First Report of Bacterial Leaf Spot Caused by Pseudomonas cichorii on Schefflera arboricola in Turkey

In late winter and spring of 2006 and 2008, leaf spots with yellow halos were observed on dwarf schefflera (Schefflera arboricola cvs. Gold Capella, Trinette, and Green Gold) that were grown as potted plants in two commercial ornamental greenhouses in Adana and Mersin, Turkey. Average disease incidence was assessed as 10% during the term of the study. Isolations were made from leaf spots symptoms on King's medium B. Bacteria consistently isolated from diseased tissues formed green fluorescent colonies on the medium. Ten representative bacterial strains were examined and found to be gram negative, rod shaped, and aerobic, levan, pectolytic, and arginine dihydrolase negative, and oxidase positive. They all induced a hypersensitive response in tobacco (Nicotiana tabacum cv. Samsun). All strains were identified as Pseudomonas cichorii with similarity indices of 79 to 99% based on fatty acid methyl ester (FAME) profiles determined by Sherlock Microbial Identification System software (TSBA 6 v. 6.00; Microbial ID, Newark, DE). Pathogenicity of the strains was confirmed on five dwarf schefflera plants by leaf tissue infiltration with bacterial suspensions (107 CFU ml–1) in sterile distilled water. P. cichorii NCPPB 3802 and sterile water were used as positive and negative controls, respectively. The same symptoms as those observed in the commercial greenhouses were observed on dwarf schefflera leaves within 12 to 15 days after inoculation. The bacteria were reisolated from the inoculated plants and identified as the same as the original strain by conventional tests and FAME analysis. Negative control plants remained disease free. Occurrence of bacterial leaf spot caused by P. cichorii on vegetable crops in Turkey (1,3) and dwarf schefflera in other countries (2) has been reported previously, but to our knowledge, this is the first report of the observation of P. cichorii on dwarf schefflera in Turkey. References: (1) Y. Aysan et al. Plant Pathol. 52:782. 2003. (2) A. R. Chase and D. D. Brunk. Plant Dis. 68:73, 1984. (3) F. Sahin et al. Acta Hortic. 695:93, 2005.

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First Report of Basil Leaf Spot Caused by Pseudomonas cichorii in Louisiana and Cultivar Screening Results

Plant Disease ◽

10.1094/pdis.1998.82.11.1283d ◽

1998 ◽

Vol 82 (11) ◽

pp. 1283-1283 ◽

Cited By ~ 2

Author(s):

G. E. Holcomb ◽

P. J. Cox

Keyword(s):

Leaf Spot ◽

Screening Tests ◽

Minor Importance ◽

Bacterial Cells ◽

Bacterial Leaf Spot ◽

Pseudomonas Cichorii ◽

First Report ◽

Sweet Basil ◽

Leaf Spots ◽

Cultivar Screening

A leaf spot of basil, Ocimum basilicum L., was observed on container-grown and field plantings of cultivars Aussie Sweet and Sweet Basil. The disease was of minor importance under field conditions, but was of potential economic importance in seedling production. Gray to black, watersoaked, necrotic spots commonly developed at leaf margins. Large numbers of bacteria were released from cut lesions when viewed by light microscopy. Single colony bacterial isolates were established on nutrient dextrose agar (NDA) and yeast extract-dextrose-calcium carbonate agar (YDC). Pathogencity tests were performed by misting a water suspension containing 104 bacterial cells per ml on healthy basil plants. Plants were held for 24 h in a dew chamber at 26°C and then moved to a greenhouse for observation. Typical leaf spots developed on inoculated plants in 2 days, but not on healthy control plants, and the bacterium was reisolated. The bacterium was characterized as a gram-negative, motile rod, negative for potato rot test, positive in tobacco hypersensitivity test, and oxidase positive. Isolates were identified as Pseudomonas cichorii according to the Biolog Microplate system (similarities ranged from 0.937 to 0.995). Screening tests were conducted by inoculating 15 basil cultivars, six replicates each, and rating them for disease severity based on a scale of 1 to 5 in which 1 = no disease and 5 = dead plants. Cultivars most resistant to bacterial leaf spot (ratings in parentheses are averages of two tests and those followed by the same letter are not significantly different according to Tukey's Studentized Range Test, P = 0.05) were Green Bouquet (2.0 a), Piccolo (2.2 a), Mrs. Burn's Lemon (2.2 a), Genovese (2.4 a), and Dark Opal (2.5 ab). Moderately susceptible cultivars were Bush Green (2.8 abc), Sweet Basil (2.8 abc), Large Green (2.9 abcd), Lemon (3.1 abcd), and Mexican Spice (3.6 bcd). The most susceptible cultivars were Lettuce Leaved (3.8 cd), Thai (3.8 cd), Napoletano (4.0 de), Green Ruffles (5.0 e), and Purple Ruffles (5.0 e). Bacterial leaf spot of basil caused by P. cichorii was first reported in the U.S. from Florida (1). Other bacterial diseases reported on basil include leaf blight from Egypt caused by P. syringae (2) and leaf necrosis from California caused by P. viridiflava (3). This is the first report on the occurrence of basil bacterial leaf spot in Louisiana and the first reported information on cultivar susceptibility. References: (1) S. M. Burgess et al. Proc. Fla. State Hortic. Soc. 99:249, 1986. (2) S. A. M. El-Sadek et al. Assiut J. Agric. Sci. 22:2, 1991. (3) E. L. Little et al. Plant Dis. 78:831, 1994.

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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 Bacterial Leaf Spot of Spinach Caused by a Pseudomonas syringae Pathovar in California

Plant Disease ◽

10.1094/pdis.2002.86.8.921a ◽

2002 ◽

Vol 86 (8) ◽

pp. 921-921 ◽

Cited By ~ 3

Author(s):

S. T. Koike ◽

H. R. Azad ◽

D. C. Cooksey

Keyword(s):

Brassica Oleracea ◽

Beta Vulgaris ◽

Pseudomonas Syringae ◽

Leaf Spot ◽

The United States ◽

Nutrient Broth ◽

Bacterial Leaf Spot ◽

First Report ◽

Leaf Spots ◽

Initial Symptoms

In 2000 and 2001, a new disease was observed on commercial spinach (Spinacia oleracea) in the Salinas Valley, Monterey County, CA. Initial symptoms were water-soaked, irregularly shaped leaf spots (2 to 3 mm diameter). As the disease developed, spots enlarged to as much as 1 to 2 cm, were vein-delimited, and turned dark brown. Faint chlorotic halos sometimes surrounded the spots. Death of large areas of the leaf occurred if spots coalesced. Spots were visible from the adaxial and abaxial sides of leaves, and no fungal structures were observed. The disease occurred on newly expanded and mature foliage. No fungi were isolated from the spots. However, cream-colored bacterial colonies were consistently isolated on sucrose peptone agar, and these strains were nonfluorescent on King's medium B. Strains were positive for levan and negative for oxidase, arginine dihydrolase, and nitrate reductase. Strains did not grow at 36°C, did not rot potato slices, but induced a hypersensitive reaction in tobacco (Nicotiana tabacum cv. Turk). These results suggested the bacterium was similar to Pseudomonas syringae. Fatty acid methyl ester (FAME) analysis (MIS-TSBA 4.10, MIDI Inc., Newark, DE) indicated the strains were highly similar (80.1 to 89.3%) to P. syringae pv. maculicola. However, in contrast to P. syringae pv. maculicola, the spinach strains did not utilize the carbon sources erythritol, L+tartrate, L lactate, and DL-homoserine. Pathogenicity of 10 strains was tested by growing inoculum in nutrient broth shake cultures for 48 h, diluting to 106 CFU/ml, and spraying 4-week-old plants of spinach cv. Bossanova. Control plants were sprayed with sterile nutrient broth. After 5 to 8 days in a greenhouse (24 to 26°C), leaf spots identical to those observed in the field developed on cotyledons and true leaves of inoculated plants. Strains were reisolated from the spots and identified as P. syringae. Control plants remained symptomless. The 10 strains were also inoculated on beet (Beta vulgaris), Swiss chard (Beta vulgaris subsp. cicla), cilantro (Coriandrum sativum), and spinach. Spinach showed leaf spots after 8 days; however, none of the other plants developed symptoms. Two strains were inoculated onto spinach cvs. Califlay, Lion, Nordic IV, Polka, Resistoflay, Rushmore, RZ 11, Spinnaker, Springfield, Viroflay, and Whitney. Leaf spot developed on all cultivars, and the pathogen was reisolated. Because the FAME data indicated a similarity between the spinach pathogen and P. syringae pv. maculicola, we inoculated sets of spinach cv. Bolero, cabbage (Brassica oleracea subsp. capitata cv. Grenedere), and cauliflower (Brassica oleracea subsp. botrytis cv. White Rock) with three P. syringae pv. maculicola and three spinach strains. Cabbage and cauliflower developed leaf spots only when inoculated with P. syringae pv. maculicola; spinach had leaf spots only when inoculated with the spinach strains. All inoculation experiments were done twice, and the results of the two tests were the same. To our knowledge, this is the first report of bacterial leaf spot of spinach in California caused by a nonfluorescent P. syringae, and the first record of this disease in the United States. Biochemical characteristics and limited host range of the pathogen indicate the California strains are likely the same as the P. syringae pv. spinaciae pathogen that was reported in Italy (1) and Japan (2). References: (1) C. Bazzi et al. Phytopathol. Mediterr. 27:103, 1988. (2) K. Ozaki et al. Ann. Phytopathol. Soc. Jpn. 64:264, 1998.

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First Report of Leaf Spot Caused by Pseudomonas cichorii on Coreopsis lanceolata in Italy

Plant Disease ◽

10.1094/pdis-93-9-0967a ◽

2009 ◽

Vol 93 (9) ◽

pp. 967-967 ◽

Cited By ~ 1

Author(s):

A. Garibaldi ◽

G. Gilardi ◽

C. Moretti ◽

M. L. Gullino

Keyword(s):

Leaf Spot ◽

Casein Hydrolysate ◽

Its Region ◽

Soft Rot ◽

Chrysanthemum Morifolium ◽

Luria Bertani ◽

Nutrient Broth ◽

Bacterial Leaf Spot ◽

Pseudomonas Cichorii ◽

First Report

Coreopsis lanceolata L. (Compositae), an ornamental species grown in parks and gardens, is very much appreciated for its long-lasting flowering period. In August of 2008, pot-grown plants with necrotic leaf lesions were observed in a commercial nursery located near Biella (northern Italy). Lesions were present, especially along the margin of basal leaves, and sometimes had a chlorotic halo. On infected leaves, dark brown necrosis developed. Leaf stalks were sometimes affected. In many cases, the leaves, especially those at collar level, were withered. Of 1,500 plants, 15% were infected by the disease. Microscopic examination did not reveal any fungal structures within the lesions. Small fragments of tissue from 30 affected leaves were macerated for 15 min in casein hydrolysate and 0.1-ml aliquots of the resulting suspension were spread onto Luria Bertani agar (LB) and potato dextrose agar (PDA). Plates were maintained at 22 ± 1°C for 48 h. No fungi were isolated from the leaf spots on LB or PDA. Colonies similar to those of Pseudomonas spp. were consistently isolated on LB. Colonies were fluorescent on King's medium B, levan negative, oxidase positive, potato soft rot negative, arginine dihydrolase negative, and tobacco hypersensitivity positive (LOPAT test). The bacterial colonies were identified as Pseudomonas cichorii (2). The internal transcribed spacer (ITS) region of rDNA was amplified using primers 27F and 1492R and sequenced (GenBank Accession No. FJ534557). BLAST analysis (1) of the 998-bp segment showed a 98% homology with the sequence of P. cichorii. The pathogenicity of one isolate was tested twice by growing the bacterium in nutrient broth shake cultures for 48 h at 20 ± 1°C. The suspension was centrifuged, the cell pellet resuspended in sterile water to a concentration of 107 CFU/ml, and 30 4-month-old healthy coreopsis plants were sprayed with the inoculum. The same number of plants was sprayed with sterile nutrient broth as a control. After inoculation, plants were covered with plastic bags for 48 h and placed in a growth chamber at 20 ± 1°C. Five days after inoculation, lesions similar to those seen in the field were observed on all plants inoculated with the bacterium, but not on the controls. Ten days later, 40% of the leaves were withered. Isolations were made from the lesion margins on LB and the resulting bacterial colonies were again identified as P. cichorii. The pathogen caused the same symptoms also on plants of Dendranthema frutescens (cv. Camilla), Chrysanthemum morifolium (cvs. Eleonora and Captiva), and an Osteospermum sp. (cv. Wild side) when artificially inoculated with the pathogen with the same methodology. The same bacterial leaf spot caused by P. cichorii was observed in 2005 in other nurseries in the same area on Phlox paniculata (3). To our knowledge, this is the first report of bacterial leaf spot caused by P. cichorii on C. lanceolata in Italy. References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997. (2) H. Bergey et al. Bergey's Manual on Determinative Bacteriology. Williams and Wilkins, Baltimore, MD, 1994. (3) A. Garibaldi et al. Plant Dis. 89:912, 2005.

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First Report of Bacterial Leaf Spot of Cucumber Caused by Pseudomonas cichorii in China

Plant Disease ◽

10.1094/pdis-02-18-0267-pdn ◽

2019 ◽

Vol 103 (1) ◽

pp. 147

Author(s):

X. Y. Fu ◽

R. Y. Zhang ◽

Z. Q. Tan ◽

T. Liu ◽

Z. Q. Peng

Keyword(s):

Leaf Spot ◽

Bacterial Leaf Spot ◽

Pseudomonas Cichorii ◽

First Report

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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 Bacterial Leaf Spot Caused by Pseudomonas syringae pv. aptata on Swiss Chard, Beta vulgaris subsp. vulgaris, in Arizona

Plant Disease ◽

10.1094/pdis-12-20-2554-pdn ◽

2021 ◽

Author(s):

Marilen Nampijja ◽

Mike Derie ◽

Lindsey J. du Toit

Keyword(s):

Beta Vulgaris ◽

Pseudomonas Syringae ◽

Leaf Spot ◽

Phosphate Buffer ◽

Negative Control ◽

Bacterial Suspension ◽

Bacterial Leaf Spot ◽

First Report ◽

Leaf Spots ◽

Swiss Chard

Arizona is an important region of the USA for winter production of baby leaf crops such as spinach (Spinacia oleracea), table beet (Beta vulgaris subsp. vulgaris Condivita Group), and Swiss chard (B. vulgaris subsp. vulgaris Cicla Group). In the winter of 2019, severe leaf spots were observed at 80% incidence and 40% severity per plant in a 1-ha baby leaf Swiss chard crop of an (unknown cultivar) in Arizona. The lesions were circular to irregular, necrotic, water-soaked, and 1 to 5 mm in diameter. Symptomatic leaf sections (1-cm2) were surface-sterilized with 0.6% NaOCl, rinsed, and macerated in sterilized, deionized water. An aliquot of each macerate was streaked onto King’s B (KB) agar medium. Cream-colored, non-fluorescent colonies typical of Pseudomonas were isolated consistently, and all were non-fluorescent. A dozen isolates selected randomly were all negative for potato soft rot, oxidase, and arginine dihydrolase, and positive for levan production and tobacco hypersensitivity, which is typical of fluorescent P. syringae isolates, but can also include non-fluorescent strains (Lelliot et al. 1966). Three isolates were tested for pathogenicity on the table beet cv. Red Ace and Swiss chard cv. Silverado. Strain Pap009 of P. syringae pv. aptata (Psa), demonstrated previously to be pathogenic on Swiss chard and table beet, served as a positive control strain (Derie et al. 2016; Safni et al. 2016). Each isolate was grown inoculated into medium 523 broth and incubated on a shaker at 175 rpm overnight at 25°C. Each bacterial suspension was adjusted to an optical density (OD) of 0.3 at 600 nm (108 CFU/ml), and diluted in 0.0125M phosphate buffer to 107 CFU/ml. Thirty-day-old seedlings grown in Redi-Earth Plug and Seedling Mix in a greenhouse at 22 to 26°C were inoculated by rubbing the abaxial and adaxial leaf surfaces of each plant with a cotton swab dipped in inoculum to which Carborundum had been added (0.06 g/10 ml). The negative control plants were treated similarly with phosphate buffer with Carborundum. The experiment was set up as a randomized complete block design with 4 replications per treatment and 6 seedlings per experimental unit. In both trials, leaf spots resembling those on the original plants developed on all table beet and Swiss chard plants inoculated with the Arizona isolates and Pap009, but not on negative control plants. Disease severity was greater on Swiss chard (average 39% leaf area with spots) than on table beet (14%). Re-isolates obtained from inoculated seedlings using the same method as the original isolations resembled Psa. Multilocus sequence analysis (MLSA) was carried out for the original three Arizona isolates and the re-isolates using DNA amplified from the housekeeping genes gyrB, rpoD, gapA, and gltA (Hwang et al. 2005; Sarkar and Guttman 2004). Sequence identities of these genes of the Arizona isolates (GenBank accession numbers MW291615 to MW291618 for strain Pap089; MW291619 to MW291622 for Pap095; and MW291623 to MW291626 for Pap096 for gltA, gyrB, rpoD, and gapA, respectively) and the re-isolates ranged from 98 to 100% with those of Psa pathotype strain CFBP 1617 in the PAMDB database (Almeida et al. 2010; Altschul et al. 1997). Based on Koch’s postulates, colony characteristics, and MLSA, Psa was the causal agent of leaf spots in the Arizona Swiss chard crop. To our knowledge, this is the first report of bacterial leaf spot on chard in Arizona. The pathogen could have been introduced on infected seed as Psa is readily seedborne and seed transmitted.

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First Report of Pseudomonas cichorii Causing Leaf Spot of Vegetable Sponge Gourd in China

Plant Disease ◽

10.1094/pdis-03-13-0312-pdn ◽

2014 ◽

Vol 98 (1) ◽

pp. 153-153 ◽

Cited By ~ 3

Author(s):

B. J. Li ◽

H. L. Li ◽

Y. X. Shi ◽

X. W. Xie

Keyword(s):

Leaf Spot ◽

Pathogenic Bacteria ◽

Identification System ◽

Pathogenicity Test ◽

Distilled Water ◽

Pseudomonas Cichorii ◽

First Report ◽

Microbial Identification ◽

Pectolytic Activity ◽

Sponge Gourd

A suspect bacterial leaf spot on vegetable sponge gourd (Luffa cylindrical (L.) Roem.) was found in a commercial greenhouse in Pi County, Chengdu City, Sichuan Province, China, in February 2011. Approximately 20 to 30% of plants were affected, causing serious economic loss. Symptoms occurred only on seedlings and consisted of water-soaked, irregularly shaped, black lesions on the surface and margins of cotyledons. A bacterium was consistently isolated on nutrient agar from diseased leaf tissues that had been surface disinfected in 70% ethyl alcohol for 30 s. The bacterium produced small gray colonies with smooth margins, was gram negative, fluoresced on King's B medium, and showed pectolytic activity when inoculated on potato slices. The partial sequences of 16SrRNA gene (1,377 bp) of the bacterium (GenBank Accession No. KC762217), amplified by using universal PCR primers 16SF (5′-AGAGTTTGATCCTGGCTCAG-3′) and 16SR (5′-GGTTACCTTGTTACGACTT-3′), shared 100% similarity with that of Pseudomonas cichorii (GenBank Accession No. HM190228). The vegetable sponge gourd isolate was also identified by using the Biolog Microbial Identification System (version 4.2, Biolog Inc., Hayward, CA) as P. cichorii with the following characteristics (1): negative for arginine dihydrolase, gelatin liquefaction, and N2 production. Positive reactions were obtained in tests for catalase, oxidase, potato rot, utilization of melibiose, and mannitol. Tests were negative for utilization of sucrose, trehalose, D-arabinose, raffinose, cellobiose, and rhamnose. A pathogenicity test was conducted on 4-week-old vegetable sponge gourd plants by spray-inoculation with 108 CFU/ml sterile distilled water on the leaves of 15 vegetable sponge gourd plants and by needle puncture on the stems of 15 other plants with P. cichorii, respectively. Control plants were misted with sterile distilled water or punctured on the stem with a clean needle. Plants were placed in a greenhouse maintained at 28 ± 2°C with relative humidity of 80 to 85%. Symptoms, the same as seen on the original diseased plants, developed after 7 to 10 days on inoculated plants. Control plants remained healthy. The bacterium was readily re-isolated from inoculated plants and identified as P. cichorii using P. cichorii-specific primer hrpla/hrp2a (1). To our knowledge, this is the first report of P. cichorii causing disease on commercially grown vegetable sponge gourd in China. This new finding will provide the basis for developing resources for diagnostics and management, including screening varieties for resistance. References: (1) S. Mazurier et al. J. FEMS Microbiol. Ecol. 49:455, 2004. (2) N. W. Schaad et al., eds. Laboratory Guide for Identification of Plant Pathogenic Bacteria, 3rd ed. APS Press, St. Paul, MN, 2001.

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First Report of Bacterial Leaf Spot of Swiss Chard Caused by Pseudomonas syringae pv. aptata in California

Plant Disease ◽

10.1094/pdis.2003.87.11.1397b ◽

2003 ◽

Vol 87 (11) ◽

pp. 1397-1397 ◽

Cited By ~ 6

Author(s):

S. T. Koike ◽

D. M. Henderson ◽

C. T. Bull ◽

P. H. Goldman ◽

R. T. Lewellen

Keyword(s):

Fatty Acid ◽

Sugar Beet ◽

Pseudomonas Syringae ◽

Leaf Spot ◽

Nutrient Broth ◽

Pcr Analysis ◽

Bacterial Leaf Spot ◽

First Report ◽

Leaf Spots ◽

Swiss Chard

From 1999 through 2003, a previously unreported disease was found on commercial Swiss chard (Beta vulgaris subsp. cicla) in the Salinas Valley, (Monterey County) California. Each year the disease occurred sporadically throughout the long growing season from April through September. Initial symptoms were water-soaked leaf spots that measured 2 to 3 mm in diameter. As disease developed, spots became circular to ellipsoid, 3 to 8 mm in diameter, and tan with distinct brown-to-black borders. Spots were visible from the adaxial and abaxial sides. Cream-colored bacterial colonies were consistently isolated from spots. Strains were fluorescent on King's medium B, levan positive, oxidase negative, and arginine dihydrolase negative. Strains did not rot potato slices but induced a hypersensitive reaction on tobacco (Nicotiana tabacum cv. Turk). The isolates, therefore, belong in LOPAT group 1 (1). Fatty acid methyl esters (FAME) analysis (MIS-TSBA version 4.10, MIDI Inc., Newark, DE) gave variable results that included Pseudomonas syringae, P. cichorii, and P. viridiflava with similarity indices ranging from 0.91 to 0.95. BOX-polymerase chain reaction (PCR) analysis gave identical banding patterns for the chard isolates and for known P. syringae pv. aptata strains, including the pathotype strain CFBP1617 (2). The bacteria were identified as P. syringae. Pathogenicity of 11 strains was tested by growing inoculum in nutrient broth shake cultures for 48 h, diluting to 10 × 6 CFU/ml, and spraying onto 5-week-old plants of Swiss chard cvs. Red, White, Silverado, and CXS2547. Untreated control plants were sprayed with sterile nutrient broth. After 7 to 10 days in a greenhouse (24 to 26°C), leaf spots similar to those observed in the field developed on all inoculated plants. Strains were reisolated from the spots and identified as P. syringae. Control plants remained symptomless. To investigate the host range of this pathogen, the same procedures were used to inoculate three strains onto other Chenopodiaceae plants: five cultivars of sugar beet (B. vulgaris), and one cultivar each of spinach (Spinacia oleracea) and Swiss chard. In addition, five chard strains and strain CFBP1617 were inoculated onto two cultivars of sunflower (Helianthus annuus), and one cultivar each of cantaloupe (Cucumis melo), sugar beet, spinach, and Swiss chard. All Swiss chard, cantaloupe, sunflower, and sugar beet plants developed leaf spots after 7 days. The pathogen was reisolated from spots and confirmed to be the same bacterium using BOX-PCR analysis. Spinach and untreated controls failed to show symptoms. All inoculation experiments were done at least twice and the results were the same. The phenotypic data, fatty acid and genetic analyses, and pathogenicity tests indicated that these strains are P. syringae pv. aptata. To our knowledge this is the first report of bacterial leaf spot of commercially grown Swiss chard in California caused by P. syringae pv. aptata. The disease was particularly damaging when it developed in Swiss chard fields planted for “baby leaf” fresh market products. Such crops are placed on 2-m wide beds, planted with high seed densities, and are sprinkler irrigated. This disease has been reported from Asia, Australia, Europe, and other U.S. states. References: (1) R. A. Lelliott et al. J. Appl. Bacteriol. 29:470, 1966. (2) J. L. W. Rademaker et al. Mol. Microbiol. Ecol. Man. 3.4.3:1–27, 1998.

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