First Report of Leaf Blight Caused by Rhizoctonia solani AG 1B on Madagascar Periwinkle (Catharanthus roseus) in Italy

Madagascar periwinkle (Catharanthus roseus), a plant belonging to the Apocynaceae family, is used for parks and gardens and sometimes grown in pots. At the end of the summer of 2005, a leaf blight was observed on plants in a public park of Torino. Semicircular, water-soaked lesions developed on leaves just above the soil line at the leaf-petiole junction and later along the leaf margins. Lesions expanded for several days along the midvein until the entire leaf was destroyed. Blighted leaves turned brown, withered, clung to the shoots, and matted on the surrounding foliage. Although lesions were not seen on the stem, affected plants often died leaving wide empty areas. Mycelia of the pathogen were often seen on and suspended between the leaves. Blight progressed from the leaves to the shoot tip. The diseased tissue was disinfected for 1 min in 1% NaOCl and plated on potato dextrose agar (PDA) amended with 100 μg/l streptomycin sulphate. A fungus with the morphological characters of Rhizoctonia solani was consistently and readily isolated and maintained in pure culture after single-hyphal tipping (4). The isolates of R. solani obtained from affected plants were successfully anastomosed with tester isolate AG 1 (ATCC 58946). The hyphal diameter at the point of anastomosis was reduced, the anastomosis point was obvious, and cell death of adjacent cells was observed. These results are consistent with other reports on anastomosis reactions (2). Pairing was also made with AG 2, 3, 4, 5, 7, and 11, with no anastomoses observed between the isolates and testers. Sclerotia were subspheroid in shape and had a size of 1 mm, which indicated that this pathogen was in subgroup 1B (4). For pathogenicity tests, the inoculum of R. solani was prepared by growing the pathogen on PDA for 7 days. Plants of C. roseus were grown in 3-liter containers (2 plants per pot) on a steam disinfested substrate (peat/ pomix/pine bark/clay). Artificial inoculation was carried out on 7-day-old plants by placing numerous fragments of PDA cultures on the leaves of the plants. Plants inoculated with PDA alone served as control treatments. Three replicates were used. Plants were maintained in a glasshouse at 20 to 25°C. The first symptoms, similar to those observed in the public park, developed 5 days after inoculation, and R. solani was consistently reisolated from infected plants. Control plants remained healthy. The pathogenicity test was carried out twice with similar results. This is, to our knowledge, the first report of R. solani on periwinkle in Italy. The same disease was reported in India (1) and the United States (3). References: (1) R. Balasubramanian and K. S. Bhama. Indian Phytopathol. 30:556, 1977. (2) D. E. Carling. Grouping in Rhizoctonia solani by hyphal anastomosis reactions. Pages 37–47 in: Rhizoctonia Species: Taxonomy, Molecular Biology, Ecology, Pathology and Disease Control. B. Sneh et al., eds. Kluwer Academic Publishers, the Netherlands, 1996. (3) A. K. Hagan and J. M. Mullen Plant Dis. 77:1169, 1993. (4) B. Sneh et al. Identification of Rhizoctonia Species. The American Phytopathological Society, St Paul, MN, 1991.

Download Full-text

First Report of Leaf Blight on Hosta fortunei Caused by Rhizoctonia solani AG 4 in Italy

Plant Disease ◽

10.1094/pdis-93-4-0432c ◽

2009 ◽

Vol 93 (4) ◽

pp. 432-432 ◽

Cited By ~ 3

Author(s):

A. Garibaldi ◽

D. Bertetti ◽

M. L. Gullino

Keyword(s):

United States ◽

Rhizoctonia Solani ◽

Aqueous Suspension ◽

Its Region ◽

The United States ◽

Morphological Characters ◽

Leaf Blight ◽

Pathogenicity Test ◽

First Report ◽

Leaf Petiole

Hosta fortunei (Liliaceae) is used in semishaded areas of gardens for its lavender-colored flowers produced in midsummer. In April of 2008, in a greenhouse at the University of Torino, located in Grugliasco (northern Italy), a leaf blight was observed on 15% of potted 60-day-old plants growing at temperatures ranging between 20 and 25°C and relative humidity of 60 to 90%. Semicircular, water-soaked lesions developed on leaves just above the soil line at the leaf-petiole junction and later along leaf margins. Lesions expanded for several days along the midvein until the entire leaf was destroyed. Blighted leaves turned brown, withered, and clung to the shoots. Severely infected plants died. Diseased tissue was disinfested for 10 s in 1% NaOCl, rinsed with sterile water, and plated on potato dextrose agar (PDA) amended with 25 mg/liter streptomycin sulfate. A fungus with the morphological characters of Rhizoctonia solani (4) was consistently recovered, then transferred and maintained in pure culture. Ten-day-old mycelium grown on PDA at 22 ± 1°C appeared light brown, rather compact, and had radial growth. Sclerotia were not present. Isolates of R. solani obtained from affected plants were successfully anastomosed with tester isolate AG 4 (AG 4 RT 31 obtained from tobacco plants). Results were consistent with other reports on anastomosis reactions (2). Pairings were also made with tester isolates of AG 1, 2.1, 2.2, 3, 6, 7, 11, and BI, but no anastomosis was observed. The internal transcribed spacer (ITS) region of rDNA was amplified using primers ITS4/ITS6 and sequenced. BLASTn analysis (1) of the 646-bp fragment showed a 100% homology with the sequence of R. solani AG-4 AB000018. The nucleotide sequence has been assigned GenBank Accession No. FJ 534556. For pathogenicity tests, the inoculum of R. solani was prepared by growing the pathogen on PDA for 10 days. Six-month-old plants of H. fortunei were grown in 1-liter pots. Inoculum, which consisted of an aqueous suspension of PDA and mycelium disks (10 g of mycelium per pot), was placed at the collar of plants. Plants inoculated with water and PDA fragments alone served as control treatments. Five plants per treatment were used. Plants were maintained in a growth chamber at 20 ± 1°C. The first symptoms, similar to those observed in the nursery, developed 15 days after inoculation. R. solani was consistently reisolated from infected leaves and stems. Control plants remained healthy. The pathogenicity test was carried out twice with similar results. R. solani was reported on plants belonging to the genus Hosta in the United States (3). This is, to our knowledge, the first report of leaf blight of H. fortunei caused by R. solani in Italy as well as in Europe. References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997. (2) D. E. Carling. Grouping in Rhizoctonia solani by hyphal anastomosis reactions. In: Rhizoctonia Species: Taxonomy, Molecular Biology, Ecology, Pathology and Disease Control. Kluwer Academic Publishers, The Netherlands, 1996. (3) D. F. Farr et al. Fungi on Plants and Products in the United States. The American Phytopathology Society, St Paul, MN, 1989. (4) B. Sneh et al. Identification of Rhizoctonia species. The American Phytopathological Society, St Paul, MN, 1991.

Download Full-text

First Report of Leaf Blight on Fan Columbine (Aquilegia flabellata) Caused by Rhizoctonia solani AG 4 in Italy

Plant Disease ◽

10.1094/pdis-93-4-0433a ◽

2009 ◽

Vol 93 (4) ◽

pp. 433-433 ◽

Cited By ~ 2

Author(s):

A. Garibaldi ◽

G. Gilardi ◽

D. Bertetti ◽

M. L. Gullino

Keyword(s):

United States ◽

Rhizoctonia Solani ◽

Aqueous Suspension ◽

Morphological Characteristics ◽

The United States ◽

Leaf Blight ◽

Herbaceous Plant ◽

Pathogenicity Test ◽

First Report ◽

Leaf Petiole

Aquilegia flabellata (Ranunculaceae), fan columbine, is a perennial herbaceous plant with brilliant blue-purple flowers with white petal tips. It can also be grown for cut flower production. In April of 2008, in several nurseries located near Biella (northern Italy), a leaf blight was observed on 10 to 15% of potted 30-day-old plants grown on a sphagnum peat substrate at 15 to 20°C and relative humidity of 80 to 90%. Semicircular, water-soaked lesions developed on leaves just above the soil line at the leaf-petiole junction and later along the leaf margins. Lesions expanded over several days along the midvein until the entire leaf was destroyed. Blighted leaves turned brown, withered, and abscised. Severely infected plants died. Diseased tissue was disinfested for 10 s in 1% NaOCl, rinsed with sterile water, and plated on potato dextrose agar (PDA) amended with 25 mg/liter streptomycin sulfate. A fungus with the morphological characteristics of Rhizoctonia solani was consistently recovered, then transferred and maintained in pure culture. Ten-day-old mycelium grown on PDA at 22 ± 1°C appeared light brown, rather compact, and had radial growth. Sclerotia were not present. Isolates obtained from affected plants successfully anastomosed with tester isolate AG 4 (AG 4 RT 31, obtained from tobacco plants). Results were consistent with other reports on anastomosis reactions (2). Pairings were also made with tester isolates of AG 1, 2.1, 2.2, 3, 6, 7, 11, and BI with no anastomoses observed between the recovered and tester isolates. The internal transcribed spacer (ITS) region of rDNA was amplified using primers ITS4/ITS6 and sequenced. BLASTn analysis (1) of the 648-bp fragment showed a 100% homology with the sequence of R. solani AG-4 AB000018. The nucleotide sequence has been assigned GenBank Accession No. FJ 534555. For pathogenicity tests, the inoculum of R. solani was prepared by growing the pathogen on PDA for 10 days. Five plants of 30-day-old A. flabellata were grown in 3-liter pots. Inoculum consisting of an aqueous suspension of PDA and mycelium disks (5 g of mycelium + agar per plant) was placed at the collar of plants. Five plants inoculated with water and PDA fragments alone served as control treatments. Plants were maintained in a greenhouse at temperatures between 20 and 24°C. The first symptoms, similar to those observed in the nursery, developed 7 days after the artificial inoculation. R. solani was consistently reisolated from infected leaves and stems. Control plants remained healthy. The pathogenicity test was carried out twice with similar results. The presence of R. solani AG1-IB on A. flabellata has been reported in Japan (4), while in the United States, Rhizoctonia sp. is described on Aquilegia sp. (3). This is, to our knowledge, the first report of leaf blight of A. flabellata caused by R. solani in Italy as well as in Europe. References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997. (2) D. E. Carling. Grouping in Rhizoctonia solani by hyphal anastomosis reactions. In: Rhizoctonia Species: Taxonomy, Molecular Biology, Ecology, Pathology and Disease Control. Kluwer Academic Publishers, The Netherlands, 1996. (3) D. F. Farr et al. Fungi on Plants and Products in the United States. The American Phytopathological Society, St Paul, MN, 1989. (4) E. Imaizumi et al. J. Gen. Plant Pathol. 66:210, 2000.

Download Full-text

First Report of Leaf Blight on Coral Bells (Heuchera sanguinea) Caused by Rhizoctonia solani AG 1A in Italy

Plant Disease ◽

10.1094/pdis-91-9-1206b ◽

2007 ◽

Vol 91 (9) ◽

pp. 1206-1206

Author(s):

A. Garibaldi ◽

G. Gilardi ◽

D. Bertetti ◽

M. L. Gullino

Keyword(s):

Rhizoctonia Solani ◽

Aqueous Suspension ◽

Morphological Characters ◽

Leaf Blight ◽

Pathogenicity Test ◽

Uniform Size ◽

First Report ◽

Leaf Petiole ◽

Pathogenicity Tests ◽

Hyphal Diameter

Heuchera sanguinea (Saxifragaceae), coral bells or alum root, is an herbaceous perennial used in parks and gardens and sometimes grown in pots for its heart-shaped leaves and upright panicles of bright red, tiny flowers produced in late spring. At the end of fall 2006, a leaf blight was observed on 50% of a crop of potted 45-day-old plants grown in a sphagnum peat/clay/perlite (70:20:10) substrate at temperatures ranging between 20 and 25°C in a nursery. Semicircular, water-soaked lesions developed on leaves just above the soil line at the leaf-petiole junction and later along the leaf margins. For several days, lesions expanded along the midvein until the entire leaf was destroyed. Blighted leaves turned brown, withered, clung to the shoots, and matted on the surrounding foliage. Mycelia were often seen on and suspended between leaves. Blight progressed up the plant from the leaves to the shoot tip. Affected plants often died leaving wide empty areas. Diseased tissue was disinfected for 1 min in 1% NaOCl, rinsed with sterile water, and plated on potato dextrose agar (PDA) amended with 100 μg/liter of streptomycin sulfate. A fungus with the morphological characters of Rhizoctonia solani was consistently and readily recovered, then transferred and maintained in pure culture (3). The isolates of R. solani obtained from affected plants were successfully anastomosed with tester isolate AG 1 (ATCC 58946). The hyphal diameter at the point of anastomosis was reduced, the anastomosis point was obvious, and cell death of adjacent cells was observed. Results were consistent with other reports on anastomosis reactions (1). Pairings were also made with tester isolates of AG 2, 3, 4, 5, 6, 7, and 11 with no anastomoses observed between the recovered and tester isolates. Sclerotia were of uniform size with a diameter from 0.4 to 4 mm and sometimes joined laterally. The description of sclerotia was typical for subgroup 1A Type 2 (2). For pathogenicity tests, the inoculum of R. solani was prepared by growing three isolates of the pathogen on PDA for 7 days. Plants of 30-day-old H. sanguinea were grown in 10-liter containers (6 plants per container) on a steam disinfested peat/clay/perlite substrate (70:20:10)). Inoculum consisted of an aqueous suspension of PDA and mycelium disks (1 cm2 of mycelium per plant) and was placed at the base of the plant stems and on leaves. Plants inoculated with water and PDA fragments alone served as control treatments. Three replicates were used. Plants were maintained in a growth chamber at 24°C with 12 h of light/dark. The first symptoms, similar to those observed in the nursery, developed 12 days after the artificial inoculation. R. solani was consistently reisolated from infected leaves and stems. Control plants remained healthy. The pathogenicity test was carried out twice with similar results. This is, to our knowledge, the first report of leaf blight of H. sanguinea caused by R. solani in Italy and probably in the world. References: (1) D. E. Carling. Grouping in Rhizoctonia solani by hyphal anastomosis reactions. In: Rhizoctonia Species: Taxonomy, Molecular Biology, Ecology, Pathology and Disease control. Kluwer Academic Publishers, the Netherlands, 1996. (2) R. T. Sherwood. Phytopathology, 59:1924, 1969. (3) B. Sneh et al. Identification of Rhizoctonia species. The American Phytopathological Society, St Paul, MN, 1991.

Download Full-text

First Report of Leaf Blight on Woodland Sage Caused by Rhizoctonia solani AG 1 in Italy

Plant Disease ◽

10.1094/pdis-94-8-1071c ◽

2010 ◽

Vol 94 (8) ◽

pp. 1071-1071 ◽

Cited By ~ 2

Author(s):

A. Garibaldi ◽

G. Gilardi ◽

D. Bertetti ◽

M. L. Gullino

Keyword(s):

Rhizoctonia Solani ◽

Aqueous Suspension ◽

Its Region ◽

Morphological Characters ◽

Leaf Blight ◽

Pathogenicity Test ◽

First Report ◽

Leaf Petiole ◽

Perennial Plant ◽

Potted Plants

Woodland sage (Salvia nemorosa L.; Lamiaceae) is a hardy herbaceous perennial plant that is easy to grow and propagate and is used in parks and grown as potted plants. During the summer of 2009 in a nursery near Torino in northern Italy, a leaf blight was observed on 30-day-old plants of cv. Blau Koenigin grown in pots under shade. Semicircular, water-soaked lesions developed on leaves just above the soil line at the leaf-petiole junction and later along leaf margins. Lesions expanded along the midvein until the entire leaf was destroyed. Blighted leaves turned brown, withered, and clung to the shoots. No symptoms were observed on the roots. Severely infected plants died. Diseased tissue was disinfested for 10 s in 1% NaOCl, rinsed with sterile water, and plated on potato dextrose agar (PDA) amended with 25 mg/liter of streptomycin sulfate. A fungus with morphological characters of Rhizoctonia solani (3) was consistently recovered. Ten-day-old mycelium grown on PDA at 22 ± 1°C appeared light brown, rather compact, and with radial growth. Sclerotia were irregular and measured between 0.5 and 2 mm. Pairings were made with tester isolates of AG 1, 2, 3, 4, 5, 6, 7, 11, and AG B1. The only successful anastomosis was with tester isolate AG 1 (ATCC 58946). The hyphal diameter at the point of anastomosis was reduced, the anastomosis point was obvious, and cell death of adjacent cells was observed. Results were consistent with other reports on anastomosis reactions (2). The description of sclerotia of the isolate AG1 was typical for subgroup 1A Type 2 (3). The internal transcribed spacer (ITS) region of rDNA was amplified using primers ITS4/ITS6 and sequenced. BLASTn analysis (1) of the 688 bp showed a 100% homology with the sequence of R. solani AG-1A and the nucleotide sequence has been assigned (GenBank Accession No. HM044764). For pathogenicity tests, the inoculum of one isolate of R. solani from the nursery was prepared by growing the pathogen on PDA for 7 days. The foliage of 30-day-old potted plants of S. nemorosa cv. Blau Koenigin was artificially inoculated with an aqueous suspension of PDA and mycelium fragments (1 g per mycelium per plant) prepared from cultures with a blender. Plants were covered with plastic bags for 3 days. Plants inoculated with water and PDA fragments alone served as control treatments. Plants were maintained in a glasshouse at 20 to 25°C. The first symptoms, similar to those observed in the nursery, developed 7 days after foliar inoculation. R. solani was consistently reisolated from infected leaves. Control plants remained healthy. The pathogenicity test was carried out twice with similar results. To our knowledge, this is the first report of leaf blight of S. nemorosa caused by R. solani in Italy as well as worldwide. The importance of the disease is still unknown. References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997. (2) D. E. Carling. Page 35 in: Rhizoctonia Species: Taxonomy, Molecular Biology, Ecology, Pathology and Disease Control. Kluwer Academic Publishers, the Netherlands, 1996. (3) B. Sneh et al. Identification of Rhizoctonia Species. The American Phytopathological Society, St Paul, MN, 1991.

Download Full-text

Report of Leaf Blight on Washington Lupine (Lupinus polyphyllus) Caused by Rhizoctonia solani AG 4 in Italy

Plant Disease ◽

10.1094/pdis-93-4-0429a ◽

2009 ◽

Vol 93 (4) ◽

pp. 429-429

Author(s):

A. Garibaldi ◽

G. Gilardi ◽

D. Bertetti ◽

M. L. Gullino

Keyword(s):

Rhizoctonia Solani ◽

Aqueous Suspension ◽

Morphological Characteristics ◽

Its Region ◽

Leaf Blight ◽

Herbaceous Plant ◽

Pathogenicity Test ◽

Lupinus Polyphyllus ◽

Leaf Petiole ◽

Sphagnum Peat

Lupinus polyphyllus (Leguminosae), Washington lupine, is a perennial herbaceous plant. In March 2008, in a campus greenhouse at the University of Torino, Grugliasco (northern Italy), a leaf blight was observed on 20% of potted 30-day-old plants. Semicircular, water-soaked lesions developed on leaves just above the soil line at the leaf-petiole junction and later along the leaf margins. Lesions expanded for several days along the midvein until the entire leaf was destroyed. Blighted leaves turned brown, withered, clung to the shoots, and matted on the surrounding foliage. Severely infected plants died. Plants were grown in a sphagnum peat/perlite/clay (70:20:10) substrate at temperatures between 18 and 25°C and relative humidity of 60 to 80%. Diseased tissue was disinfested for 10 s in 1% NaOCl, rinsed with sterile water, and plated on potato dextrose agar (PDA) amended with 25 mg/liter of streptomycin sulfate. A fungus with the morphological characteristics of Rhizoctonia solani (4) was consistently and readily recovered, then transferred and maintained in pure culture. Ten-day-old mycelium grown on PDA at 20 ± 1°C appeared light brown, rather compact, and exhibited radial growth. The isolates of R. solani successfully anastomosed with tester isolate AG 4 (AG 4 RT 31, obtained from tobacco plants). The hyphal diameter at the point of anastomosis was reduced, the anastomosis point was obvious, and cell death of adjacent cells was observed. Results were consistent with other reports on anastomosis reactions (3). Pairings were also made with tester isolates AG 1, 2.1, 2.2, 3, 6, 7, 11, and BI with no anastomoses observed between the recovered and tester isolates. The internal transcribed spacer (ITS) region of rDNA was amplified using primers ITS4/ITS6 and sequenced. BLASTn analysis (1) of the 660-bp fragment showed 100% homology with the sequence of R. solani. The nucleotide sequence has been assigned GenBank Accession No. FJ486272. For pathogenicity tests, the inoculum of R. solani was prepared by growing the pathogen on PDA for 10 days. Plants of 30-day-old L. polyphyllus were grown in 10-liter containers (10 plants per container) on a steam disinfested sphagnum peat/perlite/clay (70:20:10) medium. Inoculum, consisting of an aqueous suspension of mycelium disks prepared from PDA cultures (5 g of mycelium per plant), was placed at the collar of plants. Plants inoculated with water and PDA fragments alone served as control treatments. Three replicates were used. Plants were maintained in a greenhouse at temperatures between 18 and 23°C. First symptoms, similar to those observed in the nursery, developed 10 days after the artificial inoculation. R. solani was consistently reisolated from infected leaves and stems. Control plants remained healthy. The pathogenicity test was repeated twice. The susceptibility of L. polyphyllus to R. solani was reported in Poland (2). This is, to our knowledge, the first report of leaf blight of L. polyphyllus caused by R. solani in Italy. The importance of the disease is at the moment limited. References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997. (2) W. Blaszczak. Rocz. Nauk. Roln. Ser A 85:705, 1962. (3) D. E. Carling. Grouping in Rhizoctonia solani by hyphal anastomosis reactions. In: Rhizoctonia Species: Taxonomy, Molecular Biology, Ecology, Pathology and Disease Control. Kluwer Academic Publishers, The Netherlands, 1996. (4) B. Sneh et al. Identification of Rhizoctonia species. The American Phytopathological Society, St Paul, MN, 1991.

Download Full-text

First Report of Web Blight on Oregano (Origanum vulgare L.) Caused by Rhizoctonia solani AG-1-IB in Italy

Plant Disease ◽

10.1094/pdis-02-13-0138-pdn ◽

2013 ◽

Vol 97 (8) ◽

pp. 1119-1119 ◽

Cited By ~ 2

Author(s):

A. Garibaldi ◽

D. Bertetti ◽

P. Pensa ◽

A. Poli ◽

M. L. Gullino

Keyword(s):

Rhizoctonia Solani ◽

Its Region ◽

Morphological Characters ◽

Anastomosis Group ◽

Morphological Identification ◽

Pathogenicity Test ◽

Origanum Vulgare ◽

First Report ◽

Plastic Bags ◽

Hyphal Diameter

Origanum vulgare L., common name oregano, family Labiatae, is grown for its aromatic and medicinal properties and as ornamental. In the fall of 2012, a blight was observed in a farm located near Albenga (northern Italy) on 6% of 30,000 50-day-old plants, grown in trays in a peat/perlite mix. Semicircular, water soaked lesions appeared on leaves and stems, starting from the basal ones. As the disease progressed, blighted leaves turned brown, withered, clung to the shoots, and matted on the surrounding foliage. Eventually, infected plants died. Leaf and stem fragments taken from the margin of the diseased tissues belonging to 10 plants were disinfected for 10 s in 1% NaOCl, rinsed with sterile water, and plated on potato dextrose agar (PDA). A fungus with the morphological characters of Rhizoctonia solani was consistently recovered. Three isolates of R. solani obtained from affected plants were successfully anastomosed with R. solani isolate AG 1 (ATCC 58946). Three pairings were made for each tester strain. The hyphal diameter at the point of anastomosis was reduced, the anastomosis point was obvious, and death of adjacent cells was observed. Results were consistent with other reports on anastomosis reactions (2). Isolates from oregano were paired with R. solani isolates AG 2, 3, 4, 6, 7, or 11 and examined microscopically. Anastomosis was not observed in any of the pairings. Tests were conducted twice. Mycelium of 10-day-old isolates from oregano appeared reddish brown, coarse, and radiate. Numerous dark brown sclerotia, 0.3 to 1.0 mm diameter (average 0.7) developed within 10 days after transfer of mycelia to PDA in 90 mm diameter petri dishes at 21 to 24°C. The descriptions of mycelium and sclerotia were typical for subgroup IB Type 1 (4). The internal transcribed spacer (ITS) region of rDNA was amplified using the primers ITS1/ITS4 and sequenced. BLASTn analysis (1) of the 538 bp showed a 99% homology with the sequence of R. solani FJ746937, confirming the morphological identification of the species. The nucleotide sequence has been assigned the GenBank Accession KC493638. For pathogenicity tests, one of the isolates assigned to the anastomosis group AG-1-IB was tested by placing 9 mm diameter mycelial disks removed from PDA 10-day-old cultures of the fungus on leaves of 90-day-old oregano plants (n = 35). Thirty-five plants inoculated with non-inoculated PDA disks served as controls. Plants were covered with plastic bags and maintained in a growth chamber at 25 ± 1°C with 12 h light/dark. The first symptoms, similar to those observed in the farm, developed 3 days after inoculation. Nine days after the artificial inoculation, 50% of plants were dead. About 10 colonies of R. solani were reisolated from infected leaves of inoculated plants. Control plants remained healthy. The pathogenicity test was carried out twice with similar results. Symptoms caused by R. solani have been recently observed on O. vulgare in Greece (3). This is, to our knowledge, the first report of blight of O. vulgare caused by R. solani in Italy. References: (1) S. F. Altschul et al. Nucleic Acids Res., 25:3389, 1997. (2) D. E. Carling. Grouping in Rhizoctonia solani by hyphal anastomosis reactions. In: Rhizoctonia Species: Taxonomy, Molecular Biology, Ecology, Pathology and Disease control. Kluwer Academic Publishers, The Netherlands, pp. 37-47, 1996. (3) C. D. Holevas et al. Benaki Phytopathol. Inst., Kiphissia, Athens, 19:1-96, 2000. (4) R. T. Sherwood. Phytopathology 59:1924, 1969.

Download Full-text

First Report of Sclerotium rolfsii on Catharanthus roseus

Plant Disease ◽

10.1094/pdis.2000.84.2.200d ◽

2000 ◽

Vol 84 (2) ◽

pp. 200-200

Author(s):

G. E. Holcomb

Keyword(s):

Catharanthus Roseus ◽

Fungal Pathogen ◽

Baton Rouge ◽

Sclerotium Rolfsii ◽

The United States ◽

Madagascar Periwinkle ◽

Basal Stem Rot ◽

First Report ◽

Pathogenicity Tests ◽

Stem Necrosis

Wilt, blight, and stem necrosis were observed on Catharanthus roseus (L.) G. Don ‘Mediterranean Deep Rose’ (MDR) plants (Madagascar or rose periwinkle) in August 1999 at Burden Research Plantation in Baton Rouge, LA. MDR was the only prostrate-form cultivar and the only cultivar of 11 that was diseased. Twelve of twenty-four plants of cv. MDR were killed in the trial planting. White mycelia and small (1 mm diameter) light brown sclerotia were present at the base of infected plants. The suspect fungus was isolated consistently on acidified water agar and maintained on acidified potato dextrose agar (APDA). Pathogenicity tests were done by pipetting 1 ml of blended inoculum (contents of one 7-day-old plate culture grown on APDA in 100 ml of deionized water) at the base of nine 15-cm-tall Madagascar periwinkle plants. Inoculated and noninoculated plants were held in a dew chamber for 3 days at 28°C and placed in a greenhouse where temperatures ranged between 25 and 31°C. All inoculated plants showed wilt, blight, and basal stem rot after 3 days and were dead after 10 days. Noninoculated plants remained symptomless. The fungal pathogen was identified as Sclerotium rolfsii Sacc. and was reisolated from inoculated plants. The fungus was previously reported on Lochnera rosea (L.) Rchb. (=C. roseus) from Taiwan (1). This is the first report of the occurrence of S. rolfsii on Madagascar periwinkle in the United States. Reference: (1) K. Goto. Trans. Nat. Hist. Soc. Formosa 23:37, 1933.

Download Full-text

First Report of Damping-Off on Basella rubra Caused by Rhizoctonia solani Anastomosis Group 4 in Florida

Plant Disease ◽

10.1094/pdis-08-11-0639 ◽

2012 ◽

Vol 96 (2) ◽

pp. 288-288 ◽

Cited By ~ 2

Author(s):

X. Liao ◽

Y. Fu ◽

S. Zhang ◽

Y. P. Duan

Keyword(s):

Rhizoctonia Solani ◽

The United States ◽

Anastomosis Group ◽

Pathogenicity Test ◽

Damping Off ◽

Ambient Conditions ◽

Microscopic Appearance ◽

Stem Base ◽

First Report ◽

Intergenic Spacer Region

Indian spinach (Basella rubra L.) is a red stem species of Basella that is cultivated worldwide as an ornamental and the aerial parts are also consumed as a vegetable. In May of 2011, symptoms of damping-off were observed on approximately 10% of the plants at the stem base around the soil line of seedlings in a greenhouse in Homestead, FL. Lesions were initially water soaked, grayish to dark brown, irregular in shape, and sunken in appearance on large plants, causing the infected seedlings to collapse and eventually die. Symptomatic stem tissue was surface sterilized with 0.6% sodium hypochlorite, rinsed in sterile distilled water, air dried, and plated on potato dextrose agar (PDA). Plates were incubated at 25°C in darkness for 3 to 5 days. A fungus was isolated in all six isolations from symptomatic tissues on PDA. Fungal colonies on PDA were light gray to brown with abundant growth of mycelia, and the hyphae tended to branch at right angles when examined under a microscope. A septum was always present in the branch of hyphae near the originating point and a slight constriction at the branch was observed. Neither conidia nor conidiophores were found from the cultures on PDA. The characteristics of hyphae, especially the right angle branching of mycelia, indicate close similarity to those of Rhizoctonia solani (2,3). The internal transcribed spacer (ITS) region of rDNA was amplified with the primers ITS1/ITS4 and sequenced (GenBank Accession No. JN545836). Subsequent database searches by the BLASTN program indicated that the resulting sequence had a 100% identity over 472 bp with the corresponding gene sequence of R. solani anastomosis group (AG) 4 (GenBank Accession No. JF701752.1), a fungal pathogen reported to cause damping-off on many crops. Pathogenicity was confirmed through inoculation of healthy India spinach plants with the hyphae of isolates. Four 4-week-old plants were inoculated with the isolates by placing a 5-mm PDA plug of mycelia at the stem base and covering with a thin layer of the soil. Another four plants treated with sterile PDA served as a control. After inoculation, the plants were covered with plastic bags for 24 h and maintained in a greenhouse with ambient conditions. Four days after inoculation, water-soaked, brown lesions, identical to the symptoms described above, were observed on the stem base of all inoculated plants, whereas no symptoms developed on the control plants. The fungus was isolated from affected stem samples, and the identity was confirmed by microscopic appearance of the hyphae and sequencing the ITS1/ITS4 intergenic spacer region, fulfilling Koch's postulates. This pathogenicity test was conducted twice. R. solani has been reported to cause damping-off of B. rubra in Ghana (1) and Malaysia (4). To our knowledge, this is the first report of damping-off caused by R. solani AG-4 on Indian spinach in Florida and the United States. With the increased interest in producing Asian vegetables for food and ornamental purposes, the occurrence of damping-off on Indian spinach needs to be taken into account when designing programs for disease management in Florida. References: (1) H. A. Dade. XXIX. Bull. Misc. Inform. 6:205, 1940. (2) J. R. Parmeter et al. Phytopathology 57:218, 1967. (3) B. Sneh et al. Identification of Rhizoctonia species. The American Phytopathological Society, St Paul, MN, 1991. (4) T. H. Williams and P. S. W. Liu. Phytopathol. Pap. 19:1, 1976.

Download Full-text

First Report of Web Blight on Rosemary (Rosmarinus officinalis) Caused by Rhizoctonia solani AG-1-IA in Italy

Plant Disease ◽

10.1094/pdis-11-12-1012-pdn ◽

2013 ◽

Vol 97 (6) ◽

pp. 844-844 ◽

Cited By ~ 4

Author(s):

A. Garibaldi ◽

D. Bertetti ◽

P. Pensa ◽

A. Poli ◽

M. L. Gullino

Keyword(s):

Rhizoctonia Solani ◽

Ground Cover ◽

Its Region ◽

Morphological Characters ◽

Anastomosis Group ◽

Rosmarinus Officinalis ◽

Economic Losses ◽

Pathogenicity Test ◽

First Report ◽

Wheat Kernels

Rosmarinus officinalis L., family Labiatae, is an evergreen shrub used in gardens as an aromatic or ground cover plant. In the summer of 2012, a blight was observed in a farm located near Albenga (northern Italy) on 20% of 150,000 70-day-old plants, grown in trays. Water soaked lesions appeared on leaves and stems. As the disease progressed, blighted leaves turned brown, withered, clung to the shoots, and matted on the surrounding foliage. A light mycelium spread on the substrate. Disease progressed from infected plants to healthy ones and, eventually, infected plants died. Leaf and stem fragments taken from the margin of the diseased tissues belonging to 10 plants were disinfected for 10 s in 1% NaOCl, rinsed with sterile water, and plated on potato dextrose agar (PDA). A fungus with the morphological characters of Rhizoctonia solani was consistently and readily recovered. Three isolates of R. solani obtained from affected plants were successfully paired with R. solani tester strains AG 1, 2, 3, 4, 6, 7, or 11 and examined microscopically. Three pairings were made for each recovered isolate. The isolates of R. solani from rosemary anastomosed only with tester strain AG 1 (ATCC 58946). Results were consistent with other reports on anastomosis reactions (2). Tests were repeated once. Mycelium of 10-day-old isolates from rosemary appeared light brown, compact, and radiate. Numerous dark brown sclerotia, 0.7 to 2.0 mm diameter (average 1.3), developed within 10 days at 20 to 26°C. The descriptions of mycelium and sclerotia were typical for subgroup IA Type 2 (4). The internal transcribed spacer (ITS) region of rDNA was amplified using the primers ITS1/ITS4 and sequenced (GenBank Accession No. KC005724). BLASTn analysis (1) of the 657-bp showed a 99% similarity with the sequence of R. solani GU596491. For pathogenicity tests, inoculum of R. solani was prepared by growing the pathogen on wheat kernels autoclaved in 1-liter glass flasks for 8 days. One of the isolates assigned to the anastomosis group AG 1 IA was tested. Fifteen 90-day-old rosemary plants were grown in 15-liter pots in a steam disinfested peat:pomice:pine bark:clay mix (50:20:20:10) infested with 3 g/liter of infested wheat kernels, placed at the base of the stem. Fifteen plants inoculated with non-infested wheat kernels served as control treatments. Plants were covered with plastic bags and arranged in a growth chamber at 20 to 24°C with 12 h light/dark for 15 days. The first symptoms, similar to those observed in the farm, developed 10 days after inoculation. About 10 colonies of R. solani were reisolated from infected leaves and stems of each inoculated plant. Control plants remained healthy. The pathogenicity test was carried out twice with similar results. Symptoms caused by R. solani have been recently observed on R. officinalis in United States (3), India, and Brazil. This is, to our knowledge, the first report of blight of R. officinalis caused by R. solani in Italy. This disease could cause serious economic losses, because rosemary is one of the most cultivated aromatic plants in the Mediterranean region. References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997. (2) D. E. Carling. Grouping in Rhizoctonia solani by hyphal anastomosis reactions. In: Rhizoctonia Species: Taxonomy, Molecular Biology, Ecology, Pathology and Disease control. Kluwer Academic Publishers, The Netherlands, 1996. (3) G. E. Holcomb. Plant Dis. 76:859, 1992. (4) R. T. Sherwood. Phytopathology 59:1924, 1969.

Download Full-text

First Report of Alternaria Leaf Blight of Aralia japonica Caused by Alternaria panax in Europe

Plant Disease ◽

10.1094/pdis.2004.88.1.82b ◽

2004 ◽

Vol 88 (1) ◽

pp. 82-82 ◽

Cited By ~ 4

Author(s):

A. Garibaldi ◽

G. Gilardi ◽

M. L. Gullino

Keyword(s):

Central Italy ◽

The United States ◽

Leaf Blight ◽

Plant Diseases ◽

Fluorescent Light ◽

Pathogenicity Test ◽

Single Spore ◽

Aesthetic Quality ◽

First Report ◽

Alternaria Panax

Aralia japonica (synonym Fatsia japonica), belonging to the Araliaceae family, is a foliage plant highly valued in Italy for landscape and interior decoration. In the fall of 2002, a leaf blight disease was observed on plants grown in pots that were maintained under shade at a density of 15 to 20 pots per m2 at a nursery located in central Italy (Teramo Province). Typical symptoms were tan-to-dark brown leaf spots and rapid blighting of foliage under moist conditions. Chlorotic zones around necrotic lesions were common, and considerable leaf drop was associated with the disease. Affected plants were rarely killed, but the presence of lesions on mature plants reduced aesthetic quality and market value. The disease occurred on 70% of the plants. A fungus identified morphologically as Alternaria panax (2) was consistently isolated from infected leaves on potato dextrose agar (PDA). The fungus grows slowly and sparsely on PDA and produces a light brown mycelium, a characteristic red diffusible pigment in the agar medium, and rare conidia under 12-hr photoperiods. Measurements were carried out on conidia formed from single-spore isolates grown on autoclavated host tissue on water agar (LWA) at 24°C for 10 days. In LWA culture, conidia were borne singly or in chains of two to four conidia. Conidia produced in culture were smaller than those formed on the host and were highly variable in shape. They appeared obclavate, ellipsoidal, and obpyriform and pale to dark brown with relatively short or false beaks. Conidial bodies were 14.4 to 48.0 μm long (average 30.5 μm) and 7.2 to 12.0 μm wide (average 9.9 μm) with 3 to 10 transverse and a few longitudinal septa. Length of appendages was 9.6 to 26.0 μm (average 16.0 μm). Pathogenicity tests were performed by inoculating leaves of healthy Aralia japonica and Schefflera actinophylla plants by placing mycelial disks (5 mm in diameter) directly on wounded leaf tissues. Uninoculated, wounded plants served as controls. Four plants of each species were used. Plants were covered for 72 h with plastic bags and maintained in a growth chamber at 20°C (12 hours per day of fluorescent light). Control plants were maintained similarly. The first lesions developed on leaves of inoculated plants of both species after 7 days. A. panax was consistently reisolated from the lesions. The pathogenicity test was carried out twice. The presence of A. panax on Aralia japonica has been reported in Japan, Korea (2), and the United States (1) but to our knowledge, this is the first report of A. panax on Aralia japonica in Europe. References: (1) S. Alfieri et al. Index of plant diseases in Florida. Bull. 11:52, Florida Department of Agriculture and Consumer Services, 1984 (2) S. H. Yu et al. Ann. Phytopathol. Soc. Jpn. 50:313, 1984.

Download Full-text