First Report of Didymella bryoniae Causing Gummy Stem Blight of Chayote in Taiwan

Chayote (Sechium edule (Jacq.) Swartz, Cucurbitaceae), originally native to Mexico, is an important vegetable known as “dragon-whisker vegetable” and is cultivated for its shoots in Ji-an, Hualien County in eastern Taiwan. In June 2010, 70 to 80% of the chayote plants grown in Ji-an developed necrotic spots on stems, leaves, and fruits. The disease was severe during the warm and rainy season from June to August. The symptoms on stems, leaves, and fruits were water-soaked lesions that eventually dried up, cracked, and produced perithecia on necrotic tissues. A single ascospore was isolated from perithecia harvested from diseased stems and cultured on potato dextrose agar (PDA) at 25°C for 1 month. Colonies of three isolates (SE5, SE6, and SE7) were white to olivaceous green bearing unicellular conidia measuring 2 to 5 × 3 to 10 μm, which is consistent with the morphological characteristics of Didymella bryoniae (Auersw.) Rehm (anamorph Phoma cucurbitacearum (Fr.:Fr.) Sacc.) (1,2,3). DNA of SE5, SE6, and SE7 isolates were obtained using microwave-based method (4). The internal transcribed spacer (ITS) rDNA (GenBank accessions AB714984, AB714985, and AB714986), PCR-amplified using primers ITS1 and ITS4, had 98 to 99% nucleotide sequence identity with D. bryoniae (GenBank Accession Nos. GU045304 and GU592001). A pathogenicity test was conducted in a greenhouse with temperature ranging from 20 to 30°C. Three-day-old mycelial plugs (5 × 5 mm) of the three isolates were placed on the needle-pricked wounds of stems and leaves of 36 4-month-old potted chayote plants wrapped in plastic bags to maintain 100% relative humidity for 2 days. Six days after inoculation, water-soaked lesions formed on the stems and leaves. Controls inoculated with sterile water had no symptoms. The fungus reisolated from the lesions of diseased stems and leaves had morphological characteristics of D. bryoniae. Based on the results of morphology, molecular data, and pathogenicity tests, we reported for the first time to our knowledge that gummy stem blight of chayote is caused by D. bryoniae in Taiwan. References: (1) J. W. Huang and W. R. Hsieh. Plant Prot. Bull. 27:325, 1985. (2) A. P. Keinath et al. Phytopathology 85:364, 1995. (3) E. Punithalingam and P. Holliday. P. 332 in: Descriptions of Pathogenic Fungi and Bacteria. CMI, Kew, Surrey, UK, 1972. (4) S. R. Tendulkar et al. Biotechnol. Lett. 22:1941, 2003.

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First Report of Gummy Stem Blight Caused by Didymella bryoniae on Watermelon and Confirmation of the Disease on Pumpkin in Tanzania

Plant Disease ◽

10.1094/pdis-01-11-0044 ◽

2011 ◽

Vol 95 (6) ◽

pp. 768-768 ◽

Cited By ~ 7

Author(s):

B. D. Jensen ◽

A. Massawe ◽

I. S. Swai

Keyword(s):

Citrullus Lanatus ◽

Morphological Characteristics ◽

Pathogenic Fungi ◽

Weather Conditions ◽

Fruit Rot ◽

Didymella Bryoniae ◽

First Report ◽

Stem Blight ◽

Gummy Stem Blight ◽

Specific Pcr

Foliar, stem, and fruit lesions were observed on watermelon (Citrullus lanatus (Thunb.) Matsum. & Nakai) and pumpkin (Cucurbita maxima Duchesne) in two separate research fields in the district of Arusha, Tanzania during the warm, rainy season from February to April 2010. Similar symptoms were observed in commercial watermelon fields and intercropped pumpkin fields in Same and Moshi districts with as much as 100% fruit loss in watermelon. Disease symptoms on watermelon were dark brown, V-shaped leaf lesions. On pumpkin, V-shaped leaf lesions were light brown. On both hosts, stems showed water-soaked lesions after rain, which dried up and cracked. On pumpkin, a gummy, amber exudate was seen after rain on stem and fruit lesions. Flowers and fruits of both hosts developed black rot spots and aborted. Isolation of the causal agent on potato dextrose agar (PDA) from leaf and stem pieces of watermelon and pumpkin plants in Arusha showed white-to-olivaceous green mycelium. Pycnidia formed on one-quarter-strength PDA and produced hyaline, oblong conidia mainly with two guttules, nonseptate, 5 to 11 × 3 to 5 μm. Pathogenicity was tested with three isolates from watermelon and one from pumpkin on four 1-month-old plants per watermelon cvs. Sugar Baby and Charleston Grey and pumpkin cv. Small Sugar per isolate. The test was repeated on the watermelon cultivars. One site on the main stem and two leaves per plant were misted, pricked with a scalpel, inoculated with 3-day-old mycelial plugs (5 × 5 mm), and kept humid at 20 to 30°C in cellophane bags for 3 days. All plants developed leaf and/or stem lesions. Detached, misted leaves were also laid on 2% water agar and inoculated as above. Water-soaked lesions developed around inoculation sites and microscopy of infected tissue revealed pycnidia with conidia as described above. All isolates infected both hosts. A set of control plants and detached leaves, mock inoculated with agar plugs, remained symptomless. The fungus was reisolated from infected leaves and stems of both hosts. On the basis of the morphological characteristics, the fungus was identified as Didymella bryoniae (Auersw.) Rehm (anamorph Phoma cucurbitacearum (Fr.:Fr.) Sacc.) (1,3) and this was confirmed by amplification of species-specific PCR products. The isolates from both hosts were cultured in liquid medium, and DNA was extracted using a DNeasy Plant Mini Kit (Qiagen, Valencia, CA). PCR and multiplex PCR involving D. bryoniae-unique primer sequences D6 and D7S, in combination with primer UNLO28S22, produced the expected band sizes (2). To our knowledge, this is the first report of gummy stem blight and black fruit rot of watermelon caused by D. bryoniae in Tanzania, which confirms a previous report of leaf spot on pumpkin (4), and the first report of black fruit rot on pumpkin. The disease was previously an unidentified problem in watermelon and the severe outbreak was associated with favorable weather conditions. References: (1) A. P. Keinath et al. Phytopathology 85:364, 1995. (2) C. A. Koch and R. S. Utkhede. Can. J. Plant Pathol. 26:291, 2004. (3) E. Punithalingam and P. Holliday. No. 332 in: Descriptions of Pathogenic Fungi and Bacteria. CMI, Kew, Surrey, UK, 1972. (4) E. A. Riley. Mycol. Pap. 75:1, 1960.

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First Report of Leaf Spot and Root Rot Caused by Phoma betae on Beta vulgaris subsp. vulgaris (Garden Beet Group) in Italy

Plant Disease ◽

10.1094/pdis-91-11-1515c ◽

2007 ◽

Vol 91 (11) ◽

pp. 1515-1515 ◽

Cited By ~ 7

Author(s):

A. Garibaldi ◽

G. Gilardi ◽

D. Bertetti ◽

M. L. Gullino

Keyword(s):

Beta Vulgaris ◽

Morphological Characteristics ◽

Its Region ◽

Pathogenicity Test ◽

Vegetable Crops ◽

Plastic Bags ◽

Blastn Analysis ◽

Commercial Farms ◽

Pathogenicity Tests ◽

Phoma Betae

In the winter of 2007 in Piedmont (northern Italy), symptoms of a previously unknown disease were observed on beet (Beta vulgaris L. subsp. vulgaris) (garden beet group) grown under a tunnel on several commercial farms near Cuneo. First symptoms appeared on 1-month-old plants, occurring as brown, round-to-oval spots as much as 2 cm in diameter with dark concentric rings near the perimeter. Small, dark pycnidia were present throughout the spots in concentric rings. Generally, older, lower leaves were affected more than the younger ones. Ten to fifteen percent of the plants were affected. Symptoms on the roots began near the crown as small, dark, sunken spots that became soft and water soaked. Eventually, spots on the roots turned dark brown to black and black lines separated diseased and healthy tissues. Older infected tissues were black, dry, shrunken, and spongy. Pycnidia were not observed on affected roots. From infected leaves and roots, a fungus was consistently isolated on potato dextrose agar (PDA) amended with 25 mg/l of streptomycin. The fungus was grown on PDA and maintained at 22°C (12 h of light, 12 h of dark). After 10 days, black pycnidia (130 to 328 [204] μm in diameter) developed, releasing abundant hyaline, elliptical, nonseptate conidia measuring 3.9 to 6.7 (5.1) × 2.4 to 5.9 (3.6) μm. On the basis of its morphological characteristics, the fungus was identified as a Phoma sp. (1). The internal transcribed spacer (ITS) region was amplified using primers ITS4/ITS6 (2) and sequenced. BLASTn analysis of the 557 bp obtained showed an E-value of 0.0 with Phoma betae. The nucleotide sequence has been assigned GenBank Accession No. EU003450. Pathogenicity tests were performed by spraying leaves of healthy 20-day-old potted B. vulgaris plants with a spore and mycelial suspension (1 × 106 spores or mycelial fragments per ml). Noninoculated plants sprayed only with water served as controls. Fifteen plants (three per pot) were used for each treatment. Plants were covered with plastic bags for 5 days after inoculation and kept in a growth chamber at 20°C. Symptoms previously described developed on leaves of all inoculated plants 5 days after inoculation, while control plants remained healthy. Later, pycnidia and conidia, with the same dimensions and characteristics previously described, were observed on the infected leaves. The fungus was consistently reisolated from the lesions of the inoculated plants. The pathogenicity test was carried out twice. P. betae on B. vulgaris var. cycla has been reported in Canada (3) as well as in other countries. The same pathogen was reported in Italy on sugar beet (2). References: (1) G. H. Boerema and G. J. Bollen. Persoonia 8:111, 1975. (2) A. Canova. Inf. Fitopatol. 16:207, 1966. (3) D. E L. Cooke and J. M. Duncan. Mycol. Res. 101:667, 1997. (4) J. R. Howard et al. Diseases of Vegetable Crops in Canada. Canadian Phytopathological Society, 1994.

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First Report of Leaf Spot of Saponaria officinalis Caused by Alternaria nobilis in Italy

Plant Disease ◽

10.1094/pdis-09-12-0839-pdn ◽

2013 ◽

Vol 97 (3) ◽

pp. 424-424 ◽

Cited By ~ 2

Author(s):

A. Garibaldi ◽

D. Bertetti ◽

A. Poli ◽

M. L. Gullino

Keyword(s):

Morphological Characteristics ◽

Pathogenicity Test ◽

Academic Press ◽

First Report ◽

Perennial Plant ◽

Plastic Bags ◽

Pcr Product ◽

Pathogenicity Tests ◽

Alternaria Sp ◽

Saponaria Officinalis

Saponaria officinalis (Vize) Simmons (common name bouncingbet) is a low maintenance perennial plant belonging to the Caryophyllaceae family, typically grown in parks and gardens. During the summers of 2011 and 2012, extensive necrosis were observed on leaves of plants grown in private gardens, near Biella (northern Italy). The disease affected 90% of 1- to 2-year-old plants. The first symptoms were usually pale brown lesions 1 to 5 mm in diameter and sometimes coalesced. Lesions were circular to irregular with a dark purple halo, with infected leaves eventually turning chlorotic. The conidia observed on infected leaves were olivaceous brown and obclavate, with a beak. Conidia showed 8 to 15 (average 12) transverse and 4 to 14 (average 11) longitudinal septa, with slight constrictions connected with septa, and were 78.3 to 177.7 (average 135.5) × 19.0 to 34.3 (average 26.5) μm. The beak was 20.0 to 62.2 (average 33.7) μm in length, with 0 to 6 (average 3) transverse septa and no longitudinal septa. The fungus was consistently isolated from infected leaves on potato dextrose agar (PDA). The isolate, grown for 14 days at 20 to 24°C with 10 h of darkness and 14 h of light on sterilized host leaves plated on PDA, produced conidiophores single, unbranched, flexuous, septate with conidia in short chains, similar to those observed on the leaves and previously described. On the basis of its morphological characteristics, the pathogen was identified as Alternaria sp. (3). DNA was extracted using Nucleospin Plant Kit (Macherey Nagel) and PCR carried out using ITS 1/ITS 4 primer (4). A 542-bp PCR product was sequenced and a BLASTn search confirmed that the sequence corresponded to A. dianthi (AY154702), recently renamed A. nobilis (2). The nucleotide sequence has been assigned the GenBank Accession No. JX647848. Pathogenicity tests were performed by spraying leaves of healthy 3-month-old plants of S. officinalis with an aqueous 2 × 105 spore/ml suspension. The inoculum was obtained from cultures of the fungus grown on PDA amended with host leaves for 14 days, in light-dark, at 22 ± 1°C. Plants sprayed only with water served as controls. Four pots (1 plant/pot) were used for each treatment. Plants were covered with plastic bags for 4 days after inoculation and maintained in a glasshouse at 21 ± 1 °C. Lesions developed on leaves 9 days after inoculation with the spore suspension, whereas control plants remained healthy. A. nobilis was consistently reisolated from these lesions. The pathogenicity test was carried out twice. The presence of A. dianthi was reported on S. officinalis in Denmark (1) and Turkey. This is, to our knowledge, the first report of A. nobilis on S. officinalis in Italy. The presence and importance of this disease is, at present, limited. References: (1) P. Neergaard. Danish species of Alternaria and Stemphylium. Oxford University Press, 1945. (2) E. G. Simmons. Mycotaxon 82:7, 2002. (3) E. G. Simmons. Alternaria: An Identification Manual. CBS Biodiversity Series 6, Utrecht, The Netherlands, 2007. (4) T. J. White et al. In: 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 Leaf Spot Caused by Phoma multirostrata on Fuchsia × hybrida in Italy

Plant Disease ◽

10.1094/pdis-94-3-0382a ◽

2010 ◽

Vol 94 (3) ◽

pp. 382-382 ◽

Cited By ~ 4

Author(s):

A. Garibaldi ◽

G. Gilardi ◽

M. L. Gullino

Keyword(s):

Leaf Surface ◽

Morphological Characteristics ◽

Its Region ◽

Northern Italy ◽

Pathogenicity Test ◽

First Report ◽

Plastic Bags ◽

Pathogenicity Tests ◽

Necrotic Spots ◽

Mycelial Suspension

Fuchsia × hybrida (Onagraceae) is widely used in gardens and very much appreciated as a potted plant. During the summer of 2008, a severe foliar disease was observed on 1- to 2-year-old plants in several gardens located near Biella (northern Italy). Small necrotic spots were observed on the upper and lower sides of infected leaves. Spots enlarged to form round areas of 2 to 12 mm in diameter and were well defined by a brown-purple margin at temperatures between 15 and 25°C. Severely infected leaves wilted and abscised as disease progressed. The disease occurred on 100% of the plants and at least 30% of the leaf surface was affected. Stems and flowers were not affected by the disease. A fungus was consistently isolated from infected leaves on potato dextrose agar amended with 25 mg/liter of streptomycin. The fungus was grown on leaf extract agar, including 30 g of autoclaved fuchsia leaves per liter, and maintained at 22°C (12-h light, 12-h dark). After 30 days, black pycnidia 150 to 450 μm in diameter developed, releasing abundant hyaline, elliptical, nonseptate conidia measuring 5.6 to 14.3 (10.3) × 1.9 to 5.6 (3.5) μm. On the basis of these morphological characteristics, the fungus was identified as a Phoma sp. (2). The internal transcribed spacer (ITS) region of rDNA of the isolate coded FuHy1 was amplified using primers ITS4/ITS6 (3) and sequenced. BLAST analysis (1) of the 488-bp segment obtained showed an E-value of 0.0 with Phoma multirostrata. The nucleotide sequence has been assigned GenBank Accession No. GU220539. Pathogenicity tests were performed by spraying leaves of healthy 6-month-old potted Fuchsia × hybrida plants with a spore and mycelial suspension (1 × 106 spores or mycelial fragments per milliliter). Noninoculated plants sprayed with water served as controls. Five plants were used for each treatment. Plants were covered with plastic bags for 5 days after inoculation and kept under greenhouse conditions at 20 to 24°C. Symptoms previously described developed on leaves 12 days after inoculation, whereas control plants remained healthy. The fungus was consistently reisolated from the lesions of the inoculated plants. The pathogenicity test was carried out twice. To our knowledge, this is the first report of the presence of P. multirostrata on fuchsia in Italy as well as worldwide. The importance of the disease is still limited in Italy. References: (1) S. F. Altschud et al. Nucleic Acids Res. 25:3389, 1997. (2) G. H. Boerema and G. J. Bollen. Persoonia 8:111, 1975. (3) D. E. L. Cooke and J. M. Duncan. Mycol. Res. 101:667, 1997.

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First Report of Leaf Spot of Wild (Diplotaxis tenuifolia) and Cultivated (Eruca vesicaria) Rocket Caused by Alternaria japonica in Italy

Plant Disease ◽

10.1094/pdis-04-11-0280 ◽

2011 ◽

Vol 95 (10) ◽

pp. 1316-1316 ◽

Cited By ~ 13

Author(s):

A. Garibaldi ◽

G. Gilardi ◽

C. Bertoldo ◽

M. L. Gullino

Keyword(s):

Morphological Characteristics ◽

Northern Italy ◽

Pathogenicity Test ◽

Academic Press ◽

First Report ◽

Plastic Bags ◽

Pcr Product ◽

Pathogenicity Tests ◽

Alternaria Sp ◽

Potential Impact

Wild (Diplotaxis tenuifolia) and cultivated (Eruca vesicaria) rocket, popular crops in Italy as well as in many Mediterranean areas, are grown for fresh consumption as well as for dish decoration. During fall and winter of 2010 to 2011, extensive necroses were observed on leaves of D. tenuifolia and E. vesicaria that were grown in commercial greenhouses in Piedmont and Liguria (northern Italy). The disease affected 30 to 40% of 60-day-old plants. First symptoms were usually black-brown lesions, 1 to 30 mm in diameter, which progressively turned black. Lesions usually started on the upper side of older leaves at the leaf margins and tips and developed a yellow halo. Eventually, lesions also affected leaf veins and stems. A fungus was consistently isolated from infected leaves on potato dextrose agar and was grown on water agar (15 g/liter) amended with autoclaved rocket tissues (100 g/liter). After 12 days of growth at 22°C and 12-h dark/12-h light, conidia that were produced were dark brown, obclavate, obpyriform, ovoid or ellipsoid, with beaks. Round conidia without beaks were also present. Conidia showed two to seven (average three to four) transverse and one to three longitudinal septa, and measured 17.7 to 56.2 (average 30.9) × 6.6 to 17.8 (average 10.8) μm. Conidia were produced singly or in short chains (two to three elements) and mostly presented a conical or cylindrical beak, 1.8 to 7.3 (average 3.6) μm, pale light brown to brown. On the basis of its morphological characteristics, the pathogen was identified as an Alternaria sp. (3). DNA was extracted with Terra PCR Direct Polymerase Mix (Clontech, Mountain View, CA) and PCR was carried out with ITS 1/ ITS 4 primer (4). A 553-bp PCR product was sequenced and a BLASTn search (1) confirmed that the sequence corresponded to Alternaria japonica. The nucleotide sequence has been assigned the GenBank Accession No. JP 742643. Pathogenicity tests were performed by spraying leaves of healthy 30-day-old wild and cultivated rocket plants with an aqueous 1 × 105 spore/ml suspension. The inoculum was obtained from cultures of the fungus grown on sterilized host leaves placed on water agar for 20 days in light/dark at 22 ± 1°C. Plants sprayed only with water served as controls. Three pots (four plants per pot) were used for each treatment. Plants were covered with plastic bags for 4 days after inoculation and maintained in a glasshouse at 22 ± 1°C. Lesions developed on leaves 7 days after inoculation with the spore suspension, whereas control plants remained healthy. A. japonica was consistently reisolated from these lesions. The pathogenicity test was carried out twice. The presence of A. japonica has been reported on several brassica hosts, such as Brassica napus, B. nigra, B. oleracea, and B. rapa (2). This is, to our knowledge, the first report of A. japonica on wild and cultivated rocket in Italy as well as in Europe. Because of the importance of rocket in many countries, the potential impact of this disease is high. References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997 (2) J. C. David, IMI Description of Fungi and Bacteria. 144:1432, 2000. (3) E. G. Simmons. Alternaria. An Identification Manual. CBS Biodiversity Series 6, Utrecht, The Netherlands, 2007. (4) T. J. White et al. In: 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 Leaf Spot Caused by a Phoma sp. on Clematis × jackmanii in Italy

Plant Disease ◽

10.1094/pdis-91-10-1363c ◽

2007 ◽

Vol 91 (10) ◽

pp. 1363-1363 ◽

Cited By ~ 1

Author(s):

A. Garibaldi ◽

D. Bertetti ◽

M. L. Gullino

Keyword(s):

Morphological Characteristics ◽

The United States ◽

Northern Italy ◽

Pathogenicity Test ◽

Internal Transcribed Spacer Region ◽

Flower Production ◽

Plastic Bags ◽

Pathogenicity Tests ◽

Necrotic Spots ◽

Mycelial Suspension

The genus Clematis, belonging to the Ranunculaceae family, is widely used in gardens and is very much appreciated for its climbing attitude as well as rich flower production. In the fall of 2006, in a private garden located near Biella (northern Italy), a severe foliar disease was observed on 2-year-old plants of Clematis × jackmanii. Small necrotic spots were observed on the upper and lower sides of infected leaves. At temperatures of 15 to 25°C, spots enlarged to form round areas that were 2 to 7 cm in diameter and well defined by a brown margin. Severely infected leaves wilted without abscising. The disease occurred on 100% of the plants of the C. × jackmanii hybrid in one garden. Stems and flowers were not affected by the disease. From infected leaves, a fungus was consistently isolated on potato dextrose agar (PDA) amended with 25 mg/liter of streptomycin. The fungus was grown on PDA and maintained at 22°C (12-h light, 12-h dark). After 10 days, black pycnidia 132 to 340 μm in diameter developed, releasing abundant hyaline, elliptical, nonseptate, conidia measuring 5.1 to 8.3 (6.8) × 1.6 to 3.4 (2.7) μm. On the basis of its morphological characteristics, the fungus was identified as a Phoma sp. (2). The internal transcribed spacer region of rDNA was amplified using primers ITS4/ITS6 (1,3), sequenced (GenBank Accession No. EF566917), and identified as a Phoma sp. Pathogenicity tests were performed by spraying leaves of healthy 1-year-old potted C. × jackmanii (cvs. Superba, Mrs N. Thomson, and Vagebond) plants with a spore and mycelial suspension (4 × 105 spores or mycelial fragments per ml). Noninoculated plants served as controls. Five plants per cultivar were used for each treatment. Plants were covered with plastic bags for 3 days after inoculation and kept in a growth chamber at 18 to 20°C. Symptoms previously described developed on leaves of all tested cultivars 10 days after inoculation, while control plants remained healthy. On the infected leaves, pycnidia and conidia with the same dimensions and characteristics as previously described were observed. The fungus was consistently reisolated from the lesions of the inoculated plants. The pathogenicity test was carried out twice. The presence of Ascochyta clematidina, then renamed as Phoma clematidina, on Clematis species has been reported in the United States (4) and subsequently in the Netherlands, Britain, and New Zealand. References: (1) S. F. Altschud et al. Nucleic Acids Res. 25:3389, 1997. (2) G. H. Boerema and G. J. Bollen. Persoonia 8:111, 1975. (3) D. E. L. Cooke and J. M. Duncan. Mycol. Res. 101:667, 1997. (4) W. O. Gloyer. J. Agric. Res. 4:331, 1915.

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Factors Promoting Pycnidia Production of Didymella bryoniae, the Causal of Gummy Stem Blight in Cucurbits

Egyptian Journal of Phytopathology ◽

10.21608/ejp.2017.89736 ◽

2017 ◽

Vol 45 (1) ◽

pp. 173-187

Author(s):

Abdel-Fattah El-Wakil ◽

Amal Khalil ◽

Ibrahim El -Abbasi

Keyword(s):

Didymella Bryoniae ◽

Stem Blight ◽

Gummy Stem Blight

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Boscalid Insensitivity Documented in Didymella bryoniae Isolated from Watermelon in Florida and North Carolina

Plant Health Progress ◽

10.1094/php-2012-0518-01-br ◽

2012 ◽

Vol 13 (1) ◽

pp. 42

Author(s):

Katherine L. Stevenson ◽

Anthony P. Keinath ◽

Anna Thomas ◽

David B. Langston ◽

Pamela D. Roberts ◽

...

Keyword(s):

North Carolina ◽

South Carolina ◽

High Frequency ◽

In Vitro Assays ◽

Didymella Bryoniae ◽

Triazole Fungicides ◽

Stem Blight ◽

Gummy Stem Blight ◽

Commercial Mixture

The fungicide Pristine, a commercial mixture of pyraclostrobin and boscalid, has been used widely on watermelon and other cucurbits to control gummy stem blight, caused by the fungus Didymella bryoniae. Since 2007, isolates of D. bryoniae insensitive to boscalid have been found in Georgia, Indiana, and South Carolina. Most isolates of D. bryoniae obtained in 2009 and 2010 from diseased watermelon leaves collected in several counties in Florida and North Carolina were found to be insensitive to boscalid using in vitro assays. Gummy stem blight would not be effectively managed with Pristine in any of the counties where samples were collected due to the high frequency of insensitivity to boscalid. Fortunately growers can instead use several triazole fungicides registered for use on cucurbits since 2009. Accepted for publication 30 March 2012. Published 18 May 2012.

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Identification of Fusarium Species Isolated From Stored Apple Fruit in Croatia / Identifikacija Vrsta Roda Fusarium Izoliranih S Plodova Jabuke Nakon Skladištenja

Archives of Industrial Hygiene and Toxicology ◽

10.2478/10004-1254-63-2012-2227 ◽

2012 ◽

Vol 63 (4) ◽

pp. 463-470 ◽

Cited By ~ 12

Author(s):

Zdravka Sever ◽

Dario Ivić ◽

Tomislav Kos ◽

Tihomir Miličević

Keyword(s):

Fusarium Species ◽

Morphological Characteristics ◽

Molecular Data ◽

Apple Fruit ◽

Fusarium Avenaceum ◽

Human Consumption ◽

Low Oxygen ◽

Fusarium Rot ◽

Pathogenicity Tests ◽

Apple Fruits

AbstractSeveral species of the genus Fusarium can cause apple fruit to rot while stored. Since Fusarium taxonomy is very complex and has constantly been revised and updated over the last years, the aim of this study was to identify Fusarium species from rotten apples, based on combined morphological characteristics and molecular data.We identified 32 Fusarium isolates from rotten apple fruit of cultivars Golden Delicious, Jonagold, Idared, and Pink Lady, stored in Ultra Low Oxygen (ULO) conditions. Fusarium rot was detected in 9.4 % to 33.2 % of naturally infected apples, depending on the cultivar. The symptoms were similar in all four cultivars: a soft circular brown necrosis of different extent, with or without visible sporulation. Fusarium species were identified by the morphology of cultures grown on potato-dextrose agar (PDA) and carnation leaf agar (CLA). Twenty one isolates were identified as Fusarium avenaceum and confirmed as such with polymerase chain reaction (PCR) using specific primer pair FA-ITSF and FA-ITSR. F. pseudograminearum,F. semitectum, F. crookwellense, and F. compactum were identified by morphological characteristics. F.avenaceum can produce several mycotoxins and its dominance in Fusarium rot points to the risk of mycotoxin contamination of apple fruit juices and other products for human consumption. Pathogenicity tests showed typical symptoms of Fusarium rot in most of the inoculated wounded apple fruits. In this respect Fusarium avenaceum, as the dominant cause of Fusarium rot in stored apple fruits is a typical wound parasite.

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First Report of Rhizoctonia solani AG 4 on Lamb's Lettuce in Italy

Plant Disease ◽

10.1094/pd-90-1109c ◽

2006 ◽

Vol 90 (8) ◽

pp. 1109-1109 ◽

Cited By ~ 2

Author(s):

A. Garibaldi ◽

G. Gilardi ◽

M. L. Gullino

Keyword(s):

Rhizoctonia Solani ◽

Morphological Characteristics ◽

Northern Italy ◽

Crown Rot ◽

Pathogenicity Test ◽

First Report ◽

Pathogenicity Tests ◽

Hyphal Diameter ◽

Wheat Kernels ◽

Extensive Necrosis

Lamb's lettuce or corn salad (Valerianella olitoria) is increasingly grown in Italy and used primarily in the preparation of mixed processed salad. In the fall of 2005, plants of lamb's lettuce, cv Trophy, exhibiting a basal rot were observed in some commercial greenhouses near Bergamo in northern Italy. The crown of diseased plants showed extensive necrosis, progressing to the basal leaves, with plants eventually dying. The first symptoms, consisting of water-soaked zonate lesions on basal leaves, were observed on 30-day-old plants during the month of October when temperatures ranged between 15 and 22°C. Disease was uniformly distributed in the greenhouses, progressed rapidly in circles, and 50% of the plants were affected. Diseased tissue was disinfested for 1 min in 1% NaOCl and plated on potato dextrose agar amended with 100 μg/liter of streptomycin sulfate. A fungus with the morphological characteristics of Rhizoctonia solani was consistently and readily isolated and maintained in pure culture after single-hyphal tipping (3). The five isolates of R. solani, obtained from affected plants successfully anastomosed with tester isolate AG 4, no. RT 31, received from R. Nicoletti of the Istituto Sperimentale per il Tabacco, Scafati, Italy (2). The hyphal diameter at the point of anastomosis was reduced, and cell death of adjacent cells occurred (1). Pairings were also made with AG 1, 2, 3, 5, 7, and 11 with no anastomoses observed between the five isolates and testers. For pathogenicity tests, the inoculum of R. solani (no. Rh. Vale 1) was grown on autoclaved wheat kernels at 25°C for 10 days. Plants of cv. Trophy were grown in 10-liter containers (20 × 50 cm, 15 plants per container) on a steam disinfested substrate (equal volume of peat and sand). Inoculations were made on 20-day-old plants by placing 2 g of infected wheat kernels at each corner of the container with 3 cm as the distance to the nearest plant. Plants inoculated with clean wheat kernels served as controls. Three replicates (containers) were used. Plants were maintained at 25°C in a growth chamber programmed for 12 h of irradiation at a relative humidity of 80%. The first symptoms, consisting of water-soaked lesions on the basal leaves, developed 5 days after inoculation with crown rot and plant kill in 2 weeks. Control plants remained healthy. R. solani was consistently reisolated from infected plants. The pathogenicity test was carried out twice with similar results. This is, to our knowledge, the first report of R. solani on lamb's lettuce in Italy as well as worldwide. The isolates were deposited at the AGROINNOVA fungal collection. The disease continues to spread in other greenhouses in northern Italy. References: (1) D. Carling. Rhizoctonia Species: Pages 37–47 in: Taxonomy, Molecular Biology, Ecology, Pathology and Disease Control. B. Sneh et al., eds. Kluwer Academic Publishers, the Netherlands, 1996. (2) J. Parmeter et al. Phytopathology, 59:1270, 1969. (3) B. Sneh et al. Identification of Rhizoctonia Species. The American Phytopathological Society, St. Paul, MN, 1996.

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