (average 27.2) μm (2). The internal transcribed spacer (ITS) rDNA region was amplified using the primers ITS1/ITS4 and sequenced. BLASTn analysis of the 527-bp amplicon (GenBank Accession No. HQ644423) obtained had 98% sequence identity with F. oxysporum (GenBank Accession No. FJ605247). The translation elongation factor-1α (EF-1α) gene was amplified using primers EF-1/EF-2 and sequenced (GenBank Accession No. GU564259). The 663-bp fragment had 99% sequence identity with F. oxysporum (GenBank Accession Nos. EU313540, EU313539, and DQ837696). Pathogenicity tests were conducted on 15-day-old chicory plants from two cultivars (Clio and Katia). Thirty-five plants per cultivar were inoculated by dipping their roots in a 1 × 106 CFU/ml suspension of isolate FusCic45B recovered from wilted chicory. Inoculated and noninoculated plants were transplanted into five pots filled with 10 liters of steamed mix (peat/perlite/sand, 60:20:20 vol/vol) and were maintained in a glasshouse at 25 to 27°C. Wilt symptoms and vascular discoloration of the roots, crown, and veins developed 15 days after inoculation on all inoculated plants. Plants of cv. Clio were more susceptible. F. oxysporum was always reisolated from infected plants using the Fusarium-selective medium. All noninoculated plants remained healthy. The pathogenicity test was conducted twice. To our knowledge, this is the first report of wilt caused by F. oxysporum on chicory, C. intybus, in Italy as well as worldwide. References: (1) H. Komada. Rev. Plant Prot. Res. 8:114, 1975. (2) E. Nelson et al. Fusarium Species: An Illustrated Manual for Identification. The Pennsylvania State University Press, University Park, 1983.

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First Report of Fusarium Wilt on Paris Daisy (Argyranthemum[Dendranthema] frutescens)

Plant Disease ◽

10.1094/pdis.1998.82.12.1403c ◽

1998 ◽

Vol 82 (12) ◽

pp. 1403-1403 ◽

Cited By ~ 7

Author(s):

A. Garibaldi ◽

A. Minuto ◽

M. L. Gullino

Keyword(s):

Fusarium Oxysporum ◽

Fusarium Wilt ◽

Vascular System ◽

Northern Italy ◽

Artificial Inoculation ◽

Rooted Cuttings ◽

First Report ◽

Soil Inoculation ◽

Brown Discoloration ◽

Dark Blue

Paris daisy (Argyranthemum frutescens) is an economically important crop on the Riviera Ligure (Northern Italy), where approximately 10 million plants per year are produced for export. In September 1997, a serious wilt of plants (cv. Camilla) grown in plastic pots (14 to 18 cm in diameter) was observed. The leaves of the affected plants turned yellow unilaterally and eventually wilted. Both yellowing and wilting progressed acropetally. Eventually, affected plants were completely wilted and the stems showed dark blue-black necrosis. An intense brown discoloration of the vascular system was evident, particularly after yellowing of the foliage was visible. Fusarium oxysporum was consistantly isolated from diseased plants on Komada's medium (1). Two monoconidial isolates of F. oxysporum freshly isolated from A. frutescens wilted plants were used for artificial inoculation of healthy cv. Camilla plants in order to complete Koch's postulates. Rooted cuttings were inoculated by a root dip (for 30 s, with 5 × 107 CFU per ml) and by infesting soil (1 × 103 CFU per ml of soil). Inoculation was carried out on 20 plants belonging to five cultivars. Noninoculated plants of each cultivar served as control. Plants were maintained in a glasshouse at 22 to 23°C. Symptoms developed 13 to 14 days after and were similar to those observed on naturally infected plants. F. oxysporum was consistantly reisolated from artificially inoculated plants. Fusarium wilt of A. frutescens is favored by temperatures higher than 20°C. To our knowledge, this is the first report of Fusarium wilt on A. frutescens. Reference: (1) H. Komada. Rev. Plant Prot. Res. 8:114, 1975.

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First Report of Fusarium oxysporum Causing Vascular Wilt of Lamb's Lettuce (Valerianella olitoria) in Italy

Plant Disease ◽

10.1094/pdis.2004.88.1.83c ◽

2004 ◽

Vol 88 (1) ◽

pp. 83-83 ◽

Cited By ~ 3

Author(s):

A. Garibaldi ◽

G. Gilardi ◽

M. L. Gullino

Keyword(s):

Fusarium Oxysporum ◽

Vascular Tissue ◽

Selective Medium ◽

Northern Italy ◽

Growth Chamber ◽

Pathogenicity Test ◽

Vascular Wilt ◽

First Report ◽

Forma Specialis ◽

Vascular Discoloration

Lamb's lettuce (Valerianella olitoria), also known as corn salad, is increasingly grown in Italy and used primarily in the preparation of mixed processed salad. In the summer of 2003, plants of lamb's lettuce cvs. Trophy and Palmares exhibiting wilt symptoms were observed in several commercial greenhouses near Bergamo in northern Italy. Wilted 30-day-old plants were observed first during the month of June, at the time of thinning when temperatures ranged between 28 and 35°C. Disease was generally uniform in the greenhouses and 30 to 50% of the plants were affected. Vascular tissue of affected seedlings appeared red or brown but later turned brown or black. Affected plants were stunted and developed yellowed leaves. Vascular discoloration was continuous from the upper taproot through the crown to the leaf. Fusarium oxysporum was consistently isolated from symptomatic vascular tissue onto a Fusarium-selective medium (1). Seeds of the same cultivars (Trophy and Palmares) affected by the wilt in the field were artificially inoculated by dipping them for 15 min into spore suspensions (1 × 106 conidia per ml) of three isolates of F. oxysporum obtained from infected plants. Noninoculated seeds served as control treatments. Forty seeds per treatment were sown in pots (1-liter volume) containing steam-sterilized soil and maintained at 25°C in a growth chamber programmed for 12 hours of light per day. Wilt symptoms developed on both cultivars 20 days after seeding, and F. oxysporum was consistently reisolated from infected plants. The plants obtained from noninoculated seeds remained healthy. The pathogenicity test was carried out twice with similar results. To our knowledge, this is the first report of F. oxysporum causing vascular wilt of lamb's lettuce and may warrant a new forma specialis designation. Reference: (1) H. Komada. Rev. Plant Prot. Res. 8:114, 1975.

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First Report of Fusarium Wilt of Endive (Cichorium endivia) Caused by Fusarium oxysporum in Italy

Plant Disease ◽

10.1094/pdis-93-10-1078c ◽

2009 ◽

Vol 93 (10) ◽

pp. 1078-1078 ◽

Cited By ~ 5

Author(s):

A. Garibaldi ◽

G. Gilardi ◽

M. Troisi ◽

M. L. Gullino

Keyword(s):

Fusarium Oxysporum ◽

Vascular Tissue ◽

Vascular System ◽

Elongation Factor ◽

Intergenic Spacer ◽

Proximal Part ◽

Selective Medium ◽

Pathogenicity Test ◽

First Report ◽

Cichorium Endivia

In the summer of 2007, a wilt of endive (Cichorium endivia) cv. Myrna plants was observed on several commercial farms near Alessandria in northern Italy. Approximately 40% of the plants on each farm were symptomatic. Affected plants were stunted and yellow and their root systems were poorly developed. Basal leaves eventually wilted. Black streaks were observed in the proximal part of the leaf vascular system. Fusarium oxysporum was consistently isolated from symptomatic vascular tissue on a Fusarium-selective medium (1). To confirm identification of the pathogen, the translation elongation factor 1α and the ribosomal DNA intergenic spacer (IGS) region were partially sequenced (2). Genomic DNA was extracted from mycelia growing on potato dextrose agar. Amplification of the EF-1α region generated a sequence of 648 bp; the IGS amplicon was 2,500 bp. The EF-1α sequence (GenBank Accession No GQ398152) was 99% similar to the sequence of a F. oxysporum strain isolated from soil and a strain pathogenic on cotton plants (GenBank Accession No. EU246574). The IGS sequence (GenBank Accession No GQ398153) was 97% similar to the sequence of a F. oxysporum strain (GenBank Accession No. EF661647). Pathogenicity tests were conducted on 15-day-old endive plants (cv. Myrna). Ten plants were inoculated by dipping their roots in a 1 × 106 CFU/ml suspension of one of the isolates recovered from a wilted endive plant. Inoculated and noninoculated plants were transplanted into pots filled with steamed soil and maintained in a glasshouse at 23 to 28°C. Wilt symptoms and vascular discoloration of the roots, crown, and veins developed 60 days after inoculation. F. oxysporum was consistently reisolated from infected plants. Noninoculated plants remained healthy. The pathogenicity test was conducted twice. To our knowledge, this is the first report of wilt caused by F. oxysporum on endive in Italy. References: (1) H. Komada. Rev. Plant Prot. Res. 8:114, 1975. (2) G. Mbofung et al. Phytopathology 97:87, 2007.

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Fusarium Wilt of Bitterroot (Lewisia cotyledon) in Italy Caused by Fusarium oxysporum

Plant Disease ◽

10.1094/pd-89-0684a ◽

2005 ◽

Vol 89 (6) ◽

pp. 684-684 ◽

Cited By ~ 1

Author(s):

A. Garibaldi ◽

G. Gilardi ◽

M. L. Gullino

Keyword(s):

Fusarium Oxysporum ◽

Vascular Tissue ◽

Vascular System ◽

Casein Hydrolysate ◽

Culture Collection ◽

Selective Medium ◽

Pathogenicity Test ◽

Conidial Suspension ◽

Climatic Chamber ◽

Brown Discoloration

During the spring of 2004, bitterroot (Lewisia cotyledon (S. Wats.) B.L. Robins), a flowering perennial of interest for rock gardens, showed symptoms of a wilt disease in several commercial nurseries located in Piedmont (northern Italy). Ten to thirty percent of plants from several different nurseries were affected. Wilted plants were first observed approximately 20 days after being transplanted into containers when outside temperatures ranged from 15 to 22°C. Symptomatic plants were stunted with yellowed leaves and brown-to-black veins. The vascular browning extended into the crown and was continuous with a brown discoloration in the vascular system of the crown and upper taproot. Fusarium oxysporum, identified on the basis of colony and conidia morphology (1), was consistently and readily isolated from symptomatic vascular tissue onto a Fusarium-selective medium (2). Three isolates were transferred to casein hydrolysate and grown for 10 days to produce conidial inoculum. Healthy 30-day-old plants were inoculated by dipping roots into a (1 × 106 CFU/ml) conidial suspension. Plants were then transplanted into pots filled with steam-sterilized soil. Noninoculated plants served as a control. Plants (12 per treatment) were placed in a climatic chamber at 25°C. Wilt symptoms and vascular discoloration in the roots, crown, and veins developed within 20 days on each inoculated plant, while noninoculated plants remained healthy. F. oxysporum was consistently reisolated from symptomatic plants. The pathogenicity test was conducted twice with the same result. One isolate of the pathogen has been deposited in the ATCC culture collection. To our knowledge, this is the first report of F. oxysporum on L. cotyledon in Italy and elsewhere in the world. Currently, this disease is present in several nurseries in the Piedmont Region of Italy. References: (1) C. Booth. Fusarium. CMI, Kew, UK, 1977. (2) H. Komada. Rev. Plant Prot. Res. 8:114, 1975.

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First Report of Fusarium Wilt on Hebe sp. in Italy and Europe

Plant Disease ◽

10.1094/pdis.2000.84.6.705a ◽

2000 ◽

Vol 84 (6) ◽

pp. 705-705 ◽

Cited By ~ 3

Author(s):

A. Garibaldi ◽

A. Minuto ◽

G. Gilardi ◽

M. L. Gullino

Keyword(s):

Fusarium Wilt ◽

Vascular System ◽

The United States ◽

Selective Medium ◽

Artificial Inoculation ◽

Infested Soil ◽

Single Spore ◽

First Report ◽

Single Spore Isolate ◽

Whole Plants

Hebe (showy speedwell), an increasingly important crop in the Riviera Ligure (northern Italy), is cultivated in greenhouses and open fields. During summer 1999, a serious wilt of hybrids (Hebe speciosa × H. franciscana cvs. Paula, Linda, and Heidi) grown in plastic pots (14 to 16 cm diameter) in a peat/pomix/clay (70:20:10, vol/vol) substrate was observed. Symptoms appeared on one side of the plant or on a single branch. Affected plants showed only slight yellowing before wilting. Wilting progressed acropetally. Eventually, affected plants were completely wilted, and stems showed dark blue-black necrosis, often covered by mycelia. An intense brown discoloration of the vascular system was evident shortly after the appearance of the first symptoms. In some cases, whole plants suddenly wilted. Infected plants generally were stunted and eventually died. Fusarium oxysporum was isolated consistently from diseased plants on Komada's (1) Fusarium-selective medium. One single-spore isolate of F. oxysporum, freshly isolated from wilted plants, was used for artificial inoculation of healthy plants to complete Koch's postulates. Rooted cuttings were transplanted in soil artificially infested with 1 × 103 CFU/ml of soil. Inoculation was performed on 20 plants belonging to two cultivars (Paula and Heidi). Noninoculated plants of each cultivar served as controls. Plants were maintained in a glasshouse at 25°C. The first symptoms developed 20 days after transplanting in infested soil. Symptoms resulting from artificial inoculation were similar to those observed on naturally infected plants. F. oxysporum was consistently reisolated from inoculated plants. Fusarium wilt of Hebe is favored by temperatures higher than 20°C. Symptoms did not develop on inoculated plants maintained in the open field during the month of October nor in the greenhouse at temperatures lower than 18°C. This is the first report of Fusarium wilt on Hebe sp. in Italy and Europe. A similar wilt on H. buxifolia and other Hebe spp. has been reported by Raabe in the United States (2,3). References: (1) H. Komada. Rev. Plant Prot. Res 8:114, 1975. (2) R. D. Raabe. Phytopathology 47:532, 1957. (3) R. D. Raabe. Plant Dis. 69:450, 1985.

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Fusarium Wilt Caused by Fusarium oxysporum on Lettuce in Espirito Santo, Brazil

Plant Disease ◽

10.1094/pdis-92-6-0976c ◽

2008 ◽

Vol 92 (6) ◽

pp. 976-976 ◽

Cited By ~ 15

Author(s):

J. A. Ventura ◽

H. Costa

Keyword(s):

Fusarium Oxysporum ◽

Vascular System ◽

Infectious Agent ◽

The United States ◽

Selective Medium ◽

Pathogenicity Test ◽

Espírito Santo ◽

Randomized Design ◽

Crown Tissue ◽

Espirito Santo

Plants of lettuce cv. Salad Regina that showed symptoms of a wilt disease were observed in commercial fields in the Marechal Floriano and Caxixe production regions in the highlands of Espirito Santo State (ES), Brazil. Wilted plants were first observed during the 2000 cropping season (June to September) when temperatures were between 26 and 34°C. Outbreaks of wilt in the Caxixe Region also occurred in the last 2 years on cultivars of the Lisa type. Symptoms were observed on seedlings and adult plants. Affected plants appeared wilted, showed red-to-brown discoloration of vascular tissues, were stunted, and developed yellow leaves that had brown or black streaks in the vascular system. The vascular streaks in the yellow leaves were continuous from the red-brown vascular discoloration in the crown. A Fusarium sp. was consistently and readily isolated by plating surface-sterilized (with NaOCl) root and crown tissue segments from symptomatic plants onto lactic-acid-amended potato dextrose agar and a Fusarium-selective medium (4). To complete Koch's postulates, a single hyphal tip of the isolated fungi was transferred to carnation leaf agar. Micro- and macroconidia formed abundantly within 8 days and matched the description of Fusarium oxysporum Schlechtend. Fr. Two- to three-week-old lettuce seedlings of each of six cultivars (Monalisa AG-819, Grand Rapids Nacional, Regina, Carolina AG-576, Vitória, and Grandes Lagos), representing the range of lettuce genetic diversity typically planted in Espirito Santo, were inoculated with the isolated fungus by dipping the roots of each plant in a spore suspension (1 × 105 CFU/ml) or planting the seedlings in a steam-sterilized soil infested with the fungus at 1 × 105 conidia/ml potting medium. Ten inoculated seedlings of each cultivar were arranged in a completely randomized design and placed in a greenhouse (26 ± 2°C) to allow development of the infectious agent. Ten noninoculated plants of each cultivar served as control treatments. Wilt symptoms developed on all inoculated plants 20 to 30 days after inoculation, and infected plants showed the same symptoms as observed on the original plants from which the pathogen was isolated. Noninoculated plants remained symptomless. F. oxysporum was consistently reisolated from the inoculated seedlings. The pathogenicity test was conducted twice. A wilt of lettuce attributed to F. oxysporum f. sp. lactucae was previously reported in Japan (3) and later in the United States where the disease was attributed to F. oxysporum f. sp. lactucum (2). In 2002, a lettuce wilt caused by F. oxysporum f. sp. lactucae was reported in Italy (1). Studies are being carried out to determine the formae speciales of these Brazilian lettuce isolates of F. oxysporum. To our knowledge, this is the first report of F. oxysporum on cultivated lettuce in Brazil. References: (1) A. Garibaldi et al. Plant Dis. 86:1052, 2002. (2) J. C. Hubbard and J. S. Gerik. Plant Dis. 77:750, 1993. (3) T. Matuo and S. Motohashi. Trans. Mycol. Soc. Jpn. 8:13,1967. (4) J. A. Ventura. Rev. Ann. Patologia de Plantas 7:271, 1999.

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First Report of Fusarium oxysporum Causing Wilt on Jade Plant (Crassula ovata) in Italy

Plant Disease ◽

10.1094/pdis-12-10-0897 ◽

2011 ◽

Vol 95 (9) ◽

pp. 1191-1191 ◽

Cited By ~ 1

Author(s):

A. Garibaldi ◽

D. Bertetti ◽

P. Pensa ◽

A. Poli ◽

M. L. Gullino

Keyword(s):

Fusarium Oxysporum ◽

Vascular System ◽

Apical Cell ◽

Aerial Mycelium ◽

Selective Medium ◽

Fluorescent Light ◽

Pathogenicity Test ◽

Conidial Suspension ◽

Single Spore ◽

First Report

During summer 2010, symptoms of a wilt disease were observed in a commercial farm in northern Italy on Crassula ovata (jade plant). First symptoms consisted of chlorosis and premature drop of still turgid leaves. As the disease progressed, leaves turned yellow and wilted before dropping off and the stem wilted, bent, and eventually rotted starting from the base. In some cases, the stem broke or the basal portion of the leaf rotted. Brown discolorations were observed in the vascular system. Of 10,000 plants, 65% (cv. Mini) and 5% of 600 plants (cv. Magical Tree) were affected. Premature dropping of leaves was more frequent on cv. Magical Tree. Using the Komada's Fusarium-selective medium, a fungus was consistently and readily isolated from symptomatic vascular tissues of plants belonging to both cultivars. Isolates obtained from both cultivars were purified, subcultured on potato dextrose agar (PDA), and single-spore cultures were obtained. On PDA, both isolates produced pale violet, abundant, aerial mycelium, felted in old cultures, with purple pigments in the agar. The isolates were grown on Spezieller Nährstoffarmer agar for characterization of macroconidia and microconidia (1). Both isolates produced sparse, 3 to 5 septate, nearly straight macroconidia measuring 30 to 56 × 3 to 5 (average 40 × 4) μm with a short apical cell and a foot-shaped basal cell. Sporodochia were not observed. Unicellular, oval-elliptical microconidia measuring 5 to 13 × 3 to 4 (average 8 × 3) μm were produced on short monophialides. Chlamydospores were abundant, single and sometime in pairs, terminal and intercalary, rough walled, and measured 6 to 9 μm. Such characteristics are typical of Fusarium oxysporum (3). The ITS region (internal transcribed spacer) of rDNA was amplified with primers ITS1/ITS4 (4) and sequenced. BLASTn analysis of an isolate from C. ovata cv. Mini (515 bp, Accession No. HQ682196) and C. ovata cv. Magical Tree (509 bp, Accession No. HQ682197) showed an E-value of 0.0 with F. oxysporum. For these sequences, pairwise alignment of EMBOSS (E.B.I. - The European Bioinformatics Institute) revealed identity and similarity of 99.0%. To confirm pathogenicity, tests were conducted on 5-month-old plants of cvs. Mini and Magical Tree. Plants (three per treatment) were inoculated by dipping roots in a 1 × 106 CFU/ml conidial suspension of the two isolates of F. oxysporum prepared from 10-day-old cultures grown on casein liquid medium (2), shaken (90 rpm) for 10 days at 24°C ± 1 (12-h fluorescent light, 12-h dark). Inoculated plants were transplanted into pots filled with steamed mix (sphagnum peat/perlite/pine bark/clay; 50:20:20:10) and maintained in a plant growth chamber at 25 ± 1°C under a regimen of 12 h per day of fluorescent light. Inoculated plants belonging to both cultivars showed typical first symptoms of Fusarium wilt after 13 days. In the following days, leaves dropped, stems wilted, and plants died. Noninoculated plants remained healthy. F. oxysporum was reisolated from inoculated plants. The pathogenicity test was conducted twice. This is, to our knowledge, the first report of F. oxysporum on C. ovata in Italy or worldwide. References: (1) J. F. Leslie and B. A. Summerell. The Fusarium Laboratory Manual. Blackwell Professional, Ames, IA, 2006. (2) A. Minuto et al. Phytoparasitica 36:294, 2008. (3) B. A. Summerell et al. Plant Dis. 87:117, 2003. (4) T. J. White et al. PCR Protocols: A Guide to Methods and Applications. M. A. Innis et al., eds. Academic Press, San Diego, 1990.

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