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

A. Garibaldi; G. Gilardi; M. L. Gullino

doi:10.1094/pdis.2004.88.1.82b

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.

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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 a Leaf Spot Caused by Alternaria compacta on Hydrangea anomala subsp. petiolaris in Italy

Plant Disease ◽

10.1094/pdis-92-1-0173c ◽

2008 ◽

Vol 92 (1) ◽

pp. 173-173 ◽

Cited By ~ 2

Author(s):

A. Garibaldi ◽

D. Bertetti ◽

M. L. Gullino

Keyword(s):

Morphological Characteristics ◽

The United States ◽

Plant Diseases ◽

Spore Suspension ◽

Pathogenicity Test ◽

Aesthetic Quality ◽

First Report ◽

Plastic Bags ◽

Alternaria Sp ◽

The Aesthetic

Hydrangea anomala subsp. petiolaris (synonym H. petiolaris and H. scandens), also known as climbing hydrangea, is cultivated as an ornamental for landscaping in parks and gardens. This species, belonging to the Hydrangeaceae and native to the woodlands of Japan and coastal China, is widely appreciated for its abundant, creamy white flowers with a sweet aroma, particularly in shade gardens. During the summer of 2006, extensive necroses were observed on leaves and young stems of 3-year-old plants grown outdoors in several gardens of Piedmont of northern Italy. In many cases, on the upper side of the leaves, necrotic spots (4 to 10 mm in diameter) turned progressively black. Lesions often coalesced, generating larger (2 to 6 cm in diameter) necrotic areas. Necroses initially developed mainly at leaf margins and near petioles, and severely affected plants were defoliated. Infected plants rarely died, but the presence of lesions reduced the aesthetic quality and subsequently the commercial value. The disease occurred on 50 of 100 plants. A fungus was consistently isolated from infected leaves on potato dextrose agar (PDA) and identified on the basis of its morphological characteristics as an Alternaria sp. Conidia were dark gray, multicellular, clavate to pear shaped, measuring 23 to 54 × 10 to 13 μm (average 38 × 12 μm), with five longitudinal crosswalls and a relatively short apical beak. DNA was extracted with a Nucleospin Plant Kit (Macherey Nagel, Brockville, ON, Canada) and PCR was carried out with ITS 6/ITS 4 primer (2). A 557-bp PCR product was sequenced, and a BLASTn search (1) confirmed that the sequence corresponded to Alternaria compacta (99% homology). The nucleotide sequence has been assigned GenBank Accession No. EU 128529. Pathogenicity tests were performed by spraying leaves of healthy 1-year-old potted H. anomala plants with an aqueous 105 CFU/ml spore suspension. The inoculum was obtained from cultures of the fungus grown on sterilized host leaves placed on PDA for 20 days in light/dark at 23 ± 1°C. Plants sprayed only with water served as controls. Five plants were used for each treatment. Plants were covered with plastic bags for 3 days after inoculation and maintained between 12 and 22°C. Lesions developed on leaves 8 days after inoculation with the spore suspension, whereas control plants remained healthy. A. compacta was consistently reisolated from these lesions. The pathogenicity test was repeated twice. The presence of an Alternaria sp. on H. macrophylla was reported in the United States (3), whereas A. hortensiae was observed in Spain on H. hortensis. Recently, A. alternata belonging to the alternata group was reported on H. macrophylla in Italy (4). This is, to our knowledge, the first report of A. compacta on H anomala subsp. petiolaris in Italy. References: (1) S. F. Altschud et al. Nucleic Acids Res. 25:3389, 1997. (2) D. E. L. Cooke and J. M. Duncan. Mycol. Res. 101:667, 1997. (3) M. L. Daughtrey et al. Page 9 in: Compendium of Flowering Potted Plant Diseases. American Phytopathological Society. St. Paul, MN, 1995. (4) A. Garibaldi et al. Plant Dis. 91:767, 2007.

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First Report of Leaf Spot Caused by Alternaria alternata on Hydrangea macrophylla in Italy

Plant Disease ◽

10.1094/pdis-91-6-0767a ◽

2007 ◽

Vol 91 (6) ◽

pp. 767-767 ◽

Cited By ~ 1

Author(s):

A. Garibaldi ◽

G. Gilardi ◽

S. Frati ◽

M. L. Gullino

Keyword(s):

Single Cells ◽

Morphological Characteristics ◽

The United States ◽

Major Allergen ◽

Plant Diseases ◽

Pathogenicity Test ◽

Aesthetic Quality ◽

First Report ◽

Hydrangea Macrophylla ◽

Alternaria Sp

Hydrangea macrophylla is cultivated as an ornamental and also used in the landscape. During the fall of 2005, leaves and young stems on 12-month-old plants (cvs. Hanabi, Nigra, and Zaffiro) grown in pots in several gardens and commercial nurseries in the Piedmont (northern Italy) had extensive necrosis. In many cases, 4-mm-diameter spots on the upper side of the leaves were surrounded by a chlorotic halo, which turned progressively black. Lesions often coalesced into 3- to 8-cm-diameter necrotic areas. Initial necrosis developed mainly on the leaf margins and near the petioles. Severely affected plants were defoliated. Infected plants rarely died, but the presence of lesions reduced the aesthetic quality and subsequently the commercial value. The disease occurred on 30 to 50% of the plants. Leaf spots contained dark brown, multicellular, pear-shaped conidia. Conidia were 19.2 to 36.5 μm (average 26.3 μm) long and 7.7 to 11.5 μm (average 8.9 μm) wide, with 3 to 4 longitudinal cross walls and an average of 4.4 single cells. A fungus identified on the basis of its morphological characteristics as an Alternaria sp. was consistently isolated from symptomatic leaves onto potato dextrose agar. DNA was extracted from mycelium (Nucleospin Plant Kit, Macherey Nagel, Brockville, ON, Canada) and PCR was completed using Alt-for/Alt-rev primers (3), which amplified a part of the gene that encodes for the protein Alt a 1, the major allergen produced by the genus Alternaria. A 305-bp fragment was amplified, sequenced, and the sequence was subjected to BLASTn analysis (1), which confirmed that the isolate belonged to the genus Alternaria and to the alternata group (3). The nucleotide sequence has been deposited in GenBank (Accession No. EF446670). Pathogenicity tests were performed by spraying leaves of healthy potted H. macrophylla plants, cvs. Zaffiro (6-month-old) and Hanabi (12-month-old) with a spore suspension (105 conidia/ml). Plants sprayed with water only served as a control. Ten plants per cultivar were used for each treatment. Plants were covered with plastic bags for 5 days after inoculation and maintained at 20°C for an additional 7 days. Plants were transferred outdoors and kept at temperatures ranging from 19 to 25°C. The first foliar lesions developed on leaves 15 days after inoculation, whereas control plants remained healthy. Alternaria sp. was consistently reisolated from these lesions. The pathogenicity test was completed twice. The presence of Alternaria sp. on Hydrangea spp. was reported in the United States (2), whereas A. hortensiae was observed in Spain (4). To our knowledge, this is the first report of Alternaria sp. belonging to the alternata group infecting H. macrophylla in Italy. The disease is currently spreading in other Italian areas. References: (1) S. F. Altschud et al. Nucleic Acids Res. 25:3389, 1997. (2) M. L. Daughtrey et al. Page 9 in: Compendium of Flowering Potted Plant Diseases. The American Phytopathological Society, St. Paul, MN, 1995. (3) S. Gyu Hong et al. Fungal Genet. Biol. 42:119, 2005. (4) L. M. Unamuno. An. Jard. Bot. Madr. 4:145, 1944.

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First Report of Alternaria Leaf Spot on Camellia in Italy

Plant Disease ◽

10.1094/pdis-91-3-0324c ◽

2007 ◽

Vol 91 (3) ◽

pp. 324-324 ◽

Cited By ~ 2

Author(s):

A. Garibaldi ◽

G. Gilardi ◽

M. L. Gullino

Keyword(s):

Single Cells ◽

Morphological Characteristics ◽

The United States ◽

Tea Plant ◽

Northern Italy ◽

Plant Diseases ◽

Pathogenicity Test ◽

Camellia Japonica ◽

Aesthetic Quality ◽

First Report

Camellia cultivation has a long history in the Lake Maggiore area of northern Italy where a wide selection of varieties is present. Camellias are appreciated for their large, colorful flowers that bloom from late fall through early spring. In July 2005, a previously unknown foliar disease was observed on a collection of 2- to 12-month-old camellia cultivars (Camellia japonica) grown in several nurseries located in the Verbania Province (northern Italy). The disease was observed on plants grown in pots (10 to 24 cm in diameter) that were maintained either in the open or in a greenhouse and was present for the entire growing season. However, symptoms were more severe during the summer with temperatures ranging between 25 and 30°C with high relative humidity values. During the months of June and July of 2005, severe attacks involving as much as 70% of plants were observed on C. japonica cvs. Mrs. Tingley, Burnside, Hagoromo (synonym Magnoliaeflora), and Giuseppe Traverso. The disease was again observed in 2006. On the upper side of the younger leaves, small necrotic spots (3 to 8 mm in diameter) initially developed mainly at the margin of the leaves and near the petioles. Necrotic areas were surrounded by a chlorotic halo that turned progressively black. The necrotic areas often coalesced, generating larger spots with a diameter ranging from 15 to 30 mm. Severely affected plants were defoliated. Infected plants sometimes died. The presence of lesions on mature plants decreased aesthetic quality and market value. Leaf spots contained dark brown, multicellular, pyriform conidia. Conidia, generally in short chains, were 20.5 to 34.8 μm (average 29.3 μm) long, 6.9 to 12.2 μm (average 9.9 μm) wide, with 3 to 4 longitudinal cross walls, and an average of 5.7 single cells. From 15 samples of infected leaves, several isolates of a fungus identified on the basis of its morphological characteristics as belonging to the Alternaria alternata complex (2) were consistently isolated on potato dextrose agar containing 25 mg/l of streptomycin sulfate. Pathogenicity tests were performed by spraying leaves of healthy 6-month-old potted C. japonica cv. Burnside plants with a spore and mycelial suspension (1 × 105 CFU/ml) prepared by using a mixture of three isolates obtained in 2005 grown on PDA for 30 days at 23 ± 2°C in a growth chamber (12 h of light per day). Plants without inoculation served as a control. Five plants were used for each treatment. Plants were covered with plastic bags for 3 days after inoculation and maintained at 25°C in growth chambers. The first lesions developed on leaves 3 days after inoculation, while control plants remained healthy. Sixty days after artificial inoculation, 25% of the inoculated plants were dead, while the control plants remained healthy. From lesions of infected plants, a fungus belonging to the A. alternata complex was consistently reisolated. The pathogenicity test was carried out twice. The presence of A. alternata on C. sinensis, the commercial tea plant, was reported in India (1). Previously, a flower blight caused by A. tenuis was reported in the United States (3). This is, to our knowledge, the first report of A. alternata on C. japonica in Italy and probably in the world. The disease was present in 2005 and 2006 in several commercial nurseries affecting 50% of plants of susceptible cultivars. References: (1) B. N. Chakraborty et al. Plant Pathol. 55:303, 2006. (2) E. G. Simmons. Pages 1–35 in: Alternaria Biology, Plant Diseases and Metabolites. J. Chelchowski and A. Visconti, eds. Elsevier, Amsterdam, 1992. (3) A. J. Watson. Plant Dis. Rep. 34:186, 1950.

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First Report of Botrytis Blight Caused by Botrytis cinerea on Periwinkle (Catharanthus roseus) in Italy

Plant Disease ◽

10.1094/pdis-93-5-0554b ◽

2009 ◽

Vol 93 (5) ◽

pp. 554-554 ◽

Cited By ~ 2

Author(s):

A. Garibaldi ◽

D. Bertetti ◽

M. L. Gullino

Keyword(s):

Botrytis Cinerea ◽

Catharanthus Roseus ◽

Warm Season ◽

Its Region ◽

The United States ◽

Plant Diseases ◽

Fluorescent Light ◽

Pathogenicity Test ◽

First Report ◽

Bedding Plant

Catharanthus roseus (periwinkle), a perennial plant belonging to the Apocynaceae family, is grown as a warm-season bedding plant in temperate gardens. This species is characterized by a long flowering period and prized for its white-to-dark pink flowers. In October of 2008, 15% of C. roseus plants in a public garden located in Torino (northern Italy) showed symptoms of a previously unknown blight. When the disease developed, temperatures ranged between 10 and 24°C (average 17.3°C) and plants were being watered through sprinkle irrigation. Necrosis developed on the stems first, eventually spreading to leaf stalks, and the the entire leaf. Subsequently, the pathogen developed a scant, delicate, gray mycelium on affected tissues, particularly diffused on the stems. Severely infected leaves and stems eventually became completely rotted and desiccated. Tissues were excised from diseased leaves, immersed in a solution containing 1% sodium hypochlorite for 10 s, and cultured on potato dextrose agar (PDA) medium. The fungus produced abundant mycelium on PDA medium when incubated under constant fluorescent light at 22 ± 1°C. Numerous sclerotia were produced on PDA plates incubated for 20 days at 8 ± 1°C. Sclerotia were dark and irregular, measuring 0.5 to 2.8 × 0.5 to 2.2 (average 1.4 × 1.1) mm. Conidia were smooth, ash colored, ovoid, measuring 8 to 16 × 6 to 10 (average 10 × 7) μm, and similar to those described for Botrytis cinerea (2). The internal transcribed spacer (ITS) region of rDNA was amplified with primers ITS4/ITS6 and sequenced. BLAST analysis (1) of the 780-bp segment showed a 100% homology with the sequence of Botryotinia fuckeliana (perfect stage of B. cinerea). The nucleotide sequence has been assigned GenBank Accession No. FJ486271. Pathogenicity tests were performed by placing numerous fragments of PDA cultures on leaves of healthy, potted, 8-month-old C. roseus plants. Plants inoculated with PDA alone served as controls. Three plants per treatment were used. Plants were covered with plastic bags for 5 days after inoculation and maintained in a greenhouse at temperatures ranging between 18 and 25°C. The first foliar lesions developed on leaves 5 days after inoculation, whereas control plants remained healthy. B. cinerea was consistently reisolated from these lesions. The pathogenicity test was completed twice. To our knowledge, this is the first report of the presence of B. cinerea on C. roseus in Italy. The same disease was previously reported in many countries including the United States (3) and Taiwan (4). References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997. (2) H. L. Barnett and B. B. Hunter. Illustrated Genera of Imperfect Fungi. Burgess Publishing Company, Minneapolis, MN, 1972. (3) M. L. Daughtrey et al. Compendium of Flowering Potted Plant Diseases. The American Phytopathological Society, St Paul, MN, 1995. (4) W. Ou-Yang and W. S. Wu. Plant Pathol. Bull. 7:147, 1998.

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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.

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First Report of Passalora Leaf Spot Caused by Passalora bougainvilleae on Bougainvillea in Mexico

Plant Disease ◽

10.1094/pdis-11-10-0787 ◽

2011 ◽

Vol 95 (6) ◽

pp. 775-775 ◽

Cited By ~ 1

Author(s):

V. Ayala-Escobar ◽

V. Santiago-Santiago ◽

A. Madariaga-Navarrete ◽

A. Castañeda-Vildozola ◽

C. Nava-Diaz

Keyword(s):

Uv Light ◽

Disease Incidence ◽

Morphological Characteristics ◽

The United States ◽

Pathogenicity Test ◽

Commonwealth Mycological Institute ◽

Conidial Suspension ◽

Single Spore ◽

First Report ◽

Bougainvillea Spectabilis

Bougainvillea (Bougainvillea spectabilis Willd) growing in 28 gardens during 2009 showed 100% disease incidence and 3 to 7% disease severity. Bougainvilleas with white flowers were the most affected. Symptoms consisted of light brown spots with dark brown margins visible on adaxial and abaxial sides of the leaves. Spots were circular, 2 to 7 mm in diameter, often surrounded by a chlorotic halo, and delimited by major leaf veins. Single-spore cultures were incubated at 24°C under near UV light for 7 days to obtain conidia. Pathogenicity was confirmed by spraying a conidial suspension (1 × 104 spores/ml) on leaves of potted bougainvillea plants (white, red, yellow, and purple flowers), incubating the plants in a dew chamber for 48 h and maintaining them in a greenhouse (20 to 24°C). Identical symptoms to those observed at the residential gardens appeared on inoculated plants after 45 to 60 days. The fungus was reisolated from inoculated plants that showed typical symptoms. No symptoms developed on control plants treated with sterile distilled water. The fungus produced distinct stromata that were dark brown, spherical to irregular, and 20 to 24 μm in diameter. Conidiophores were simple, born from the stromata, loose to dense fascicles, brown, straight to curved, not branched, zero to two septate, 14 × 2 μm, with two to four conspicuous and darkened scars. The conidia formed singly, were brown, broad, ellipsoid, obclavate, straight to curved with three to four septa, 40 × 4 μm, and finely verrucous with thick hilum at the end. Fungal DNA from the single-spore cultures was obtained using a commercial DNA Extraction Kit (Qiagen, Valencia, CA); ribosomal DNA was amplified with ITS5 and ITS4 primers and sequenced. The sequence was deposited at the National Center for Biotechnology Information Database (GenBank Accession Nos. HQ231216 and HQ231217). The symptoms (4), morphological characteristics (1,2,4), and pathogenicity test confirm the identity of the fungus as Passalora bougainvilleae (Muntañola) Castañeda & Braun (= Cercosporidium bougainvilleae Muntañola). This pathogen has been reported from Argentina, Brazil, Brunei, China, Cuba, El Salvador, India, Indonesia, Jamaica, Japan, Thailand, the United States, and Venezuela (3). To our knowledge, this is the first report of this disease on B. spectabilis Willd in Mexico. P. bougainvilleae may become an important disease of bougainvillea plants in tropical and subtropical areas of Mexico. References: (1) U. Braun and R. R. Castañeda. Cryptogam. Bot. 2/3:289, 1991. (2) M. B. Ellis. More Dematiaceous Hypomycetes. Commonwealth Mycological Institute, Kew, Surrey, UK, 1976. (3) C. Nakashima et al. Fungal Divers. 26:257, 2007. (4) K. L. Nechet and B. A. Halfeld-Vieira. Acta Amazonica 38:585, 2008.

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Leaf Spot Caused by Alternaria sp. on Iberis sempervirens in Italy

Plant Disease ◽

10.1094/pd-89-1243b ◽

2005 ◽

Vol 89 (11) ◽

pp. 1243-1243 ◽

Cited By ~ 1

Author(s):

A. Garibaldi ◽

A. Minuto ◽

M. L. Gullino

Keyword(s):

Leaf Spot ◽

Single Cells ◽

Morphological Characteristics ◽

Weather Conditions ◽

The United States ◽

Plant Diseases ◽

Pathogenicity Test ◽

Aesthetic Quality ◽

Leaf Spots ◽

Alternaria Sp

Iberis sempervirens (candytuft) is increasingly grown in Liguria (northern Italy) as a potted plant for ornamental purposes, particularly under cool-weather conditions. At the end of the summer of 2003, extensive necrosis was observed on leaves and young stems of 4-month-old plants grown in 14-cm diameter pots outdoors at a commercial farm. In many cases, on the upper side of the leaves, necrotic spots were surrounded by a chlorotic halo that turned progressively black. The necrotic areas often coalesced, generating larger and irregularly shaped spots. On the lower side of the leaves, no chlorotic areas were observed. Severely affected plants were defoliated. Infected plants rarely died, but the presence of lesions on mature plants decreased aesthetic quality and subsequently market value. The disease occurred on 40% of plants at each of the two farms. Leaf spots contained dark brown, multicellular pear-shaped conidia. Conidia were 22.5 to 50.0 μm (average 32.8 μm) long and 7.5 to 15.0 μm (average 12.3 μm) wide, with 5 to 7 longitudinal cross walls and an average of 6 to 7 single cells. From infected leaves, a fungus identified on the basis of its morphological characteristics as Alternaria sp. was consistently isolated on potato dextrose agar. Pathogenicity tests were performed by spraying leaves of healthy 12-month-old potted I. sempervirens plants with a spore and mycelial suspension (105 CFU/ml). Plants without inoculation served as control. Ten plants were used for each treatment. Plants were covered with plastic bags for 10 days after inoculation and kept outdoors for 60 days at temperatures ranging from 0 to 32°C (average 12°C). The first lesions developed on leaves 45 days after inoculation, while control plants remained healthy. From such lesions, Alternaria sp. was consistently reisolated. The pathogenicity test was carried out twice. The presence of A. brassicae was reported in Tanganica on Iberis sp., I. umbellata in Denmark (2), and I. amara in the United States (4); A. matthiolae was observed on seeds of I. amara and I. umbellata (3). A leaf spot incited by Alternaria sp. on I. amara was observed in Florida (1). This is, to our knowledge, the first report of Alternaria sp. on I. sempervirens in Italy as well as worldwide. References: (1) S. A. Alfieri et al. Index of Plant Diseases in Florida. Bull. 11, 1984. (2) P. Neergaard. Rev. Appl. Micol. 18:572, 1939. (3) P. Neergaard. Rev. Appl. Micol. 25:382, 1946). (4) R. D. Raabe. Comb. Proc. Int. Plant Propagators Soc. 40:160, 1991.

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First Report of Leaf Spot of Lettuce (Lactuca sativa L.) Caused by Phoma tropica in Italy

Plant Disease ◽

10.1094/pdis-04-12-0394-pdn ◽

2012 ◽

Vol 96 (9) ◽

pp. 1380-1380 ◽

Cited By ~ 4

Author(s):

A. Garibaldi ◽

G. Gilardi ◽

G. Ortu ◽

M. L. Gullino

Keyword(s):

Relative Humidity ◽

Lactuca Sativa ◽

Leaf Spot ◽

Morphological Characteristics ◽

The United States ◽

Fluorescent Light ◽

Malt Extract ◽

Pathogenicity Test ◽

First Report ◽

Lactuca Sativa L

Lettuce (Lactuca sativa L.) is widely grown in Italy, with the production for the preparation of ready-to-eat salads becoming increasingly important. During the spring of 2011, a previously unknown leaf spot was observed on L. sativa plants, cv Rubia, grown in several plastic tunnels in Lumbardy (northern Italy), 20 to 25 days after sowing. Thirty to forty per cent of leaves of the plants growing in the part of the tunnel with the highest relative humidity were affected. Leaves of infected plants showed extensive, irregular, dark brown, necrotic lesions with a chlorotic halo. Lesions initially ranged from 0.5 to 3 mm, then eventually coalesced, reaching 2 to 3 cm, showing a well-defined, dark brown border. Affected leaves senesced and withered. The crown was not affected by the disease. Diseased tissue was excised, immersed in a solution containing 1% sodium hypochlorite for 60 s, rinsed in water, then cultured on potato dextrose agar (PDA), amended with 25 mg/l of streptomycin sulphate. After 5 days, a fungus developed, producing a greenish grey mycelium with a white border when incubated under 12 h/day of fluorescent light at 21 to 23°C. In order to favor the production of conidia, the fungus was transferred on malt extract agar (MA) and maintained under 12 h/day of fluorescent light at 22°C. After 15 days, black pycnidia, 175 to 225 μm, developed, with hyaline, elliptical, unicellular conidia, measuring 3.21 to 6.7 × 1.08 to 3.2 (average 5.5 × 1.9) μm. On the basis of these morphological characteristics, the fungal causal agent of the disease could be related to the genus Phoma (2). The internal transcribed spacer (ITS) region of rDNA of the isolate PHT30 was amplified using the primers ITS1/ITS4 and sequenced. BLAST analysis (1) of the 466-bp segment showed a 99% similarity with the sequence of Phoma tropica (GenBank Accession No. JF923820.1). The nucleotide sequence has been assigned the GenBank Accession No. JQ954396. Pathogenicity tests were performed by spraying healthy 20-day-old lettuce plants, cv Rubia, with a spore suspension (1 × 105 conidia/ml) prepared from 14-day-old colonies of the strain PHT30 grown on MA cultures. Plants inoculated with water alone served as controls. Ten plants per isolate were used. Plants were covered with plastic bags for 5 days after inoculation and maintained in a growth chamber at 20°C and 80% relative humidity. The first foliar lesions, similar to those occurring on the naturally infected plants, developed on leaves 12 days after inoculation. Control plants remained healthy. The pathogen was consistently reisolated from leaf lesions. The pathogenicity test was completed twice. To our knowledge, this is the first report of the presence of P. tropica on lettuce in Italy as well as worldwide. In the United States, the presence of P. exigua was reported in 2006 (3). The economic importance of the disease at present is limited, probably also because symptoms can be confused with those caused by Botrytis cinerea. However, P. tropica could become a more significant problem because of the importance of the crop. References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997. (2) G. H. Boerema. Trans. Br. Mycol. Soc. 67:289, 1976. (3) S. Y. Koike. Plant Dis. 90:1268, 2006.

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First Report of Botrytis Blight Caused by Botrytis cinerea on Platycodon grandiflorum in Italy

Plant Disease ◽

10.1094/pdis-93-9-0969b ◽

2009 ◽

Vol 93 (9) ◽

pp. 969-969

Author(s):

A. Garibaldi ◽

D. Bertetti ◽

M. L. Gullino

Keyword(s):

United States ◽

Botrytis Cinerea ◽

Its Region ◽

The United States ◽

Fluorescent Light ◽

Pathogenicity Test ◽

Commonwealth Mycological Institute ◽

Platycodon Grandiflorum ◽

First Report ◽

Bedding Plant

Platycodon grandiflorum (balloon flower), a perennial plant belonging to the Campanulaceae family, is widely grown as a bedding plant in temperate gardens. This species is characterized by the ability to bloom profusely throughout the summer into early fall and for its white to blue and pink flowers. In September 2008, symptoms of a previously unknown blight were observed in six gardens located in the Biella Province of northern Italy. When the disease developed, temperatures ranged between 15 and 22°C with frequent rains (149.8 mm of rainfall registered in September 2008 by the meteorological station of Oropa, located in the same area in which the disease appeared). Initially, leaves and petioles appeared chlorotic. Subsequently, lesions developed on the stems and flowers were sometimes affected. In each garden examined, approximately 50% of the plants were affected by the disease. A soft, gray mycelium was observed on symptomatic tissues, especially the stems. Severely infected leaves and stems eventually became completely rotted and later desiccated. Diseased tissue was excised from affected leaves, immersed in a solution containing 1% sodium hypochlorite for 10 s, and then cultured on potato dextrose agar (PDA) medium. A fungus developed that produced abundant mycelium on PDA medium when incubated under constant fluorescent light at 22 ± 1°C. Numerous sclerotia were produced on PDA plates incubated for 20 days at 8 ± 1°C. Sclerotia were dark, irregular, and measured 1 to 3.5 × 0.9 to 2.5 (average 2.1 × 1.5) mm. Conidia were smooth, ash colored, unicellular, ovoid, and measured 11 to 19 × 7 to 13 (average 15 × 11) μm. These morphological features were typical of those described for Botrytis cinerea (2). The internal transcribed spacer (ITS) region of rDNA was amplified using primers ITS4/ITS6 and sequenced. BLAST analysis (1) of the 539-bp segment showed 100% similarity with the sequence of Botryotinia fuckeliana (perfect stage of B. cinerea). The nucleotide sequence has been assigned the GenBank Accession No. GQ149480. Pathogenicity tests were performed by placing 1-cm2 fragments removed from PDA cultures of B. cinerea isolated from balloon flower on leaves of healthy potted P. grandiflorum plants (4-month-old). Five fragments were placed on each plant. Plants inoculated with PDA alone served as controls. Ten plants per treatment were used. Plants were covered with plastic bags for 5 days after inoculation and maintained in a greenhouse at temperatures between 18 and 23°C. The first foliar lesions developed on leaves 3 days after inoculation, and after 5 days, 80% of the leaves were severely infected. As the infection progressed after the inoculation, the stems also became infected. Control plants remained healthy. B. cinerea was consistently reisolated from leaf and stem lesions. The pathogenicity test was completed twice. To our knowledge, this is the first report of the presence of B. cinerea on P. grandiflorum in Italy, as well as in Europe. Blight on balloon flower attributed to Botrytis spp. was previously reported in the United States (3). References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997. (2) M. B. Ellis. Dematiaceous Hyphomycetes. Commonwealth Mycological Institute, Kew, England, 1971. (3) D. F. Farr et al. Fungi on Plants and Plant Products in the United States. The American Phytopathological Society, St. Paul, MN, 1989.

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