scholarly journals First Report of Fire Blight on Pear Trees Caused by Erwinia amylovora in Kurdistan Province, Iran

Plant Disease ◽  
2013 ◽  
Vol 97 (8) ◽  
pp. 1111-1111 ◽  
Author(s):  
S. N. Mollaei ◽  
B. Harighi
Keyword(s):  
Fire Blight ◽  
Erwinia Amylovora ◽  
Reca Gene ◽  
Phylogenetic Position ◽  
Bacterial Suspension ◽  
Sodium Hypochlorite Solution ◽  
Pathogenicity Test ◽  
First Report ◽  
Appl Environ ◽  
Pear Trees

Pear (Pyrus L.) is one of the most widely grown crops in western Iran. Since 2010, an outbreak of a disease with symptoms similar to fire blight has been observed on pear trees in various locations of Kurdistan Province. Initial flower symptoms include water-soaking and rapidly shriveling, infected flowers that remained hanging on the trees. Immature fruits become water-soaked, turned brown, and shriveled. Infected flowers and immature fruits were collected from different locations in the province. Small pieces (about 1 mm2) were excised from infected tissues, surface sterilized with 0.5% sodium hypochlorite solution, followed by rinsing in sterile-distilled water (SDW). Each piece was macerated in 2 to 3 ml of SDW, streaked onto nutrient agar sucrose or eosin methylene blue agar media, and incubated at 27 to 29°C. After 48 to 72 h, single colonies were subcultured onto the same media and stored at 4°C. In total, 74 bacteria were isolated from infected tissues. All isolates were gram-negative and rod-shaped. Based on other phenotypic properties, strains were grouped into three clusters at a similarity level of 65% (data not shown). Forty-one and 23 strains showed properties as expected for Erwinia amylovora and Enterobacter sp., respectively. Other strains showed properties resembling Pantoea agglomerans. All strains identified as E. amylovora produced an expected DNA fragment of about 900 bp by PCR using primers PE29A and PE29B corresponding to plasmid pEA29 (1). The result was confirmed by using primers AMSbL and AMSbR derived from the ams region required for amylovoran synthesis of E. amylovora. E. amylovora strains produced an expected 1,600-bp fragment (2). For the pathogenicity test, a bacterial suspension was adjusted to approximately 1 × 107 CFU/ml from cell cultures grown in nutrient broth at 27°C for 48 h. Immature pear fruits sterilized with 70% ethanol and rinsed with SDW were injected with the bacterial suspension using a 25-gauge sterile needle. Fruits injected with sterile water were used as controls. Pear fruits were kept in a mist chamber at 27 to 29°C. Symptoms were assessed up to 2 weeks after inoculation. All E. amylovora strains produced typical symptoms on inoculated immature pear fruits. Necrosis and oozing of bacterial exudates were observed after 3 to 7 days. The phylogenetic position of two selected strains was analyzed by sequence comparison of recA gene among other species in the genus Erwinia and related bacteria. The recA sequence of bacterial strains identified as E. amylovora revealed high similarity (99%) to the E. amylovora type strain (CFBP 1430). Genetic diversity of selected strains was assessed and compared with E. amylovora reference strain CFBP 1430 using ERIC and REP primers in rep-PCR analysis. (3). UPGMA cluster analysis of the combined data obtained in the rep-PCR experiments using Dice's coefficient revealed that the majority of E. amylovora strains showed the same fingerprint patterns at a similarity level of 93%, indicating genetic homogeneity among strains but clearly separated from Enterobacter sp. and P. agglomerans strains. To our knowledge, this is the first report that characterizes the phenotypic and genetic properties of E. amylovora in western part of Iran. References: (1) S. Bereswill et al. Appl. Environ. Microbiol. 58:3522, 1992. (2) S. Bereswill et al. Appl. Environ. Microbiol. 61:2636, 1995. (3) J. Versalovic et al. Mol. Cell Biol. 5:25, 1994.

scholarly journals First Report of Fire Blight Caused by Erwinia amylovora on Cotoneaster dammeri cv. Skogholm in Croatia

Plant Disease ◽  
2008 ◽  
Vol 92 (10) ◽  
pp. 1468-1468
Author(s):  
I. Križanac ◽  
A. Vukadin ◽  
E. Ðermić ◽  
B. Cvjetković
Keyword(s):  
Fire Blight ◽  
Erwinia Amylovora ◽  
Polyclonal Antibodies ◽  
Immunofluorescence Assay ◽  
Plant Tissues ◽  
Species Identity ◽  
First Report ◽  
Appl Environ ◽  
Inoculation Site ◽  
Plant Pathol

In July of 2007, fire blight symptoms were observed on Cotoneaster dammeri cv. Skogholm in a nursery near Županja, Vukovarsko-Srijemska County, in eastern Croatia. In this region, the first outbreak of fire blight was noted on apple in 1995 (2). Symptoms on cotoneaster were necrotic shoots and petioles. Immunofluorescence assay (IFA) with polyclonal antibodies (Loewe Biochemica GmbH, Sauerlach, Germany) was performed on extracts from blighted C. dammeri cv. Skogholm shoots and were found to be positive for Erwinia amylovora. Round, mucoid, whitish colonies were isolated from extracts of plant tissues with symptoms of fire blight spread on King's medium B and incubated for 2 days at 28°C. Bacterial ooze and necrosis of the inoculation site were observed on immature pear fruits inoculated with a 106 CFU/ml suspension of the isolate. Bacteria were reisolated and the species identity was confirmed by PCR and primers targeting pEA29 DNA (1). E. amylovora was previously reported only on native Cotoneaster spp. (3). To our knowledge, this is the first report of fire blight on C. dammeri cv. Skogholm from a commercial ornamental nursery in Croatia. References: (1) S. Bereswill et al. Appl. Environ. Microbiol. 58:3522, 1992. (2) B. Cvjetković et al. Glas. zaštite bilja 1:13, 1996. (3) E. Halupecki et al. Eur. J. Plant Pathol. 114:435, 2006.

scholarly journals First Report of Fire Blight Caused by Erwinia amylovora on Crabapple (Malus floribunda) in Turkey

Plant Disease ◽  
2013 ◽  
Vol 97 (9) ◽  
pp. 1244-1244
Author(s):  
K. K. Bastas ◽  
A. Y. Ozturk
Keyword(s):  
Fire Blight ◽  
Erwinia Amylovora ◽  
Hypodermic Needle ◽  
Bacterial Suspension ◽  
Bacterial Strains ◽  
First Report ◽  
Molecular Tests ◽  
Malus Floribunda ◽  
Shoot Blight ◽  
Reference Strains

Fire blight is a destructive and sporadic disease of crabapple (Malus floribunda) and other plants in the Rosaceae in many areas of the world. From 2007 to 2010, sudden wilting, shriveling of flowers, leaf and shoot blight, and cankers with brown discoloration on twigs of crabapple were observed in residential landscapes of Konya Province, Turkey. Disease incidence ranged from 20 to 40% in different areas of this province, and surveys showed that ~163 ha were infested. Isolations were made from sections of symptomatic leaves, shoots, and cankers using 70% ethanol for 1 s to surface-sterilize the tissue sections, followed by rinsing three times in sterilized distilled water (SDW). Then, a 1 g subsample of each tissue section was homogenized in 10 ml phosphate buffered saline (PBS), and a 10-fold serial dilution of each homogenate prepared for six dilutions. From each homogenate, an aliquot of each dilution was plated onto 5% nutrient sucrose agar and King's B agar media, and the plates incubated for 2 to 3 days at 27°C (3). Bacterial strains were identified on the basis of biochemical, physiological (2), and molecular tests (1). Twenty-seven representative bacterial strains were each gram negative, rod-shaped, mucoid, fermentative, yellow-orange on Miller and Scroth agar medium, positive for levan formation and acetoin production, and showed no growth at 36°C. The strains were also positive for gelatin hydrolysis and negative for esculin hydrolysis, indole, urease, catalase, oxidase, arginine dihydrolase, reduction of nitrate, and acid production from lactose and inositol (2). Two reference strains of Erwinia amylovora (EaP28 and NCPPB 2791) from a culture collection at Selcuk University were used as positive control strains. All strains induced a hypersensitive response in tobacco (Nicotiana tabaccum cv. White Burley) plants within 24 h after inoculation with a 108 CFU/ml bacterial suspension in SDW (~50 μl), and the strains produced ooze on inoculated immature pear fruit slices cv. Ankara. All strains were identified as E. amylovora using the species-specific primers A/B (1), which amplified a 1 kb DNA fragment by PCR assay. Pathogenicity was confirmed by inserting a suspension (108 CFU/ml SDW) of each of the 27 bacterial strains and two reference strains, EaP28 and NCPPB 2791, into actively growing shoot tips of 3-year-old plants of M. floribunda cv. Hilleri, using a 0.46 mm-diameter hypodermic needle. Leaf and shoot blight symptoms typical of fire blight were observed within 2 weeks. SDW was injected similarly as a negative control treatment, and no symptoms were observed. All tests were repeated three times with the same results. Re-isolations were done from the control plants as well as shoots and leaves inoculated with the two reference strains and the 27 bacteria identified as E. amylovora. Bacteria isolated from inoculated plants were identified as E. amylovora using the biochemical, physiological, and molecular tests described above, but this bacterium was not isolated from the control plants. To our knowledge, this is the first report of E. amylovora on crabapple in Turkey. References: (1) S. Bereswill et al. Appl. Environ. Microbiol. 58:3522, 1992. (2) A. L. Jones and K. Geider. Laboratory Guide for Identification of Plant Pathogenic Bacteria, pp. 40-55, American Phytopathological Society, St. Paul, MN, 2001. (3) R. A. Lelliott and D. E. Stead. Methods for Diagnosis of Bacterial Diseases of Plants (Methods in Plant Pathology). Oxford, UK, 1987.

scholarly journals First Report of Bleeding Canker of Pear Tree Trunks Caused by Dickeya fangzhongdai in Korea

Plant Disease ◽  
2021 ◽  
Author(s):  
Eu Ddeum Choi ◽  
Youngmin Kim ◽  
Yerim Lee ◽  
Min-Hye Jeong ◽  
Gyoung Hee Kim ◽  
...  
Keyword(s):  
16S Rrna ◽  
Intergenic Spacer ◽  
Fine Powder ◽  
Luria Bertani ◽  
Bacterial Suspension ◽  
Post Inoculation ◽  
Pathogenicity Test ◽  
Flower Bud ◽  
First Report ◽  
Pear Tree

Pears (Pyrus pylifolia L.) are cultivated nationwide as one of the most economically important fruit trees in Korea. At the end of October 2019, bleeding canker was observed in a pear orchard located in Naju, Jeonnam Province (34°53′50.54″ N, 126°39′00.32″ E). The canker was observed on trunks and branches of two 25-year-old trees, and the diseased trunks and branches displayed partial die-back or complete death. When the bark was peeled off from the diseased trunks or branches, brown spots or red streaks were found in the trees. Bacterial ooze showed a rusty color and the lesion was sap-filled with a yeasty smell. Trunks displaying bleeding symptoms were collected from two trees. Infected bark tissues (3 × 3 mm) from the samples were immersed in 70% ethanol for 1 minute, rinsed three times in sterilized water, ground to fine powder using a mortar and pestle, and suspended in sterilized water. After streaking each suspension on Luria-Bertani (LB) agar, the plates were incubated at 25°C without light for 2 days. Small yellow-white bacterial colonies with irregular margins were predominantly obtained from all the samples. Three representative isolates (ECM-1, ECM-2 and ECM-3) were subjected to further characterization. These isolates were cultivated at 39 C, and utilized (-)-D-arabinose, (+) melibiose, (+)raffinose, mannitol and myo-inositol but not 5-keto-D-gluconate, -gentiobiose, or casein. These isolates were identified as Dickeya sp. based on the sequence of 16S rRNA (MT820458-820460) gene amplified using primers 27f and 1492r (Heuer et al. 2000). The 16S rRNA sequences matched with D. fangzhongdai strain ND14b (99.93%; CP009460.1) and D. fangzhongdai strain PA1(99.86%; CP020872.1). The recA, fusA, gapA, purA, rplB, and dnaX genes and the intergenic spacer (IGS) regions were also sequenced as described in Van der wolf et al. (2014). The recA (MT820437-820439), fusA (MT820440-820442), gapA (MT820443-820445), purA (MT820446-820448), rplB (MT820449-820451), dnaX (MT820452-820454) and IGS (MT820455-820457) sequences matched with D. fangzhongdai strains JS5, LN1 and QZH3 (KT992693-992695, KT992697-992699, KT992701-992703, KT992705-992707, KT992709-992711, KT992713-992715, and KT992717-992719, respectively). A neighbor-joining phylogenetic analysis based on the concatenated recA, fusA, gapA, purA, rplB, dnaX and IGS sequences placed the representative isolates within a clade comprising D. fangzhongdai. ECM-1 to 3 were grouped into a clade with one strain isolated from waterfall, D. fangzhongdai ND14b from Malaysia. Pathogenicity test was performed using isolate ECM-1. Three two-year-old branches and flower buds on 10-year-old pear tree (cv. Nittaka), grown at the National Institute of Horticultural and Herbal Science Pear Research Institute (Naju, Jeonnam Province in Korea), were inoculated with 10 μl and 2 μl of a bacterial suspension (108 cfu/ml), respectively, after wounding inoculation site with a sterile scalpel (for branch) or injecting with syringe (for flower bud). Control plants were inoculated with water. Inoculated branches and buds in a plastic bag were placed in a 30℃ incubator without light for 2 days (Chen et al. 2020). Both colorless and transparent bacterial ooze and typical bleeding canker were observed on both branches and buds at 3 and 2 weeks post inoculation, respectively. No symptoms were observed on control branches and buds. This pathogenicity assay was conducted three times. We reisolated three colonies from samples displaying the typical symptoms and checked the identity of one by sequencing the dnaX locus. Dickeya fangzhongdai has been reported to cause bleeding canker on pears in China (Tian et al. 2016; Chen et al. 2020). This study will contribute to facilitate identification and control strategies of this disease in Korea. This is the first report of D. fangzhongdai causing bleeding canker on pears in Korea.

scholarly journals Characterization of Serracin P, a Phage-Tail-Like Bacteriocin, and Its Activity against Erwinia amylovora, the Fire Blight Pathogen

2002 ◽  
Vol 68 (11) ◽  
pp. 5704-5710 ◽  
Author(s):  
Abdelhamid Jabrane ◽  
Ahmed Sabri ◽  
Philippe Compère ◽  
Philippe Jacques ◽  
Isabel Vandenberghe ◽  
...  
Keyword(s):  
Fire Blight ◽  
Erwinia Amylovora ◽  
Culture Supernatant ◽  
Bacterial Disease ◽  
Amino Acid Sequence Analysis ◽  
Terminal Amino Acid ◽  
Phage Tail ◽  
Terminal Amino ◽  
Pear Trees

ABSTRACT Serratia plymithicum J7 culture supernatant displayed activity against many pathogenic strains of Erwinia amylovora, the causal agent of the most serious bacterial disease of apple and pear trees, fire blight, and against Klebsiella pneumoniae, Serratia liquefaciens, Serratia marcescens, and Pseudomonas fluorescens. This activity increased significantly upon induction with mitomycin C. A phage-tail-like bacteriocin, named serracin P, was purified from an induced culture supernatant of S. plymithicum J7. It was found to be the only compound involved in the antibacterial activity against sensitive strains. The N-terminal amino acid sequence analysis of the two major subunits (23 and 43 kDa) of serracin P revealed high homology with the Fels-2 prophage of Salmonella enterica, the coliphages P2 and 168, the φCTX prophage of Pseudomonas aeruginosa, and a prophage of Yersinia pestis. This strongly suggests a common ancestry for serracin P and these bacteriophages.

scholarly journals First report of Erwina amylovora in Tuscany, Italy

2021 ◽  
Vol 60 (2) ◽  
pp. 253-257
Author(s):  
Duccio MIGLIORINI ◽  
Francesco PECORI ◽  
Aida RAIO ◽  
Nicola LUCHI ◽  
Domenico RIZZO ◽  
...  
Keyword(s):  
Fire Blight ◽  
Erwinia Amylovora ◽  
Chromosomal Region ◽  
Reca Gene ◽  
Plant Tissues ◽  
Molecular Assays ◽  
Pcr Assays ◽  
Blight Disease ◽  
Fruit Orchards ◽  
Symptomatic Plant

2-years-old plants of Pyrus communis showing symptoms of fire blight disease were sampled in an orchard in Tuscany (Italy) during Autumn 2020. Plants were obtained the previous spring from a commercial nursery located in a region where the disease is present since 1994. The collected material was processed in the lab in order to verify the presence of the bacterium Erwinia amylovora, the causal agent of fire blight. Pure isolates showing white mucoid colonies and levan producers on Levan medium were putatively assimilated to E. amylovora. DNA was extracted from the cultures and analysed with three molecular assays, including duplex PCR of the 29-Kb plasmid pEA29 and the ams chromosomal region, sequencing of the 16S rDNA and recA gene regions, two real-time PCR assays on symptomatic plant tissues. All tests confirmed the presence of E. amylovora. Symptomatic and surrounding plants were removed and immediately destroyed according to the regional phytosanitary protocol. This outcome poses a serious threat for fruit orchards in the area.

scholarly journals First Report of Fire Blight on Pyrus elaeagrifolia and Amelanchier sp. in Bulgaria

Plant Disease ◽  
2007 ◽  
Vol 91 (1) ◽  
pp. 110-110 ◽  
Author(s):  
S. G. Bobev ◽  
J. Van Vaerenbergh ◽  
M. Maes
Keyword(s):  
Fire Blight ◽  
Erwinia Amylovora ◽  
Hypersensitive Reaction ◽  
Sterile Water ◽  
First Report ◽  
Progressive Necrosis ◽  
Park Area ◽  
First Time ◽  
Pyrus Elaeagrifolia ◽  
Positive Results

In 2005, a fire blight epidemic occurred for the second time within the last 3 years, and severe damages were observed on pome fruits trees in many regions of Bulgaria. For the first time, we found fire blight on Pyrus elaeagrifolia and Amelanchier sp. grown in a park area (Plovdiv Region), providing evidence of continuing spread of the pathogen in Bulgaria. The symptoms on P. elaeagrifolia were necrotic, immature fruitlets and progressive necrosis toward the adjacent branches, thus forming cankers and leading to death of the plant above the canker. Many Amelanchier sp. shrubs had severely blighted flowers, fruitlets, shoots, and branches and dried, amber ooze droplets on the shoots. All the isolations made from blighted hosts' shoots and cankers on King's medium B (2 to 3 days, 26 to 27°C) yielded whitish, glistening, round bacterial colonies. Infiltration of the suspensions of randomized isolates from both hosts into tobacco leaves resulted in a typical hypersensitive reaction. Subsequently, some strains showed a typical ooze production on immature pear fruits (cv. Conference) and were also successfully reisolated from artificially inoculated quince shoots (1.2 × 109 CFU, cv. Portugalska, three replicates), where typical fire blight symptoms were observed, thereby fulfilling Koch's postulates. No symptoms or bacteria were found within any of the shoots from the same plant species injected with sterile water. The identity of the isolates was confirmed as Erwinia amylovora by an antibody-based slide agglutination test (Neogen_Express; Neogen Europe, Ltd., UK) and PCR test with primers derived from the ams region (1). On the basis of the symptoms, cultural characteristics, and positive results in pathogenicity, serological, and PCR tests, the isolates were considered to be E. amylovora. To our knowledge, this is the first report of fire blight on P. elaeagrifolia and Amelanchier sp. in Bulgaria. Reference: (1) S. Bereswill et al. Appl. Environ. Microbiol. 61:2636, 1995.

scholarly journals First Report of Fire Blight Caused by Erwinia amylovora on Meadowsweet (Spirea prunifolia) in Turkey

Plant Disease ◽  
2014 ◽  
Vol 98 (1) ◽  
pp. 153-153 ◽  
Author(s):  
K. K. Bastas ◽  
F. Sahin
Keyword(s):  
Pathogenic Bacteria ◽  
Fire Blight ◽  
Erwinia Amylovora ◽  
Natural Infection ◽  
Hypodermic Needle ◽  
Identification System ◽  
Bacterial Strains ◽  
First Report ◽  
Molecular Tests ◽  
Initial Symptoms

Fire blight, caused by Erwinia amylovora (Burr.) Winslow et al., affects plants in the Rosaceae family, which includes trees and shrubs in orchards, nurseries, and landscape plantations. During the springs and summers of 2008 and 2010, dying branches, necrotic leaves attached to shoots, and blighted twigs of meadowsweet (Spirea prunifolia) were observed at three different locations of landscape areas in Konya Province, Turkey. Disease incidence was approximately 1% on the plants during the surveys. Initial symptoms of reddish to brownish streaks on the shoots of infected plants were observed in spring. Nine representative bacterial strains were isolated from the lesions on shoots of seven meadowsweet plants on nutrient sucrose agar (NSA) medium and identified as E. amylovora on basis of biochemical, physiological (2,3) and molecular tests (1). Bacteria were gram-negative, rod shaped, aerobic, fermentative, yellow-orange on Miller and Scroth medium (2), positive for levan formation and acetoin production, did not grow at 36°C, positive for gelatin hydrolysis, and negative for esculin hydrolysis, indole, urease, catalase, oxidase, arginine dehydrolase, reduction of nitrate, acid production from lactose, and inositol. All strains were hypersensitive response-positive on tobacco (Nicotiana tabacum var. White Burley) plants. All strains were identified as E. amylovora using the species-specific primers set, A/B (1), by PCR assay, and by fatty acid methyl ester (FAME) profiles determined by Sherlock Microbial Identification System software (TSBA 6 v. 6.00; Microbial ID, Newark, DE) with similarity indices ranging from of 79 to 99%. Pathogenicity was tested by injecting of petioles and actively growing three shoot tips of 2-year-old S. prunifolia seedlings cv. number 29 using a 0.46 mm-diameter hypodermic needle with bacterial suspensions containing 108 CFU mL–1 in sterile distilled water (SDW) Plants were inoculated with each of the nine bacterial strains and two references strains, Ea29 and NCPPB 2791 (Selcuk University, Department of Plant Protection, Konya, Turkey). Symptoms resembling those associated with natural infection appeared on the inoculated plants 7 days after inoculation. Plants inoculated with SDW served as a negative control treatment, and no symptoms were observed on these plants. All tests were repeated three times with the same results. Bacterial re-isolations were attempted from the control plants as well as shoots and leaves inoculated with the two reference strains and the nine bacteria identified as E. amylovora. Bacteria isolated from inoculated plants were identified as E. amylovora using the biochemical, physiological, and molecular tests described above, but this bacterium was not isolated from the control plants. Phytosanitary measures must be taken to avoid spread of the pathogen to ornamentals in new landscape areas in Turkey. This report is important because infected Spirea spp. can be a potential inoculum source for other rosaceous ornamentals. To our knowledge, this is the first report of the occurrence of fire blight on meadowsweet in Turkey. References: (1) S. Bereswill et al. Appl. Environ. Microbiol. 58:3522, 1992. (2) A. L. Jones and K. Geider. Laboratory Guide for Identification of Plant Pathogenic Bacteria, pp. 40-55. American Phytopathological Society, St. Paul, MN, 2001. (3) R. A. Lelliott and D. E. Stead. Methods for Diagnosis of Bacterial Diseases of Plants (Methods in Plant Pathology). Oxford, UK, 1987.

Description of the elongation of fire blight canker, caused by Erwinia amylovora, in trunks of pear trees

2007 ◽  
Vol 26 (4) ◽  
pp. 618-624
Author(s):  
G. Yom Din ◽  
Z. Zugman ◽  
N. Sheglov ◽  
S. Manulis ◽  
M. Reuveni
Keyword(s):  
Fire Blight ◽  
Erwinia Amylovora ◽  
Pear Trees

scholarly journals Investigating Survival of Erwinia amylovora from Fire Blight-Diseased Apple and Pear Trees Buried in Soil as Control Measure

2019 ◽  
Vol 38 (4) ◽  
pp. 269-272
Author(s):  
Ye Eun Kim ◽  
Jun Young Kim ◽  
Hyeong Jin Noh ◽  
Dong Hyeung Lee ◽  
Su San Kim ◽  
...  
Keyword(s):  
Fire Blight ◽  
Erwinia Amylovora ◽  
Control Measure ◽  
Pear Trees

scholarly journals First Report of Stewart's Wilt of Maize in Argentina Caused by Pantoea stewartii

Plant Disease ◽  
2012 ◽  
Vol 96 (12) ◽  
pp. 1819-1819 ◽  
Author(s):  
A. G. Albarracín Orio ◽  
E. Brücher ◽  
M. C. Plazas ◽  
P. Sayago ◽  
F. Guerra ◽  
...  
Keyword(s):  
Leaf Growth ◽  
Leaf Blight ◽  
Bacterial Suspension ◽  
Post Inoculation ◽  
Pathogenicity Test ◽  
First Report ◽  
Pantoea Stewartii ◽  
Maize Plants ◽  
Stewart's Wilt ◽  
Negative Controls

Stewart's wilt is a serious disease of corn (Zea mays L.) caused by the bacterium Pantoea stewartii subsp. stewartii (Pss). Typical symptoms of infected fields and dent corn are longitudinal streaks with irregular or wavy margins, which are parallel to the veins and may extend the length of the leaf. These pale to green yellow lesions become dry and brown as the disease progresses producing a leaf blight (4). During the growing seasons 2010 to 2011 and 2011 to 2012, symptoms of bacterial leaf blight of corn were observed in central Argentina maize fields, with an incidence of 54% in Córdoba province. To identify the pathogen, leaves from 10 symptomatic maize plants per field were collected from 15 fields covering a representative geographical area. High populations of morphologically uniform bacteria were isolated from leaf tissues by conventional methods using King's medium B agar (2). Ten representative facultatively anaerobic gram-negative, non-fluorescing, non-motile, catalase positive and oxidase negative rod-shaped and yellow-pigmented bacterial isolates were evaluated further. The biochemical profile obtained was: fermentative metabolism, negative indol, acetoin and hydrogen sulfide production, negative gelatin hydrolysis (22°C), positive acid production from D-glucose and lactose, negative gas production from D-glucose, and negative nitrate reduction (1). All the isolates produced a 300-bp band with PCR using the species specific primer pair PST3581/PST3909c (3). The Pss ATCC 8199 and Pseudomonas fluorescens ATCC 13525 strains were used as positive and negative controls for the PCR assays, respectively. The pathogenicity test was performed by stem inoculation of five to ten P2069 YR maize plants (one to two leaf growth stage) grown in growth chamber. Plants were inoculated by syringe with a 107 to 108 cell/ml bacterial suspension and kept in a humid chamber at 25 to 27°C. Plants inoculated with Pss ATCC 8199 or with sterile water were used as positive and negative control treatments, respectively. The development of symptoms similar to those originally found in the field was observed on all the plants inoculated with the different isolates at 7 to 10 days post inoculation. In addition, symptoms on inoculated plants were similar to those observed for the positive control treatment. No symptoms were found on negative controls. Koch's postulates were fulfilled since bacteria isolated from symptomatic tissue had identical characteristics to isolates used to inoculate plants and to the reference Pss strain for biochemical tests and PCR reaction mentioned above. To our knowledge, this is the first report of P. stewartii subsp. stewartii isolated from diseased maize in Argentina. References: (1) J. G. Holt et al. Page 179 in: Bergey's manual of determinative bacteriology. Williams and Wilkins, Baltimore, MD, 1994. (2) OEPP/EPPO. Bulletin OEPP/EPPO Bulletin, 36: 111, 2006. Pantoea stewartii subsp. stewartii diagnostic. (3) A. Wensing et al. Appl. Environ. Microbiol. 76:6248, 2010. (4) D. G. White Page 4 in: Compendium of corn disease. The American Phytopathology Society, 1999.

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