First Report of Alternaria Leaf Blight on Bupleurum chinense Caused by Alternaria alternata in China

Bupleurum chinense DC. (family Umbelliferae) is an important medicinal herb in traditional Chinese medicine and is cultivated as an economically important plant in China (2). From 2006 to 2009, severe foliar disease was observed on B. chinense in Haidian, Changping, and Shunyi districts, Beijing, China. Approximately 75 to 85% of fields were affected with disease incidence ranging from 65 to 90%. Distribution of the disease in affected B. chinense fields was generally associated with high soil moisture, often corresponding to poor drainage. Initial symptoms first appeared on older leaves as irregularly shaped, minute, dark brown-to-black spots, with yellow borders on the edge of the affected leaflet blade. As the disease progressed, the lesions expanded, causing the leaflets to turn brown, shrivel, and die. Isolations performed on potato dextrose agar (PDA) initially resulted in white colonies. After 7 days of incubation at 25°C, the colonies turned gray or brown. Conidia varied in size from 10 × 6 to 40 × 12 μm, appeared brown to dark brown or olive-brown, were short beaked and borne in long chains, oval and bean-shaped with one to six transverse septa and zero to three longitudinal septa. Sequences of the rDNA from the internal transcribed spacer regions 1 and 2 and the 5.8S gene were amplified using primers ITS1 and ITS4, were obtained from three isolates, and comparisons with GenBank showed 100% similarity with A. alternata (Genbank Accession No. AB470912.1). For pathogenicity tests, three isolates were grown on PDA for 14 days. Inoculations were performed on detached, surface-sterilized, and healthy B. chinense leaflets following the method of Belisario (1). A 5-μl drop of conidial suspension containing 1 × 105 CFU/ml was placed on each leaflet and 12 leaves per isolate were used. Leaves were incubated in a growth chamber (80 to 90% relative humidity; 50 to 60 klx/m2 light intensity with a 12-h photoperiod). After 5 days, leaf spots similar to the original symptoms developed on all inoculated leaves and A. alternata was consistently reisolated from symptomatic leaf tissues on PDA. Control leaflets inoculated with sterile water remained asymptomatic. The experiment was performed three times. To our knowledge, this is the first report of A. alternata on B. chinense from China. References: (1) A. Belisario et al. Plant Dis. 83:696, 1999. (2) C. Sui et al. Plant Dis. 93:844, 2009.

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First Report of a Leaf Spot Disease of Bells-of-Ireland (Moluccella laevis) Caused by Cercospora apii in California

Plant Disease ◽

10.1094/pdis.2003.87.2.203a ◽

2003 ◽

Vol 87 (2) ◽

pp. 203-203

Author(s):

S. T. Koike ◽

S. A. Tjosvold ◽

J. Z. Groenewald ◽

P. W. Crous

Keyword(s):

Leaf Spot ◽

Sequence Data ◽

Disease Incidence ◽

Leaf Spot Disease ◽

Conidial Suspension ◽

Internal Transcribed Spacer Region ◽

First Report ◽

Spot Disease ◽

Leaf Spots ◽

Initial Symptoms

Bells-of-Ireland (Moluccella laevis) (Lamiaceae) is an annual plant that is field planted in coastal California (Santa Cruz County) for commercial cutflower production. In 2001, a new leaf spot disease was found in these commercially grown cutflowers. The disease was most serious in the winter-grown crops in 2001 and 2002, with a few plantings having as much as 100% disease incidence. All other plantings that were surveyed during this time had at least 50% disease. Initial symptoms consisted of gray-green leaf spots. Spots were generally oval in shape, often delimited by the major leaf veins, and later turned tan. Lesions were apparent on both adaxial and abaxial sides of the leaves. A cercosporoid fungus having fasciculate conidiophores, which formed primarily on the abaxial leaf surface, was consistently associated with the spots. Based on morphology and its host, this fungus was initially considered to be Cercospora molucellae Bremer & Petr., which was previously reported on leaves of M. laevis in Turkey (1). However, sequence data obtained from the internal transcribed spacer region (ITS1, ITS2) and the 5.8S gene (STE-U 5110, 5111; GenBank Accession Nos. AY156918 and AY156919) indicated there were no base pair differences between the bells-of-Ireland isolates from California, our own reference isolates of C. apii, as well as GenBank sequences deposited as C. apii. Based on these data, the fungus was subsequently identified as C. apii sensu lato. Pathogenicity was confirmed by spraying a conidial suspension (1.0 × 105 conidia/ml) on leaves of potted bells-of-Ireland plants, incubating the plants in a dew chamber for 24 h, and maintaining them in a greenhouse (23 to 25°C). After 2 weeks, all inoculated plants developed leaf spots that were identical to those observed in the field. C. apii was again associated with all leaf spots. Control plants, which were treated with water, did not develop any symptoms. The test was repeated and the results were similar. To our knowledge this is the first report of C. apii as a pathogen of bells-of-Ireland in California. Reference: (1) C. Chupp. A Monograph of the Fungus Genus Cercospora. Cornell University Press, Ithaca, New York, 1954.

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First Report of Anthracnose Caused by Colletotrichum gloeosporioides on Schefflera actinophylla in China

Plant Disease ◽

10.1094/pdis-12-12-1205-pdn ◽

2013 ◽

Vol 97 (7) ◽

pp. 998-998

Author(s):

J. Huang

Keyword(s):

Dna Sequence ◽

Species Complex ◽

Colletotrichum Gloeosporioides ◽

Conidial Suspension ◽

First Report ◽

Leaf Spots ◽

Black Spots ◽

Pathogenicity Tests ◽

Colletotrichum Gloeosporioides Species Complex ◽

And Control

In China, in mild to warm climates, Schefflera actinophylla is commonly grown as a decorative tree in gardens. When mature, it has bright red flowers in inflorescences with up to 20 racemes that develop in summer or early autumn. From 2008 to 2011, lesions were observed on young and mature leaves in several locations in Guangzhou, China. The first symptoms were circular, necrotic areas that usually developed into irregular, dry, brown to reddish brown or black spots. Spots often first appeared at or near the margins of leaves. Reproductive bodies of the pathogen appeared as black specks in leaf spots. Under a 10× magnification, black, needle-like fungal structures (setae) were observed in the centers of spots on the upper leaf surface. A fungus was isolated from the lesion and was identified as Colletotrichum gloeosporioides (Penz.) Penz. & Sacc. based on cultural characteristics and conidial morphology (1). The voucher isolates were deposited in the Institute of Plant Pathology, Zhongkai University of Agriculture and Engineering. C. gloeosporioides is a species complex (2) and there is a degree of unresolved aspects of taxonomy in this species complex. Cultures on potato dextrose agar (PDA) had aerial white mycelium that turned gray to grayish black after 10 days at 25°C and a 12-h photoperiod and produced salmon to orange conidial masses. Brown, 80 to 120 μm long setae were observed in the acervulus. Conidia 14.1 to 18.0 × 4.0 to 6.1 μm in size were hyaline, thin-walled, aseptate, granular inside, clavate to slightly navicular in shape with an obtuse apex and a truncate base. To identify the fungus, a 588-bp segment of the ITS1-5.8S-ITS2 rDNA region was amplified by PCR and sequenced. The DNA sequence was submitted to GenBank as KC207404. A BLAST search of the DNA sequence showed 99% identity with accessions AY266389.1, EF423519.1, and HM575258.1 of C. gloeosporioides. Pathogenicity tests were conducted under greenhouse conditions at 25 ± 2°C. A total of 15 leaves from three 1-year-old S. actinophylla plants were inoculated with mycelial PDA plugs that were placed on 0.5-cm2 leaf wounds and then wrapped with Parafilm. Control leaves were treated similarly except that they were inoculated with PDA plugs without the fungus. No symptoms developed on control leaves after 10 days. Foliar lesions on inoculated leaves closely resembled those observed in the field. C. gloeosporioides was reisolated consistently from inoculated leaves. Pathogenicity was also tested by spraying leaves of potted S. actinophylla plants about 30 cm in height with 10 ml of a conidial suspension (1 × 105 conidia/ml) prepared from 7-day-old PDA cultures grown at 25°C. Leaves sprayed with distilled water were used as controls. Three plants were inoculated in each of two experiments and were incubated at 25°C and 90% relative humidity in a growth chamber. Tiny brown spots started to develop on all inoculated leaves 5 days after inoculation and the progression of symptom development was similar to that observed in the field. Control leaves remained asymptomatic. C. gloeosporioides was reisolated from inoculated leaves. To my knowledge, this is the first report of C. gloeosporioides causing anthracnose on S. actinophylla in China. References: (1) B. C. Sutton. The genus Glomerella and its anamorph Colletotrichum. In: Colletotrichum Biology, Pathology and Control. CAB International, Wallingford, UK, 1992. (2) B. S. Weir et al. The Colletotrichum gloeosporioides species complex. Stud. Mycol. 73:115, 2012.

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First Report of Anthracnose of Papaya (Carica papaya L.) Caused by Colletotrichum siamense in China

Plant Disease ◽

10.1094/pdis-10-20-2154-pdn ◽

2021 ◽

Author(s):

Yujie Zhang ◽

Wenxiu Sun ◽

Ping Ning ◽

Tangxun Guo ◽

SuiPing Huang ◽

...

Keyword(s):

Carica Papaya ◽

Disease Incidence ◽

Aerial Mycelium ◽

Postharvest Disease ◽

Distilled Water ◽

First Report ◽

Surface Samples ◽

Initial Symptoms ◽

Colletotrichum Siamense ◽

Pathogenicity Tests

Papaya (Carica papaya L.) is a rosaceous plant widely grown in China, which is economically important. Anthracnose caused by Colletotrichum sp. is an important postharvest disease, which severely affects the quality of papaya fruits (Liu et al., 2019). During April 2020, some mature papaya fruits with typical anthracnose symptoms were observed in Fusui, Nanning, Guangxi, China with an average of 30% disease incidence (DI) and over 60% DI in some orchards. Initial symptoms of these papayas appeared as watery lesions, which turned dark brown, sunken, with a conidial mass appearing on the lesions under humid and warm conditions. The disease severity varied among fruits, with some showing tiny light brown spots, and some ripe fruits presenting brownish, rounded, necrotic and depressed lesions over part of their surface. Samples from two papaya plantations (107.54°E, 22.38°N) were collected, and brought to the laboratory. Symptomatic diseased tissues were cut into 5 × 5 mm pieces, surface sterilized with 2% (v/v) sodium hypochlorite for 1 minute, and rinsed three times with sterilized water. The pieces were then placed on potato dextrose agar (PDA). After incubation at 25°C in the dark for one week, colonies with uniform morphology were obtained. The aerial mycelium on PDA was white on top side, and concentric rings of salmon acervuli on the underside. A gelatinous layer of spores was observed on part of PDA plates after 7 days at 28°C. The conidia were elliptical, aseptate and hyaline (Zhang et al., 2020). The length and width of 60 conidia were measured for each of the two representative isolates, MG2-1 and MG3-1, and these averaged 13.10 × 5.11 μm and 14.45 × 5.95 μm. DNA was extracted from mycelia of these two isolates with the DNA secure Plant Kit (TIANGEN, Biotech, China). The internal transcribed spacer (ITS), partial actin (ACT), calmodulin (CAL), chitin synthase (CHS), β-tubulin 2 (TUB2) and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) regions were amplified by PCR and sequenced. The sequences were deposited into GenBank with accessions MT904003, MT904004, and MT898650 to MT898659. BLASTN analyses against the GenBank database showed that they all had over 99% identity to the type strain of Colletotrichum siamense isolate ICMP 18642 (GenBank accession numbers JX010278, GQ856775, JX009709, GQ856730, JX010410, JX010019) (Weir et al., 2012). A phylogenetic tree based on the combined ITS, ACT, CAL, CHS, TUB2 and GAPDH sequences using the Neighbor-joining algorithm also showed that the isolates were C. siamense. Pathogenicity tests were conducted on 24 mature, healthy and surface-sterilized papaya fruits. On 12 papaya fruits, three well separated wounded sites were made for inoculation, and for each wounded site, six adjacent pinhole wounds were made in a 5-mm-diameter circular area using a sterilized needle. A 10 µl aliquot of 1 × 106 conidia/ml suspension of each of the isolates (MG2-1 and MG3-1) was inoculated into each wound. For each isolate, there were six replicate fruits. The control fruits were inoculated with sterile distilled water. The same inoculation was applied to 12 non-wound papaya fruits. Fruits were then placed in boxes which were first washed with 75% alcohol and lined with autoclaved filter paper moistened with sterilized distilled water to maintain high humidity. The boxes were then sealed and incubated at 28°C. After 10 days, all the inoculated fruits showed symptoms, while the fruits that were mock inoculated were without symptoms. Koch's postulates were fulfilled by re-isolation of C. siamense from diseased fruits. To our knowledge, this is the first report of C. siamense causing anthracnose of papaya in China. This finding will enable better control of anthracnose disease caused by C. siamense on papaya.

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First Report of Curvularia aeria on Etlingera linguiformis from Nagaland, India

Plant Disease ◽

10.1094/pdis-01-14-0060-pdn ◽

2014 ◽

Vol 98 (11) ◽

pp. 1580-1580 ◽

Cited By ~ 2

Author(s):

C. Kithan ◽

L. Daiho

Keyword(s):

Leaf Surface ◽

Agricultural Research ◽

Disease Incidence ◽

Indian Agricultural Research Institute ◽

Mountain Range ◽

Pathogenicity Test ◽

Distilled Water ◽

Conidial Suspension ◽

First Report ◽

Initial Symptoms

Etlingera linguiformis (Roxb.) R.M.Sm. of Zingiberaceae family is an important indigenous medicinal and aromatic plant of Nagaland, India, that grows well in warm climates with loamy soil rich in humus (1). The plant rhizome has medicinal benefits in treating sore throats, stomachache, rheumatism, and respiratory complaints, while its essential oil is used in perfumery. A severe disease incidence of leaf blight was observed on the foliar portion of E. linguiformis at the Patkai mountain range of northeast India in September 2012. Initial symptoms of the disease are small brown water soaked flecks appearing on the upper leaf surface with diameter ranging from 0.5 to 3 cm, which later coalesced to form dark brown lesions with a well-defined border. Lesions often merged to form large necrotic areas, covering more than 90% of the leaf surface, which contributed to plant death. The disease significantly reduces the number of functional leaves. As disease progresses, stems and rhizomes were also affected, reducing quality and yield. The diseased leaf tissues were surface sterilized with 0.2% sodium hypochlorite for 2 min followed by rinsing in sterile distilled water and transferred into potato dextrose agar (PDA) medium. After 3 days, the growing tips of the mycelium were transferred to PDA slants and incubated at 25 ± 2°C until conidia formation. Fungal colonies on PDA were dark gray to dark brown, usually zonate; stromata regularly and abundantly formed in culture. Conidia were straight to curved, ellipsoidal, 3-septate, rarely 4-septate, middle cells broad and darker than other two end cells, middle septum not median, smooth, 18 to 32 × 8 to 16 μm (mean 25.15 × 12.10 μm). Conidiophores were terminal and lateral on hyphae and stromata, simple or branched, straight or flexuous, often geniculate, septate, pale brown to brown, smooth, and up to 800 μm thick (2,3). Pathogen identification was performed by the Indian Type Culture Collection, Division of Plant Pathology, Indian Agricultural Research Institute, New Delhi (ITCC Accession No. 7895.10). Further molecular identity of the pathogen was confirmed as Curvularia aeria by PCR amplification and sequencing of the internal transcribed spacer (ITS) regions of the ribosomal DNA by using primers ITS4 and ITS5 (4). The sequence was submitted to GenBank (Accession No. MTCC11875). BLAST analysis of the fungal sequence showed 100% nucleotide similarity with Cochliobolus lunatus and Curvularia aeria. Pathogenicity tests were performed by spraying with an aqueous conidial suspension (1 × 106 conidia /ml) on leaves of three healthy Etlingera plants. Three plants sprayed with sterile distilled water served as controls. The first foliar lesions developed on leaves 7 days after inoculation and after 10 to 12 days, 80% of the leaves were severely infected. Control plants remained healthy. The inoculated leaves developed similar blight symptoms to those observed on naturally infected leaves. C. aeria was re-isolated from the inoculated leaves, thus fulfilling Koch's postulates. The pathogenicity test was repeated twice. To our knowledge, this is the first report of the presence of C. aeria on E. linguiformis. References: (1) M. H. Arafat et al. Pharm. J. 16:33, 2013. (2) M. B. Ellis. Dematiaceous Hyphomycetes. CMI, Kew, Surrey, UK, 1971. (3) K. J. Martin and P. T. Rygiewicz. BMC Microbiol. 5:28, 2005. (4) C. V. Suberamanian. Proc. Indian Acad. Sci. 38:27, 1955.

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First Report of Leaf Spot of Spinach Caused by Pleospora betae in Spain

Plant Disease ◽

10.1094/pdis-04-14-0367-pdn ◽

2014 ◽

Vol 98 (11) ◽

pp. 1583-1583 ◽

Cited By ~ 4

Author(s):

D. D. M. Bassimba ◽

J. L. Mira ◽

A. Vicent

Keyword(s):

Leaf Spot ◽

Spinacia Oleracea ◽

Disease Incidence ◽

Control Measures ◽

Conidial Suspension ◽

First Report ◽

Leaf Spots ◽

Plastic Bags ◽

Swiss Chard ◽

Spinach Leaves

The production of spinach (Spinacia oleracea L.) in Spain has increased 50% since 2009, mainly due to the commercialization of fresh-cut spinach leaves packaged in modified atmosphere containers. In October 2012, light brown leaf spots 1 to 2 cm in diameter with dark concentric rings were observed in a commercial spinach production area in Valencia Province, Spain. The initial outbreak comprised an area of about 3 ha with a 20% disease incidence. Symptomatic leaves from spinach cv. Apollo were collected in the affected area and were surface disinfected with 0.5% NaOCl for 2 min. Small fragments from lesions were placed onto potato dextrose agar (PDA) amended with 0.5 g streptomycin sulfate/liter. Fungal colonies developed after 3 days of incubation at 23°C from about 90% of the infected tissues plated. Isolates were transferred to oatmeal agar (OA) (1) and water agar (WA) amended with autoclaved pea seeds (2). Plates were incubated for 30 days at 24°C with 13 h of fluorescent light and 11 h of dark for morphological examination. Colonies were olivaceous grey in OA and pycnidia developed in WA were globose to subglobose, olivaceous black, and 100 to 200 μm in diameter. Conidia were globose to ellipsoidal, hyaline, aseptate, and 3.8 to 7.7 × 2.4 to 3.9 μm. Swollen cells were observed. Isolates showed a positive reaction to NaOH (1). Partial 18S, ITS1, 5.8S, ITS2, and partial 28S ribosomal RNA (rRNA) regions were amplified using the primers ITS1 and ITS4 (4) and sequenced from DNA extracted from the isolate designated as IVIA-V004 (GenBank Accession No. KF321782). The sequence had 100% identity (e-value 0.0) with that of Pleospora betae (Berl.) Nevod. (syn. Phoma betae A.B. Frank) representative strain CBS 523.66 (1). Pathogenicity tests were performed twice by inoculating 4-month-old plants of spinach cv. Apollo, table beet (Beta vulgaris L.) cv. Detroit, and Swiss chard (B. vulgaris subsp. cicla) cv. Verde de Penca Blanca. Plants were inoculated by spraying a conidial suspension of isolate IVIA-V004 (10 ml/plant, 105 conidia/ml water) using a manual pressure sprayer. Plants were immediately covered with black plastic bags and incubated in a growth chamber at 23°C. In each experiment, four plants of each host were inoculated with the fungus and four additional plants sprayed with sterile distilled water were used as controls. Plastic bags were removed after 48 h and leaf spots similar to those observed in affected spinach plants in the field were visible on all spinach, table beets, and Swiss chard plants 3 to 5 days after inoculation. No symptoms were observed on control plants. Fungal colonies morphologically identified as P. betae were re-isolated from leaf lesions on inoculated plants, but not from asymptomatic leaves of control plants. To our knowledge, this is the first report of leaf spot caused by P. betae on spinach in Spain, where it was previously described affecting sugar beet (3). The disease reduces the quality of spinach leaves and proper control measures should be implemented. References: (1) G. H. Boerema et al. Phoma Identification Manual, Differentiation of Specific and Infra-Specific Taxa in Culture. CABI Publishing, Wallingford, UK, 2004. (2) O. D. Dhingra and J. B. Sinclair. Basic Plant Pathology Methods, 2nd ed. CRC Press, Boca Raton, FL, 1995. (3) P. Melgarejo et al. Patógenos de Plantas Descritos en España. MARM-SEF, Madrid, 2010. (4) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, CA, 1990.

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First Report of Fusarium Blight on Majesty Palm Caused by Fusarium proliferatum in Italy

Plant Disease ◽

10.1094/pdis.2003.87.9.1149a ◽

2003 ◽

Vol 87 (9) ◽

pp. 1149-1149 ◽

Cited By ~ 6

Author(s):

G. Polizzi ◽

A. Vitale

Keyword(s):

Fusarium Proliferatum ◽

Conidial Suspension ◽

First Report ◽

Leaf Spots ◽

Initial Symptoms ◽

Mt Etna ◽

Young Leaves ◽

Pure Cultures ◽

Severe Infections ◽

Fusarium Sp

During spring 2002, a new disease of majesty palm (Ravenea rivularis Jumelle & H. Perrier) was observed on young, container-grown plants (3 to 4 years old with five to seven expanded leaves) in a nursery in eastern Sicily. Initial symptoms on the youngest, expanded leaves and especially on the unopened, spear leaves were small, reddish-brown necrotic lesions (2 to 4 mm in diameter) with a yellow halo. In high humidity, lesions increased in size and number, coalescing into large, irregular dead areas. These symptoms developed into blights of the youngest, unopened leaves. As a consequence, infected leaves would dieback and only a few plants recovered from these severe infections. On the surviving plants, reddish-brown necrotic lesions appeared on the rachis. From these lesions, 30 pieces of tissue were cut, surface sterilized (30 s in 1.2% wt/vol of NaOCl), washed with sterile water, and plated on potato dextrose agar supplemented with 1.1 μl/ml of lactic acid (stock 88 to 92%) (A-PDA). Conidia and conidiophores were collected directly from the tissue with a flamed needle and placed on A-PDA. Fusarium sp. was consistently isolated from the necrotic tissue, and after 3 days, single hyphal tips were transferred to pure cultures from which were obtained two single, conidial isolates. These fungal isolates were forwarded to the CABI Bioscience U.K. Centre, Bakeham Lane (Egham), Surrey, U.K., where both isolates were identified as Fusarium proliferatum (T. Matsushima) Nirenberg. A morpho-biometrical characterization was performed on carnation leaf agar with a photoperiod of 10 h. Macroconidia were slender, lightly falcate to almost straight, 3- to 5-septate, and ranged from 37 to 53 × 2.5 to 3 μm (average 44.1 × 2.8 μm). Microconidia, clavate or oval with a truncated base, were formed in chains from mono- or polyphialides. Chlamydospores were absent. Eight 2-year-old seedlings (three to five expanded leaves) of majesty palm had the unopened spear leaves needle-wounded and another eight were unwounded. All were sprayed with a conidial suspension (1.5 × 106 CFU/ml). An equal number of noninoculated plants were used as a control. All plants were covered with polyethylene bags and incubated in a greenhouse at 25 ± 2°C for 72 h. All wounded majesty palms showed brown areas on unopened spear leaves. When natural injures were present, reddish leaf spots appeared as early as 4 days after inoculation. Macroscopic observations revealed the presence of white mycelium on the necrotic areas and reddish spots. Koch's postulates were satisfied by reisolation of the fungus on A-PDA from artificially infected tissues. On the basis of 3 months of field observations in Sicily, spread of Fusarium blight on majesty palm was always greater when plants were injured on the tender and unopened leaves by volcanic cinders from Mt. Etna, which caused bruises on young leaves. The disease does not represent a major threat to nurseries, but it could cause loss in the cultivation of the majesty palm. F. proliferatum was previously recorded in Saudi Arabia as the causal agent of wilt and dieback of date palm (1). To our knowledge, this is the first report of F. proliferatum on palms in Italy and the first outbreak of the disease on majesty palm. Reference: (1)M. Y. Abdalla et al. Plant Dis. 84:321, 2000.

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First Report of Nigrospora sphaerica Causing Leaf Spots on Chinese Wisteria: A New Host of the Pathogen

Plant Disease ◽

10.1094/pdis-10-10-0770 ◽

2011 ◽

Vol 95 (2) ◽

pp. 219-219 ◽

Cited By ~ 3

Author(s):

S. Soylu ◽

S. Dervis ◽

E. M. Soylu

Keyword(s):

Dead Leaf ◽

Conidial Suspension ◽

New Host ◽

First Report ◽

Leaf Spots ◽

Leaf Tissues ◽

Wisteria Sinensis ◽

Polyethylene Bags ◽

Environment Chamber ◽

Leaf Pathogen

Chinese wisteria, Wisteria sinensis (Sims) DC., is a woody, twining vine and is commonly cultivated as an ornamental for its foliage and striking, drooping racemes of white, pink, or lavender sweet pea-like flower. Distinct leaf spots were observed in several gardens, retail nurseries, and parks located in Hatay Province since May 2009. The primary infection zones are frequently observed on the leaf margins and apices, brown, up to 2 mm in diameter, and often surrounded by a yellow zone. Foliar symptoms are characterized by grayish, round, semicircular or irregular-shaped, numerous spots (up to 9 mm in diameter) with dark brown borders and the appearance of black, granular structure within the dead leaf tissues. A fungus was consistently isolated from symptomatic tissues on potato dextrose agar (PDA). Fungal colonies were initially white, becoming light to dark gray with the onset of sporulation with black, spherical to subspherical single-celled conidia (15 to 18 × 12 to 15 μm), which were borne on a hyaline vesicle at the tip of the conidiophore. These characteristics agree with published descriptions of Nigrospora sphaerica (Sacc.) E.W. Mason 1927 (1,3). To fulfill Koch's postulates, a conidial suspension (106 conidia per ml) collected from PDA cultures was used to spray inoculate leaves of potted 3-year-old Chinese wisteria plants. Inoculated plants were kept for 48 h in polyethylene bags and maintained in a controlled environment chamber at 20°C with a 12-h photoperiod. The bags were removed after 3 days. In addition, five 3-year-old plants were sprayed with sterile water to serve as controls. After 14 to 20 days, inoculated leaves showed infection symptoms similar to those observed on naturally infected leaves with N. sphaerica. The pathogen was reisolated from the margins of necrotic tissues, but not from the controls. Although N. sphaerica is frequently encountered as a secondary invader or as a saprophyte on many plant species, this fungal agent is also known as a leaf pathogen on several hosts worldwide (2,4). To our knowledge, this is the first report of N. sphaerica as a leaf pathogen of Chinese wisteria in Turkey or worldwide. References: (1) M. B. Ellis. Dematiaceous Hyphomycetes. CMI, Kew, Surrey, UK, 1971. (2) D. F. Farr and A. Y. Rossman. Fungal Databases. Systematic Mycology and Microbiology Laboratory. Online publication. ARS, USDA. Retrieved 28 October from http://nt.ars-grin.gov/fungaldatabases/ , 2010. (3) P. M. Kirk. IMI Descr. Fungi Bact. 106:1056, 1991. (4) E. R. Wright et al. Plant Dis. 92:171, 2008.

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First report of Bipolaris yamadae leaf spot disease on Guinea grass (Panicum maximum) in Florida.

Plant Disease ◽

10.1094/pdis-07-20-1486-pdn ◽

2020 ◽

Author(s):

Ashish Adhikari ◽

Xuechun Wang ◽

Brett Lane ◽

Philip F Harmon ◽

Erica Goss

Keyword(s):

Leaf Spot ◽

Phylogenetic Trees ◽

Leaf Spot Disease ◽

Panicum Maximum ◽

Conidial Suspension ◽

Internal Transcribed Spacer Region ◽

First Report ◽

Leaf Spots ◽

Guinea Grass ◽

Symptomatic Leaf

Guinea grass is an invasive perennial C4 grass and is a common weed around agricultural crops in Louisiana, Texas, and Hawaii, USA (Overholt and Franck 2019). In November 2018, leaf spots were observed on Guinea grass occurring in an organic garden located in Gainesville, Florida, USA. Lesions were oblong to irregular, dark grey to brownish center with pale-yellow to brownish black margin. Lesions had coalesced, forming necrotic margins that spread from the leaf tip, resulting in leaf blight and collapse of the canopy. Pieces of symptomatic leaf blades (5 sq cm) were surface sterilized (1 min), washed with sterile distilled water and plated onto water agar media plates. Plates were incubated at 27°C under 12-h light/dark for 3 to 5 days. Grey to black cottony mycelium was consistent on all plates and produced conidia characteristic of Bipolaris spp. Conidia were transferred to potato dextrose agar (PDA) plates with a 0.5 mm diameter sterile needle. Three isolates GG1, GG2 and GG3 were successfully grown on PDA. Conidia were black to brown colored, distoseptate with 3 to 8 septa and measured from (60.6- )70-105(-139.8) × (16.0-)17-23(-25.9) μm (avg: 93.3 μm, n=35, SD = 20.6; avg = 21.3 μm, n = 35, SD = 2.89). Conidiophores were in groups or single, brown, smooth and straight, septate and swollen at upper tip. Sigma Extract-N-Amp was used for genomic DNA extraction. Primers ITS1/ITS4 and GPD1/GPD2 (Berbee et al. 1999) were used to amplify and sequence the internal transcribed spacer region (ITS) and partial glyceraldehyde-3-phosphate dehydrogenase (GPDH) gene, respectively. Sequences were aligned using MUSCLE and alignment was trimmed for length. Maximum likelihood phylogenetic trees were constructed with 1,000 bootstrap samples based on the K2+G substitution model, selected by BIC for these two loci using Mega X (Kumar et al. 2018). The ITS and GPDH sequences of GG1, GG2 and GG3 (Genbank accessions MT514518-20, MT576654-56), grouped with B. yamadae isolates CPC_28807 and CBS_202.29 in phylogenetic trees (Marin-Felix et al. 2017). All three isolates from Guinea grass were inoculated on Sach’s agar (Luttrell 1958) at 27°C under 12-h light/dark for a week, but no sexual morph was observed, and consistent for two repeated inoculations. To fulfill Koch’s postulates, one isolate, GG1, was used. Conidia were harvested from a one-week-old colony grown on PDA incubated at 27°C and 12-h light/dark cycle. The concentration of the conidial suspension was adjusted to 105 conidia/ml using a hemocytometer. Using a Passche H-202S airbrush sprayer, five-week-old seedlings of Guinea grass were sprayed until runoff with the conidia suspension or 0.5% tween water only. Each treatment included four replicates and the experiment was repeated. Leaf spot symptoms were observed on the seedlings inoculated with conidia, whereas seedlings sprayed with water were asymptomatic. Cultures with the expected morphology were isolated from symptomatic leaf blades and absent from control plants. To our knowledge, this is the first report of leaf spot on Guinea grass caused by B. yamadae in Florida, USA. B. yamadae was previously reported from Guinea grass in India, and from other Panicum species in the northern USA (Farr and Rossman 2019). B. yamadae was also isolated from sugarcane in Cuba and China, and corn in Japan (Manamgoda et al. 2014, Raza et al. 2019), which suggests that it has the potential to impact agronomic crops in Florida, such as sugarcane and corn.

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First report of Colletotrichum siamense causing anthracnose on Erythrina crista-galli in China

Plant Disease ◽

10.1094/pdis-05-20-1080-pdn ◽

2020 ◽

Author(s):

Min Li ◽

Zhaoyin Gao ◽

Xiaoyu Hong ◽

Zhang Shao Gang ◽

Chao Zhao ◽

...

Keyword(s):

Leaf Spot ◽

Phylogenetic Analyses ◽

Conidial Suspension ◽

Disease Symptoms ◽

First Report ◽

Brown Center ◽

Detached Leaves ◽

Leaf Tissues ◽

Pathogenicity Tests ◽

White Mycelium

Erythrina crista-galli L. (Fabaceae) is a popular ornamental plant in tropical and subtropical regions of South Asia. In October 2019, anthracnose-like lesions were observed on the leaves of E. crista-galli planted in Haikou, China. 5-30% of leaves were infected. At first, the circular spots of 1-2 mm in diameter were reddish-brown on the leaves, and then enlarged to circular, subcircular or irregular spots with reddish-brown center and surrounded by a diffuse yellow margin. Neighboring spots sometimes coalesced. Under continuously wet or humid conditions, the lesions expanded quickly, and became gray, subcircular or irregular spots covered by grayish-white mycelium and orange-pink conidial masses. Diseased leaves eventually fell off the trees. To identify the pathogen, diseased leaves were sampled from four gardens. Leaf tissues (5×5 mm) were cut from the margins of typical symptomatic lesions, surface-sterilized in 1% sodium hypochlorite for 1 min, plated on potato dextrose agar (PDA) medium, and incubated at 28.0±0.5℃ in the dark. Similar fungal colonies were obtained from all plated tissues after 3 days. The single-conidium colonies of all isolates were white to pale gray and cottony with visible orange conidial masses. Conidia were one-celled, aseptate, hyaline, straight, cylindrical to fusiform with obtuse ends, and ranged from 14.2-18.6 µm (16.4 µm)× 3.8-5.4 µm (4.7 µm) (n=100). After germination, conidia formed single, brown, oval or slightly irregular appressoria ranging from 8.0 to 11.8 μm (9.6 µm), and from 4.8 to 6.0 μm (5.4 µm). Sexual stage was absent. These characteristics of conidia and appressoria were matched with C. siamense belonging to the C. gloeosporioides complex (Prihastuti et al. 2009; Yang et al. 2009; Weir et al. 20012; Hu et al. 2015). To accurately identify the species, DNA was extracted from four purified isolates (JG-1, JG-3-1, SWS-1-3, SWS-2-1) （Fu et al. 2019）. The internal transcribed spacer of rDNA region (ITS), glyceraldehydes-3-phosphate dehydrogenase (GAPDH), calmodulin (CAL), actin (ACT) and chitin synthase (CHS) genes were amplified and sequenced. The nucleotide sequences were all deposited in GenBank (ITS: MT229427-MT229430, GAPDH: MT250821-MT250824, CAL: MT258893-MT258896, ACT: MT258897-MT258900 and CHS: MT258901-MT258904). Multi-locus phylogenetic analyses (ITS, GAPDH, CAL, ACT and CHS) (Weir et al. 2012) showed that the four isolates were clustered with C. siamense, which was in accordance with BLAST results. Pathogenicity tests of the four isolates were repeated three times on detached leaves (Ji et al. 2019). The conidial suspension (1×106 conidia/mL) was prepared using the conidia from 10-day-old cultures grown on PDA. Two 20-µL drops of conidial suspension were inoculated on non-wounded young healthy leaves, and each isolate was inoculated on 10 leaves. Two 20-µL drops of sterile water were inoculated on non-wounded young healthy leaves as control. The samples were maintained in containers at a relative humidity of 90± 5 per cent inside and 28℃ with a 12-h photoperiod. Gray, subcircular spots similar to the field disease symptoms were observed on the all inoculated leaves after 7 days, whereas no visible symptoms appeared on the non-inoculated leaves. The pathogen was re-isolated from inoculated leaves thus fulfilling Koch’s postulates. C. gloeosporioides has been previously reported as a pathogen causing leaf spot on Erythrina (E. indica var. picta, E. variegata var. orientalis) in Guam in 1983 and Brazil in 2012. (Russo et al. 1983; Oliveira et al. 2012). To our knowledge, this is the first report of C. siamense causing leaf spot of E. crista-galli in China.

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First Report of Verticillium dahliae Causing Wilt on Solanum cardiophyllum and Solanum ehrenbergii

Plant Disease ◽

10.1094/pdis.2000.84.7.808c ◽

2000 ◽

Vol 84 (7) ◽

pp. 808-808

Author(s):

G. Rodríguez-Alvarado ◽

S. P. Fernández-Pavía ◽

J. Galindo-Alonso

Keyword(s):

Verticillium Dahliae ◽

Tap Water ◽

Disease Incidence ◽

Solanum Species ◽

Conidial Suspension ◽

First Report ◽

Tissue Sections ◽

Initial Symptoms ◽

Solanum Cardiophyllum ◽

Verticillium Dahliae Kleb

Solanum cardiophyllum Lindl and Solanum ehrenbergii (Bitt) Rydb are wild edible potato plants found throughout central Mexico (2). These plants are not cultivated, but farmers collect tubers for their own consumption and to sell at local markets (2). Wilted plants were observed in experimental plots of these wild potatoes established near Chapingo, Mexico, during spring 1983. Initial symptoms included wilting and dark yellowing of lower leaves. As the disease advanced, all of the foliage became chlorotic and the plants wilted and eventually died. Disease incidence was 13.4% for S. ehrenbergii and 0.2% for S. cardiophyllum. Verticillium dahliae Kleb. was consistently isolated from the roots and lower stems of diseased plants of both Solanum species. The isolating procedure consisted of thoroughly rinsing roots and lower stems with tap water and cutting roots and stems into 3- to 6-cm sections that were placed in 10% bleach for 3 to 5 min. Bleach excess was removed with sterile paper, and the tissue sections were cut into smaller pieces (0.5 cm) and placed on potato dextrose agar (PDA) plates. Cultures of Verticillium produced numerous dark microsclerotia of various shapes and sizes (0.05 to 0.1 mm); erect, slender, hyaline, and branched conidiophores; and elliptical and hyaline, single-celled conidia characteristic of V. dahliae (1). Pathogenicity studies were conducted in a greenhouse on 2-month-old S. cardiophyllum and S. ehrenbergii plants grown from tubers. Inoculum was obtained from colonies growing on PDA for 10 days producing abundant conidia. Conidial suspensions were obtained by flooding the plate cultures with sterile distilled water, filtering the suspension with two layers of cheesecloth, and adjusting the inoculum to 1.0 × 106 conidia/ml (3). Ten ml of the conidial suspension were applied to each of four holes 5 cm deep and 3 to 5 cm next to the crown of each plant. Symptoms similar to those observed on field-grown plants were observed 15 days after inoculation, and V. dahliae was re-isolated from lower stems and roots. All inoculated plants were dead 4 weeks after inoculation. Water-inoculated plants remained healthy throughout the experiments. This is the first report of V. dahliae on S. cardiophyllum and S. ehrenbergii. References: (1) G. R. Dixon. Vegetable Crop Diseases. Avi Publishing, Westport, Connecticut. 1981. (2) J. Galindo. Naturaleza 13:175, 1982. (3) H. A. Melouk and C. E. Horner. Phytopathology 65:767, 1975.

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