First Report of Cochliobolus sativus on Guzmania sp. in Belgium

In 2001 and again in December 2005, an outbreak of leaf spots was observed on Guzmania sp. ‘Gwendolyne’ (Bromeliaceae) in a Belgian nursery. Typical disease symptoms were irregular spots with a grayish center and a narrow red-brown margin. Identification was based on morphological characteristics and molecular techniques. Isolations of diseased leaf tissues previously washed with sterile distilled water on potato dextrose agar (PDA) resulted in mycelial colonies after 7 to 8 days. Fungal mycelium grew at a linear rate of 30.4 mm per 24 h at 21°C in the dark. The pathogen produced aerial mycelium and sporulation was abundant. The color of the colonies on PDA was pale to dark brown and conidial characteristics similar to those of Cochliobolus sativus (anamorph Bipolaris sorokiniana) (1) were observed: brown ellipsoidal spores rounded at the top, 3 to 12 distoseptate, with average dimensions of 40 to 120 × 17 to 28 μm. The pathogen was also characterized with molecular tools. DNA was isolated from mycelium from a PDA plate. The ribosomal DNA region ITS1-5.8S-ITS2 was amplified and cloned. The ITS1 sequences (174 bp) of two independent clones were analyzed. The three highest similarity scores (E = 2e-71) obtained in BLAST were C. sativus (GenBank Accession Nos. AF158105 and AF071329) and B. sorokiniana strain BS11 (GenBank Accession No. AY372677). For these, pairwise alignments resulted in an identical score of 97.1% (169 identical bases, four indels, and one transversion). The new Genbank Accession No. of the ITS1 sequence is DQ 641269. To prove pathogenicity of the isolate, inoculations were done by spraying leaves of three young Guzmania sp. ‘Gwendolyne’ plants with a 20-ml spore suspension (106 spores/ml). Three plants were sprayed with sterile distilled water as controls. The plants were kept for 48 h under a humid chamber and subsequently at room temperature (20 to 25°C) on the laboratory bench. Three to four days after inoculation, leaf spots were observed and C. sativus (anamorph B. sorokiniana) was reisolated, completing Koch's postulates successfully. On the basis of symptoms, morphological characteristics, and pathogenicity tests, the pathogen was identified as C. sativus (anamorph B. sorokiniana). To our knowledge, this is the first record of C. sativus (anamorph B. sorokiniana) on Guzmania sp. in Belgium. References: (1) A. Sivanesan and P. Holliday. Description of Pathogenic Fungi and Bacteria. CMI, Kew, Surrey, England, UK, 1981.

Download Full-text

First Report of Leaf Spot of Sweet Basil Caused by Cercospora guatemalensis in Korea

Plant Disease ◽

10.1094/pdis-05-12-0436-pdn ◽

2012 ◽

Vol 96 (10) ◽

pp. 1580-1580

Author(s):

J. H. Park ◽

K. S. Han ◽

J. Y. Kim ◽

H. D. Shin

Keyword(s):

Leaf Spot ◽

Morphological Characteristics ◽

Its Region ◽

Culture Collection ◽

Distilled Water ◽

First Report ◽

Sweet Basil ◽

Organic Farm ◽

Leaf Spots ◽

Close Phylogenetic Relationship

Sweet basil, Ocimum basilicum L., is a fragrant herb belonging to the family Lamiaceae. Originated in India 5,000 years ago, sweet basil plays a significant role in diverse cuisines across the world, especially in Asian and Italian cooking. In October 2008, hundreds of plants showing symptoms of leaf spot with nearly 100% incidence were found in polyethylene tunnels at an organic farm in Icheon, Korea. Leaf spots were circular to subcircular, water-soaked, dark brown with grayish center, and reached 10 mm or more in diameter. Diseased leaves defoliated prematurely. The damage purportedly due to this disease has reappeared every year with confirmation of the causal agent made again in 2011. A cercosporoid fungus was consistently associated with disease symptoms. Stromata were brown, consisting of brown cells, and 10 to 40 μm in width. Conidiophores were fasciculate (n = 2 to 10), olivaceous brown, paler upwards, straight to mildly curved, not geniculate in shorter ones or one to two times geniculate in longer ones, 40 to 200 μm long, occasionally reaching up to 350 μm long, 3.5 to 6 μm wide, and two- to six-septate. Conidia were hyaline, acicular to cylindric, straight in shorter ones, flexuous to curved in longer ones, truncate to obconically truncate at the base, three- to 16-septate, and 50 to 300 × 3.5 to 4.5 μm. Morphological characteristics of the fungus were consistent with the previous reports of Cercospora guatemalensis A.S. Mull. & Chupp (1,3). Voucher specimens were housed at Korea University herbarium (KUS). An isolate from KUS-F23757 was deposited in the Korean Agricultural Culture Collection (Accession No. KACC43980). Fungal DNA was extracted with DNeasy Plant Mini DNA Extraction Kits (Qiagen Inc., Valencia, CA). The complete internal transcribed spacer (ITS) region of rDNA was amplified with the primers ITS1/ITS4 and sequenced. The resulting sequence of 548 bp was deposited in GenBank (Accession No. JQ995781). This showed >99% similarity with sequences of many Cercospora species, indicating their close phylogenetic relationship. Isolate of KACC43980 was used in the pathogenicity tests. Hyphal suspensions were prepared by grinding 3-week-old colonies grown on PDA with distilled water using a mortar and pestle. Five plants were inoculated with hyphal suspensions and five plants were sprayed with sterile distilled water. The plants were covered with plastic bags to maintain a relative humidity of 100% for 24 h and then transferred to a 25 ± 2°C greenhouse with a 12-h photoperiod. Typical symptoms of necrotic spots appeared on the inoculated leaves 6 days after inoculation, and were identical to the ones observed in the field. C. guatemalensis was reisolated from symptomatic leaf tissues, confirming Koch's postulates. No symptoms were observed on control plants. Previously, the disease was reported in Malawi, India, China, and Japan (2,3), but not in Korea. To our knowledge, this is the first report of C. guatemalensis on sweet basil in Korea. Since farming of sweet basil has recently started on a commercial scale in Korea, the disease poses a serious threat to safe production of this herb, especially in organic farming. References: (1) C. Chupp. A Monograph of the Fungus Genus Cercospora. Ithaca, NY, 1953. (2) D. F. Farr and A. Y. Rossman. Fungal Databases. Systematic Mycology & Microbiology Laboratory, ARS, USDA. Retrieved from http://nt.ars-grin.gov/fungaldatabases/ , May 5, 2012. (3) J. Nishikawa et al. J. Gen. Plant Pathol. 68:46, 2002.

Download Full-text

First Report of Cochliobolus sativus Causing Leaf Spot on Paper Mulberry in China

Plant Disease ◽

10.1094/pdis-04-11-0319 ◽

2011 ◽

Vol 95 (12) ◽

pp. 1586-1586 ◽

Cited By ~ 1

Author(s):

P. S. Wu ◽

K. Chen ◽

H. Z. Du ◽

J. Yan ◽

Q. E. Zhang

Keyword(s):

Leaf Spot ◽

Leaf Tissue ◽

Pathogenic Fungi ◽

Bipolaris Sorokiniana ◽

Causal Agent ◽

Cochliobolus Sativus ◽

Conidial Suspension ◽

Sterile Water ◽

First Report ◽

Forest Park

Paper mulberry, Broussonetia papyrifera (L.) Vent., is a highly adaptable, fast-growing tree that is native to eastern Asia. Its ability to absorb pollutants makes it ideal for ornamental landscapes, especially in industrial and mining areas. During the summer of 2010, brown lesions were observed on leaves of paper mulberry in Baiwangshan Forest Park, Beijing, China. These lesions were ovoid to fusiform and 4 to 9 × 2 to 4 mm with dark brown centers and light brown irregular edges. Spots on severely infected leaves sometimes coalesced to form long stripes with gray centers. To isolate the causal agent of the lesions, 4-mm2 pieces of diseased leaf tissue from 12 leaves were collected at the lesion margins and surface disinfected in 0.5% NaOCl for 3 min, rinsed three times with sterile water, plated on water agar, and incubated at 25°C with a 12-h photoperiod. After 5 days, the cultures, which became dark brown to black, were observed. Conidiophores (120 to 220 × 4 to 7 μm) were solitary or in groups of two to five, straight or flexuous with swollen bases, and light or dark brown. Conidia were dark olive brown, spindle- or oval-shaped with truncated ends (60 to 120 × 15 to 30 μm), slightly curved, and containing 3 to 12 distoseptate (mostly 6 to 10). Pseudothecia, produced after 14 days in culture, were dark brown to black and flask shaped (420 to 530 μm in diameter with 85 to 100 × 75 to 90 μm ostiolar beaks). Asci were cylindrical (100 to 220 × 30 to 40 μm) and contained eight ascospores. Ascospores were filiform, (150 to 360 × 6 to 9 μm), hyaline, with 6 to 11 septations. Isolates were identified as Cochliobolus sativus (Ito & Kurib.) Drechsler & Dastur (anamorph Bipolaris sorokiniana (Sacc. & Sorok.) Shoem.) on the basis of culture color and dimensions and colors of pseudothecia, asci, ascospores, conidiophores, and conidia (2,3). The identity of one isolate was confirmed by ITS1-5.8S-ITS2 rDNA sequence (GenBank Accession No. HQ 654781) analysis that showed 100% homology to C. sativus listed in Berbee et al. (1). Koch's postulates were performed with six potted 3-month-old paper mulberry plants. An isolate was grown on potato dextrose agar for 14 days to obtain conidia for a conidial suspension (3 × 104 conidia/ml). Three of the potted plants were sprayed with the conidial suspension and three were sprayed with sterile water as controls. Each plant was covered with a plastic bag for 24 h to maintain high humidity and incubated at 25°C with a 12-h photoperiod. After 7 days, the inoculated plants showed leaf symptoms identical to those previously observed on paper mulberry trees in the Baiwangshan Forest Park, while control trees remained symptom free. Reisolation of the fungus from the inoculated plants confirmed that the causal agent was C. sativus. C. sativus is widely distributed worldwide causing a variety of cereal diseases. Wheat and barley are the most economically important hosts. To our knowledge, this is the first report of C. sativus as a pathogen causing leaf spot of paper mulberry in China. References: (1) M. L. Berbee et al. Mycologia 91:964, 1999. (2) M. B. Ellis. Dematiaceous Hyphomycetes. CABI, Oxon, UK, 1971. (3) A. Sivanesan et al. No.701 in: Descriptions of Pathogenic Fungi and Bacteria. CAB, Kew, Surrey, U.K., 1981.

Download Full-text

First Report of Fusarium proliferatum Causing Rot of Garlic Bulbs (Allium sativum) in India

Plant Disease ◽

10.1094/pdis-08-11-0649 ◽

2012 ◽

Vol 96 (2) ◽

pp. 290-290 ◽

Cited By ~ 9

Author(s):

N. Ravi Sankar ◽

Gundala Prasad Babu

Keyword(s):

Sodium Hypochlorite ◽

Allium Sativum ◽

Morphological Characteristics ◽

Aerial Mycelium ◽

Its Region ◽

Fusarium Proliferatum ◽

Distilled Water ◽

Sequence Comparisons ◽

First Report ◽

Plant Pathol

In September 2009, diseased garlic bulbs (Allium sativum L. cv. Yamuna Safed) were received from producers and exporters in Hyderabad, Andra Pradesh, India. From 2009 to 2010, similar symptoms were observed on stored garlic bulbs (cvs. Yamuna Safed and Agrifound White) in Chittoor, Kadapa, and Hyderabad districts. In some locations, approximately 60% of the garlic bulbs were affected. At first, infected bulbs showed water-soaked, brown spots and then the disease progressed as small, slightly depressed, tan lesions. A total of 120 diseased samples were collected from all localities. Infected tissues were surface sterilized in 1% sodium hypochlorite for 2 min, rinsed three times in sterile distilled water, plated on potato dextrose agar (PDA), and incubated at 25°C for 7 days. Resultant fungal colonies were fast growing with white aerial mycelium and violet to dark pigments. Hyphae were septate and hyaline. Conidiophores were short, simple, or branched. Microconidia were abundant, single celled, oval or club shaped, measuring 4.5 to 10.5 × 1.3 to 2.5 μm, and borne in chains from both mono-and polyphialides. Macroconidia were not produced. On the basis of morphological characteristics, the pathogen was identified as Fusarium proliferatum (Matsushima) Nirenberg (2). Identification was confirmed by amplification of the internal transcribed spacer (ITS) region. Genomic DNA was extracted from pure cultures of an isolate, and the ITS region was amplified using the ITS4/5 primer pair. PCR amplicons of approximately 574 bp were obtained from isolates, and sequence comparisons with GenBank showed 99% similarity with F. proliferatum (Accession No. FN868470.1). Sequence from this study was submitted to GenBank nucleotide database (Accession No. AB646795). Pathogenicity tests were conducted with three isolates of the fungus following the method of Dugan et al. (1). Each assay with an isolate consisted of 10 garlic cloves disinfected in 1% sodium hypochlorite for 45 s, rinsed with sterile distilled water, and injured to a depth of 4 mm with a sterile 1-mm-diameter probe. The wounds were filled with PDA colonized by the appropriate isolate from a 5-day-old culture. Ten cloves for each tested isolate received sterile PDA as a control. The cloves were incubated at 25°C for 5 weeks; tests were repeated once. After 17 days, rot symptoms similar to the original symptoms developed on all inoculated cloves and F. proliferatum was consistently reisolated from symptomatic tissue, fulfilling Koch's postulates. No fungi were recovered from control cloves. F. proliferatum has been reported on garlic in the northwestern United States (1), Serbia (4), and Spain (3). To our knowledge, this is the first report of F. proliferatum causing rot disease on garlic bulbs in India. References: (1) F. M. Dugan et al. Plant Pathol. 52:426, 2003. (2) J. F. Leslie and B. A. Summerell. The Fusarium Laboratory Manual. Blackwell Publishing, Oxford, UK, 2006. (3) D. Palmero et al. Plant Dis. 94:277, 2010. (4) S. Stankovic et al. Eur. J. Plant Pathol. 48:165, 2007.

Download Full-text

First Report of a Chaetomella sp. Causing a Leaf Spot on Sansevieria trifasciata in China

Plant Disease ◽

10.1094/pdis-10-12-0993-pdn ◽

2013 ◽

Vol 97 (7) ◽

pp. 992-992 ◽

Cited By ~ 4

Author(s):

Y. L. Li ◽

Z. Zhou ◽

W. Lu ◽

J. R. Ye

Keyword(s):

Leaf Spot ◽

Disease Incidence ◽

Morphological Characteristics ◽

Leaf Tissue ◽

Aerial Mycelium ◽

Control Treatment ◽

Distilled Water ◽

First Report ◽

Potted Plants ◽

Fungal Isolates

Sansevieria trifasciata originates from tropical West Africa. It is widely planted as a potted ornamental in China for improving indoor air quality (1). In February 2011, leaves of S. trifasciata plants in an ornamental market of Anle, Luoyang City, China, were observed with sunken brown lesions up to 20 mm in diameter, and with black pycnidia present in the lesions. One hundred potted plants were examined, with disease incidence at 20%. The symptomatic leaves affected the ornamental value of the plants. A section of leaf tissue from the periphery of two lesions from a plant was cut into 1 cm2 pieces, soaked in 70% ethanol for 30 s, sterilized with 0.1% HgCl2 for 2 min, then washed five times in sterilized distilled water. The pieces were incubated at 28°C on potato dextrose agar (PDA). Colonies of two isolates were brown with submerged hyphae, and aerial mycelium was rare. Abundant and scattered pycnidia were reniform, dark brown, and 200 to 350 × 100 to 250 μm. There were two types of setae on the pycnidia: 1) dark brown setae with inward curved tops, and 2) straight, brown setae. Conidia were hyaline, unicellular, cylindrical, and 3.75 to 6.25 × 1.25 to 2.50 μm. Morphological characteristics suggested the two fungal isolates were a Chaetomella sp. To confirm pathogenicity, six mature leaves of a potted S. trifasciata plant were wounded with a sterile pin after wiping each leaf surface with 70% ethanol and washing each leaf with sterilized distilled water three times. A 0.5 cm mycelial disk cut from the margin of a 5-day-old colony on a PDA plate was placed on each pin-wounded leaf, ensuring that the mycelium was in contact with the wound. Non-colonized PDA discs were placed on pin-wounded leaves as the control treatment. Each of two fungal isolates was inoculated on two leaves, and the control treatment was done similarly on two leaves. The inoculated plant was placed in a growth chamber at 28°C with 80% relative humidity. After 7 days, inoculated leaves produced brown lesions with black pycnidia, but no symptoms developed on the control leaves. A Chaetomella sp. was reisolated from the lesions of inoculated leaves, but not from the control leaves. An additional two potted plants were inoculated using the same methods as replications of the experiment, with identical results. To confirm the fungal identification, the internal transcribed spacer (ITS) region of rDNA of the two isolates was amplified using primers ITS1 and ITS4 (2) and sequenced. The sequences were identical (GenBank Accession No. KC515097) and exhibited 99% nucleotide identity to the ITS sequence of an isolate of Chaetomella sp. in GenBank (AJ301961). To our knowledge, this is the first report of a leaf spot of S. trifasciata caused by Chaetomella sp. in China as well as anywhere in the world. References: (1) X. Z. Guo et al. Subtropical Crops Commun. Zhejiang 27:9, 2005. (2) T. J. White et al. PCR Protocols: A Guide to Methods and Applications. M. A. Innis et al., eds. Academic Press, San Diego, CA, 1990.

Download Full-text

First Report of Stem and Leaf Anthracnose on Blueberry Caused by Colletotrichum gloeosporioides in China

Plant Disease ◽

10.1094/pdis-11-12-1056-pdn ◽

2013 ◽

Vol 97 (6) ◽

pp. 845-845 ◽

Cited By ~ 1

Author(s):

C. N. Xu ◽

Z. S. Zhou ◽

Y. X. Wu ◽

F. M. Chi ◽

Z. R. Ji ◽

...

Keyword(s):

Colletotrichum Gloeosporioides ◽

Morphological Characteristics ◽

Its Region ◽

Pathogenic Fungi ◽

Molecular Characteristics ◽

First Report ◽

Potted Plants ◽

Leaf Spots ◽

Pathogenicity Tests ◽

Highbush Blueberries

Blueberry (Vaccinium spp.) is becoming increasingly popular in China as a nutritional berry crop. With the expansion of blueberry production, many diseases have become widespread in different regions of China. In August of 2012, stem and leaf spots symptomatic of anthracnose were sporadically observed on highbush blueberries in a field located in Liaoning, China, where approximately 15% of plants were diseased. Symptoms first appeared as yellow to reddish, irregularly-shaped lesions on leaves and stems. The lesions then expanded, becoming dark brown in the center and surrounded by a reddish halo. Leaf and stem tissues (5 × 5 mm) were cut from the lesion margins and surface-disinfected in 70% ethanol for 30 s, followed by three rinses with sterile water before placing on potato dextrose agar (PDA). Plates were incubated at 28°C. Colonies were initially white, becoming grayish-white to gray with yellow spore masses. Conidia were one-celled, hyaline, and cylindrical with rounded ends, measuring 15.0 to 25.0 × 4.0 to 7.5 μm. No teleomorph was observed. The fungus was tentatively identified as Colletotrichum gloeosporioides (PenZ.) PenZ & Sacc. (teleomorph Glomerella cingulata (Stoneman) Spauld. & H. Schrenk) based on morphological characteristics of the colony and conidia (1). Genomic DNA was extracted from isolate XCG1 and the internal transcribed spacer (ITS) region of the ribosomal DNA (ITS1–5.8S-ITS2) was amplified with primer pairs ITS1 and ITS4. BLAST searches showed 99% identity with C. gloeosporioides isolates in GenBank (Accession No. AF272779). The sequence of isolate XCG1 (C. gloeosporioides) was deposited into GenBank (JX878503). Pathogenicity tests were conducted on 2-year-old potted blueberries, cv. Berkeley. Stems and leaves of 10 potted blueberry plants were wounded with a sterilized needle and sprayed with a suspension of 105 conidia per ml of sterilized water. Five healthy potted plants were inoculated with sterilized water as control. Dark brown lesions surrounded by reddish halos developed on all inoculated leaves and stems after 7 days, and the pathogen was reisolated from lesions of 50% of inoculated plants as described above. The colony and conidial morphology were identical to the original isolate XCG1. No symptoms developed on the control plants. The causal agent of anthracnose on blueberry was identified as C. gloeosporioides on the basis of morphological and molecular characteristics, and its pathogenicity was confirmed with Koch's postulates. Worldwide, it has been reported that blueberry anthracnose might be caused by C. acutatum and C. gloeosporioides (2). However, we did not isolate C. acutatum during this study. To our knowledge, this is the first report of stem and leaf anthracnose of blueberry caused by C. gloeosporioides in China. References: (1) J. M. E. Mourde. No 315. CMI Descriptions of Pathogenic Fungi and Bacteria. Kew, Surrey, UK, 1971. (2) N. Verma, et al. Plant Pathol. 55:442, 2006.

Download Full-text

First Report of Calonectria Leaf Spot Caused by Calonectria colhounii (Anamorph Cylindrocladium colhounii) on Rhododendron in Belgium

Plant Disease ◽

10.1094/pdis-04-11-0343 ◽

2011 ◽

Vol 95 (11) ◽

pp. 1477-1477 ◽

Cited By ~ 1

Author(s):

S. Inghelbrecht ◽

B. Gehesquière ◽

K. Heungens

Keyword(s):

Dna Sequence ◽

Morphological Characteristics ◽

Leaf Tissue ◽

Leading Edge ◽

Aerial Mycelium ◽

The United States ◽

Fluorescent Light ◽

Cycle Sequencing ◽

Leaf Spots ◽

Β Tubulin

Belgium is one of the most important Rhododendron-producing areas in Europe, with an annual sale of approximately 1.6 million plants. In June 2010, an outbreak of leaf spots on several thousands of Rhododendron cv. Marcel Menard plants took place at a nursery near Gent. Diseased plants showed dark brown leaf spots that enlarged and finally resulted in leaf drop. Symptoms developed most explicitly on this cultivar, especially after standard repotting during May or June and when repotting was followed by a few days of unusually warm temperatures (30 to 35°C). The leading edge of diseased leaf tissue was excised, surface disinfected with 1% NaOCl for 60 s, and rinsed twice with sterile distilled water before being plated onto potato dextrose agar (PDA). After 5 days of incubation at 21°C in the dark, Cylindrocladium-like fungal colonies with white aerial mycelium and amber-brown growth within the agar consistently developed. Mycelium was transferred aseptically to fresh plates of PDA and incubated for 10 to 14 days at 17°C under a 12-h fluorescent light regimen to study the morphological characteristics. Conidiophores showed a penicillate arrangement of fertile branches, producing two to six phialides. They arose from a stipe and terminated in a clavate vesicle (3 to 5 μm). Conidia were straight, cylindrical, rounded at both ends, three septate, and measured 60 to 70 × 4 to 6 μm. Yellow subglobose to oval perithecia were abundantly produced. Asci were clavate, four spored, and measured 100 to 150 × 15 to 30 μm. Ascospores were hyaline, three septate, and measured 50 to 65 × 5 to 6 μm. These characteristics are consistent with those of Calonectria colhounii Peerally (anamorph Cylindrocladium colhounii) (1). The β-tubulin gene was PCR-amplified with DNA extracted from the mycelium and the T1 and T2 primers (3), sequenced directly with a BigDye Terminator Cycle Sequencing Kit (Applied Biosystems, Carlsbad, CA), and the DNA sequence was deposited (GenBank Accession No. JF802784). BLASTn alignment showed 99% identity (525 of 526 nucleotides) with the β-tubulin DNA sequence derived from Calonectria colhounii CBS 293.79 (GenBank Accession No. DQ190564). A spore suspension (105 conidia per ml) was prepared from a 1-week-old culture, and 50-μl drops were used to inoculate the abaxial side of 10 detached 1-year-old leaves from Rhododendron cv. Cunningham's White. Ten control leaves were inoculated with water. The leaves were placed in a moist chamber and incubated at 21°C in the dark. After 5 to 6 days, all spore-inoculated leaves showed lesions identical to those on the naturally infected leaves, while the water-inoculated leaves remained symptom free. Following the original procedure, the fungus was reisolated from the diseased leaves and the morphological characteristics of the resulting culture were the same as those of the inoculated isolate, completing Koch's postulates. This fungus has been described on Rhododendron in the United States (2), but to our knowledge, this is the first record of Calonectria colhounii on Rhododendron in Belgium. References: (1) P. W. Crous. Taxonomy and Pathology of Cylindrocladium (Calonectria) and Allied Genera. The American Phytopathological Society, St. Paul, MN, 2002. (2) P. W. Crous et al. Stud. Mycol. 55:213, 2006. (3) K. O'Donnell and E. Cigelnik. Mol. Phylogenet. Evol. 7:103, 1997.

Download Full-text

First Report of Blueberry Botrytis Blight in Buenos Aires, Entre Ríos, and Córdoba, Argentina

Plant Disease ◽

10.1094/pdis-91-5-0639c ◽

2007 ◽

Vol 91 (5) ◽

pp. 639-639 ◽

Cited By ~ 8

Author(s):

P. Vasquez ◽

J. A. Baldomá ◽

E. R. Wright ◽

A. Pérez ◽

M. Divo de Sesar ◽

...

Keyword(s):

Botrytis Cinerea ◽

Buenos Aires ◽

Morphological Characteristics ◽

Leaf Tissue ◽

Pathogenic Fungi ◽

Vaccinium Corymbosum ◽

Distilled Water ◽

First Report ◽

Conidial State ◽

Entre Rios

Since 2003, a new field disease has been observed on several cultivars of highbush blueberry (Vaccinium corymbosum L.) in Buenos Aires (Baradero, Colonia Urquiza, Lima, Mercedes, and San Pedro), Entre Ríos (Concordia, Gualeguaychú, and Larroque), and Córdoba (Capilla del Monte and La Cumbre). Infected flowers turned brown to tan with a water-soaked appearance and shriveled up. Blighted flowers typically did not produce fruits; even an entire cluster of berries could be aborted. A chlorotic area, that later became necrotic and turned light brown, developed when leaves were in contact with blighted flowers. A watery rot developed on fruit occasionally before harvest but more generally after harvest. Infected tender green twigs also became blighted, with leaf tissue becoming brown to black. Older twigs and stems were also blighted. Abundant, gray mycelium with conidial masses developed on all affected tissues under moist conditions. Sections of infected leaves, twigs, stems, flowers, and fruits were surfaced sterilized with 0.2% NaOCl, plated on 2% potato dextrose agar (pH 7), and incubated at 22°C. Pure cultures formed a whitish dense mycelial mat and turned gray after 72 h. Conidia were ellipsoid, hyaline, nonseptate, and formed on botryose heads. They ranged from 5.8 to 9 × 8.1 to 13.7 μm (average 8.6 × 10.2 μm). Black, round, and irregular microsclerotia developed on 7-day-old cultures with an average size of 1.1 × 1.7 mm. Morphological characteristics agree with those described for Botrytis cinerea Pers.:Fr (1). Pathogenicity was tested on 10 12-month-old potted blueberry plants cv. O'Neal by spraying a suspension of 1 × 106 conidia per ml of sterile distilled water. Ten plants used as controls were sprayed with sterile distilled water. Each plant was covered with a transparent polyethylene bag for 48 h and incubated at 20 ± 2°C in humid chambers for 15 days. Lesions similar to those observed in the fields developed after 4 days and asexual fructifications developed after 5 days. The same pathogen was reisolated from the lesions, thus completing Koch's postulates. Water-treated plants remained symptomless. To our knowledge, this is the first report of a disease caused by B. cinerea on blueberry in Buenos Aires, Córdoba, and Entre Ríos provinces of Argentina. References: (1) M. V. Ellis and J. M. Waller. Sclerotinia fuckeliana (conidial state: Botrytis cinerea) No. 431 in: Descriptions of Pathogenic Fungi and Bacteria. CMI, Kew, Surrey, UK, 1974.

Download Full-text

First Report of Seedling Stem Rot on Jinxianlian (Anoectochilus roxburghii) Caused by Fusarium oxysporum in China

Plant Disease ◽

10.1094/pdis-09-21-2066-pdn ◽

2021 ◽

Author(s):

Chuan-Qing Zhang ◽

X. Y. Chen ◽

Ya-hui Liu ◽

Dejiang Dai

Keyword(s):

Fusarium Oxysporum ◽

Morphological Characteristics ◽

Aerial Mycelium ◽

Morphological Features ◽

Stem Rot ◽

Broad Host Range ◽

Distilled Water ◽

Internal Transcribed Spacer Region ◽

First Report ◽

Anoectochilus Roxburghii

Anoectochilus roxburghii is an important Chinese herbal medicine plant belonging to Orchidaceae and known as Jinxianlian. This orchid is cultivated and mostly adopted to treat diabetes and hepatitis. About 2 billion artificially cultivated seedlings of Jinxianlian are required each year and approximately $600 million in fresh A. roxburghii seedlings is produced in China. From 2011, sporadic occurrence of stem rot on Jinxianlian have been observed in greenhouses in Jinhua City (N29°05′, E119°38′), Zhejiang Province. In 2018, nearly 30% of seedlings of Jinxianlian grown in greenhouse conditions were affected by stem rot in Jinhua City. Symptoms initially occurred in the stem at the soil line causing dark discoloration lesions, rotted tissues, wilting, and eventually leading to the death of the plants. A total of 23 diseased seedlings collected from seven different greenhouses were surface sterilized with 1.5% sodium hypochlorite for 3 min, then rinsed in water. Pieces of tissues disinfected from each sample were plated on 2% potato dextrose agar (PDA), and incubated at 25°C in the dark for 5 days (Kirk et al. 2008). A total of 19 isolates were recovered. They developed colonies with purple mycelia and beige or orange colors after 7 days of incubation under 25°C on PDA and carnation leaf agar (CLA) media (Kirk et al. 2008; Zhang et al. 2016). Colonies on PDA had an average radial growth rate of 3.1 to 4.0 mm /d at 25°C. Colony surface was pale vinaceous, floccose with abundant aerial mycelium. On CLA, aerial mycelium was sparse with abundant bright orange sporodochia forming on the carnation leaves. Microconidia were hyaline and oval-ellipsoid to cylindrical (3.7 to 9.3 × 1.3 to 2.9 μm) (n=19). Macroconidia were 3 to 5 septate and fusoid-subulate with a pedicellate base (27.4 to 35.6 × 3.2 to 4.2 μm) (n=19). These morphological features were consistent with Fusarium oxysporum (Sun et al. 2008; Lombard et al., 2019). To confirm the identification based on these morphological features, the internal transcribed spacer region (ITS) and translation elongation factor1 (TEF) were amplified from the DNA of 3 out of 19 isolates chosen at random respectively using the set primer ITS1/ITS4 and EF1/ EF2 (Sun, S., et al. 2018; Lombard et al., 2019). BLAST analysis revealed that the ITS sequences (OK147619, OK147620, OK147621) had 99% identity to that of F. oxysporum isolate JJF2 (GenBank MN626452) and TEF sequence (OK155999, OK156000, OK156001) had 100% identity to that of F. oxysporum isolate gss100 (GenBank MH341210). A multilocus phylogenetic analysis by Bayesian inference (BI) and maximum likelihood (ML) trees based on ITS and TEF indicated that the pathogen grouped consistently with F. oxysporum. Three out of 19 isolates chosen at random were selected to evaluate pathogenicity. Uninfected healthy A. roxburghii seedlings about 40 day-old planted in sterilized substrates were sprayed with distilled water containing 2 x 106 conidia per ml suspensions as inoculums, and plants sprayed with distilled water alone served as controls. Plants were then incubated at 25°C and 85% relative humidity. Ten plants were inoculated for each isolate. After 10 days, all plants inoculated developed stem rot symptoms, while control plants remained healthy. Cultures of Fusarium spp. were re-isolated only from inoculated plants with the frequency of 100% and re-identified by morphological characteristics as F. oxysporum, fulfilling Koch’s postulates. To the best of our knowledge, this is the first report of F. oxysporum causing stem rot on A. roxburghii seedlings. As F. oxysporum is a devastating pathogenic fungus with a broad host range, measures should be taken in advance to manage stem rot of A. roxburghii.

Download Full-text

First Report of Corynespora cassiicola Causing Leaf Spot of Cassava in China

Plant Disease ◽

10.1094/pdis-94-7-0916a ◽

2010 ◽

Vol 94 (7) ◽

pp. 916-916 ◽

Cited By ~ 1

Author(s):

X.-B. Liu ◽

T. Shi ◽

C.-P. Li ◽

J.-M. Cai ◽

G.-X. Huang

Keyword(s):

Leaf Spot ◽

Morphological Characteristics ◽

Its Region ◽

Pathogenic Fungi ◽

Commonwealth Mycological Institute ◽

Corynespora Cassiicola ◽

Single Spore ◽

First Report ◽

Leaf Spots ◽

Main Vein

Cassava (Manihot esculenta) is an important economic crop in the tropical area of China. During a survey of diseases in July and September of 2009, leaf spots were observed on cassava plants at three separate plantations in Guangxi (Yunfu and Wuming) and Hainan (Baisha) provinces. Circular or irregular-shaped leaf spots were present on more than one-third of the plants. Spots were dark brown or had white papery centers delimited by dark brown rims and surrounded by a yellow halo. Usually, the main vein or small veinlets adjacent to the spots were dark. Some defoliation of plants was evident at the Wuming location. A fungus was isolated from symptomatic leaves from each of the three locations and designated CCCGX01, CCCGX02, and CCCHN01. Single-spore cultures of these isolates were incubated on potato dextrose agar (PDA) for 7 days with a 12-h light/dark cycle at a temperature of 28 ± 1°C. Conidiophores were straight to slightly curved, unbranched, and pale to light brown. Conidia were formed singly or in chains, obclavate to cylindrical, straight or curved, subhyaline-to-pale olivaceous brown, 19.6 to 150.3 μm long and 5.5 to 10.7 μm wide at the base, with 4 to 13 pseudosepta. Morphological characteristics of the specimen and their conidia were similar to the descriptions for Corynespora cassiicola (2). The isolate CCCGX01 was selected as a representative for molecular identification. Genomic DNA was extracted by the cetyltrimethylammoniumbromide protocol (3) from mycelia and used as a template for amplification of the internal transcribed spacer (ITS) region of rDNA with primer pair ITS1/ITS4. The sequence (GenBank Accession No. GU138988) exactly matched several sequences (e.g., GenBank Accession Nos. FJ852715, EF198117, and AY238606) of C. cassiicola (1). Young, healthy, and fully expanded green leaves of cassava cv. SC205 were surface sterilized. Ten leaves were inoculated with 10-μl drops of 104 ml suspension of conidia and five leaves were inoculated with the same volume of sterile water to serve as controls. After inoculation, leaves were placed in a dew and dark chamber for 36 h at 25°C and subsequently transferred to the light for 5 days. All inoculated leaves with isolates showed symptoms similar to those observed in natural conditions, whereas the controls remained symptom free. The morphological characteristics of reisolated conidia that formed on the diseased parts were identical with the nature isolates. To our knowledge, this is the first report of leaf spot caused by C. cassiicola on cassava in China. References: (1) L. J. Dixon et al. Phytopathology 99:1015, 2009. (2) M. B. Ellis et al. Corynespora cassiicola. No. 303 in: CMI Description of Pathogenic Fungi and Bacteria. Commonwealth Mycological Institute, Kew, UK 1971. (3) J. R. Xu et al. Genetics 143:175, 1996.

Download Full-text

First Report of Diaporthe phaseolorum on Sunflower (Helianthus annuus) in Croatia

Plant Disease ◽

10.1094/pdis-93-10-1074c ◽

2009 ◽

Vol 93 (10) ◽

pp. 1074-1074 ◽

Cited By ~ 2

Author(s):

K. Vrandecic ◽

J. Cosic ◽

D. Jurkovic ◽

T. Duvnjak ◽

L. Riccioni

Keyword(s):

New York ◽

Helianthus Annuus ◽

Morphological Characteristics ◽

Aerial Mycelium ◽

Petri Dish ◽

Aluminum Foil ◽

Pathogenic Fungi ◽

Fungal Species ◽

Universal Primers ◽

First Report

Sunflower (Helianthus annuus L.) is a crop that is grown worldwide for the production of edible oil. In Croatia, it has considerable economic significance. From 2004 to 2007, sunflower stems showed light-to-dark brown lesions of different sizes and shapes. The lesions were observed for the presence of pycnidia in affected areas. Isolations from infected tissue on potato dextrose agar (PDA) yielded in two fungal species. One, which was isolated in most cases, was the well known sunflower pathogen Diaporthe helianthi Munt. Cvet. Morphological characteristics, stromata pattern, formation of alpha and beta conidia, and ascostromata characteristic of the other isolated fungus matched the description of D. phaseolorum (Cooke & Ellis) Sacc. (2). D. phaseolorum frequency was 5%. On PDA, the fungus formed white, floccose, aerial mycelium that filled a petri dish (9 cm) in 6 days. D. phaseolorum produces conidiomata in black stromatic structures, which consist of pycnidia with alpha and beta conidia. The alpha conidia were unicellular, hyaline, ellipsoidal to fusiform, and 5.6 to 10.0 × 1.9 to 4.8 μm. The beta conidia were hyaline, elongated, filiform, straight, curved at one or both ends, and 11.7 to 27.6 × 0.7 to 2.0 μm. After 50 days, perithecia were formed. Asci were clavate and 27.64 to 40.1 × 5.70 to 8.2 μm. Eight ascospores formed within asci. Ascospores were two-celled, elliptic, hyaline, and slightly constricted at the septa, and 8.93 to 13.5 × 2.1 to 4.0 μm. Amplification and sequencing of the internal transcribed spacer (ITS) rDNA region were performed with ITS4 and ITS5 universal primers (3) on two isolates (Su9 and Su10) and data were deposited in GenBank (Accession Nos. GQ149763 and GQ149764). Comparison of sequences available in GenBank revealed that the ITS sequence was identical to D. phaseolorum found on Stokesia laevis Hill (Greene) (U11323/U11373) and identical to the strain CBS 116020 isolated from Aster exilis Elliot. (AY745018). On the basis of the obtained results of morphological characteristics and molecular approaches, the pathogen was identified as D. phaseolorum. Pathogenicity evaluation consisted of artificial infections on field-grown sunflower plants at the full button stage as described by Bertrand and Tourvielle (1). A leaf test was done by placing a mycelial plug of 5 × 5 mm from a cork borer of two isolates (Su9 and Su10) on the tip of the main vein. The inoculation site was covered with moistened, cotton wool and wrapped in aluminum foil to prevent the inoculum from drying out. Ten plants of each of the four replications were inoculated. Control plants were inoculated with pure PDA plugs. Lesions of 12 to 40 mm long were observed on the sunflower leaf 10 days after inoculation. Control plants did not develop symptoms. The pathogen was reisolated from the infected plants. To our knowledge, this is the first report of the finding of D. phaseolorum on sunflower in Croatia and we have no literature data about the occurrence of this fungus on sunflower in the world. References: (1) F. Bertrand and D. Tourvielle. Inf. Tech. CETIOM 98:12,1972. (2) E. Punithalingma and P. Holliday. No. 336 in: Descriptions of Pathogenic Fungi and Bacteria. CMI/CAB, Kew, Surrey, England, 1972. (3) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. M. A. Innis et al., eds. Academic Press, Inc., New York, 1990.

Download Full-text