First Report of bacterial speck caused by Pseudomonas syringae pv. tomato Race 1 affecting tomato in different Regions of Chile

In Chile, tomato is one of the most widely cultivated vegetables, with around 5,000 ha for fresh market and 8,000 ha for processing industry. During recent years, symptoms of bacterial speck caused by Pseudomonas syringae pv. tomato, have been observed more frequently in tomato plants in different regions of Chile. This pathogen was first identified in Chile in 1987 (Latorre & Lolas, 1988) and the presence of an apparent new variant was reported in 2004 (Besoain et al. 2004). To characterize the pathogen that was affecting this crop, samples of diseased tomato plants were taken in three regions of Chile. The samples were collected in 2016 in Northern Chile in Lluta Valley from the Arica y Parinacota Region, and in Central Chile, in 2014 in Limache from Valparaíso Region and in 2015 in Pichidegua from O´Higgins Region. Affected tomato plants exhibited dark brown to black lesions surrounded by yellow halos in the leaves, and dark brown to black lesions in the stems, pedicels, and peduncles. Plants tissues were macerated, and the suspension was spread on King’s B medium, resulting in fluorescent colonies visualized under 366 nm UV light. LOPAT tests results of three selected isolates from different Regions, were: levan production (+), oxidase reaction (-), potato soft rot (-), arginine dihydrolase production (-), and tobacco hypersensitivity (+) (Lelliot et al. 1966). Molecular identification was carried out by amplification and sequence analysis of housekeeping genes cts, encoding citrate synthase, gyrB, encoding DNA gyrase B, and rpoD, encoding sigma factor 70 (Hwang et al. 2005; Sarkar & Guttmann 2004) (GenBank Accessions No. OK001658-OK001666). BLAST analysis of cts and rpoD genes of the three isolates resulted in a match with a 100% identity (919 bp and 491 bp respectively) with Pseudomonas syringae pv. tomato strain B13-200 (GenBank: CP019871.1). BLAST analysis of gyrB gene of two isolates resulted in a match with a 100% identity (684 bp) and one isolate with 99.85% (683 bp) with Pseudomonas syringae pv. tomato strain B13-200. To identify the race 1, each strain was inoculated in five tomato plants cv. San Pedro, susceptible to both races of P. syringae pv. tomato, and cv. Rio Grande, resistant to race 0. The tomato plants were slightly wounded with a metal sponge and then sprayed with the bacterial suspension (108 CFU mL-1) of each isolate, including the reference strain DC3000 (race 0). Negative controls were sprayed with water. The plants inoculated with Chilean strains in both cv. San Pedro and cv. Rio Grande, showed symptoms of bacterial speck after 7 days. Plants inoculated with DC3000 strain showed symptoms only in cv. San Pedro, whereas control plants remained asymptomatic. Strains were re-isolated from symptomatic plants and identified by gene sequence analyses as Pseudomonas syryngae pv. tomato. This is the first report of Pseudomonas syryngae pv. tomato race 1 in Chile. Race 1 was previously reported in Canada (Lawton and MacNeill. 1986), in Italy (Buonaurio et al. 1996), in California (Arredondo and Davis 2000), in Portugal (Cruz et al. 2010), and in other states in the USA and countries in South America, Europe, Africa, and Australia, becoming the most commonly isolated race today (Cai et al 2011). These results will be the base for future studies of epidemiology, characterization, and virulence in order to explain the outbreak of this disease and the severity of symptoms observed.

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First Report of Copper-Tolerant Pseudomonas syringae pv. tomato in Virginia

Plant Disease ◽

10.1094/pdis.1999.83.10.964c ◽

1999 ◽

Vol 83 (10) ◽

pp. 964-964 ◽

Cited By ~ 11

Author(s):

S. A. Alexander ◽

S. H. Kim ◽

C. M. Waldenmaier

Keyword(s):

Pseudomonas Syringae ◽

Untreated Control ◽

Block Design ◽

Cupric Sulfate ◽

Fresh Market ◽

Tomato Plants ◽

First Report ◽

Bacterial Speck ◽

Significant Difference ◽

Copper Tolerant

Bacterial speck of tomato, caused by Pseudomonas syringae pv. tomato, is an important disease of fresh-market tomatoes along the Eastern Shore of Virginia. P. syringae pv. tomato was first identified in Northampton County on 17 May 1993, using the Biolog software program. During the spring of 1998, a field of tomato plants showed symptoms of bacterial speck. Three isolations on tryptic soy agar were made from symptomatic leaves and fruit tissues taken from young transplanted tomato plants, cv. Sunpride. The isolates were identified as P. syringae pv. tomato, using Biolog. A representative isolate was sent to the Pennsylvania Department of Agriculture, Plant Disease Diagnostic Laboratory, Harrisburg, for confirmation. The Virginia isolate was transferred to King's medium B, and identification of P. syringae pv. tomato was confirmed by fulfilling Koch's postulates, matching with the Biolog database, and testing for levan production (+), oxidase reaction (-), potato soft rot (-), arginine dihydrolase production (-), and tobacco hypersensitivity (+). In vitro growth inhibition of the 1998 Virginia P. syringae pv. tomato isolate required anhydrous cupric sulfate at 368 μg/ml compared with only 175 μg/ml for a known copper-sensitive 1998 Pennsylvania isolate. Therefore, the 1998 Virginia isolate was considered a copper-tolerant strain of P. syringae pv. tomato. For field evaluation, three copper treatments and two noncopper treatments were established in a randomized complete block design replicated four times. Treatments were initiated on 19 May and reapplied every 7 days for a total of 10 applications. Three disease ratings were taken every 7 days beginning on 30 June. For copper hydroxide (2.24 kg/ha; Kocide DF) plus mancozeb (2.24 kg/ha; Dithane); chlorothalonil (2.34 liters/ha; Bravo) plus copper salts of fatty and rosin acids (2.34 liters/ha; Tenncop); 2% maneb plus 66% copper sulfate (6.72 kg/ha; Cuprofix); and an untreated control, area under the disease progress curve (AUDPC) values were 319, 468, 478, and 438, respectively. There was no significant difference (P = 0.05) between the copper treatments and untreated control, confirming laboratory findings. In contrast, noncopper treatments of acibenzolar (21g/ha; Actigard), and acibenzolar (21 g/ha) plus mancozeb (2.24 kg/ha) (Actigard plus Dithane) were significantly different (P = 0.05) from the untreated control and copper treatments with AUDPC values of 116 and 160, respectively. This is the first report of copper-tolerant P. syringae pv. tomato in Virginia.

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Pseudomonas syringae pv. tomato Strains from New York Exhibit Virulence Attributes Intermediate Between Typical Race 0 and Race 1 Strains

Plant Disease ◽

10.1094/pdis-03-17-0330-re ◽

2017 ◽

Vol 101 (8) ◽

pp. 1442-1448 ◽

Cited By ~ 5

Author(s):

Christine M. Kraus ◽

Carolina Mazo-Molina ◽

Christine D. Smart ◽

Gregory B. Martin

Keyword(s):

New York ◽

Pseudomonas Syringae ◽

Host Immune System ◽

Fresh Market ◽

Tomato Plants ◽

Persistent Problem ◽

Population Sizes ◽

Bacterial Speck Disease ◽

Race 1 ◽

Susceptible Tomato

Bacterial speck disease, caused by Pseudomonas syringae pv. tomato, is a persistent problem for fresh-market tomato growers in New York. Race 0 strains of this pathogen express either or both of the type III effectors AvrPto or AvrPtoB, which are recognized by tomato varieties expressing the Pto resistance gene. Pto encodes a protein kinase that activates the host immune system, thereby inhibiting bacterial multiplication and preventing disease development. Race 1 P. syringae pv. tomato strains do not express these effectors and are virulent on tomato whether or not the variety expresses Pto. Very few fresh-market tomato varieties have the Pto gene. We collected six P. syringae pv. tomato strains from naturally infected tomato plants across New York in 2015 and characterized them for their virulence and for the presence of specific effectors. In experiments conducted in the greenhouse, all strains reached population sizes in Pto-expressing tomato leaves that were intermediate between typical race 0 and race 1 strains. This phenotype has not been observed previously and suggests that the strains are recognized by Pto but such recognition is compromised by another P. syringae pv. tomato factor. The strains were found to encode avrPto, which is transcribed and translated. They also express avrPtoB although, as reported for other P. syringae pv. tomato strains, protein expression for this effector was not detectable. Deletion of avrPto from a representative New York strain allowed it to reach high populations in Pto-expressing tomato varieties, without compromising its virulence on susceptible tomato plants. Collectively, our data suggest that introgression of the Pto gene into fresh-market tomato varieties could enhance protection against extant P. syringae pv. tomato strains.

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First Report of Bacterial Speck of Tomato Caused by Pseudomonas syringae pv. tomato Race 1 in Portugal

Plant Disease ◽

10.1094/pdis-06-10-0415 ◽

2010 ◽

Vol 94 (12) ◽

pp. 1504-1504 ◽

Cited By ~ 4

Author(s):

L. Cruz ◽

J. Cruz ◽

M. Eloy ◽

H. Oliveira ◽

H. Vaz ◽

...

Keyword(s):

Resistance Gene ◽

Open Field ◽

Pseudomonas Syringae ◽

Biochemical Characterization ◽

Negative Control ◽

Scientific Publications ◽

First Report ◽

Bacterial Speck ◽

Rpod Gene ◽

Race 1

Protected and open field tomato crops are economically important for Portuguese agriculture. In 1983, Pseudomonas syringae pv. tomato (Okabe, 1933) Young, Dye & Wilkie, 1978 was first reported affecting protected crops (3) and then later under open field conditions (1). In the 2009 spring/summer season, several outbreaks of bacterial speck of tomato showing an unusual degree of severity were observed in open fields from the Tagus Valley Region. Typical symptoms included necrotic specks surrounded by a yellow halo on younger and older leaves with losses higher than 60% due to the heavy floral bud abortion. Abnormal lesions on the stems, as well as on the petioles and fruits, together with reduced growth of the entire plant, which is normally uncommon, were frequently observed in affected plants from distinct tomato cultivars (H-9665, H-9776, and CDX 255), two of them carrying the Pto resistance gene. Samples collected from different fields and cultivars were observed and used for isolation of the causal agent on King's medium B. The isolates were characterized (2) and Koch's postulates were fulfilled by carrying out pathogenicity tests. Ten plants from three commercial cultivars carrying the Pto resistance gene (CXD 255, Defender F1, and H-9775) were inoculated by spraying bacterial water suspensions (108 CFU ml–1) and kept under environmental conditions favorable for disease development. Positive and negative controls were also performed using P. syringae pv. tomato type strain (CFBP 2212T; race 0) and sterile distilled water, respectively. Cultural and biochemical characterization of the isolates showed their ability to produce levan, use sucrose, and induce a hypersensitivity reaction on tobacco leaves. Moreover, the isolates were oxidase negative, did not hydrolyze arginine nor produce soft rot on potato slices, and did not use erythritol as well as dl-lactate, identifying them as P. syringae pv. tomato. Typical and severe bacterial speck symptoms were produced in the Pto resistant tomato plants 4 days after inoculation and the isolates could be recovered after reisolation. Negative control plants showed no disease symptoms and CFBP 2212 was unable to produce typical lesions, except for a few in the older leaves. Altogether these results pointed to P. syringae pv. tomato race 1 as the disease causative agent. Further confirmation was achieved by partial sequencing of the rpoD gene using primers PsrpoD FNP1 and PsrpoDnprpcr1 (4). rpoD sequences, obtained from two isolates (CPBF 1288, GenBank HM368535; CPBF 1290, GenBank HM368537), were compared by nucleotide BLAST at NCBI displaying a 100% level of DNA similarity with strain Pto T1 belonging to P. syringae pv. tomato race 1. To our knowledge, this is the first report of the occurrence of Pseudomonas syringae pv. tomato race 1 in Portugal. References: (1) L. Cruz et al. ATTI Giornate Fitopatol, 2:399, 1992. (2) R. Lelliott and D. Stead. Methods for the Diagnosis of Bacterial Diseases of Plants. Blackwell Scientific Publications, Oxford, 1987. (3) H. Oliveira and J. Santa-Marta. Pseudomonas syringae pv. tomato (Okabe, 1933) Young, Dye & Wilkie, 1978. Uma nova bacteriose do tomateiro em Portugal. Publicação do Laboratório de Patologia Vegetal “Veríssimo de Almeida”, 1983. (4). S. Sarkar et al. Genetics 174:1041, 2006.

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Occurrence of Pseudomonas syringae pv. Tomato race 1 in Italy on Pto Gene-Bearing Tomato Plants

Journal of Phytopathology ◽

10.1111/j.1439-0434.1996.tb00320.x ◽

1996 ◽

Vol 144 (9-10) ◽

pp. 437-440 ◽

Cited By ~ 14

Author(s):

R. Buonaurio ◽

V. M. Stravato ◽

C. Cappelli

Keyword(s):

Pseudomonas Syringae ◽

Tomato Plants ◽

Race 1

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Protection of Tomato Seedlings against Infection by Pseudomonas syringae pv. Tomato by Using the Plant Growth-Promoting Bacterium Azospirillum brasilense

Applied and Environmental Microbiology ◽

10.1128/aem.68.6.2637-2643.2002 ◽

2002 ◽

Vol 68 (6) ◽

pp. 2637-2643 ◽

Cited By ~ 72

Author(s):

Yoav Bashan ◽

Luz E. de-Bashan

Keyword(s):

Plant Growth ◽

Pseudomonas Syringae ◽

Azospirillum Brasilense ◽

Dry Weight ◽

Tomato Plants ◽

Bacterial Speck ◽

Plant Growth Promoting ◽

Bacterial Speck Disease ◽

Growth Promoting ◽

Mist Chamber

ABSTRACT Pseudomonas syringae pv. tomato, the causal agent of bacterial speck of tomato, and the plant growth-promoting bacterium Azospirillum brasilense were inoculated onto tomato plants, either alone, as a mixed culture, or consecutively. The population dynamics in the rhizosphere and foliage, the development of bacterial speck disease, and their effects on plant growth were monitored. When inoculated onto separate plants, the A. brasilense population in the rhizosphere of tomato plants was 2 orders of magnitude greater than the population of P. syringae pv. tomato (107 versus 105 CFU/g [dry weight] of root). Under mist chamber conditions, the leaf population of P. syringae pv. tomato was 1 order of magnitude greater than that of A. brasilense (107 versus 106 CFU/g [dry weight] of leaf). Inoculation of seeds with a mixed culture of the two bacterial strains resulted in a reduction of the pathogen population in the rhizosphere, an increase in the A. brasilense population, the prevention of bacterial speck disease development, and improved plant growth. Inoculation of leaves with the mixed bacterial culture under mist conditions significantly reduced the P. syringae pv. tomato population and significantly decreased disease severity. Challenge with P. syringae pv. tomato after A. brasilense was established in the leaves further reduced both the population of P. syringae pv. tomato and disease severity and significantly enhanced plant development. Both bacteria maintained a large population in the rhizosphere for 45 days when each was inoculated separately onto tomato seeds (105 to 106 CFU/g [dry weight] of root). However, P. syringae pv. tomato did not survive in the rhizosphere in the presence of A. brasilense. Foliar inoculation of A. brasilense after P. syringae pv. tomato was established on the leaves did not alleviate bacterial speck disease, and A. brasilense did not survive well in the phyllosphere under these conditions, even in a mist chamber. Several applications of a low concentration of buffered malic acid significantly enhanced the leaf population of A. brasilense (>108 CFU/g [dry weight] of leaf), decreased the population of P. syringae pv. tomato to almost undetectable levels, almost eliminated disease development, and improved plant growth to the level of uninoculated healthy control plants. Based on our results, we propose that A. brasilense be used in prevention programs to combat the foliar bacterial speck disease caused by P. syringae pv. tomato.

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First Report of Bacterial Canker Caused by Pseudomonas syringae pv. morsprunorum Race 1 on Peach from Khyber Pakhtunkhwa Province of Pakistan

Plant Disease ◽

10.1094/pdis-10-17-1618-pdn ◽

2018 ◽

Vol 102 (10) ◽

pp. 2027-2027 ◽

Cited By ~ 2

Author(s):

R. Ahmed ◽

M. Inam-ul-Haq ◽

U. Shahzad ◽

S. Hyder ◽

S. Shahzaman ◽

...

Keyword(s):

Pseudomonas Syringae ◽

Bacterial Canker ◽

First Report ◽

Khyber Pakhtunkhwa ◽

Race 1 ◽

Khyber Pakhtunkhwa Province

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The Ptr1 locus of Solanum lycopersicoides confers resistance to race 1 strains of Pseudomonas syringae pv. tomato and to Ralstonia pseudosolanacearum by recognizing the type III effectors AvrRpt2/RipBN

10.1101/518399 ◽

2019 ◽

Author(s):

Carolina Mazo-Molina ◽

Samantha Mainiero ◽

Sara R. Hind ◽

Christine M. Kraus ◽

Mishi Vachev ◽

...

Keyword(s):

Pseudomonas Syringae ◽

Genetic Resistance ◽

Site Directed Mutagenesis ◽

Type Iii Effector ◽

Bacterial Speck ◽

Solanum Lycopersicoides ◽

Type Iii ◽

Bacterial Speck Disease ◽

Race 1 ◽

Ralstonia Pseudosolanacearum

AbstractRace 1 strains of Pseudomonas syringae pv. tomato, which causes bacterial speck disease of tomato, are becoming increasingly common and no simply-inherited genetic resistance to such strains is known. We discovered that a locus in Solanum lycopersicoides, termed Pseudomonas tomato race 1 (Ptr1), confers resistance to race 1 Pst strains by recognizing the type III effector AvrRpt2. In Arabidopsis, AvrRpt2 degrades the RIN4 protein thereby activating RPS2-mediated immunity. Ptr1 also recognized homologs of AvrRpt2 from diverse bacteria including one in Ralstonia pseudosolanacearum and this correlated with the ability of AvrRpt2 to degrade RIN4. Using site-directed mutagenesis of AvrRpt2 we found that Ptr1 and RPS2 recognize identical features of AvrRpt2. However, the genome sequence of S. lycopersicoides revealed no RPS2 homolog in the Ptr1 region. Ptr1 could play an important role in controlling bacterial speck disease and its future cloning may shed light on an example of convergent evolution for recognition of a widespread type III effector.

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Sources of resistance to races R0 and R1 of Pseudomonas syringae PV. tomato - agent of bacterial speck on tomato

Genetika ◽

10.2298/gensr1701139g ◽

2017 ◽

Vol 49 (1) ◽

pp. 139-149 ◽

Cited By ~ 1

Author(s):

Daniela Ganeva ◽

Nevena Bogatzevska

Keyword(s):

Pseudomonas Syringae ◽

Morphological Characters ◽

Sources Of Resistance ◽

Breeding Lines ◽

Bacterial Speck ◽

Development Of Resistance ◽

Gene Carriers ◽

Race 1 ◽

Tomato Breeding ◽

Selection Of

Tomato breeding lines with fruit colour different from the traditional red colour were studied in order to search for sources of resistance to races R0 and R1 of Pseudomonas syringae pv. tomato. As a result of selection of healthy plants with hypersensitive response (HR), the resistance was stabilized and perspective lines gene-carriers of resistance to bacterial speck were chosen. Lines L1078 and L1083 with brown-red (black) coloured fruits and line L1130 with purple-red fruits possess a complex resistance to races R0 and R1. It was established that two of the lines with rose-coloured tomato fruits (L1088 and L584) were resistant to race 1 of P. syringae pv. tomato. These lines possessed valuable economic and morphological characters and they could be used in combinative and heterosis breeding for development of resistance to bacterial speck varieties.

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First Report of Bacterial Canker Caused by Pseudomonas syringae pv. morsprunorum Race 1 on Cherry in Chile

Plant Disease ◽

10.1094/pdis-11-20-2524-pdn ◽

2021 ◽

Author(s):

Hector Garcia ◽

Elisa Miranda ◽

Miguel Abelardo López ◽

Samuel Parra ◽

Carlos Rubilar ◽

...

Keyword(s):

Pseudomonas Syringae ◽

Prunus Avium ◽

Disease Incidence ◽

Agar Plate ◽

Bacterial Suspension ◽

Post Inoculation ◽

Accession Number ◽

First Report ◽

Race 1 ◽

Necrotic Spots

Chile is the main exporter of sweet cherries (Prunus avium), with a total of 228.6 thousand tons exported in the 2019-20 season, and a production from the Coquimbo to the Aysén region (http://www.iqonsulting.com/yb/). In January 2019, cherry trees from a commercial orchard located near Osorno city (40°37'S, 72°54'W), Region de Los Lagos, Chile, showed symptoms such as the presence of wood cankers, necrotic spots in leaves, and premature defoliation, with a mean disease incidence near 40%. Symptomatic leaves with necrotic spots were collected for analysis, from which all the necrotic spots were extracted by incision with a sterile scalpel, macerated in 30 mL of AFT buffer and subsequently, 100 µL of the suspension was plated on King’s B (KB) agar and incubated for 48 to 72 h at 27°C, obtaining a total of two bacterial colonies identified as 7684.1 and 7684.2. Afterward, each colony was stroked in a new KB agar plate, incubated for 16 h at 27°C, and the obtained biomass was used in subsequent experiments. In KB agar, both colonies exhibited fluorescence under UV light and, according to the LOPAT method (Lelliott et al., 1966), they were gram negative, positive to levan and tobacco hypersensitivity tests and negative to oxidase, potato soft rot, arginine dihydrolase and gelatin tests, and were confirmed as Pseudomonas syringae. Then, the 16s and gyrB genes of each isolate were amplified by PCR, sequenced, and compared with the NCBI Genbank database (Weisburg et al., 1991; Sarkar and Guttman, 2004), finding a 99,93% genetic similarity (1064/1065) with a previously reported 16s sequence of a Pseudomonas syringae pv. morsprunorum (Psm) isolate (accession number CP026558.1), and a 99,69% (636/638) with a previously reported gyrB gene of Psm (accession number LC364094.1), respectively. Additionally, the closest pathovar different to morsprunorum aligned with our gyrB sequence was P. syringae pv. aesculin, with 97,8% of identity (624/638). Our sequences were deposited in Genbank with the accession numbers MN528473 (16s), MN535696 (gyrB) for 7684.1, and MN528474 (16s), MN535697 (gyrB) for 7684.2. To identify if the isolates correspond to Psm races 1 (Psm1) or 2 (Psm2), race-specific conventional PCRs and qPCRs assays were carried out using the specific primers described by Kaluzna et al., (2016), showing that the two isolates were positive to Psm1 in both PCR assays. Pathogenicity was tested by inoculating immature cherry fruitlets (cv. Sweetheart) with bacterial suspension at 108 CFU/mL. For each strain, ten fruitlets were inoculated by pricking with a sterile needle previously immersed in the bacterial suspension (Ruinelli et al., 2019). Sterile distilled water was used as negative control. Seven to fourteen days post-inoculation, necrotic and water-soaked brown lesions with yellow margins were observed on the fruits inoculated with bacterial strains. The pathogen was reisolated and confirmed as Pseudomonas syringae pv. morsprunorum by 16s and gyrB sequencing, and as race 1 by race-specific PCRs. Our results were confirmed by the National Plant Protection Organization, (Servicio Agrícola y Ganadero de Chile, SAG), generating the first report of Psm race 1 in Chile. Thus, SAG established new protocols for quarantine of absent pests in the national territory (Resol. N°3080, SAG, Chile), and an immediate phytosanitary program for Psm (Resol. Exenta N°8948/2019, SAG, Chile). In conclusion, our discovery contributes to the monitoring and control of the disease in Chile.

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

Plant Disease ◽

10.1094/pdis-91-4-0462c ◽

2007 ◽

Vol 91 (4) ◽

pp. 462-462 ◽

Cited By ~ 13

Author(s):

K. C. Shenge ◽

R. B. Mabagala ◽

C. N. Mortensen ◽

D. Stephan ◽

K. Wydra

Keyword(s):

Pseudomonas Syringae ◽

Uv Light ◽

Disease Incidence ◽

Leaf Spot Disease ◽

Polymorphism Analysis ◽

Tomato Fruits ◽

First Report ◽

Bacterial Speck ◽

Small Water ◽

Tomato Seedlings

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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