First Report of a Fruit Rot of Pumpkin Caused by Acidivorax avenae subsp. citrulli in Georgia

In September 1998, a fruit rot was reported affecting pumpkin (Cucurbita pepo) in a commercial field in Terrell Co., Georgia. Symptoms on the surface of fruit occurred as round, necrotic spots or cracks a few millimeters in diameter. With age, the tissue surrounding these lesions became soft and wrinkled. A soft rot expanded into the flesh of the pumpkin, originating from the lesions observed on the surface. In time, infected pumpkins totally collapsed. V-shaped, necrotic lesions occurred at the margin of the leaf and extended inward toward the mid-rib. Samples were collected from the field and bacteria were isolated from fruit and leaf lesions onto King's medium B (1). The bacterium isolated was rod shaped, gram negative, nonflourescent, oxidase positive, Tween 80 positive, carboxymethyl cellulose positive, β-OH butyrate positive, and malonate negative. The bacterium reacted positively with polyclonal antibodies specific for the watermelon fruit blotch pathogen Acidivorax avenae subsp. citrulli and was identified as A. avenae subsp. citrulli by MIDI (Microbial Identification System, Newark, DE) according to statistical analysis of fatty acid data. Results from polymerase chain reaction (PCR) amplification of the bacterium isolated from pumpkin yielded 360-bp fragments that, when digested with the restriction enzyme HaeIII, had DNA banding patterns identical to those of stock A. avenae subsp. citrulli DNA. Koch's postulates were completed successfully with 2-week-old watermelon seedlings. This is the first report of A. avenae subsp. citrulli causing fruit rot of pumpkin in Georgia. Reference: (1) E. O. King et al. J. Lab. Clin. Med. 44:301, 1954.

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Natural Outbreak of a Bacterial Fruit Rot of Cantaloupe in Georgia Caused by Acidovorax avenae subsp. citrulli

Plant Disease ◽

10.1094/pdis.2000.84.3.372d ◽

2000 ◽

Vol 84 (3) ◽

pp. 372-372 ◽

Cited By ~ 3

Author(s):

R. R. Walcott ◽

D. B. Langston ◽

F. H. Sanders ◽

R. D. Gitaitis ◽

J. T. Flanders

Keyword(s):

Tween 80 ◽

Soft Rot ◽

Fatty Acid Analysis ◽

Fruit Rot ◽

Enzyme Linked Immunosorbent Assay ◽

Identification System ◽

Microbial Identification ◽

Leaf Tissues ◽

Different Sources ◽

Natural Outbreak

In April and July 1999, cantaloupe plants (Cucumis melo) from commercial greenhouses and fields in Grady, Colquitt, Mitchell, and Tift counties, GA, exhibited severe foliar necrosis and a fruit rot. Foliar symptoms were V-shaped, necrotic lesions occurring at the margin of the leaf and extending inward toward the midrib. Symptoms on the fruit surface were observed after net development and occurred randomly as round, necrotic, sunken spots or cracks a few millimeters in diameter. A soft rot originating from lesions on the surface of the fruit expanded into the flesh. Approximately 5% of the fruits were affected. Bacteria recovered from cantaloupe fruit and leaf tissues produced nonfluorescent, smooth, off-white colonies on King's medium B. Characteristic of Acidovorax avenae subsp. citrulli, the bacteria produced pits in carboxymethyl cellulose media (WFB 44), and reduced Tween 80 to give a visible precipitate on WFB 68 media (1). Based on fatty acid analysis, all strains were identified as A. avenae subsp. citrulli by Microbial Identification System software, version 3.6 (MIDI, Newark, DE), and similarity indices of 0.06, 0.79, 0.21, and 0.43 were recorded for strains recovered form Grady, Tift, Colquitt, and Mitchell counties, respectively. Using specific oligonucleotide primers (WFB 1/2) (2), PCR conducted on DNA from each strain yielded a 390-bp DNA fragment, confirming similarity to A. avenae subsp. citrulli. Indirect enzyme-linked immunosorbent assay with genus-specific antibodies also verified that the bacteria were Acidovorax spp. Pathogenicity of the A. avenae subsp. citrulli strains was confirmed by inoculating and observing symptom development on 2-week-old watermelon seedlings. Although all strains were identified and confirmed as A. avenae subsp. citrulli, restriction fragment length polymorphism data indicated that the Tift County strain was distinguishable from the others, suggesting that inoculum for these outbreaks may have originated from at least two different sources. References: (1) R. D. Gitaitis. 1993. Development of a seedborne assay for watermelon fruit botch. Pages 9–18 in: Proc. 1st Int. Seed Testing Assoc. Plant Dis. Commit., Ottawa, Canada. (2) R. R. Walcott and R. D. Gitaitis. (Abstr.) Phytopathology 88(suppl.):S92, 1998.

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First Report of Soft Rot Caused by Pectobacterium carotovorum on Pinellia ternata in China

Plant Disease ◽

10.1094/pdis-91-10-1359c ◽

2007 ◽

Vol 91 (10) ◽

pp. 1359-1359 ◽

Cited By ~ 5

Author(s):

F. X. Ying ◽

X. F. Hu ◽

J. S. Chen

Keyword(s):

Disease Outbreaks ◽

Soft Rot ◽

Shanxi Province ◽

Identification System ◽

Pectobacterium Carotovorum ◽

Gene Encoding ◽

Pinellia Ternata ◽

First Report ◽

Microbial Identification ◽

Physiological And Biochemical Characteristics

Pinellia ternata (Thumb.) Breit. (Araceae) is a traditional herb used as an antivomit, anticough, analgesic, and sedative in China for more than 1,000 years. From the summer through fall of 2003 to 2005, a high incidence (approximately 10 to 25%) of disease outbreaks characterized by water-soaked lesions and soft rot with a stinky odor were observed in the cultivated P. ternata in Shanxi Province. Water-soaked lesions were first observed on the stem base and then the plant collapsed, although the upper portion remained asymptomatic. Subsequently, the lesions expanded rapidly over the entire plant. The macerated tuber was usually reduced to a whitish, mushy, and foul-smelling pulp surrounded by undecayed periderm. A Pectobacterium species was consistently recovered from the diseased tubers on nutrient agar media. Koch's postulates were completed by stab inoculating 6-week-old peach- and willow-leaved P. ternata cultivars with the bacterial suspensions (1 × 108 CFU/ml) (1). Ten control plants for each cultivar were inoculated with sterile water. After inoculation, plants were maintained in a growth chamber at 25°C with relative humidity ranging from 80 to 90%. After 2 to 3 days, typical soft rot symptoms were observed on the inoculated plants. A Pectobacterium species was reisolated from the symptomatic tubers while control plants remained healthy. This experiment was repeated in May, July, and September. The pathogenic isolates were identified as typical Pectobacterium carotovorum on the basis of morphological, physiological, and biochemical characteristics (2). The Microlog system (version 3.5; Biolog, Hayward, CA) and Sherlock Microbial Identification System (version 4.5; MIDI Newark, DE) also identified them as Pectobacterium carotovorum on the basis of similarity indices more than 66.9 and 78.2%, respectively. Their identity was then confirmed by sequencing the gene encoding the 16S rRNA (GenBank Accession No DQ785511). To our knowledge, this is the first report of Pectobacterium carotovorum as the cause of soft rot of P. ternata. References: (1) H. R. Azad et al. Plant Dis.84:973, 2000. (2) L. Hauben et al. Syst. Appl. Microbiol. 21:384, 1998.

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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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Fruit Rot of Tinda Caused by Pseudomonas aeruginosa–A New Report from India

Plant Disease ◽

10.1094/pdis-05-11-0404 ◽

2012 ◽

Vol 96 (1) ◽

pp. 141-141 ◽

Cited By ~ 3

Author(s):

K. K. Mondal ◽

C. Mani ◽

J. Singh ◽

S. R. Dave ◽

D. R. Tipre ◽

...

Keyword(s):

Pseudomonas Aeruginosa ◽

16S Rrna ◽

Bacterial Species ◽

Soft Rot ◽

Fruit Rot ◽

Polar Flagellum ◽

Identification System ◽

Rrna Gene ◽

Causal Bacterium ◽

Praecitrullus Fistulosus

Fruit rot disease (FRD), an emerging problem of tinda (Praecitrullus fistulosus) in India. FRD epidemics begin during rainy and warm weather and often spoil marketable produce. Symptoms appear as numerous, pale brown-to-dark brown, deeply penetrating circular soft rot lesions on fleshy fruit tissues. Noneffervescent bacterial exudates occasionally form on lesions. Repeated isolations from FRD-affected tinda fruits consistently yielded the same bacterial species. Inoculation of the isolated bacterium into asymptomatic tinda fruits produced identical soft rot symptoms. Fruits were inoculated with the isolate ITCC B0030 (0.1 OD) by removing a 2.0-cm deep tissue plug with a sterile cork borer (5 mm in diameter) and injecting the inoculum with a syringe in the cylindrical cavity. After inoculation, the plug (upper 5 mm) was reinserted, sealed with sterile paraffin, and covered with a small piece of wet absorbent cotton to prevent dehydration. High humidity (>90%) and 30 to 33°C temperature was maintained after inoculation in a glasshouse. After 4 to 10 days, fruits showed FRD symptoms. The reisolated bacterium from artificially inoculated symptomatic fruits was identical with the original inoculated bacterium. Identity of the bacterial pathogen for FRD was confirmed by phenotypic and genotypic methods. The causal bacterium was a gram-negative, non-sporing motile rod with a single polar flagellum. The bacterium produced yellowish green and blue-green diffusible pigments on King's B (KB) medium. On yeast dextrose calcium carbonate agar at 30°C, the colonies produced abundant, blue, diffusible pigment within 48 h. The bacterium grew at temperatures up to 42°C but not at 4°C. Excellent growth occurred on Salmonella-Shigella agar and MaConkey's medium, as reported also for Pseudomonas aeruginosa strain P8. The bacterium produced ammonia, hydrogen sulfide, arginine dihydrolase, urease, lipase, catalase, gelatinase, and casinase but not amylase, indole, or acetyl methyl carbinol. The bacterium was identified as P. aeruginosa using Biolog based Bacterial Identification System version 4.2 (Biolog Inc., Hayward, CA). The bacterium did not utilize cellobiose, dulcitol, maltose, sorbitol, sucrose, arabinose, and starch. Upon infiltration on tobacco leaves (Nicotiana tabacum cv. Xanthi) at 107 or more cells ml–1, the bacterium gave a strong hypersensitive reaction within 24 h. Transmission electron micrographs (TEM, KYKY 1000B, Japan) of the causal bacterium revealed a single, polar flagellum. Identity was further confirmed as P. aeruginosa based on 16S rRNA sequence (1,491 nt) analysis with universal primers F1 (5′-GAGTTTGATCCTGGCTCAG-3′) and R13 (5′-AGAAAGGAGGTGATCCAGCC-3′). A blastN search of GenBank revealed a >99% nt identity with P. aeruginosa strain TAUC 7 (HQ914782). The 16S rRNA gene sequence (1,491 nt) was deposited in Bankit GenBank (JF797204). To our knowledge, this is the first report of fruit rot of tinda caused by P. aeruginosa in India (ITCC B0030) and a new record of bacterial rot of Praecitrullus fistulosus induced by a fluorescent and blue-green pigment producing P. aeruginosa. To date, P. syringae pv. lachrymans and a nonfluorescent P. pseudoalcaligenes subsp. citrulli were reported to infect Citrullus lanata (1) and Praecitrullus fistulosus (2), respectively. References: (1) D. L. Hopkins and N. C. Schenck. Phytopathology 62:542, 1972. (2) N. W. Schaad et al. Int. J. Syst. Bacteriol. 28:117, 1978.

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First Report of Bacterial Leaf Spot of Basil Caused by Pseudomonas viridiflava in Argentina

Plant Disease ◽

10.1094/pdis.1999.83.9.876b ◽

1999 ◽

Vol 83 (9) ◽

pp. 876-876 ◽

Cited By ~ 4

Author(s):

A. M. Alippi ◽

S. Wolcan ◽

E. Dal Bó

Keyword(s):

Leaf Spot ◽

Disease Incidence ◽

Tween 80 ◽

Pathogenic Fungi ◽

Soft Rot ◽

Bacterial Leaf Spot ◽

First Report ◽

Arginine Dihydrolase ◽

Pseudomonas Viridiflava ◽

Physiological Tests

In June 1998, during a cool, humid period, typical bacterial spot symptoms were observed on basil plantlets (Ocimun basilicum L. ‘Royal Louis’ and ‘Zaes’) in a commercial greenhouse in La Plata, Argentina. Affected plants had dark brown to black lesions on cotyledons. Spots on leaves were first water soaked, then became necrotic and progressed inward from the margins. Disease incidence approached 30%. Symptoms were similar to those reported by Little et al. (2) on basil affected by Pseudomonas viridiflava. No pathogenic fungi or viruses were associated with symptomatic plants. Bacterial streaming was observed from lesion margins. Bacteria consistently isolated from leaf lesions formed cream-colored, glistening, convex colonies on sucrose peptone agar and a green fluorescent pigment on King's medium B. Bacterial growth produced a distinctive olive green pigment on glycerol agar medium and a pink pigment on T-5 medium (1). Four isolates selected for further study were aerobic, Gram-negative, non-spore-forming rods. In LOPAT (levan-oxidase-potato rot-arginine dihydrolase-tobacco hypersensitivity) tests, all induced a hypersensitive response in tobacco plants, caused soft rot of potato tubers, and were negative for levan, oxidase, and arginine dihydrolase. In addition, strains rotted onion slices and produced a reddish sunken lesion on bean pods. Acid was produced aerobically from D-glucose, mannitol, mesoinositol and sorbitol, but not from D-arabinose, L-rhamnose, melibiose, amygdalin, or sucrose. Bacteria used D-tartrate, pyruvate, and citrate, but not benzoate. The strains did not hydrolyze starch, exhibited an oxidative metabolism of glucose, and did not reduce nitrates to nitrites or accumulate poly-β-hydroxybutyrate inclusions. Negative reactions were obtained with indole, ornithine, and D-tryptophan. Isolates hydrolyzed gelatine, used Tween 80, were positive for catalase, and were unable to grow in the presence of 5% NaCl. Colonies developed at 4°C but not 37°C. Reactions were identical to those of reference strains ICMP 5776 and 12363, which were included in all tests for comparison. Pathogenicity was verified on 35-day-old basil plants by both spraying and infiltration inoculations with bacterial suspensions (108 and 105 cells per ml, respectively). Carborundum was included in the inoculum used for a set of plants inoculated by spraying. Controls were injected or sprayed (with and without Carborundum) with sterile, distilled water. In addition, bean (Phaseolus vulgaris cv. Nag12 INTA) and lettuce (Lactuca sativa cv. criolla), both reported as host plants, were inoculated by spraying with bacterial suspensions of 107 cells per ml plus Carborundum. After 48 h in a humid chamber, inoculated plants and controls were maintained at 23 ± 3°C. Symptoms on basil plants inoculated by injection or spraying with Carborundum were identical to those observed on basil in the field. Symptoms on bean and lettuce were similar to those described for P. viridiflava. The bacterium was reisolated from lesions of all species tested, fulfilling Koch's postulates. No lesions were observed on controls or on plants sprayed without Carborundum, suggesting that bacteria gain entry through wounds. The microorganism was identified by physiological tests and polymerase chain reaction as P. viridiflava. This is the first report of bacterial leaf spot of basil in Argentina. References: (1) R. Gitaitis et al. Plant Dis. 81:897, 1997. (2) E. L. Little et al. Plant Dis. 78:831, 1994.

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First Report of a Lasmenia sp. Causing Rachis Necrosis, Flower Abortion, Fruit Rot, and Leaf Spots on Rambutan in Puerto Rico

Plant Disease ◽

10.1094/pdis-05-11-0366 ◽

2011 ◽

Vol 95 (10) ◽

pp. 1313-1313 ◽

Cited By ~ 5

Author(s):

L. M. Serrato-Diaz ◽

L. I. Rivera-Vargas ◽

R. Goenaga ◽

G. J. M. Verkley ◽

R. D. French-Monar

Keyword(s):

Puerto Rico ◽

Plant Tissue ◽

Fruit Rot ◽

Conidial Suspension ◽

University Of Puerto Rico ◽

Tropical Fruit ◽

First Report ◽

Flower Abortion ◽

Necrotic Spots ◽

The University

Rambutan (Nephelium lappaceum L.) is a tropical fruit tree that has increased in importance for fruit growers in Puerto Rico. In 2008 and 2009, fruit rot and lesions on leaves and inflorescences were observed. A total of 276 diseased samples were collected from commercial orchards, orchards at the University of Puerto Rico, and the USDA-ARS in Mayaguez. Plant tissue was disinfested and plated on acidified potato dextrose agar (APDA). Besides other typical fungi associated with these tissue samples (2,3), 130 unknown isolates were identified as a Lasmenia sp. at the Fungal Biodiversity Centre (CBS), the Netherlands and the University of Puerto Rico using taxonomic keys (1,4). Sequencing of the rDNA with primers ITS 1 and ITS 4 and Lr5 and LR0R corresponding to the (internal transcribed spacer) ITS1-5.8S-ITS2 region and the partial region of the large ribosomal subunit (LSU), respectively, was completed. Five isolates (CBS 124122 to 124126) were deposited at the CBS. In APDA, colonies of a Lasmenia sp. were cream-colored with dark brown concentric rings and immersed, hyaline, branched, and septate mycelium. Acervuli were produced on APDA and plant tissue that was sampled from field and clean tissue that was inoculated with a Lasmenia sp. Conidia were 10 to 12 × 4 to 5 μm, light brown, thick walled, obclavate, aseptate, and the apex was obtuse with a scar at the base. Conidiophores were hyaline, septate, cylindrical, and sparingly branched. The conidiogenous cells were hyaline, cylindrical, and holoblastic. Pathogenicity tests were done on 12 healthy, superficially sterilized fruits under laboratory conditions, on four random leaves in each of six 6-month-old rambutan seedlings under greenhouse conditions, and on four flowers in six random inflorescences for each of six mature trees from an orchard. Tests were repeated. Either wounded or unwounded tissues were inoculated with a conidial suspension (2 to 4.5 × 106 conidia/ml) and 5-mm mycelial disks from each fungal isolate grown in APDA. After 5 days, a Lasmenia sp. produced necrotic spots on leaves, rachis necrosis and flower abortion, fruit rot, and water-soaked lesions on the fruit surface that spread to cause an aril (flesh) rot. Acervuli were produced on fruit spintems (hair-like appendages). Koch's postulates were fulfilled by reisolation of inoculated fungi from diseased tissue. A complete sequence for the ITS region for four isolates of a Lasmenia sp. was submitted to NCBI GenBank (Accession Nos. GU797405, GU797406, GU797407, and JF838336). Complete sequences of the LSU region for all five isolates were submitted to GenBank (Accession Nos. JF838337, JF838338, JF838339, JF838340, and JF838341). For both types of sequences, the identity was 100% between isolates. Although there is no DNA sequence data for the genus Lasmenia, a BLASTN search indicates a closer affinity to the Cryphonectriaceae (Diaporthales) (1). A Lasmenia sp. has been reported from Hawaii as causing fruit rot in rambutan (2). To our knowledge, this is the first report of a Lasmenia sp. causing rachis necrosis and flower abortion worldwide, and the first report of fruit rot and necrotic spots on leaves of rambutan in Puerto Rico. References: (1) M. N. Kamat et al. Rev. Mycol. 38:19, 1973. (2) K. A. Nishijima and P. A. Follett. Plant Dis. 86:71, 2002. (3) L. M. Serrato et al. Phytopathology (Abstr.) 100(suppl):S176, 2010. (4) B. C. Sutton. The Coelomycetes: Fungi Imperfecti with Pycnidia Acervuli and Stromata. CMI. Kew, Surrey, England, 1980.

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First Report of Fusarium solani Fruit Rot of Pumpkin (Cucurbita pepo) in Trinidad

Plant Disease ◽

10.1094/pdis-93-5-0547b ◽

2009 ◽

Vol 93 (5) ◽

pp. 547-547

Author(s):

S. N. Rampersad

Keyword(s):

Fusarium Solani ◽

Cucurbita Pepo ◽

Morphological Characteristics ◽

Soft Rot ◽

The United States ◽

Fruit Rot ◽

Laboratory Manual ◽

First Report ◽

Pathogenicity Tests ◽

Negative Controls

Trinidad is a major exporter of pumpkins (Cucurbita pepo L.) to other Caribbean countries, Canada, and the United States. Producers and exporters have reported 50 to 80% yield losses because of soft rot and overnight collapse of fruit at the pre- and postharvest stages. Severe fruit rot occurred in fields in Victoria County in South Trinidad between April and May 2006 (mid-to-late dry season) with an increase in the severity and number of affected fruit in the rainy season (July to December). Symptoms began as water-soaked lesions on the fruit of any age at the point of contact with the soil. The disease progressed to a soft rot with leakage and whole fruit collapse. A dark brown, soft decay also developed at the base of the main vines. Fusarium solani was isolated on selective fusarium agar and potato dextrose agar (PDA) (1) after 7 to 10 days of incubation at 25°C. The pathogen was identified by morphological characteristics and pathogenicity tests. Colonies were fast growing with white aerial mycelia and a cream color on the reverse side; hyphae were septate and hyaline, conidiophores were unbranched, and microconidia were abundant, thin walled, hyaline, fusiform to ovoid, generally one to two celled, and 8 to 10 × 2 to 4 μm. Macroconidia were hyaline, two to three celled, moderately curved, thick walled, and 25 to 30 × 4 to 6 μm. Pathogenicity tests for 10 isolates were conducted on 2-week-old pumpkin seedlings (cv. Jamaican squash; seven plants per isolate) and mature pumpkin fruit (2). Briefly, seedlings were inoculated by dipping their roots in a spore suspension (1 × 104 spores per ml) for 20 min. The plants were repotted in sterile potting soil. For negative controls, plant roots were dipped in sterile water. After the rind of fruit was swabbed with 70% ethanol followed by three rinses with sterile distilled water, 0.4-cm-diameter agar plugs of the isolates were inserted into wounds made with a sterile 1-cm-diameter borer. Sterile PDA plugs served as negative controls. Fruit were placed in sealed, clear, plastic bags. Inoculated plants and fruit were placed on greenhouse benches (30 to 32°C day and 25 to 27°C night temperatures) and monitored over a 30-day period. Tests were repeated once. Inoculated fruit developed a brown, spongy lesion that expanded from the initial wound site over a period of approximately 17 days after inoculation. White mycelia grew diffusely over the lesion. Inoculated plants developed yellow and finally necrotic leaves and lesions developed on stems at the soil line approximately 21 days after inoculation. No symptoms developed on the control plants. The fungus was reisolated from symptomatic tissue, fulfilling Koch's postulates. To my knowledge, this is the first report of Fusarium fruit rot of pumpkin in Trinidad. References: (1) J. Leslie and B. Summerell. Page 1 in: The Fusarium Laboratory Manual. Blackwell Publishing, Oxford, 2006. (2) W. H. Elmer. Plant Dis. 80:131, 1996.

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First Report of Leaf Blight of Onion Caused by Xanthomonas campestris in the Continental United States

Plant Disease ◽

10.1094/pdis.2000.84.2.201c ◽

2000 ◽

Vol 84 (2) ◽

pp. 201-201 ◽

Cited By ~ 13

Author(s):

T. Isakeit ◽

M. E. Miller ◽

L. W. Barnes ◽

E. R. Dickstein ◽

J. B. Jones

Keyword(s):

United States ◽

Xanthomonas Campestris ◽

Acid Methyl Ester ◽

Leaf Blight ◽

Nutrient Agar ◽

Identification System ◽

Sterile Water ◽

First Report ◽

Microbial Identification ◽

Similarity Indices

In March 1998, a leaf blight of onion (Allium cepa L. ‘1015’) was found on many plants in a plot on the Texas A&M Agricultural Experiment Station in Weslaco. The symptoms were longitudinal chlorotic areas on one side of the leaf, containing sunken, elliptical necrotic lesions. Affected leaves ultimately died. Chlorotic lesions were swabbed with 70% ethanol, and tissue from beneath the epidermis was placed in a drop sterile water for 20 min. Drops were streaked on nutrient agar and incubated at 30°C. Isolations yielded gram-negative, rod-shaped bacteria that formed dark yellow, gummy colonies on yeast dextrose carbonate agar medium, hydrolyzed starch, and had a single, polar flagellum. Analysis of fatty acid methyl ester (FAME) profiles, using the Microbial Identification System (MIS, version 4.15; Microbial Identification, Newark, DE), done at the Texas Plant Disease Diagnostic Laboratory, College Station, identified nine isolates as Xanthomonas campestris (similarity indices of 0.31 to 0.54). Tests at the University of Florida supported this identification: FAME profiles using MIS version 3.9 gave similarity indices of 0.89 to 0.95, and profiles using Biolog GN Microplates, MicroLog database release 3.50 (Biolog, Hayward, CA), gave similarity indices of 0.03 to 0.76. Leaves (15 to 20 cm long) of potted onions (cv. 1015 at the five- to six-leaf stage) were infiltrated with a suspension of bacteria (107 CFU per ml), using a needle and syringe. Plants were maintained in mist chamber in a greenhouse at 24°C. Water-soaking and development of pale green color of the inoculated leaf occurred after 2 days, followed by death after 4 days. There were no symptoms on leaves inoculated with sterile water. Pathogenicity tests on four isolates were repeated once. Bacteria were reisolated on nutrient agar from symptomatic tissue but not from controls. In the field plot, disease severity did not increase as season progressed nor were there any symptoms on bulbs. Symptoms were not observed on onion during the 1999 season. X. campestris was first reported on onion from Hawaii (1). This is the first report of this pathogen on onion in the continental United States. Reference: (1) A. M. Alvarez et al. Phytopathology 68:1132, 1978.

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Wildfire of Soybean Caused by Pseudomonas syringae pv. tabaci, a New Disease in Korea

Plant Disease ◽

10.1094/pdis-93-11-1214a ◽

2009 ◽

Vol 93 (11) ◽

pp. 1214-1214 ◽

Cited By ~ 3

Author(s):

I.-S. Myung ◽

J.-W. Kim ◽

S. H. An ◽

J. H. Lee ◽

S. K. Kim ◽

...

Keyword(s):

Pseudomonas Syringae ◽

Pathogenic Bacteria ◽

Similarity Index ◽

Soft Rot ◽

Universal Primers ◽

Identification System ◽

Bacterial Disease ◽

Bacterial Strains ◽

Microbial Identification ◽

Soybean Leaves

In 2006 and 2007, a new bacterial disease was observed in field-cultivated soybeans in Boeun District and Munkyung City of Korea. The disease caused severe blighting of soybean (Glycine max) leaves. Soybean leaves in fields showed yellowish spots with brown centers. Brown and dead areas of variable size and shape were surrounded by wide, yellow haloes with distinct margins. Spots might coalesce and affected leaves fell readily. Seven bacterial strains were isolated from chlorotic areas of soybean leaves and all produced white colonies on trypticase soy agar. With the Biolog Microbial Identification System, version 4.2, (Biolog Inc., Hayward, CA) all strains and Pseudomonas syringae pv. tabaci CFBP2106T were identified as P. syringae pv. tabaci with a Biolog similarity index of 0.28 to 0.52 and 0.48 after 24 h. Pathogenicity of the strains (three plants per strain) on soybean leaves at the V5 stage (cv. Hwanggeum) was confirmed by rub inoculation with bacterial suspensions (1 × 108 CFU/ml) in sterile distilled water on the lesions cut 1 cm long on the upper side of the leaves with razor blades and by pinprick on 3-week-old leaves of tobacco (Nicotiana tabacum cv. Samsun) in the greenhouse. Wildfire symptoms on the soybean leaves and faint halos on tobacco leaves were observed 4 days after inoculation. The identification of reisolated bacterial strains was confirmed with the metabolic fingerprintings on Biolog. LOPAT tests (1) and phenotypic characteristics (3) of the strains were similar to those of the CFBP2106T. Colonies were levan positive, oxidase negative, potato soft rot negative, arginine dihydrase negative, and tobacco hypersensitivity negative. All strains were gram-negative, aerobic rods with a polar flagellum. Strains were negative for esculin hydrolysis, gelatin liquefaction, urea production, accumulation of poly-β-hydroxy butyrate, starch hydrolysis, ornithine dihydrolase, lysine dihydrolase, growth at 37°C, utilization of geraniol, benzoate, cellobiose, sorbitol, trehalose, l-rhamnose, and adonitol. Positive reactions were catalase and arbutin hydrolysis, utilization of sorbitol, d-arabinose, and dl-serine. The strains were variable in utilization of mannitol, sucrose, and d-arabinose. The 1,472-bp PCR fragments of strains, BC2366 (GenBank Accession No. FJ755788) and BC2367 (No. FJ755789) was sequenced using 16S rDNA universal primers (2). The sequences shared 100% identity with the analogous sequences of P. syringae pv. glycenea (GenBank Accession No. AB001443) available in NCBI databases. Based on the phenotypic, genetic, and pathological characteristics, all strains were identified as P. syringae pv. tabaci. To our knowledge, this is the first report of P. syringae pv. tabaci causing wildfire on soybean in Korea. References: (1) R. A. Lelliott et al. J. Appl. Bacteriol. 29:470, 1966. (2) I.-S. Myung et al. Plant Dis. 92:1472, 2008. (3) N. W. Schaad et al., eds. Laboratory Guide for Identification of Plant Pathogenic Bacteria. 3rd ed. The American Phytopathological Society, St. Paul, MN, 2001.

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First Report of Fusarium proliferatum Infecting Pimento Chili Peppers in Trinidad

Plant Disease ◽

10.1094/pdis-03-11-0194 ◽

2011 ◽

Vol 95 (10) ◽

pp. 1313-1313 ◽

Cited By ~ 1

Author(s):

S. N. Rampersad ◽

L. D. Teelucksingh

Keyword(s):

Pcr Amplification ◽

Fusarium Proliferatum ◽

Fruit Rot ◽

Universal Primers ◽

Its2 Region ◽

Distilled Water ◽

Marketable Yield ◽

First Report ◽

Plant Pathol ◽

Chili Peppers

In Trinidad, pimento chili peppers (Capsicum annuum L.) are grown for large domestic and regional export markets. Production is intensive during the rainy season (June to December). In August 2010, pimento fruits with symptoms of fruit rot were collected from fields located in Tableland, Valencia, Aranguez-North and -South, and Macoya. Symptoms began as a discoloration and soft rot of the peduncle and calyx (green to brown then black); a tan, watery lesion (with irregular margins) developed and expanded rapidly from the calyx down the sides of the fruit with internal rot of the placenta. Excessive fruit drop was also common. Estimated yield loss was ~20 to 60% for each field. Symptoms were observed on green and red fruits. Fruits were surface disinfected (2 min in 70% ethanol, 2 min in 0.5% NaOCl, followed by three rinses with sterile distilled water) and then a 4-mm3 block of tissue was taken from the lesion edge and placed on water agar. After 7 days at 25 ± 1°C, a 4-mm3 block of agar that contained the advancing hyphal edge of each colony was transferred to selective fusarium agar (3) and incubated as previously described. Colonies were fast growing with white, fluffy, aerial mycelia; hyphae densely branched; polyphialides abundant; microconidia abundant, thin walled, hyaline, ovoid, aseptate or 1-celled, and 5.5 to 12.2 × 2.0 to 3.2 μm. Macroconidia were moderately curved to straight, hyaline, 3- to 4-celled, thick walled, and 20.5 to 35.0 × 3.5 to 5.0 μm. Molecular characterization was based on a two-loci approach. PCR amplification was carried out with universal primers (ITS4/5) and translation elongation factor primers (EF1/2) (2). Sequences of the ITS1-5.8S-ITS2 region of rDNA (GenBank Accession No. HQ333547) and partial EF-1α gene (GenBank Accession No. HQ333548) were compared to cognate sequences available in GenBank and the FUSARIUM-ID databases (2). Comparisons revealed 100% similarity to Fusarium proliferatum (Matsush.) Nirenberg ex Gerlach & Nirenberg 1982. F. proliferatum (synonym Gibberella intermedia) is the anamorphic form of the G. fujikuroi complex that belongs to the Nectriaceae family (4). Pathogenicity tests were conducted by dispensing 10 μl of a prepared spore suspension (106 spores/ml) onto nonwounded and wounded sites of pimento fruits (landrace ‘Trinidad seasoning’, 10 fruits per isolate, 8 isolates). Negative controls were fruits inoculated with sterile distilled water. Inoculated fruits were kept at 25 ± 1°C in partially sealed plastic containers and monitored for the onset of symptoms for 7 days. The test was conducted twice. Lesions, similar to those recorded on field infected fruit, developed on inoculated fruits that were wounded and nonwounded, but not on water controls. The pathogen was reisolated from infected tissues, thereby fulfilling Koch's postulates. F. proliferatum is associated with disease of a number of economically important crops and ornamental plants worldwide (1). Fusarium fruit rot of pepper has been shown to significantly reduce marketable yield and shelf life of infected fruits. To our knowledge, this is the first report of Fusarium fruit rot of pimento chili peppers caused by F. proliferatum in Trinidad. References: (1) J. Armengol et al. Eur. J. Plant Pathol. 112:123, 2005. (2) D. M. Geiser et al. Eur. J. Plant Pathol. 110:473, 2004. (3) J. Leslie and B. Summerell. Page 1 in: The Fusarium Laboratory Manual. Blackwell Publishing, Oxford, UK, 2006. (4) H. Nirenberg and K. O'Donnell. Mycologia 90:434, 1998.

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