First Report of Phytophthora citricola on Cornus mas in Bulgaria

Cornelian cherry dogwood (Cornus mas) is a widespread species in Bulgaria and some cultivars with large fruits are the subject of propagation. In the springs of 2007 and 2008, severe, unusual damages were observed on sporadically scattered plantlets of ‘Kazanlashki’ (known also as ‘Kazanlaker’) in a nursery located near Vratza in northwestern Bulgaria. Symptoms were identical in both years and expressed on the leaves, young shoots, and adjacent rootstock wood. Dark brown, necrotic leaf spots initiated most often from the leaf periphery and quickly covered more than half of the leaf area. Necrosis of the leaves and shoots spread toward the older woody tissues and the plantlets died within a couple of weeks. Isolations from symptomatic leaves, shoots, and rootstocks (three to five samples per plant organ) on potato dextrose agar always revealed a fungus-like organism that formed relatively fast-growing white, radial, petaloid colonies. Numerous, ovoid to obpyriform, noncaducous, semipapillate sporangia occasionally with two papilla were observed after 1 or 2 days of incubation at 20°C in nonsterile soil extract (1). Average sporangium size was 39 (35 to 45) × 31 (20 to 35) μm with a ratio between both parameters of approximately 1.26. The pathogen's paragynous antheridia and smooth-walled spherical oogonia (20 to 32 μm in diameter) yielded spherical aplerotic to almost plerotic oospores on V8 medium with an average size of 25 μm. The morphological data identified the organism as Phytophthora citricola (1). Isolates had identical cultural and morphological characteristics, and pathogenicity was tested by laboratory inoculations carried out in 2007 (two isolates) and twice in 2008 (three isolates). Separately, detached leaves of C. mas seedlings and ‘Kazanlashki’ were wiped with 70% ethanol, punctured with a needle, and the wounds inoculated with 5-mm mycelial plugs from a 7-day-old V8 growth plate. Sterile V8 plugs were placed onto similar wounds of control leaves. Leaf samples were incubated at 20°C in a humidified chamber. Necrosis similar to that observed in the field became visible around the mycelia plugs 4 days after inoculation. The necrotic lesions enlarged to 20 to 25 mm in diameter within the next 2 days, whereas the control leaves did not show any symptoms. Subsequently, the pathogen was reisolated solely from all the mycelium-inoculated samples. By means of the same inoculation method, pathogenicity was also demonstrated on shoots and mature fruits of C. mas. DNA was isolated from mycelium of an isolate and the internal transcribed spacer (ITS) region was amplified using ITS6 and ITS4 primers. The PCR product was sequenced (GenBank Accession No. FJ269034) and the BLAST search showed 100% homology with P. citricola, type II (2). To our knowledge, this is the first report of P. citricola on C. mas in Bulgaria, thus confirming its ability to attack Cornus spp. (3). Taking the lethal results of the disease and the polyphagous nature of the causal agent into consideration, this report is a serious warning for nurserymen and consumers. References: (1) D. C. Erwin and O. K. Ribeiro. Phytophthora Diseases Worldwide. The American Phytopathological Society, St. Paul, MN, 1996. (2) M. E. Gallegly and C. X. Hong. Phytophthora: Identifying Species by Morphology and DNA Fingerprints. The American Phytopathological Society, St. Paul, MN, 2008. (3) F. N. Martin and P. W. Tooley. Mycologia 95:269, 2003.

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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.

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First Report of Alternaria heveae Causing Black Leaf Spot of Rubber Tree in China

Plant Disease ◽

10.1094/pdis-01-14-0065-pdn ◽

2014 ◽

Vol 98 (7) ◽

pp. 1011-1011 ◽

Cited By ~ 1

Author(s):

Z. Y. Cai ◽

Y. X. Liu ◽

G. X. Huang ◽

M. Zhou ◽

G. Z. Jiang ◽

...

Keyword(s):

Rubber Tree ◽

Morphological Characteristics ◽

Black Spot ◽

Its Region ◽

Post Inoculation ◽

First Report ◽

Leaf Spots ◽

Plastic Bags ◽

Manual Pressure ◽

Tree Leaf

Rubber tree (Hevea brasiliensis Muell. Arg.) is an important industrial crop of tropical areas for natural rubber production. In October 2013, foliar spots (0.1 to 0.4 mm in diameter), black surrounded by a yellow halo, and with lesions slightly sunken were observed on the rubber tree leaf in a growing area in Heikou County of Yunnan Province. Lesion tissues removed from the border between symptomatic and healthy tissue were surface sterilized in 75% ethanol and air-dried, plated on PDA plates, and incubated at 28°C with alternating day/night cycles of light. The pathogen was observed growing out of many of the leaf pieces, and produced abundant conidia. Colonies 6.1 cm in diameter developed on potato carrot agar (PCA) after 7 days, with well-defined concentric rings of growth. Colonies on PCA were composed of fine, dark, radiating, surface and subsurface hyphae. Conidia produced in PCA culture were mostly solitary or in short chains of 2 to 5 spores, long ovoid to clavate, and light brown, 40 to 81.25 × 8 to 20 μm (200 colonies were measured), with 3 to 6 transverse septa and 0 to 2 longitudinal or oblique septa. Morphological characteristics were similar to those described for Alternaria heveae (3,4). A disease of rubber tree caused by Alternaria sp. had been reported in Mexico in 1947 (2). DNA of Ah01HK13 isolate was extracted for PCR and sequencing of the ITS region with ITS1 and ITS4 primers was completed. From the BLAST analysis, the sequence of Ah01HK13 (GenBank Accession No. KF953884), had 97% similarity to A. dauci, 96% identical to A. macrospora (AY154701.1 and DQ156342.1, respectively), indicating the pathogen belonged to Alternaria genus. According to morphological characteristics, this pathogen was identified as A. heveae. Pathogenicity of representative isolate, Ah01HK13 was confirmed using a field rubber tree inoculation method. Three rubber plants (the clone of rubber tree Yunyan77-4) were grown to the copper-colored leaf stage and inoculated by spraying spore suspension (concentration = 104 conidia/ml) to the copper-colored leaves until drops were equally distributed on it using manual pressure sprayer. Three rubber plants sprayed with sterile distilled water were used as controls. After inoculation, the plants were covered with plastic bags. The plastic bags were removed after 2 days post-inoculation (dpi) and monitored daily for symptom development (1). The experiment was repeated three times. The typical 0.1 to 0.4 mm black leaf spots were observed 7 dpi. No symptoms were observed on control plants. A fungus with the same colony and conidial morphology as A. heveae were re-isolated from leaf lesions on inoculated rubber plants, but not from asymptomatic leaves of control plants, fulfilling Koch's postulates. Based on these results, the disease was identified as black spot of rubber tree caused by A. heveae. To our knowledge, this is the first report of A. heveae on rubber tree in China. References: (1) Z. Y. Cai et al. Microbiol Res. 168:340, 2013. (2) W. J. Martin. Plant Dis. Rep. 31:155, 1947. (3) E. G. Simmons. Mycotaxon 50:262, 1994. (4) T. Y. Zhang. Page 111 in: Flora Fungorum Sinicorum: Alternaria, Science Press, Beijing, 2003.

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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.

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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.

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First Report of Pestalotiopsis microspora Causing Leaf Spot of Hidcote (Hypericum patulum) in Japan

Plant Disease ◽

10.1094/pdis-94-8-1064b ◽

2010 ◽

Vol 94 (8) ◽

pp. 1064-1064 ◽

Cited By ~ 3

Author(s):

M. Zhang ◽

H. Y. Wu ◽

T. Tsukiboshi ◽

I. Okabe

Keyword(s):

Leaf Spot ◽

Morphological Characteristics ◽

Its Region ◽

Basal Cells ◽

Single Spore ◽

Management Options ◽

First Report ◽

Leaf Spots ◽

Plastic Bags ◽

Pestalotiopsis Microspora

Hidcote, Hypericum patulum Thunb. ex Murray, is a deciduous shrub that is cultivated as an ornamental in landscape gardens and courtyards in Japan. In early August 2008, severe leaf spotting was observed on plants growing in a courtyard in Nasushiobara, Tochigi, Japan. More than 30% of the leaves on five shrubs exhibited leaf spot symptoms. Small, round, pale brown lesions were initially observed. Later, they expanded to 5 to 12 mm in diameter, round to irregular-shaped with pale brown centers and dark brown margins. Under continuously wet or humid conditions, black acervuli developed on the leaf lesions. Conidia were straight or slightly curved, fusiform to clavate, and five-celled with constrictions at the septa. Conidia ranged from 17 to 21 × 5 to 8 μm with hyaline apical and basal cells. Fifteen percent of apical cells had two and the rest had three appendages (setulae) ranging from 10 to 21 μm long. The basal hyaline cell tapered into a 2 to 4 μm pedicel. The three median cells ranged from light or dark brown to olive green. These morphological characteristics matched those of Pestalotiopsis microspora (Speg.) G.C. Zhao & N. Li (1,2). The identity of the fungus was confirmed by DNA sequencing of the internal transcribed spacer (ITS) region (GenBank Accession No. GU908473) from single-spore isolates, which revealed 100% homology with those of other P. microspora isolates (e.g., GenBank Accession Nos. FJ459950 and DQ456865). Koch's postulates were confirmed using leaves of three detached branches of a field-grown asymptomatic plant of H. patulum. Thirty leaves of each branch were inoculated by placing mycelial plugs obtained from the periphery of 7-day-old single-spore cultures on the leaf surface. Potato dextrose agar plugs without mycelium served as controls. Leaves on branches were covered with plastic bags for 24 h to maintain high relative humidity in a greenhouse (approximately 24 to 28°C). After 5 days, all inoculated leaves showed symptoms identical to those described above, whereas control leaves remained symptom free. Reisolation of the fungus from lesions on inoculated leaves confirmed that the causal agent was P. microspora. To our knowledge, this is the first report of leaf spots on H. patulum caused by P. microspora in Japan. Management options may have to be developed and implemented to protect Hidcote plants in areas where leaf spot cannot be tolerated. References: (1) P. A. Saccardo. Sylloge Fungorum III:789, 1884. (2) G. C. Zhao and N. Li. J. Northeast For. Univ. 23(4):21, 1995.

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First Report of a Leaf Spot on Hazel Leaves Caused by Phyllosticta coryli in Liaoning Province of China

Plant Disease ◽

10.1094/pdis-02-13-0213-pdn ◽

2013 ◽

Vol 97 (9) ◽

pp. 1254-1254 ◽

Cited By ~ 10

Author(s):

J. Sun ◽

D.-M. Wang ◽

X.-Y. Huang ◽

Z.-H. Liu

Keyword(s):

Leaf Spot ◽

Control Strategies ◽

Morphological Characteristics ◽

Leaf Tissue ◽

Its Region ◽

Liaoning Province ◽

Single Spore ◽

First Report ◽

Leaf Spots ◽

Microscopic Morphology

Hazel (Corylus heterophylla Fischl) is an important nut tree grown in China, especially in Liaoning Province, and is rich in nutritional and medicinal values. In August 2011, leaf spotting was observed on hybrid hazel (Dawei) leaves in Paotai Town, Wafangdian County of Liaoning Province. By August 2012, the disease had spread to Zhangdang Town, Fushun County. Symptoms initially appeared on both sides of leaves as pinpoint brown spots, which enlarged and developed into regular, dark brown lesions, 3 to 9 mm in diameter. The lesions were lighter in color in the center compared to the margin. To identify the pathogen, leaf pieces (3 to 5 mm) taken from the margins, including both symptomatic and healthy portions of leaf tissue, were surface-disinfected first in 75% ethanol for 5 s, next in 0.1% aqueous mercuric chloride for 50 s, and then rinsed with sterilized water three times. Leaf pieces were incubated on potato dextrose agar (PDA) at 25°C for 14 days in darkness. Single spore isolates were obtained from individual conidia. For studies of microscopic morphology, isolates were grown on synthetic nutrient agar (SNA) in slide cultures. Colonies grew up to 45 to 48 mm in diameter on PDA after 14 days. Pycnidia appeared on the colonies after 12 days. Conidiophores were short. Pycnidia were dark brown, subglobose, and 150 to 205 μm in diameter. Conidia were unicellular, colorless, ovoid to oval, and from 2.4 to 4.5 × 1.6 to 2.4 μm. On the basis of these morphological characteristics, the isolates were tentatively identified as Phyllosticta coryli Westend (2). The rDNA internal transcribed spacer (ITS) region was amplified using primers ITS1 and ITS4 and sequenced (GenBank Accession No. KC196068). The 490-bp amplicons had 100% identity to an undescribed Phyllosticta species isolated from Cornus macrophylla in Gansu, Tianshui, China (AB470897). On the basis of morphological characteristics and nucleotide homology, the isolate was tentatively identified as P. coryli. Koch's postulates were fulfilled in the growth chamber on hazelnut leaves inoculated with P. coryli conidial suspensions (107 conidia ml–1). Eight inoculated 1-year-old seedlings (Dawei) were incubated under moist conditions for 8 to 10 days at 25°C. All leaf spots that developed on inoculated leaves were similar in appearance to those observed on diseased hazel leaves in the field. P. coryli was recovered from lesions and its identity was confirmed by morphological characteristics. P. coryli was first reported as a pathogen of hazel leaves in Bull of Belgium (2). In China, P. coryli was first reported on Corylus heterophylla Fisch. in Jilin Province (1). To our knowledge, this is the first report of P. coryli causing leaf spot on hybrid hazel in Liaoning Province of China. The outbreak and spread of this disease may decrease the yield of hazelnut in northern regions of China. More studies are needed on control strategies, including the possible resistance of hazel cultivars to P. coryli. References: (1) Y. Li et al. J. Shenyang Agric. Univ. 25:153, 1994. (2) P. A. Saccardo. Sylloge Fungorum Vol. III, page 31, 1884.

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First Report of Colletotrichum lupini on Lupinus hartwegii and L. mutabilis

Plant Disease ◽

10.1094/pdis-06-13-0672-pdn ◽

2014 ◽

Vol 98 (1) ◽

pp. 161-161

Author(s):

E. N. Rosskopf ◽

J. Hong ◽

N. Kokalis-Burelle

Keyword(s):

Sequence Data ◽

Morphological Characteristics ◽

Its Region ◽

Deionized Water ◽

Hypodermic Needle ◽

Cut Flower ◽

First Report ◽

Leaf Spots ◽

Lupinus Mutabilis ◽

Colletotrichum Lupini

During the 2013 winter cut flower production season, a severe anthracnose epidemic was observed on Lupinus mutabilis (syn L. cruckshanksii) on a commercial flower farm in Martin County, FL. Approximately 50% of the crop was lost to the disease. Symptoms included dark brown, irregularly shaped leaf spots, but more typically, there was a single severe twist in the stem, forming a distinctive necrotic crook. Margins of necrotic lesions were excised and surface sterilized by immersion in 1% sodium hypochlorite for 90 s, rinsed in sterile deionized water, and plated onto potato dextrose agar (PDA). Plates were incubated at approximately 27°C with cycles of 12 h light/12 h darkness. Infected tissue consistently produced colonies that were typical of the genus Colletotrichum. Conidia were primarily oval, with one rounded end and one pointed end, and were highly variable in size, ranging from 10 to 15 μm in length and 3.5 to 5.5 μm in width. Cultures were gray with orange spots, and no setae were observed. These morphological characteristics are consistent with those of Colletotrichum lupini (2). Identification of this species was confirmed by performing a BLASTn search with ITS sequence data (primers ITS4 and ITS5), which shared 99% identity with GenBank submission AJ301968, C. lupini var. setosum strain BBA 71310, isolated from L. luteus in Poland. Inoculum was produced by flooding PDA cultures with sterile deionized water, scraping with a rubber policeman, and passing the suspension through four layers of sterile cheesecloth. This preparation was used to inoculate 10 L. mutabilis and 10 L. hartwegii plants by injecting 10 μl of a suspension of 105 conidia/ml into the stem using a hypodermic needle (1). Ten additional plants were injected with sterile deionized water and maintained with the inoculated plants in the greenhouse for 4 weeks. All of the inoculated plants developed the previously-observed necrotic crook in the stem, whereas control plants developed no symptoms. The same organism was isolated from all inoculated plants. The ITS region was again sequenced, and the Polish strain was the closest match. The Floridian isolate sequence was deposited in GenBank (KF207599). Epidemics of anthracnose on ornamental lupins are common in most areas in which they are grown. In 1939, research plots of L. angustifolius were found with symptoms of anthracnose caused by Glomerella cingulata (3). Although it is not possible to determine if this isolate would be redefined as C. lupini, it does not seem likely since pathogenicity was confirmed on L. angustifolius and L. albus, but it did not cause infection on L. luteus (3) as has been reported for C. lupini (2). The finding of a lupin anthracnose in southeastern Florida is important to both the cut flower producers as well as vegetable producers who might consider some species of Lupinus as potential green manure crops. To the best of our knowledge, this is the first report of C. lupini or any Colletotrichum species on L. hartwegii and L. mutabilis in Florida. References: (1) W. H. Elmer et al. Plant Dis 85:216, 2001. (2) H. I. Nirenger et al. Mycologia 94:307, 2002. (3) J. L. Weimer. Phytopathology 43:249, 1943.

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First Report of Bipolaris peregianensis Causing Leaf Spot of Cynodon dactylon in China

Plant Disease ◽

10.1094/pdis-12-11-1066-pdn ◽

2012 ◽

Vol 96 (6) ◽

pp. 917-917 ◽

Cited By ~ 2

Author(s):

Z. Y. Wang ◽

S. N. Xie ◽

Y. Wang ◽

H. Y. Wu ◽

M. Zhang

Keyword(s):

Leaf Spot ◽

Cynodon Dactylon ◽

Control Strategies ◽

Tap Water ◽

Morphological Characteristics ◽

Its Region ◽

Basal Cells ◽

First Report ◽

Leaf Spots ◽

Plastic Bags

Cynodon dactylon is widely cultivated as a sod crop in warm climates worldwide. In early September 2009, heavy leaf spot infection was observed on C. dactylon from Zhengzhou, Henan, China. Early symptoms appeared as small, elliptical, pale brown lesions on the leaves. Lesions later expanded to 5 to 10 mm long and 1 to 2 mm wide, becoming brown to dark brown. A fungus was consistently isolated from leaf spots on potato dextrose agar (PDA), but with poor sporulation. Morphological characteristics were observed from single-conidium cultures on tap water agar + wheat straw (TWA+W) after 5 to 7 days. Conidiophores were light to medium brown, cylindrical, solitary or clustered, unbranched, usually with basal cells enlarged, and 94.5 to 147.0 × 4.0 to 9.0 μm. Conidia were fusoid, strongly curved, end cells broadly hemiellipsoidal, brown, 58.5 to 84.5 × 13.5 to 18.5 μm, with 6 to 10 septa. These morphological characteristics are similar to those of Bipolaris peregianensis (2). The identity of our fungus was confirmed to be B. peregianensis by DNA sequencing of the internal transcribed spacer (ITS) region (GenBank Accession No. JQ316121), which was 99% homologous to those of other B. peregianensis isolates (= Cochliobolus peregianensis; Accession Nos AF071328 and AF158111) (1). Koch's postulates were performed with the leaves of three pots of C. dactylon. Leaves were sprayed with 1 × 105 conidia/ml of B. peregianensis; an equal number of leaves in the pots of the same plant sprayed with sterile distilled water served as the control. All test plants were covered with plastic bags for 24 h to maintain high relative humidity at 23 to 25°C. After 7 days, more than 50% of inoculated leaves showed symptoms identical to those observed in natural condition, whereas controls remained symptom free. Reisolation of the fungus from lesions on inoculated leaves confirmed that the causal agent was B. peregianensis. To our knowledge, this is the first report of leaf spots caused by B. peregianensis on C. dactylon in China. The disease cycle and the control strategies in the regions are being further studied. References: (1) M. L. Berbee et al. Mycologia 91:964, 1999. (2) A. Sivanesan. Mycol. Pap. 158:1, 1987.

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First Report of Daylily Leaf Streak Caused by Kabatiella microsticta in China

Plant Disease ◽

10.1094/pdis-04-12-0381-pdn ◽

2012 ◽

Vol 96 (10) ◽

pp. 1579-1579 ◽

Cited By ~ 1

Author(s):

Q. R. Bai ◽

S. Han ◽

Y. Y. Xie ◽

R. Dong ◽

J. Gao ◽

...

Keyword(s):

Morphological Characteristics ◽

Its Region ◽

The United States ◽

Control Treatment ◽

Conidial Suspension ◽

First Report ◽

Perennial Plant ◽

Leaf Spots ◽

Plastic Bags ◽

Hemerocallis Citrina

Daylily (Hemerocallis spp.) is an herbaceous, perennial plant, cultivated for its flowers. Daylily is sold in Asian markets as fresh or dried flowers (the flowers of some species, e.g., Hemerocallis citrina, are edible) or as the corm, which is used for medicinal purposes. In June 2011, daylily leaf streak was found in a nursery of Jilin Agricultural University, Jilin Province, China. Symptoms included water-soaked, irregular spots along the leaf midvein that turned orange to reddish brown and eventually enlarged to coalesce into extensive, necrotic streaks along the length of the leaf, as previously reported (2). Heavily infected leaves often withered and died. Four isolates were recovered from necrotic tissue of leaf spots and cultured on potato dextrose agar (PDA) at 25°C. All colonies were initially cream to peach colored and appeared slimy. With the maturation of the culture, the colonies became dark brown to black with sparse aerial hyphae. Blastic conidia formed simultaneously on intercalary or terminal, undifferentiated conidiogenous cells, and were scattered in dense sections on culture surface. When the conidia dropped from conidiogenous cell, an indistinct scar or a denticle remained. Conidia were hyaline, one-celled, smooth, ellipsoidal, and variable in size (2.73 to 6.01 × 8.45 to 19.36 μm), and all morphological characteristics were consistent with Kabatiella microsticta Bubak (syn. Aureobasidium microstictum; 2,4). The internal transcribed spacer (ITS) region of the nuclear rDNA was amplified using primers ITS4/ITS5 (1). ITS (534 bp) was identical among all four isolates (GenBank Accession No. HE798117) and 100% identical to that of K. microsticta CBS 114.64 (FJ150873). Pathogenicity was confirmed by spraying 20 seedlings of daylily, propagated in tissue-culture medium, with a conidial suspension (106 conidia/ml) of each isolate. A second set of 20 seedlings was sprayed with the same volume of sterile water as the noninoculated control treatment. Plants were grown in the greenhouse at 20 to 25°C and were covered with plastic bags to maintain humidity on the foliage for 72 h. After 5 days, the foliar symptoms described earlier for the field plants appeared on the leaves, whereas the control plants remained healthy. K. microsticta was reisolated from the leaf spots of all 20 inoculated plants. Leaf streak is the most destructive disease of daylily, and was previously reported in Japan and the United States (Illinois, Kentucky, Mississippi, Louisiana, Pennsylvania, Maryland, Virginia, Florida, North Carolina, and Georgia) (3). To our knowledge, this is the first report of the disease caused by K. microsticta in China. References: (1) D. E. L. Cooke et al. Mycol. Res. 101:667, 1997. (2) E. J. Hermanides-Nijhof. Stud. Mycol. 15:153, 1977. (3) R. M. Leahy et al. Plant Pathology Circular No. 376, 1996. (4) P. Zalar et al. Stud. Mycol. 61:21, 2008.

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First report of Curvularia gladioli causing leaf spots on Gladiolus gandavensis in China

Plant Disease ◽

10.1094/pdis-01-21-0016-pdn ◽

2021 ◽

Author(s):

Jingxin Zhang ◽

Huifang Shen ◽

Yongqiang Zhang ◽

Xiaoming Pu ◽

Qiyun Yang ◽

...

Keyword(s):

Management Strategies ◽

Morphological Characteristics ◽

Guangdong Province ◽

Its Region ◽

Diagnostic Methods ◽

Morphological Observation ◽

Its Sequencing ◽

First Report ◽

The Third ◽

Leaf Spots

Gladiolus (Gladiolus gandavensis Van Houtte) is a perennial plant in the family Iridaceae, which shows sword-shaped leaves and spikes of brilliantly colored irregular flowers arising from corms. It is one of the most important fresh cut flowers and is widely cultivated worldwide, including in China. In September 2020, white pinpoints were first observed on gladiolus leaves in Jiangmen City, Guangdong Province, China. The white spots eventually turned brown. The lesions then developed into oval to circular spots, which were surrounded with an obvious yellow halo. The spots expanded and coalesced, causing leaf blight. These symptoms were observed on approximately 10% of gladiolus plants in fields measuring ca. 70 ha. Symptomatic leaves were sampled from fields, surface sterilized in 75% ethanol for 30 s, submerged in a 2% NaOCl solution for 10 min, and rinsed three times with sterile water. The samples were then cut into pieces (5 × 5 mm) and incubated for 4 d on potato dextrose agar (PDA) at 25°C. A representative fungal colony was subcultured onto new PDA and grown for another 7 d, and its mycelium appeared to be grayish-black and villiform. This strain was named as Cg_TS. Its conidiophores were simple, septate, cylindrical in shape, and moderate brown in color. They occurred singly or in groups. They were straight or slightly flexuous and ranged in size from 57.0 to 80.0 μm × 4.0 to 8.0 μm. Conidia were 3-distoseptate and curved at the third cell from the base. The third cell was swollen to one side and larger than other cells. These conidia ranged in size from 23.5 to 32.0 μm × 11.5 to 16.0 μm. These morphological characteristics were consistent with the description of Curvularia gladioli Boerema & Hamers (Boerema and Hamers 1989). Using primer pair ITS1 and ITS4, PCR was applied to amplify the internal transcribed spacer (ITS) region of rDNA. This sequence (GenBank accession No. MW426196.1) was subjected to BLAST in GenBank, suggesting that it was most similar to C. gladioli sequences, LT631345.1 and HG778987.1, with both of 99.49% of similarity. To fulfill Koch's postulates, healthy two-month-old gladiolus plants were used for pathogenicity testing, and the leaves were wounded by pressing slightly with a pipette tip. Mycelium disks (3 mm diameter) were applied onto wounded leaves of 10 plants. Another 10 healthy plants were inoculated with PDA disks which served as control. Inoculated samples were placed in a greenhouse at 25°C and 90% relative humidity. After 3 d, brown leaf spots appeared on all of pathogen-inoculated leaves. The symptoms were consistent with those initially observed and C. gladioli was re-isolated from the symptomatic tissue. Identification was confirmed by morphological observation and ITS sequencing. Control leaves remained symptomless. The curvularia fungus was firstly reported on gladiolus in Florida in 1947 and spread globally via infected corms (Torre et al. 2015), it was also reported to cause leaf spots on gladiolus in Brazil in 2013 (Torres et al. 2013). Although C. gladioli had been recorded as a Curvularia species occurring in China (Zhang et al. 2006), it was not reported to cause leaf spots on gladiolus in Guangdong Province and elsewhere in China. To our knowledge, this is the first report of Curvularia gladioli causing leaf spots on gladiolus in China. Identification of this pathogen will help develop diagnostic methods for corms and seedlings, and may lead to the development of appropriate chemical management strategies.

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