First Report of Bacterial Speck of Tomato Caused by Pseudomonas syringae pv. tomato in Tanzania

In April 2004, there was a serious outbreak of a tomato (Lypersicon esculentum Mill.) leaf spot disease in Mgeta, Mvomero District of Tanzania. The disease was characterized by lesions on green tomato fruits that were small, sunken, and black and were surrounded by darker green haloes. Lesions on ripe tomato fruits were dark brown to black, superficial, and measured approximately 1 to 2 mm in diameter. On the leaves, lesions were small, black, and surrounded by chlorotic (yellow) haloes. In some cases, the specks coalesced to form large lesions on older leaves. Black lesions were also observed on stems and petioles. A disease survey of selected tomato-producing areas in Arusha, Dodoma, Iringa, and Morogoro regions of Tanzania during 2004 and 2005 revealed that the disease was widespread in farmers' fields in all areas surveyed. Disease incidence was approximately 80%, while severity, rated on the scale of Chambers and Merriman (1), ranged from moderate (11 to 40 lesions per plant) to severe (>40 lesions per plant). A bacterium that produced a greenish, diffusible pigment on King's medium B was consistently isolated from lesions on tomato fruits collected from the fields in all the surveyed areas. All 56 isolates obtained were gram negative, oxidase negative, and fluoresced on King's medium B under UV light. None utilized phenylethylamine as the sole carbon source, while three isolates utilized i-erythritol and lactulose. Biolog analysis of the isolates, along with two reference strains of P. syringae pv. tomato (Pst CEP-3 from Sokoine University of Agriculture, Tanzania and Pst BB6 [Race 1] from Göttinger Sammlung Phytopathogener Bakterien, Göttingen, Germany) identified them as P. syringae pv. tomato, with similarity indices of 0.518 to 0.933. They also were positively identified as P. syringae pv. tomato by repetitive sequence-based-PCR (2,3) and fragment length polymorphism analysis. Pathogenicity of the strains was confirmed by spraying 35-day-old tomato seedlings (cv. Tanya) with suspensions of the isolates at a concentration of 108 CFU ml-1 of sterile water. After approximately 72 h, small, water-soaked, dark brown lesions similar to those observed on the field plants were observed on leaves of all the inoculated tomato seedlings. There were no symptoms on control plants. The bacterium was reisolated from the infected plants and identified as P. syringae pv. tomato, in accordance with Koch's postulates. To our knowledge, this is the first report of the occurrence of tomato bacterial speck in Tanzania. References: (1). S. C. Chambers and P. R. Merriman. Aust. J. Agric. Res. 26:657, 1975. (2). F. J. Louws et al. Appl. Environ. Microbiol. 60:2286, 1994. (3). M. Zaccardelli et al. Eur. J. Plant Pathol. 111:85, 2005.

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An Outbreak of Bacterial Speck Caused by Pseudomonas syringae pv. tomato on Tomato Transplants Grown in Commercial Seedling Companies Located in the Western Mediterranean Region of Turkey

Plant Disease ◽

10.1094/pdis.2004.88.9.1050a ◽

2004 ◽

Vol 88 (9) ◽

pp. 1050-1050 ◽

Cited By ~ 4

Author(s):

H. Basim ◽

E. Basim ◽

S. Yilmaz ◽

E. R. Dickstein ◽

J. B. Jones

Keyword(s):

Pseudomonas Syringae ◽

Mediterranean Region ◽

Disease Incidence ◽

Western Mediterranean ◽

Leaf Spot Disease ◽

Bacterial Speck ◽

Tomato Seedlings ◽

Leaf Spots ◽

Black Spots ◽

Initial Symptoms

A serious outbreak of a leaf spot disease was observed on tomato transplants grown in commercial seedling companies in southwestern Turkey (Antalya) during the springs of 2002 and 2003. Disease incidence was more severe in the western Mediterranean Region of Turkey. Occurrence of the outbreak resulted in approximately 20 and 25% seedling losses in the springs of 2002 and 2003, respectively. The initial symptoms consisted of pronounced water-soaked, dark brown-to-black spots on young expanding leaves that were 1 to 2 mm in diameter. Later, a number of leaf spots on older leaves enlarged and coalesced, causing leaf desiccation and finally, seedling death. In addition, in 2003 the disease incidence was approximately 5% in 142 commercial greenhouses. Tomato production was unaffected since significant outbreaks did not occur on greenhouse plants. No fruit symptoms were observed. Twenty-six strains were isolated from diseased tomato seedlings and plants from different greenhouses located in different places and all were gram negative and fluorescent on King's B medium. All strains were levan and gelatin liquefaction positive and oxidase and arginine dihydrolase negative. None of the 26 strains utilized erythritol and l-lactate as the sole carbon source (1,2). Fatty acid analysis identified the strains as Pseudomonas syringae pv. tomato with similarity indices ranging from 0.876 to 0.932%. Pathogenicity of the isolates was confirmed on 4-week-old tomato seedlings (cv. Biotek Selin) sprayed with the bacterial suspensions containing 108 CFU/ml of sterile water. Later, a number of leaf spots on the leaves enlarged and coalesced, causing leaf desiccation. Inoculated and control tomato seedlings were covered with polyethylene bags and placed in a growth chamber at 25°C for 48 h and then the bags were removed. Small (1 to 2 mm), water-soaked, dark brown-to-black spots similar to those observed in the greenhouses of commercial seedling companies and commercial greenhouses that produce tomato developed on the young expanding leaves of inoculated plants within 7 to 10 days. No symptoms developed on control plants. The bacterium was reisolated from inoculated plants and identified as a strain of Pseudomonas syringae pv. tomato. Koch's postulates were fulfilled. To our knowledge, this is the first report for the occurrence and outbreak of the bacterial speck disease on tomato transplants in greenhouses of commercial tomato seedling production companies in Turkey. References: (1) D. C. Hildebrand et al. Pages 60–80 in: Laboratory Guide for Identification of Plant Pathogenic Bacteria. N. D. Schaad, ed. The American Phytopathological Society, 1988. (2) J. B. Jones et al. Plant Dis. 70:151, 1986.

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First report of banana (Musa acuminate L. AAA Cavendish, cv. Formosana) leaf spot disease caused by Curvularia geniculata in China

Plant Disease ◽

10.1094/pdis-09-21-2001-pdn ◽

2021 ◽

Author(s):

Yanxiang Qi ◽

Yanping Fu ◽

Jun Peng ◽

Fanyun Zeng ◽

Yanwei Wang ◽

...

Keyword(s):

Leaf Spot ◽

Disease Incidence ◽

Morphological Characteristics ◽

Universal Primers ◽

Leaf Spot Disease ◽

Leaf Margin ◽

Conidial Suspension ◽

Tropical Fruit ◽

First Report ◽

Spot Disease

Banana (Musa acuminate L.) is an important tropical fruit in China. During 2019-2020, a new leaf spot disease was observed on banana (M. acuminate L. AAA Cavendish, cv. Formosana) at two orchards of Chengmai county (19°48ʹ41.79″ N, 109°58ʹ44.95″ E), Hainan province, China. In total, the disease incidence was about 5% of banana trees (6 000 trees). The leaf spots occurred sporadically and were mostly confined to the leaf margin, and the percentage of the leaf area covered by lesions was less than 1%. Symptoms on the leaves were initially reddish brown spots that gradually expanded to ovoid-shaped lesions and eventually become necrotic, dry, and gray with a yellow halo. The conidia obtained from leaf lesions were brown, erect or curved, fusiform or elliptical, 3 to 4 septa with dimensions of 13.75 to 31.39 µm × 5.91 to 13.35 µm (avg. 22.39 × 8.83 µm). The cells of both ends were small and hyaline while the middle cells were larger and darker (Zhang et al. 2010). Morphological characteristics of the conidia matched the description of Curvularia geniculata (Tracy & Earle) Boedijn. To acquire the pathogen, tissue pieces (15 mm2) of symptomatic leaves were surface disinfected in 70% ethanol (10 s) and 0.8% NaClO (2 min), rinsed in sterile water three times, and transferred to potato dextrose agar (PDA) for three days at 28°C. Grayish green fungal colonies appeared, and then turned fluffy with grey and white aerial mycelium with age. Two representative isolates (CATAS-CG01 and CATAS-CG92) of single-spore cultures were selected for molecular identification. Genomic DNA was extracted from the two isolates, the internal transcribed spacer (ITS), large subunit ribosomal DNA (LSU rDNA), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), translation elongation factor 1-alpha (TEF1-α) and RNA polymerase II second largest subunit (RPB2) were amplified and sequenced with universal primers ITS1/ITS4, LROR/LR5, GPD1/GPD2, EF1-983F/EF1-2218R and 5F2/7cR, respectively (Huang et al. 2017; Raza et al. 2019). The sequences were deposited in GenBank (MW186196, MW186197, OK091651, OK721009 and OK491081 for CATAS-CG01; MZ734453, MZ734465, OK091652, OK721100 and OK642748 for CATAS-CG92, respectively). For phylogenetic analysis, MEGA7.0 (Kumar et al. 2016) was used to construct a Maximum Likelihood (ML) tree with 1 000 bootstrap replicates, based on a concatenation alignment of five gene sequences of the two isolates in this study as well as sequences of other Curvularia species obtained from GenBank. The cluster analysis revealed that isolates CATAS-CG01 and CATAS-CG92 were C. geniculata. Pathogenicity assays were conducted on 7-leaf-old banana seedlings. Two leaves from potted plants were stab inoculated by puncturing into 1-mm using a sterilized needle and placing 10 μl conidial suspension (2×106 conidia/ml) on the surface of wounded leaves and equal number of leaves were inoculated with sterile distilled water serving as control (three replicates). Inoculated plants were grown in the greenhouse (12 h/12 h light/dark, 28°C, 90% relative humidity). Necrotic lesions on inoculated leaves appeared seven days after inoculation, whereas control leaves remained healthy. The fungus was recovered from inoculated leaves, and its taxonomy was confirmed morphologically and molecularly, fulfilling Koch’s postulates. C. geniculata has been reported to cause leaf spot on banana in Jamaica (Meredith, 1963). To our knowledge, this is the first report of C. geniculata on banana in China.

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First Report of a Leaf Spot on Snow Lotus Caused by Alternaria carthami in China

Plant Disease ◽

10.1094/pdis-92-2-0318b ◽

2008 ◽

Vol 92 (2) ◽

pp. 318-318

Author(s):

S. Zhao ◽

G. Xie ◽

H. Zhao ◽

H. Li ◽

C. Li

Keyword(s):

Leaf Spot ◽

Disease Incidence ◽

Leaf Spot Disease ◽

Tianshan Mountain ◽

Causal Organism ◽

Saussurea Involucrata ◽

First Report ◽

Spot Disease ◽

Initial Symptoms ◽

Snow Lotus

Snow lotus (Saussurea involucrata Karel. & Kir. ex Sch. Bip.) is an economically important medicinal herb increasingly grown in China in recent years. In June of 2005, a leaf spot disease on commercially grown plants was found in the QiTai Region, south of the Tianshan Mountain area of Xinjiang, China at 2,100 m above sea level. Disease incidence was approximately 60 to 70% of the plants during the 2006 and 2007 growing seasons. Initial symptoms appeared on older leaves as irregularly shaped, minute, dark brown-to-black spots, with yellow borders on the edge of the leaflet blade by July. As the disease progressed, the lesions expanded, causing the leaflets to turn brown, shrivel, and die. A fungus was consistently isolated from the margins of these lesions on potato dextrose agar. Fifty-eight isolates were obtained that produced abundant conidia in the dark. Conidia were usually solitary, rarely in chains of two, ellipsoid to obclavate, with 6 to 11 transverse and one longitudinal or oblique septum. Conidia measured 60 to 80 × 20 to 30 μm, including a filamentous beak (13 to 47 × 3.5 to 6 μm). According to the morphology, and when compared with the standard reference strains, the causal organism of leaf spot of snow lotus was identified as Alternaria carthami (1,4). Pathogenicity of the strains was tested on snow lotus seedlings at the six-leaf stage. The lower leaves of 20 plants were sprayed until runoff with conidial suspensions of 1 × 104 spores mL–1, and five plants sprayed with sterile distilled water served as controls. All plants were covered with a polyethylene bag, incubated at 25°C for 2 days, and subsequently transferred to a growth chamber at 25°C with a 16-h photoperiod. Light brown lesions developed within 10 days on leaflet margins in all inoculated plants. The pathogen was reisolated from inoculated leaves, and isolates were deposited at the Key Oasis Eco-agriculture Laboratory of Xinjiang Production and Construction Group, Xinjiang and the Institute of Biotechnology, Zhejiang University. No reports of a spot disease caused by A. carthami on snow lotus leaves have been found, although this pathogen has been reported on safflower in western Canada (3), Australia (2), India (1), and China (4). To our knowledge, this is the first report of a leaf spot caused by A. carthami on snow lotus in China. References: (1) S. Chowdhury. J. Indian Bot. Soc. 23:59, 1944. (2) J. A. G. Irwin. Aust. J. Exp. Agric. Anim. Husb. 16:921, 1976. (3) G. A. Petrie. Can. Plant Dis. Surv. 54:155, 1974. (4) T. Y. Zhang. J. Yunnan Agric. Univ.17:320, 2002.

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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 Leaf Spot Disease Caused by Colletotrichum gloeosporioides on Chinese Bean Tree in China

Plant Disease ◽

10.1094/pdis-03-12-0261-pdn ◽

2013 ◽

Vol 97 (1) ◽

pp. 138-138 ◽

Cited By ~ 1

Author(s):

B. Z. Fu ◽

M. Yang ◽

G. Y. Li ◽

J. R. Wu ◽

J. Z. Zhang ◽

...

Keyword(s):

Leaf Spot ◽

Colletotrichum Gloeosporioides ◽

Disease Incidence ◽

Phylogenetic Analyses ◽

Morphological Characteristics ◽

Leaf Spot Disease ◽

First Report ◽

Spot Disease ◽

Rdna Its ◽

Its Sequence Analysis

Chinese bean tree, Catalpa fargesii f. duciouxii (Dode) Gilmour, is an ornamental arbor plant. Its roots, leaves, and flowers have long been used for medicinal purposes in China. During July 2010, severe outbreaks of leaf spot disease on this plant occurred in Kunming, Yunnan Province. The disease incidence was greater than 90%. The symptoms on leaves began as dark brown lesions surrounded by chlorotic halos, and later became larger, round or irregular spots with gray to off-white centers surrounded by dark brown margins. Leaf tissues (3 × 3 mm), cut from the margins of lesions, were surface disinfected in 0.1% HgCl2 solution for 3 min, rinsed three times in sterile water, plated on potato dextrose agar (PDA), and incubated at 28°C. The same fungus was consistently isolated from the diseased leaves. Colonies of white-to-dark gray mycelia formed on PDA, and were slightly brown on the underside of the colony. The hyphae were achromatic, branching, septate, and 4.59 (±1.38) μm in diameter on average. Perithecia were brown to black, globose in shape, and 275.9 to 379.3 × 245.3 to 344.8 μm. Asci that formed after 3 to 4 weeks in culture were eight-spored, clavate to cylindrical. The ascospores were fusiform, slightly curved, unicellular and hyaline, and 13.05 to 24.03 × 10.68 to 16.02 μm. PCR amplification was carried out by utilizing universal rDNA-ITS primer pair ITS4/ITS5 (2). Sequencing of the PCR products of DQ1 (GenBank Accession No. JN165746) revealed 99% similarity (100% coverage) with Colletotrichum gloeosporioides isolates (GenBank Accession No. FJ456938.1, No. EU326190.1, No. DQ682572.1, and No. AY423474.1). Phylogenetic analyses (MEGA 4.1) using the neighbor-joining (NJ) algorithm placed the isolate in a well-supported cluster (>90% bootstrap value based on 1,000 replicates) with other C. gloeosporioides isolates. The pathogen was identified as C. gloeosporioides (Penz.) Penz. & Sacc. (teleomorph Glomerella cingulata (Stoneman) Spauld & H. Schrenk) based on the morphological characteristics and rDNA-ITS sequence analysis (1). To confirm pathogenicity, Koch's postulates were performed on detached leaves of C. fargesii f. duciouxii, inoculated with a solution of 1.0 × 106 conidia per ml. Symptoms similar to the original ones started to appear after 10 days, while untreated leaves remained healthy. The inoculation assay used three leaves for untreated and six leaves for treated. The experiments were repeated once. C. gloeosporioides was consistently reisolated from the diseased tissue. C. gloeosporioides is distributed worldwide causing anthracnose on a wide variety of plants (3). To the best of our knowledge, this is the first report of C. gloeosporioides causing leaf spots on C. fargesii f. duciouxii in China. References: (1) B. C. Sutton. Page 1 in: Colletotrichum: Biology, Pathology and Control. CAB International. Wallingford, UK, 1992. (2) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, 1990. (3) J. Yan et al. Plant Dis. 95:880, 2011.

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First Report of Leaf Spot Disease Caused by Epicoccum nigrum on Lablab purpureus in India

Plant Disease ◽

10.1094/pdis-07-13-0798-pdn ◽

2014 ◽

Vol 98 (2) ◽

pp. 284-284 ◽

Cited By ~ 12

Author(s):

S. Mahadevakumar ◽

K. M. Jayaramaiah ◽

G. R. Janardhana

Keyword(s):

Leaf Spot ◽

Leaf Surface ◽

Disease Incidence ◽

Leaf Spot Disease ◽

Post Inoculation ◽

Conidial Suspension ◽

Lablab Purpureus ◽

First Report ◽

Spot Disease ◽

Epicoccum Nigrum

Lablab purpureus (L.) Sweet (Indian bean) is an important pulse crop grown in arid and semi-arid regions of India. It is one of the most widely cultivated legume species and has multiple uses. During a September 2010 survey, we recorded a new leaf spot disease on L. purpureus in and around Mysore district (Karnataka state) with 40 to 80% disease incidence in 130 ha of field crop studied, which accounted for 20 to 35% estimated yield loss. The symptoms appeared as small necrotic spots on the upper leaf surface. The leaf spots were persistent under mild infection throughout the season with production of conidia in clusters on abaxial leaf surface. A Dueteromyceteous fungus was isolated from affected leaf tissues that were surface sterilized with 2% NaOCl2 solution then washed thrice, dried, inoculated on potato dextrose agar (PDA) medium, and incubated at 28 ± 2°C at 12 h alternate light and dark period for 7 days. The fungal colony with aerial mycelia interspersed with dark cushion-shaped sporodochia consists of short, compact conidiophores bearing large isodiametric, solitary, muricate, brown, globular to pear shaped conidia (29.43 to 23.92 μm). Fungal isolate was identified as Epicoccum sp. based on micro-morphological and cultural features (1). Further authenticity of the fungus was confirmed by PCR amplification of the internal transcribed spacer (ITS) region using ITS1/ITS4 universal primer. The amplified PCR product was purified, sequenced directly, and BLASTn search revealed 100% homology to Epicoccum nigrum Link. (DQ093668.1 and JX914480.1). A representative sequence of E. nigrum was deposited in GenBank (Accession No. KC568289.1). The isolated fungus was further tested for its pathogenicity on 30-day-old healthy L. purpureus plants under greenhouse conditions. A conidial suspension (106 conidia/ml) was applied as foliar spray (three replicates of 15 plants each) along with suitable controls. The plants were kept under high humidity (80%) for 5 days and at ambient temperature (28 ± 2°C). The appearance of leaf spot symptoms were observed after 25 days post inoculation. Further, the pathogen was re-isolated and confirmed by micro-morphological characteristics. E. nigrum has been reported to cause post-harvest decay of cantaloupe in Oklahoma (2). It has also been reported as an endophyte (3). Occurrence as a pathogen on lablab bean has not been previously reported. To our knowledge, this is the first report of the occurrence of E. nigrum on L. purpureus in India causing leaf spot disease. References: (1) H. L. Barnet and B. B. Hunter. Page 150 in: Illustrated Genera of Imperfect Fungi, 1972. (2) B. D. Bruten et al. Plant Dis. 77:1060, 1993. (3) L. C. Fávaro et al. PLoS One 7(6):e36826, 2012.

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First Report of a Leaf Spot Disease of Tobacco Caused by Pseudomonas cichorii in China

Plant Disease ◽

10.1094/pdis-10-21-2158-pdn ◽

2021 ◽

Author(s):

Dayu Lan ◽

Fangling Shu ◽

Yanhui Lu ◽

Anfa Shou ◽

Wei Lin ◽

...

Keyword(s):

Pseudomonas Syringae ◽

Leaf Spot ◽

Leaf Spot Disease ◽

Pathogenicity Test ◽

Pseudomonas Cichorii ◽

Koch’S Postulates ◽

First Report ◽

Initial Symptoms ◽

Wide Range ◽

Koch's Postulates

Tobacco (Nicotiana tabacum L.), one of the chief commercial crops, is wildly cultivated worldwide. In June 2020 and 2021, an unknown bacterial leaf spot on tobacco was found in Hezhou and Hechi City, Guangxi, China. 30% of the tobacco were affected and the rate of diseased leaves reached about 10% in the field under high temperature and rainstorm. The disease mainly damaged the middle and top leaves of tobacco plants at vigorous growing stage. The initial symptoms were water-soaked spots on the frontal half of a leaf, and then expanded into circular to irregular spots with a yellow halo at the edge. The spots mostly appeared dark brown at high air humidity, while yellow brown at low humidity and exhibited a concentric pattern. In severe cases, the lesions coalesced and the whole leaf was densely covered with lesions, resulting in the loss of baking value. A bacterium was consistently isolated from diseased leaf tissues on nutrient agar (NA). Growth on NA was predominantly grayish white circular bacterial colonies with smooth margins, and the bacterium is rod-shaped, gram-negative and fluorescent on King’s B medium. Seven isolates (ND04A-ND04C and ZSXF02-ZSXF05) were selected for molecular identification and pathogenicity tests. Genomic DNA of the bacterium was extracted and the housekeeping gene of cts (encoding citrate synthase) was amplified with the primers cts-Fs/cts-Rs (forward primer cts-Fs: 5’-CCCGTCGAGCTGCCAATWCTGA-3’; reverse primer cts-Rs: 5’-ATCTCGCACGGSGTRTTGAACATC-3’) (Berge et al. 2014; Sarkar et al. 2004). 409-bp cts gene sequences were deposited in the GenBank database for seven isolates (accession no. OK105110-OK105116). Sequence of seven isolates shared 100% identity with several Pseudomonas cichorii strains within the GenBank database (accession no. KY940268 and KY940271), and the phylogenetic tree of cts genes of the seven isolates clustered with the phylogroup 11 of Pseudomonas syringae (accession no. KJ877799 and KJ878111), which was classified as P.cichorii. To satisfy Koch’s postulates, a pathogenicity test was tested by using a needle to dip a suspension of the bacterium (108 CFU/ml) and pricking three holes in the tobacco leaf. The control plants leaves were needled with sterile water. Each tobacco plant was inoculated with three leaves, and the test was repeated three times. All plants were placed in transparent plastic boxes and incubated in a greenhouse at 25 ± 3°C. The water-soaked spots appeared 24h after inoculation and quickly expanded through leaf veins. Three days after inoculation, all the inoculated leaves showed symptoms similar to those observed in the field. Control plants remained healthy. Only P. cichorii was successfully re-isolated from the lesions, confirming Koch’s postulates. Pseudomonas cichorii can infect eggplant, lettuce, tomatoand other crops, and has a wide range of hosts (Timilsina et al. 2017; Ullah et al. 2015). To our knowledge, this is the first report of P. cichorii causing leaf spot on tobacco in China.

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First Report of Bacterial Leaf Spot of Coriander Caused by Pseudomonas syringae pv. coriandricola in China

Plant Disease ◽

10.1094/pdis-09-21-1901-pdn ◽

2021 ◽

Author(s):

Lei Li ◽

Yishuo Huang ◽

Yanxia Shi ◽

A LI CHAI ◽

Xuewen Xie ◽

...

Keyword(s):

Pseudomonas Syringae ◽

Leaf Spot ◽

Citrate Synthase ◽

Morphological Characteristics ◽

Likelihood Method ◽

Bacterial Suspension ◽

Leaf Spot Disease ◽

Distilled Water ◽

Bacterial Leaf Spot ◽

First Report

Coriander (Coriandrum sativum L.) or Chinese parsley is a culinary herb with multiple medicinal effects that are widely used in cooking and traditional medicine. From September to November 2019, symptoms were observed in 2-month-old coriander plants from coriander ﬁelds in Lanzhou and Wenzhou, China. The disease developed rapidly under cold and wet climatic conditions, and the infection rate was almost 80% in open coriander fields. Typical symptoms on leaves included small, water-soaked blotches and irregular brown spots surrounding haloes; as the disease progressed, the spots coalesced into necrotic areas. Symptomatic leaf tissue was surface sterilized, macerated in sterile distilled water, and cultured on nutrient agar plates at 28 °C for 48 h (Koike and Bull, 2006). After incubation, six bacterial colonies, which were individually isolated from collected samples from two different areas, were selected for further study. Colonies on NA plate were small, round, raised, white to cream-colored, and had smooth margins. All bacterial isolates were gram-negative, rod-shaped and nonfluorescent on King's B medium. The bacteria were positive for levan production, Tween 80 hydrolysis, and tobacco hypersensitivity but negative for oxidase, potato slice rot test, arginine dihydrolase, ice nucleation activity, indole production and H2S production. The suspension of representative isolate for inoculating of plants was obtained from single colony on King's B medium for 2-3 days at 28 °C. DNA was extracted from bacterial suspensions of YS2003200102 cultured in 20 ml of King’s B medium broth at 28 °C for 1 day. Extraction was performed with a TIANamp Bacterial DNA Kit (TIANGEN, China) according to the manufacturer’s recommendations. The pathogen was confirmed by amplification and sequencing of the glyceraldehyde-3-phosphate dehydrogenase A (gapA) gene, the citrate synthase (gltA) gene, the DNA gyrase B (gyrB) gene and the RNA polymerase sigma factor 70 (rpoD) gene using gapA-For/gapA-Rev, gltA-For/gltA-Rev, gyrB-For/gryB-Rev, rpoD-For/rpoD-Rev primers, respectively (Popović et al., 2019). The sequences of the PCR products were deposited in GenBank with accession numbers MZ681931 (gapA), MZ681932 (gltA), MZ681933 (gyrB), and MZ681934 (rpoD). Phylogenetic analysis of multiple genes (Xu and Miller, 2013) was conducted with the maximum likelihood method using MEGA7. The sequences of our isolates and ten published sequences of P. syringae pv. coriandricola were clustered into one clade with a 100% confidence level. To confirm the pathogenicity of isolate YS2003200102, 2-month-old healthy coriander plants were inoculated by spraying the leaves with a bacterial suspension (108 CFU ml−1) at 28 °C incubation temperature and 70% relative humidity condition, and sterile distilled water was applied as a negative control treatment (Cazorla et al. 2005). Three replicates were conducted for every isolate, and each replicate included 6 coriander plants. After twelve days, only the inoculated leaves with bacterial suspension showed bacterial leaf spot resembling those observed on naturally infected coriander leaves. Cultures re-isolated from symptomatic leaves showed the same morphological characteristics and molecular traits as those initially isolated from infected leaves in the field. This bacterium was previously reported causing leaf spot of coriander in India and Spain (Gupta et al. 2013; Cazorla et al. 2005). To our knowledge, this is the first report of P. syringae pv. coriandricola causing leaf spot disease on coriander in China. Studies are needed on strategies to manage P. syringae pv. coriandricola in crops, because its prevalence may cause yield loss on coriander in China.

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

Plant Disease ◽

10.1094/pdis-11-10-0787 ◽

2011 ◽

Vol 95 (6) ◽

pp. 775-775 ◽

Cited By ~ 1

Author(s):

V. Ayala-Escobar ◽

V. Santiago-Santiago ◽

A. Madariaga-Navarrete ◽

A. Castañeda-Vildozola ◽

C. Nava-Diaz

Keyword(s):

Uv Light ◽

Disease Incidence ◽

Morphological Characteristics ◽

The United States ◽

Pathogenicity Test ◽

Commonwealth Mycological Institute ◽

Conidial Suspension ◽

Single Spore ◽

First Report ◽

Bougainvillea Spectabilis

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

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First Report of Tomato Gray Leaf Spot Disease Caused by Stemphylium solani in Malaysia

Plant Disease ◽

10.1094/pdis-03-12-0223-pdn ◽

2012 ◽

Vol 96 (8) ◽

pp. 1226-1226

Author(s):

A. Nasehi ◽

J. B. Kadir ◽

M. A. Zainal Abidin ◽

M. Y. Wong ◽

F. Mahmodi

Keyword(s):

Leaf Spot ◽

Disease Incidence ◽

Gray Leaf Spot ◽

Leaf Spot Disease ◽

Conidial Suspension ◽

Internal Transcribed Spacer Region ◽

First Report ◽

Spot Disease ◽

Pcr Product ◽

Morphological Criteria

In June 2011, tomatoes (Solanum lycopersicum) in major growing areas of the Cameron Highlands and the Johor state in Malaysia were affected by a leaf spot disease. Disease incidence exceeded 80% in some severely infected regions. Symptoms on 50 observed plants initially appeared on leaves as small, brownish black specks, which later became grayish brown, angular lesions surrounded by a yellow border. As the lesions matured, the affected leaves dried up and became brittle and later developed cracks in the center of the lesions. A survey was performed in these growing areas and 27 isolates of the pathogen were isolated from the tomato leaves on potato carrot agar (PCA). The isolates were purified by the single spore technique and were transferred onto PCA and V8 agar media for conidiophore and conidia production under alternating light (8 hours per day) and darkness (16 hours per day) (4). Colonies on PCA and V8 agar exhibited grey mycelium and numerous conidia were formed at the terminal end of conidiophores. The conidiophores were up to 240 μm long. Conidia were oblong with 2 to 11 transverse and 1 to 6 longitudinal septa and were 24 to 69.6 μm long × 9.6 to 14.4 μm wide. The pathogen was identified as Stemphylium solani on the basis of morphological criteria (2). In addition, DNA was extracted and the internal transcribed spacer region (ITS) was amplified by universal primers ITS5 and ITS4 (1). The PCR product was purified by the commercial PCR purification kit and the purified PCR product sequenced. The resulting sequences were 100% identical to published S. solani sequences (GenBank Accestion Nos. AF203451 and HQ840713). The amplified ITS region was deposited with NCBI GenBank under Accession No. JQ657726. A representative isolate of the pathogen was inoculated on detached 45-day-old tomato leaves of Malaysian cultivar 152177-A for pathogenicity testing. One wounded and two nonwounded leaflets per leaf were used in this experiment. The leaves were wounded by applying pressure to leaf blades with the serrated edge of a forceps. A 20-μl drop of conidial suspension containing 105 conidia/ml was used to inoculate these leaves (3). The inoculated leaves were placed on moist filter paper in petri dishes and incubated for 48 h at 25°C. Control leaves were inoculated with sterilized distilled water. After 7 days, typical symptoms for S. solani similar to those observed in the farmers' fields developed on both wounded and nonwounded inoculated leaves, but not on noninoculated controls, and S. solani was consistently reisolated. To our knowledge, this is the first report of S. solani causing gray leaf spot of tomato in Malaysia. References: (1) M. P. S. Camara et al. Mycologia 94:660, 2002. (2) B. S. Kim et al. Plant Pathol. J. 15:348, 1999. (3) B. M. Pryor and T. J. Michailides. Phytopathology 92:406, 2002. (4) E. G. Simmons. CBS Biodiversity Series 6:775, 2007.

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