First Report of Fusarium Wilt Caused by Fusarium oxysporum on Strawberry in Spain

In the spring of 2007, wilted and dead strawberry plants (Fragaria × ananassa Duch. cvs. Camarosa and Ventana) were observed in a soilless culture system in Huelva, southwestern Spain. Approximately 8% of the plants in the field died. Isolations from necrotic crowns and roots and necrotic flowers were made on potato dextrose agar after disinfestation in 0.6% NaOCl for 30 s. Colonies with light purple mycelia and beige or orange reverse colony colors developed after 9 days of incubation at 25°C. Colonies produced abundant microconidia, macroconidia, and chlamydospores. Microconidia were hyaline and oval-ellipsoid to cylindrical (5.9 to 9.2 × 2.1 to 3.4 μm). Macroconidia were 3 to 5 septate and fusoid-subulate with a pedicellate base (28.8 to 37.3 × 3.2 to 4.3 μm). Morphology and growth matched descriptions of Fusarium oxysporum Schlechtend emend. Snyder & Hansen (2). A PCR assay for amplification of r-DNA using primers PFO2 and PFO3 established the identity of the isolate as F. oxysporum (1). To confirm the pathogenicity of the fungus, roots of 30-day-old strawberry cvs. Camarosa and Ventana (20 plants each) were inoculated by dipping the roots into a conidial suspension (107 conidia per ml) for 15 min. The inoculated plants were transplanted into plastic pots containing sterilized peat and maintained at 25°C and 100% relative humidity in a growth chamber with a daily 12-h photoperiod of fluorescent light. The pathogenicity test was conducted twice. Within 30 days, all inoculated plants developed wilt symptoms similar to that observed in the field and eventually 75% of the plants died. No symptoms were observed on plants dipped in distilled water. The fungus was successfully reisolated from crowns, roots, and necrotic flowers, fulfilling Koch's postulates. To our knowledge, this is the first report of the occurrence of Fusarium wilt caused by F. oxysporum on strawberry plants in Spain. References: (1) V. Edel et al. Mycol. Res. 104:518, 2000. (2) W. C. Snyder and H. N. Hansen. Am. J. Bot. 27:64, 1940.

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First Report of Fusarium Wilt on Philotheca myoporoides Caused by Fusarium oxysporum in Italy

Plant Disease ◽

10.1094/pdis-03-11-0243 ◽

2011 ◽

Vol 95 (7) ◽

pp. 877-877 ◽

Cited By ~ 1

Author(s):

G. Polizzi ◽

D. Aiello ◽

V. Guarnaccia ◽

A. Vitale ◽

G. Perrone ◽

...

Keyword(s):

Fusarium Oxysporum ◽

Fusarium Wilt ◽

Morphological Characteristics ◽

Plant Production ◽

Pathogenicity Test ◽

Gene Sequences ◽

Pcr Assay ◽

First Report ◽

Gene Coding ◽

Eastern Australia

Philotheca myoporoides (DC.) M.J. Bayly (previously known as Eriostemon myoporoides), commonly called long-leaf waxflower and native to eastern Australia (Rutaceae family), is a hardy compact shrub or small tree occurring in subtropical to cool temperate regions. P. myoporoides is cultivated in Sicily (Italy) for its ornamental appeal. During April of 2010, a widespread wilting was observed on approximately 80% of 2,000 1-year-old, potted long-leaf waxflower plants grown in a commercial nursery near Catania (eastern Sicily, Italy). Internally, symptomatic plants had conspicuous vascular brown discoloration from the crown to the canopy. Diseased crown and stem tissues of 20 plants were surface disinfested for 30 s in 1% NaOCl, rinsed in sterile water, plated on potato dextrose agar (PDA) amended with 100 mg/liter of streptomycin sulfate, and incubated at 25°C. A Fusarium sp. was consistently isolated from affected plant tissues. Colonies with white or light purple aerial mycelia and violet pigmentation on the underside of the cultures developed after 9 days. On carnation leaf agar, 20 single-spore isolates produced microconidia on short monophialides, macroconidia that were three to five septate with a pedicellate base, and solitary and double-celled or aggregate chlamydospores. A PCR assay was conducted on one representative isolate (ITEM 13490) by analyzing sequences of the benA gene (coding β-tubulin protein) and CaM gene (coding calmodulin protein) using the primers reported by O'Donnell et al. (1). The benA gene sequences of ITEM 13490 (GenBank No. FR828825) exhibited an identity of 100% to Fusarium oxysporum f. sp. radicis-lycopersici strain ATCC 52429 (GenBank No. DQ092480). CaM gene sequences of ITEM 13490 (GenBank No. FR828826) exhibited an identity of 99.6% to F. oxysporum strain ITEM 2367 (GenBank No. AJ560774). Morphological characteristics of the 20 isolates, as well as the PCR assay on a representative strain, identified the isolates associated with disease symptoms as F. oxysporum Schlechtend.:Fr. A pathogenicity test was performed by placing two 1-cm2 plugs of PDA from 9-day-old mycelial cultures near the crown on potted, healthy, 2-month-old cuttings of P. myoporoides. Thirty plants were inoculated with strain ITEM 13490 and the same number of plants served as noninoculated controls. All plants were enclosed for 4 days in plastic bags and placed in a growth chamber at 25 ± 1°C. Plants were then moved to a greenhouse where temperatures ranged from 23 to 27°C. First symptoms, which were identical to those observed in the nursery, developed on one plant 15 days after inoculation. Wilting was detected on all plants after 30 days. Control plants remained symptomless. F. oxysporum was successfully reisolated from symptomatic crown and stem tissues and identified as described above, fulfilling Koch's postulates. To our knowledge, this is the first report of F. oxysporum causing disease of P. myoporoides worldwide. Moreover, this pathogen was recently reported in the same nursery on Eremophila sp. (2), confirming the presence of Fusarium wilt as a potential threat to ornamental plant production in this area, and necessitates the innovation and development of disinfection methods for alveolar trays, greenhouses, and various propagation materials to reduce future disease outbreaks. References: (1) K. O'Donnell et al. Mycoscience 41:61, 2000. (2) G. Polizzi et al. Plant Dis 94:1509, 2010.

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First Report of Fusarium Wilt in Blueberry (Vaccinium corymbosum) Caused by Fusarium oxysporum in China

Plant Disease ◽

10.1094/pdis-02-14-0167-pdn ◽

2014 ◽

Vol 98 (8) ◽

pp. 1158-1158 ◽

Cited By ~ 1

Author(s):

Y. H. Liu ◽

T. Lin ◽

C. S. Ye ◽

C. Q. Zhang

Keyword(s):

Fusarium Oxysporum ◽

Infected Plant ◽

Morphological Characteristics ◽

Vaccinium Corymbosum ◽

Morphological Characterization ◽

Internal Transcribed Spacers ◽

Fluorescent Light ◽

Pathogenicity Test ◽

Conidial Suspension ◽

First Report

Blueberry (Vaccinium corymbosum) production is developing quickly in China with about 20,000 ha presently cultivated. In 2010 in Lin'an, Zhejiang Province, plants developed an apparently new disease of blueberry (cv. Duke) with symptoms consisting of wilting of foliage, stunting of plants, and reduced fruit yields. Internal vascular and cortical tissues of plant crowns showed a brown to orange discoloration. Approximately 3% of the plants in the commercial plantings were affected and eventually died after 50 to 60 days. Infected plant samples (stems and roots) collected from different fields were surface sterilized with 1.5% sodium hypochlorite for 2 min, rinsed in water, plated on 2% potato dextrose agar (PDA), and incubated at 25°C in the dark for 1 week. Single conidium cultures were consistently isolated and cultured on acidified PDA (APDA) for morphological characterization (1,2). Colonies were light with purple mycelia, and beige or orange reverse colony colors developed after 7 days incubation at 25°C. Colonies producing abundant microconidia and macroconidia. Microconidia were hyaline and oval-ellipsoid to cylindrical (3.9 to 9.6 × 1.1 to 3.4 μm). Macroconidia were 3 to 5 septate and fusoid-subulate with a pedicellate base (28.6 to 37.5 × 3.3 to 4.2 μm). Morphology and development of macroconidia and microconida were consistent with a description of Fusarium oxysporum Schltdl (1,2). The ribosomal internal transcribed spacers ITS1 and ITS2 of eight isolates were amplified using primers ITS1/ITS4 on DNA extracted from mycelium and nucleotide sequences showed 100% similarity to that of F. oxysporum. To confirm pathogenicity, 20 blueberry plants (cv. Duke) were inoculated by dipping the roots into a conidial suspension (107 conidia per ml) for 30 min. The inoculated plants were transplanted into pots containing sterilized peat and maintained at 25°C and 100% relative humidity in a growth chamber with a daily 12-h photoperiod of fluorescent light. The pathogenicity test was conducted twice. Within 40 days, all inoculated plants developed wilt symptoms similar to that observed in the field. No symptoms were observed on plants dipped into distilled water. The fungus was successfully re-isolated from crowns and roots cultured on APDA, exhibiting morphological characteristics identical to F. oxysporum (1,2), confirming Koch's postulates. To our knowledge, this is the first report of blueberry wilt caused by Fusarium. References: (1) P. M. Kirk et al. The Dictionary of the Fungi, 10th edition, page 159. CABI Bioscience, Wallingford, UK, 2008. (2) W. C. Snyder and H. N. Hansen. Am. J. Bot. 27:64, 1940.

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First Report of Basal Stem Rot of Apple Cactus (Cereus peruvianus monstruosus) Caused by Fusarium oxysporum in Italy

Plant Disease ◽

10.1094/pdis-03-11-0216 ◽

2011 ◽

Vol 95 (7) ◽

pp. 877-877

Author(s):

A. Garibaldi ◽

P. Pensa ◽

D. Bertetti ◽

A. Poli ◽

M. L. Gullino

Keyword(s):

United States ◽

Fusarium Oxysporum ◽

The United States ◽

Stem Rot ◽

Fluorescent Light ◽

Pathogenicity Test ◽

Conidial Suspension ◽

Single Spore ◽

Basal Stem Rot ◽

First Report

During the summer of 2010, 20% of 7,000 4-month-old plants of apple cactus (Cereus peruvianus monstruosus) showed symptoms of a basal stem rot in a commercial nursery located in Liguria (northern Italy). Affected plants showed yellow orange-to-pale brown color from the crown level to the stem apex and a water-soaked rot was observed on the stem starting from the base. Brown discoloration was observed in the vascular system. Eventually stems bent, plants collapsed and died, and affected tissues dried out. A Fusarium sp. was consistently and readily isolated from symptomatic tissue on Komada selective medium. Isolates were purified and subcultured on potato dextrose agar (PDA). Single-spore cultures on PDA, Spezieller Nährstoffarmer agar (SNA) (3), and carnation leaf-piece agar (CLA) (2) were incubated at 26 ± 1°C (12-h fluorescent light, 12-h dark). On PDA, cultures produced a thick growth of white-to-pink mycelium and pale pink pigments in the agar. On SNA, cultures produced short monophialides with unicellular, ovoid-elliptical microconidia measuring 4.3 to 8.2 × 2.3 to 3.8 (average 6.0 × 2.8) μm. Chlamydospores were abundant, single or paired, terminal and intercalary, rough walled, and 6 to 8 μm in diameter. On CLA, cultures produced orange sporodochia with macroconidia that were 3 to 4 septate, nearly straight with a foot-shaped basal cell and a short apical cell, and measured 31.1 to 51.5 × 4.4 to 3.5 (average 43.2 × 3.8) μm. Such characteristics are typical of Fusarium oxysporum (3). Amplification of the ITS (internal transcribed spacer) of the rDNA using primers ITS1/ITS4 (4) yielded a 498-bp band. Sequencing and BLASTn analysis of this band showed an E-value of 0.0 with F. oxysporum. The nucleotide sequence has been assigned GenBank Accession No. JF422071. To confirm pathogenicity, five 6-month-old healthy plants of C. peruvianus monstruosus were inoculated by dipping roots in a conidial suspension (2.4 × 106 CFU/ml) of F. oxysporum isolated from affected plants. Inoculum was obtained from pure cultures of three single-spore isolates grown for 10 days on casein hydrolysate liquid medium. Roots were not wounded before the inoculation. Plants were transplanted into pots filled with steam-sterilized substrate (sphagnum peat/perlite/pine bark/clay 50:20:20:10). Five noninoculated plants served as a control. Plants were placed in a climatic chamber at 25 ± 1°C (12-h fluorescent light, 12 h-dark). Basal stem rot and vascular discoloration in the crown and stem developed within 30 days on each inoculated plant. Noninoculated plants remained healthy. F. oxysporum was consistently isolated from symptomatic plants. The pathogenicity test was conducted twice. F. oxysporum has been reported on Cereus spp. in the United States (1). To our knowledge, this is the first report of F. oxysporum on C. peruvianus monstruosus in Italy as well as in Europe. Currently, this disease is present in a few nurseries in Liguria. References: (1) D. F. Farr et al. Fungi on Plants and Plant Products in the United States. The American Phytopathological Society, St Paul, MN, 1989. (2) N. L. Fisher et al. Phytopathology 72:151, 1982. (3) J. F. Leslie and B. A. Summerell. The Fusarium Laboratory Manual. Blackwell, Ames, IA, 2006. (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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First Report of Fusarium Wilt of Strawberry Caused by Fusarium oxysporum in Serbia

Plant Disease ◽

10.1094/pdis-04-14-0346-pdn ◽

2014 ◽

Vol 98 (10) ◽

pp. 1435-1435 ◽

Cited By ~ 4

Author(s):

I. Stanković ◽

D. Ristić ◽

A. Vučurović ◽

K. Milojević ◽

D. Nikolić ◽

...

Keyword(s):

Fusarium Oxysporum ◽

Fusarium Wilt ◽

Fluorescent Light ◽

Fungal Mycelium ◽

Morphological Identification ◽

Post Inoculation ◽

Conidial Suspension ◽

First Report ◽

Vascular Tissues ◽

Initial Symptoms

Strawberry (Fragaria × ananassa Duch.) is the third most important berry crop in Serbia with average production ranging from 30,000 to 35,000 t on approximately 5,000 ha (2). In June 2013, symptoms of wilt and whole plant collapse were observed on approximately 25% plants growing in commercial strawberry crop of cv. Alba in the locality of Zablaće (Moravica district). Initial symptoms included leaf chlorosis and wilt, followed by withering and necrosis of older leaves and reduced fruit production, eventually leading to plant collapse and desiccations. Internal vascular tissues of the crown showed distinct brown reddish discoloration. Three small pieces of infected roots, petioles, or crown vascular tissues were surface disinfested with 2% NaOCl and placed on five potato dextrose agars (PDA) per sample. After 7 days incubation at 23°C under 12 h of fluorescent light, nine monoconidial isolates were obtained (1) forming colonies with light purple mycelia. Colonies produced numerous hyaline, oval to ellipsoid microconidia (5 to 15 × 2.5 to 4.5 μm, average 8.45 × 2.25 μm), 3 to 5 septate fusoid macroconidia with pedicellate bases (20 to 50 × 2.70 to 6 μm, average 32.35 × 3.25 μm from 100 measured) and chlamydospores. Morphological and growth features were similar to the descriptions of Fusarium oxysporum Schlechtend emend. Snyder & Hansen (1). Pathogenicity of one selected isolate (97-13) was tested by dipping for 15 min the roots of five plants of each cultivar: Alba, Arosa, Clery, and Roxana into a conidial suspension (1 × 106 conidia/ml) harvested from a 7-day-old culture on PDA. Control plants were dipped in sterile distilled water. The inoculated plants were transplanted into pots containing sterilized peat and maintained in the greenhouse at 25°C. Thirty to thirty-five days post-inoculation, all plants developed wilt symptoms and vascular discoloration of crown tissues from which F. oxysporum was successfully re-isolated using the same method as for isolation. No symptoms were observed on any of the control plants. Morphological identification was confirmed by amplification and sequencing of a portion of the translation elongation factor-1 alpha (EF-1α) gene. Total DNA was extracted directly from fungal mycelium with a DNeasy Plant Mini Kit (Qiagen, Hilden, Germany) and PCR amplification performed with primers EF-1/EF-2 (4). Sequence analysis of EF-1α region revealed that Serbian isolate 97-13 (GenBank Accession No. KJ647280) shared 99 to 100% identity with the F. oxysporum sequences in GenBank. To our knowledge, this is the first report of Fusarium wilt on strawberry in Serbia. The presence of a new and potentially harmful disease may represent a serious constraint for strawberry production in Serbia. References: (1) J. F. Leslie and B. A. Summerell. The Fusarium Laboratory Manual, Blackwell Publishing, London, UK, 2006. (2) M. Nikolić et al. Acta Hort. 842:615, 2009. (3) K. O'Donnell et al. Proc. Natl. Acad. Sci. USA 95:2044, 1998.

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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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First Report of Fusarium oxysporum Causing Wilt on Iceland Poppy (Papaver nudicaule) in Italy

Plant Disease ◽

10.1094/pdis-06-12-0517-pdn ◽

2012 ◽

Vol 96 (12) ◽

pp. 1823-1823 ◽

Cited By ~ 3

Author(s):

A. Garibaldi ◽

P. Martini ◽

L. Repetto ◽

M. Odasso ◽

D. Bertetti ◽

...

Keyword(s):

Fusarium Oxysporum ◽

Fusarium Wilt ◽

Vascular Tissue ◽

Agar Medium ◽

Research Center ◽

Its Sequence ◽

Pathogenicity Test ◽

Conidial Suspension ◽

Potato Dextrose Broth ◽

First Report

During fall 2011, symptoms of a wilt disease were observed in a commercial nursery near Ventimiglia as well as in the Research Center of Floriculture of Sanremo (northern Italy) on plants of Papaver nudicaule (Iceland poppy) of a local unnamed cultivar. In the commercial nursery, 15 to 20% of plants were affected, while about 3% of plants were affected at the Research Center. Symptoms consisted of chlorosis, premature leaf drop, and foliar wilting, followed by the stem wilting, bending, and eventually rotting from the base. Brown discoloration was observed in the stem vascular tissue. Using Komada's Fusarium-selective agar medium (2), a fungus was consistently and readily isolated from symptomatic vascular tissue of plants collected from both sites. The isolates were purified and subcultured on potato dextrose agar (PDA), on which medium both isolates produced pale violet, abundant, aerial mycelium, felted in old cultures, with pale purple pigments in the agar medium. The isolate generated short monophialides with unicellular, ovoid-elliptical microconidia of 3.9 to 6.7 × 1.4 to 3.0 (average 5.4 × 2.3) μm. On carnation leaf agar (CLA) (1), isolates produced pale orange sporodochia with macroconidia that were 3-septate, slightly falcate with a foot-shaped basal cell and a short apical cell, and 26.0 to 43.5 × 3.1 to 4.4 (average 35.3 × 3.7) μm. Chlamydospores were abundant, terminal, and intercalary, rough walled, mostly singles but sometime in short chains or clusters, and 5.2 to 10.1 μm in diameter. Such characteristics are typical of Fusarium oxysporum (3). The internal transcribed spacer (ITS) region of rDNA was amplified from the isolates using the primers ITS1/ITS4 (4), and sequenced. BLASTn analysis of the 507-bp ITS sequence of one isolate from P. nudicaule collected from the commercial nursery (GenBank Accession No. JX103564) showed an E-value of 0.0 and 100% identity with the ITS sequence of F. oxysporum (HQ649820). To confirm pathogenicity of one of the Iceland poppy isolates, tests were conducted on 2-month-old plants of the same cultivar on which symptoms were first observed. Plants (n = 14) were inoculated by dipping roots in a 1 × 107 CFU/ml conidial suspension of the isolate of F. oxysporum prepared from 10-day-old cultures grown in potato dextrose broth (PDB) on a shaker (90 rpm) for 10 days at 22 ± 1°C (12-h fluorescent light, 12-h dark). Non-inoculated control plants (n = 14) were dipped in sterilized water. All the plants were transplanted into pots filled with steamed potting mix (sphagnum peat/perlite/pine bark/clay at 50:20:20:10), and maintained in a glasshouse at 24 to 28°C. Inoculated plants showed typical symptoms of Fusarium wilt after 10 days. The stems then wilted and plants died. Non-inoculated plants remained healthy. F. oxysporum was reisolated from inoculated plants but not from control plants. The pathogenicity test was conducted twice with the same results. Since Fusarium wilt has not previously been described on Iceland poppy at any location, this is first report of F. oxysporum on P. nudicaule in Italy and anywhere in the world. References: (1) N. L. Fisher et al. Phytopathology 72:151, 1982. (2) H. Komada. Rev. Plant Prot. Res. 8:114, 1975. (3) J. F. Leslie and B.A. Summerell. The Fusarium Laboratory Manual, Blackwell Professional, IA, 2006. (4) T. J. White et al. PCR Protocols: A Guide to Methods and Applications. M. A. Innis et al., eds. Academic Press, San Diego, CA, 1990.

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First report of Alternaria alternata causing leaf blight on little millet (Panicum sumatrense) in India.

Plant Disease ◽

10.1094/pdis-06-20-1373-pdn ◽

2020 ◽

Author(s):

Boda Praveen ◽

A. Nagaraja ◽

M. K. Prasanna Kumar ◽

Devanna Pramesh ◽

K. B. Palanna ◽

...

Keyword(s):

Crop Yields ◽

Disease Incidence ◽

Leaf Blight ◽

Post Inoculation ◽

Pathogenicity Test ◽

Conidial Suspension ◽

Pcr Assay ◽

Causal Organism ◽

First Report ◽

Little Millet

Little millet (LM) is a minor cereal crop grown in the Indian sub-continent. During October 2018, dark brown, circular to oval necrotic spots surrounded by concentric rings were observed on the upper leaf surface of the LM (cv. VS-13) grown in the fields of the University of Agricultural Sciences, Bengaluru, India (13.0784oN, 77.5793oE). As the disease progressed, infected leaves became blighted. Disease incidence up to 53% was recorded in 3 fields of 0.4-hectare area each. Thirty symptomatic leaves were collected to isolate the associated causal organism. The margins of diseased tissue were cut into 5 × 5-mm pieces, surface-sterilized in 75% ethanol for 45 seconds followed by 1% sodium hypochlorite for 1 min, finally rinsed in sterile distilled water five times and placed on PDA. After 7 days of incubation at 25°C, greyish fungal colonies appeared on PDA. Single-spore isolations were performed to obtain ten isolates. Pure cultures of the fungus initially produced light gray aerial mycelia that later turned to dark grey. All isolates formed obclavate to pyriform conidia measured 22.66-48.97μm long and 6.55-13.79µm wide with 1-3 longitudinal and 2-7 transverse septa with a short beak (2.55-13.26µm) (n=50). Based on the conidial morphology, the fungus was identified as Alternaria sp. Further, the taxonomic identity of all ten isolates was confirmed as A. alternata using species-specific primers (AAF2/AAR3, Konstantinova et al. 2002) in a PCR assay. Later, one of the isolate UASB1 was selected, and its internal transcribed spacer (ITS) region, glyceraldehyde-3-phosphate dehydrogenase (gapdh), major allergen Alt a 1 (Alt a 1), major endo-polygalacturonase (endoPG), OPA10-2, and KOG1058 genes were amplified in PCR (White et al. 1990; Berbee et al. 1999; Woudenberg et al. 2015), and the resultant products were sequenced and deposited in the NCBI GenBank (ITS, MN919390; gapdh, MT637185; Alt a 1, MT882339; endoPG, MT882340; OPA10-2, MT882341; KOG1058, MT882342). Blastn analysis of ITS, gapdh, Alt a 1, endoPG, OPA10-2, KOG1058 gene sequences showed 99.62% (with AF347031), 97.36% (with AY278808), 99.58% (with AY563301), 99.10% (with JQ811978), 99.05% (with KP124632) and 99.23% (with KP125233) respectively, identity with reference strain CBS916.96 of A. alternata, confirming UASB1 isolate to be A. alternata. For pathogenicity assay, conidial suspension of UASB1 isolate was spray inoculated to ten healthy LM (cv. VS-13) plants (45 days old) maintained under protected conditions. The spore suspension was sprayed until runoff on healthy leaves, and ten healthy plants sprayed with sterile water served as controls. Later, all inoculated and control plants were covered with transparent polyethylene bags and were maintained in a greenhouse at 28±2 ◦C and 90% RH. The pathogenicity test was repeated three times. After 8 days post-inoculation, inoculated plants showed leaf blight symptoms as observed in the field, whereas no disease symptoms were observed on non-inoculated plants. Re-isolations were performed from inoculated plants, and the re-isolated pathogen was confirmed as A. alternata based on morphological and PCR assay (Konstantinova et al. 2002). No pathogens were isolated from control plants. There is an increasing acreage of LM crop in India, and this first report indicates the need for further studies on leaf blight management and the disease impacts on crop yields.

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First Report of Fusarium Wilt of Lavandula pubescens Caused by Fusarium oxysporum in Saudi Arabia

Plant Disease ◽

10.1094/pdis-94-9-1163b ◽

2010 ◽

Vol 94 (9) ◽

pp. 1163-1163 ◽

Cited By ~ 2

Author(s):

K. Perveen ◽

N. Bokhari

Keyword(s):

Saudi Arabia ◽

Fusarium Oxysporum ◽

Vascular Tissue ◽

Agricultural Research ◽

Indian Agricultural Research Institute ◽

Pathogenicity Test ◽

Conidial Suspension ◽

Potential Threat ◽

King Saud University ◽

First Report

In November 2008, a wilt of lavender (Lavandula pubescens) seedlings was observed in the greenhouse at King Saud University, Riyadh, Saudi Arabia. Affected seedlings were wilted and the root system was poorly developed. Diseased stems developed a dark coloration that extended down to the roots. Vascular tissue of the affected seedlings appeared red or brown. Isolations consistently yielded a fungus growing from the discolored stem tissue when placed on potato dextrose agar. The macroscopic characteristics of the colony, as well as microscopic structures, were used to identify the fungus as Fusarium oxysporum (2). Oval to elliptical microconidia without septa and originating from short phialides were used to distinguish the species from F. solani (1). The fungus was authenticated by the ITCC (Indian Type Collection Centre), Indian Agricultural Research Institute, New Delhi, India, and given I.D. No. 7532.09. For conducting further experiments, healthy seedlings of L. pubescens were obtained from the botanical garden of the King Saud University and grown in steam-sterilized soil. Healthy seedlings of lavender were inoculated using a root-dip method with a conidial suspension (1 × 107 CFU/ml) of one strain of F. oxysporum obtained from infected plants. Inoculated seedlings were then transplanted into steam-sterilized soil. Plants inoculated with sterilized water (1 ml per plant) served as control treatments. Wilt symptoms and vascular discoloration in the roots and crown developed within 20 days on all plants inoculated with the pathogen, while control plants remained asymptomatic. F. oxysporum was consistently reisolated from symptomatic plants. The pathogenicity test was conducted twice. To our knowledge, this is the first report of F. oxysporum on L. pubescens in Saudi Arabia or elsewhere in the world, and this newly identified disease may be a potential threat to commercial production of lavender. References: (1) J. F. Leslie and B. A. Summerell. Page 212 in: The Fusarium Laboratory Manual. Blackwell Publishing Professional, Hoboken, NJ, 2006. (2) P. C. Nelson et al. Clin. Microbiol. Rev. 7:479, 1994.

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First Report of Plectosphaerella cucumerina on Greenhouse Cultured Wild Rocket (Diplotaxis tenuifolia) in Italy

Plant Disease ◽

10.1094/pdis-06-12-0583-pdn ◽

2012 ◽

Vol 96 (12) ◽

pp. 1825-1825 ◽

Cited By ~ 11

Author(s):

A. Garibaldi ◽

G. Gilardi ◽

G. Ortu ◽

M. L. Gullino

Keyword(s):

Southern Italy ◽

Its Region ◽

Economic Losses ◽

Leaf Spot Disease ◽

Fluorescent Light ◽

Pathogenicity Test ◽

Conidial Suspension ◽

First Report ◽

Horticultural Crops ◽

Plectosphaerella Cucumerina

During spring 2012, symptoms of an unusual leaf spot disease were observed in several commercial greenhouses near Salerno (southern Italy) on plants of Diplotaxis tenuifolia (cv Selvatica). The first symptoms on leaves of affected plants consisted of small (1 mm) black-brown spots of irregular shape, later coalescing into larger spots, 1 cm in diameter. Spots were surrounded by a yellow halo, and were mostly located on the foliar limb, rib, and petiole. Affected leaves were often distorted, appearing hook-like. The disease was severe under 75 to 90% RH, at air temperature of 20 to 26°C, and caused severe production losses on about 50 ha. Particularly, affected tissues rotted quickly after packaging and during transit and commercialization of processed rocket. Diseased tissue was excised, immersed in a solution containing 1% sodium hypochlorite for 60 s, rinsed in water, then placed on potato dextrose agar (PDA) medium, containing 25 mg/l of streptomycin sulphate. After 5 days, a fungus developed producing a whitish-orange mycelium when incubated under 12 h/day of fluorescent light at 22°C. The isolates obtained were purified on PDA. On this medium, they produced hyaline elliptical and ovoid conidia, sometimes one-septate, measuring 4.5 to 9.2 × 1.7 to 3.5 (average 6.8 × 2.6) μm. Conidia were born on phialides, measuring 6.8 to 20.2 × 1.3 to 3.1 (average 16.5 × 2.1) μm. Such characteristics are typical of Plectosphaerella sp. (2). The internal transcribed spacer (ITS) region of rDNA was amplified using the primers ITS1/ITS4 (3) and sequenced. BLAST analysis of the 519-bp segment showed a 98% similarity with the sequence of Plectosphaerella cucumerina (GenBank Accession No. AB469880). The nucleotide sequence has been assigned the GenBank Accession JX185769. To confirm pathogenicity, tests were conducted on 45-day-old D. tenuifolia plants. Plants (21/treatment), grown in 15 liter pots (7 plants/pot) were inoculated by spraying a 1 × 106 CFU/ml conidial suspension of one isolate of P. cucumerina, prepared from 10-day-old cultures, grown on PDA. Inoculated plants were maintained in a growth chamber at 23 ± 1°C, at 90% RH for 4 days. Non-inoculated plants served as control. Inoculated plants showed the typical first leaf spots 6 days after the artificial inoculation. Four days later, spots enlarged and leaves became distorted, showing chlorosis. Non-inoculated plants remained healthy. P. cucumerina was reisolated from inoculated plants. The pathogenicity test was conducted twice with identical results. This is, to our knowledge, the first report of P. cucumerina on D. tenuifolia in Italy as well as worldwide. P. cucumerina has been described as associated with root and collar rots of other horticultural crops in southern Italy (1). Due to the importance of the crop in Italy, this disease can cause serious economic losses. References: (1) A. Carlucci et al., Persoonia, 28:34, 2012. (2) M. E. Palm et al. Mycologia, 87:397, 1995. (3) 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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First Report of Fusarium Root and Stem Rot Caused by Fusarium oxysporum f. sp. radicis-cucumerinum on Greenhouse Cucumbers in Saudi Arabia

Plant Disease ◽

10.1094/pdis-01-21-0122-pdn ◽

2021 ◽

Author(s):

Mahmoud H. El-komy ◽

Riyadh M. Al-Qahtani ◽

Arya Widyawan ◽

younes molan ◽

Ali Almasrahi

Keyword(s):

Saudi Arabia ◽

Fusarium Oxysporum ◽

Sandy Loam ◽

Economic Losses ◽

Peat Moss ◽

Post Inoculation ◽

Pathogenicity Test ◽

Distilled Water ◽

Conidial Suspension ◽

First Report

Cucumber (Cucumis sativus L.) is an important vegetable crop in Saudi Arabia. During May 2018, 45 - 60% of 5-month-old cucumber plants showed symptoms of a previously unknown wilt in commercial greenhouses around Al Kharj area of Riyadh region. Symptoms consisted of crown and root rot, wilting and stem disintegration, along with yellowish brown to brown external discoloration extended throughout the affected tissues. As the disease progressed, a pinkish-orange mycelial growth was often observed at the basis of affected stems while vessels were discolored. Subsequently, the affected plants were collapsed and died. Crown, stem, and root fragments (4 × 4 mm) were cut from symptomatic tissues, surface sterilized in 2.5% NaOCl, cultured on potato dextrose agar (PDA) with 25 mg/liter of streptomycin sulfate, and incubated at 26°C in darkness for 6 days. Single-spored cultures produced white mycelium with pink, white, or purple pigmentation in the center. The mycelium produced sporodochia. Macroconidia were mainly slightly curved with three to five septa. Microconidia were single-celled oval and produced on short lateral phialides. Chlamydospores were single or in short chains. Morphologically, the isolated fungus was characterized as Fusarium oxysporum (Leslie and Summerell 2006). To further confirm the fungus identification, DNA was extracted from a single-spored culture. Three different fungal nuclear regions of internal transcribed spacer (ITS), elongation factor 1-α, (TEF1-α) and the second largest subunit of DNA-directed RNA polymerase II (rpb2) with the following primers: ITS4 and ITS5 (White et al. 2017), EF-1 and EF-2 (O’Donnell et al. 2008), and fRPB2-5F and fRPB2-7cR (Liu et al. 1999), respectively. The ITS, TEF1-α, and rpb2 sequences of the isolate FCKSU17 were submitted to GenBank (MT232918, MW471131, and MW449833 respectively). Phylogenetic analysis based on the alignment of the ITS, TEF1-α, and rpb2 sequences using MEGA7 placed this strain in the F. oxysporum clade. To confirm the forma specialis radicis-cucumerinum, amplification with the specific primers ForcF1/ForcR2 was conducted (Lievens et al. 2007). The amplified fragment (∼ 250-bp) was sent for sequencing, and the sequence was submitted to GenBank (MW471132). BLASTn analysis of the sequences showed 100% identity with F. oxysporum radicis-cucumerinum (KP746408). To fulfill Koch’s postulates, pathogenicity test was conducted on 7-day-old plants of cucumber cultivar Beit Alpha grown into pots filled with soil mix (2:1 sandy loam-peat moss, vol/vol). The plants were inoculated through drenching with 100 ml of conidial suspension in sterile distilled water (106 spores/ml) per pot. Control plants were treated with sterile distilled water. Each treatment included 10 replicates (pots), with two plants per pot. The pathogenicity test was repeated once. Cucumber plants inoculated with the fungus showed early wilting symptoms within the first 2 weeks post inoculation. At the 6th week post inoculation, 90 to 100% of the inoculated plants developed typical symptoms. No symptoms were observed on the control plants. The pathogen was successfully re-isolated from the inoculated wilted plants and identified morphologically. To our knowledge, this is the first report of F. oxysporum f.sp. radicis-cucumerinum on cucumber in Saudi Arabia. It is recommended that preventive management should be considered as this disease may cause significant economic losses on cucumbers in Saudi Arabia.

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