scholarly journals First Report of Bacterial Leaf Spot of Basil Caused by Pseudomonas viridiflava in Hungary

Plant Disease ◽  
2012 ◽  
Vol 96 (1) ◽  
pp. 141-141 ◽  
Author(s):  
A. Végh ◽  
M. Hevesi ◽  
Zs. Némethy ◽  
L. Palkovics
Keyword(s):  
Leaf Spot ◽  
Sequence Similarity ◽  
Soft Rot ◽  
Hypersensitive Reaction ◽  
Bacterial Suspension ◽  
Bacterial Leaf Spot ◽  
Biochemical Tests ◽  
First Report ◽  
Arginine Dihydrolase ◽  
Pseudomonas Viridiflava

In April 2011, typical bacterial spot symptoms were observed on sweet basil plantlets (Ocimum basilicum L.) in a supermarket in Budapest, Hungary. Affected plants had dark brown-to-black lesions on the cotyledons. Spots on the leaves were first water soaked and then became necrotic and progressed inward from the margins. Symptoms were similar to those reported by Little et al. (3) on basil affected by Pseudomonas viridiflava. Bacteria consistently isolated from leaf lesions formed mucoid colonies with a green fluorescent pigment on King's B medium. Strains were gram negative. In LOPAT (levan-oxidase-potato rot-arginine dihydrolase-tobacco hypersensitivity) tests (2), all induced a hypersensitive reaction (HR) in tobacco (Nicotiana tabacum L. cv. White Burley) leaves (1), caused soft rot of potato tuber slices, and were negative for levan, oxidase, and arginine dihydrolase. Biochemical tests, API 20NE and API 50 CH (Biomérieux, Marcy l'Etoile, France), were also used for identification. The pathogenicity of three isolates was tested twice by injecting 20-day-old healthy basil plants with a bacterial suspension (107 CFU/ml). Controls were injected with sterile distilled water. Plants were kept at 25 to 28°C and 80 to 100% relative humidity. Forty-eight hours after inoculation, dark brown-to-black lesions were observed only on inoculated plants. The bacterium was reisolated from lesions of all plants tested, fulfilling Koch's postulates. No lesions were observed on controls. To identify the pathogen, a PCR technique was used. The 16SrDNA region was amplified with general bacterial primer pair (63f forward and 1389r reverse) (4) then the PCR products were cloned into Escherichia coli DH5α cells and a recombinant plasmid was sequenced by M13 forward and reverse primers. The sequence was deposited in GenBank (Accession No. HE585219). On the basis of the symptoms, biochemical tests, and 16SrDNA sequence homology (99% sequence similarity with a number of P. viridiflava isolates), the pathogen was identified as P. viridiflava. To our knowledge, this is the first report of bacterial leaf spot of basil in Hungary, which can seriously affect the basil production. References: (1) Z. Klement. Nature 199:299, 1963. (2) R. A. Lelliot et al. Appl. Bacteriol. 29:470, 1966. (3) E. L. Little et al. Plant Dis. 78:831, 1994. (4) A. M. Osborn et al. Environ. Microbiol. 2:39, 2000.

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

Plant Disease ◽  
1999 ◽  
Vol 83 (9) ◽  
pp. 876-876 ◽  
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.

scholarly journals First Report of Pseudomonas viridiflava Causing a Bacterial Blight of Artichoke Bract Leaves

Plant Disease ◽  
2012 ◽  
Vol 96 (8) ◽  
pp. 1223-1223 ◽  
Author(s):  
P. F. Sarris ◽  
E. A. Trantas ◽  
E. Mpalantinaki ◽  
F. N. Ververidis ◽  
S. E. Gouma ◽  
...  
Keyword(s):  
Hypersensitive Reaction ◽  
Bacterial Suspension ◽  
Biochemical Tests ◽  
First Report ◽  
Fluorescent Pigment ◽  
Initial Symptoms ◽  
Pseudomonas Viridiflava ◽  
Dark Green ◽  
Pith Necrosis ◽  
Reference Strains

In 2006, a disease was observed on two artichoke (Cynara scolymus L. cv. Lardati) fields in Crete, Greece, covering ~2 ha. Symptoms developed after several days of rainy and windy weather and >70% of capitula were affected, resulting in unmarketable produce. Initial symptoms were water-soaked, dark green spots on bracts with many sunken, necrotic, often elongated lesions, each with a brown-black center and surrounded by a water-soaked halo with a dark red-brown margin. Symptoms were more severe on inner bracts. Isolations from symptomatic, surface-disinfected bracts onto King's B agar medium (KB) consistently yielded yellow bacterial colonies that produced a green-blue fluorescent pigment. Ten selected artichoke isolates, all gram-negative, presented the LOPAT profile (- - + - +) and were levan negative, oxidase negative, potato rot positive, arginine dihydrolase negative, and showed tobacco hypersensitive reaction. All isolates used L-arabinose, D(-)-tartrate, and L-lactate, but not sucrose, L(+)-tartrate, or trigonelline. Results were identical to those obtained with the reference strain of Pseudomonas viridiflava NCPPB 1249 (3), and strains PV3005 and PV3006 from eggplant (1). Based on these biochemical tests, 10 isolates were identified as P. viridiflava group II members of the LOPAT determinative scheme of Lelliott (1,2). Two artichoke isolates (PV608 and PV609) were selected for molecular characterization. The identity and phylogenetic analysis were determined by multilocus sequence typing with the gyrB, rpoD, and rpoB genes (PV608 Accession Nos. JN383375, JN383363, and JQ267546; PV609 Accession Nos. JN383376, JN383364, and JQ267547). BLAST searches showed highest nucleotide sequence identity (96%) with GenBank sequences of P. viridiflava reference strains NCPPB 963 and CFBP 2107. Pathogenicity of 10 artichoke isolates and reference strains was tested twice on detached capitulum bracts of artichoke cv. Lardati, as well as 4-week-old tomato plants of cv. ACE, and Chrysanthemum indicum cv. Reagan plants. Each isolate was inoculated onto 10 bracts by placing 15 μl of bacterial suspension (5 × 106 CFU/ml) of a 48-h culture in KB broth on the surface of the bract, and pricking the bract through the drop of bacterial suspension with a sterile needle. Each isolate was also inoculated onto five tomato and five chrysanthemum plants by dipping a sterile toothpick in the appropriate bacterial culture and pricking the surface of the stem. Ten control plants were inoculated similarly with sterile, distilled water. Inoculated bracts and plants were kept in boxes lined with moist filter paper at 25 to 30°C and 80 to 100% relative humidity. Lesions developed on detached bracts within 72 h and were similar to those observed on the naturally infected plants. On tomato and chrysanthemum plants, pith necrosis and wilting symptoms were induced within 1 week of inoculation. Symptoms were not observed on control bracts and plants. Bacterial colonies were reisolated from bract lesions and stems with pith necrosis, but not from control plants, and the reisolates had the same LOPAT profile as the original isolates of P. viridiflava, thus fulfilling Koch's postulates. To our knowledge, this is the first report in the world of P. viridiflava causing a disease of artichoke bracts. References: (1) D. E. Goumas et al. Eur. J. Plant Pathol. 104:181, 1998. (2) Lelliott et al. J. Appl. Bacteriol. 29:470, 1966. (3) M. L. Saunier et al. Appl. Environ. Microbiol. 62:2360, 1996.

scholarly journals First Report of Bacterial Leaf Spot of Lettuce (Lactuca sativa) Caused by Xanthomonas campestris pv. vitians in Saudi Arabia

Plant Disease ◽  
2009 ◽  
Vol 93 (1) ◽  
pp. 107-107 ◽  
Author(s):  
M. Al-Saleh ◽  
Y. Ibrahim
Keyword(s):  
Saudi Arabia ◽  
Lactuca Sativa ◽  
Leaf Spot ◽  
Xanthomonas Campestris ◽  
Bacterial Suspension ◽  
Strictly Aerobic ◽  
Distilled Water ◽  
Bacterial Leaf Spot ◽  
Biochemical Tests ◽  
First Report

In April of 2008, lettuce (Lactuca sativa L. cv. Darkland) plants grown in the Al-Ouunia Region of Saudi Arabia were observed with numerous lesions typical of bacterial leaf spot. Leaf lesions were irregular, small, pale green to black, and 2 to 5 mm in diameter. Bacteria were isolated from diseased leaf tissues by cutting leaves into small pieces (0.5 mm) and soaking them in 2 ml of sterile distilled water. The resulting suspension was streaked onto yeast dextrose calcium carbonate agar (YDC) (1) and plates were incubated at 28°C. Large, round, butyrus, bright yellow colonies typical of Xanthomonas spp. formed after 48 h and five strains were selected for further tests. A yellow, mucoid bacterium was consistently isolated from lettuce samples with typical bacterial leaf spot symptoms. All five strains tested in this study were gram negative, oxidase negative, nitrate reduction negative, catalase and esculin hydrolysis positive, motile, and strictly aerobic. All were slightly pectolytic but not amylolytic. All were identified as Xanthomonas campestris pv. vitians. The bacterium was identified with specific oligonucleotide primers (2). This primer pair directed the amplification of an approximately 700-bp DNA fragment from total genomic DNA of all X. campestris pv. vitians strains tested. Pathogenicity tests were performed by using bacterial cultures grown on YDC for 48 h at 28°C. Each strain was suspended in sterile distilled water and the bacterial concentration was adjusted to 106 CFU/ml. Leaves of 5-week-old lettuce plants (cv. Darkland) were sprayed with the bacterial suspension. The inoculated and sterile-water-sprayed control plants were covered with polyethylene bags for 48 h at 25°C, after which the bags were removed and plants were transferred to a greenhouse at 25 to 28°C (1). All strains were pathogenic on the lettuce cv. Darkland, causing typical bacterial leaf spot symptoms by 2 weeks after inoculation. All inoculated plants showed typical symptoms of bacterial leaf spot and symptoms similar to those observed on the samples collected. No symptoms developed on the control plants. The bacterium was reisolated from inoculated plants and identified as X. campestris pv. vitians by morphological, physiological, and biochemical tests as described above. To our knowledge, this is the first report of bacterial leaf spot of lettuce by X. campestris pv. vitians in Saudi Arabia. References: (1) F. Sahin and A. Miller. Plant Dis.81:1443, 1997. (2) J. D. Barak. Plant Dis.85:169, 2001.

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

Plant Disease ◽  
2009 ◽  
Vol 93 (9) ◽  
pp. 967-967 ◽  
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.

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

Plant Disease ◽  
2021 ◽  
Author(s):  
Lei Li ◽  
Yishuo Huang ◽  
Yanxia Shi ◽  
A LI CHAI ◽  
Xuewen Xie ◽  
...  
Keyword(s):  
Pseudomonas Syringae ◽  
Leaf Spot ◽  
Citrate Synthase ◽  
Morphological Characteristics ◽  
Likelihood Method ◽  
Bacterial Suspension ◽  
Leaf Spot Disease ◽  
Distilled Water ◽  
Bacterial Leaf Spot ◽  
First Report

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

scholarly journals First Report of Pectobacterium carotovorum subsp. carotovorum Causing Soft Rot of Orostachys japonica in Korea

Plant Disease ◽  
2014 ◽  
Vol 98 (7) ◽  
pp. 989-989 ◽  
Author(s):  
W. Cheon ◽  
Y. H. Jeon
Keyword(s):  
16S Rrna ◽  
Pathogenic Bacteria ◽  
Sequence Similarity ◽  
Soft Rot ◽  
Bacterial Suspension ◽  
Pectobacterium Carotovorum ◽  
First Report ◽  
Biolog System ◽  
Carotovorum Subsp ◽  
Physiological Tests

Orostachys japonica (Maxim) A. Berger is an important traditional medicine in Korea. The extract of this plant has antioxidant activity and suppresses cancer cell proliferation (1). From summer through fall of 2012 and 2013, a high incidence (~10% to 30%) of disease outbreaks of all plants characterized by water-soaked lesions and soft rot with a stinky odor was observed in cultivated O. japonica around Uljin (36°59′35.04″N, 126°24′1.51″E), Korea. Water-soaked lesions were first observed on the stem base of plants. Subsequently, the plants collapsed, although the upper portion remained asymptomatic. Thereafter, the lesions expanded rapidly over the entire plant. To isolate potential pathogens from infected leaves, small sections (5 to 10 mm2) were excised from the margins of lesions. Ten bacteria were isolated from ten symptomatic plants. Three representative isolates from different symptomatic plants were used for identification and pathogenicity tests. Isolated bacteria were gram negative, pectolytic on crystal violet pectate agar, nonfluorescent on King's medium B, and elicited a hypersensitive response in tobacco plants. All isolates caused soft rot of potato tubers. These isolates also differed from isolates of Erwinia chrysanthemi (Ech) that they were insensitive to erythromycin and did not produce phosphatase. These isolates differed from known strains of E. carotovora subsp. atroseptica in that they did not produce reducing substances from sucrose (2). Use of the Biolog GN microplate and the Release 4.0 system identified the isolate as Pectobacterium carotovorum subsp. carotovorum with 81.2% similarity. The 16S rRNA of the isolated bacteria was amplified by PCR and sequenced as described by Weisburg et al. (3). A BLAST analysis for sequence similarity of the 16S rRNA region revealed 99% similarity with nucleotide sequences for P. carotovorum subsp. carotovorum isolates (KC790305, KC790280, JF926758, JX196705, and AB680074). The pathogenicity of three bacterial isolates was examined on three 2-year-old O. japonica plants by adding 50 μl of a bacterial suspension containing 108 CFU/ml when wounding the leaves with sterile needles. Ten control plants were inoculated with sterilized 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, tissue discoloration, water-soaked lesions, and soft rot developed around the inoculation point. Severe symptoms of soft rot and darkening developed on leaves of inoculated plants within 3 to 5 days after inoculation. All controls remained healthy during these experiments. The bacterial strains re-isolated from the parts of the leaf showing the symptoms and identified as P. carotovorum subsp. carotovorum on the basis of the biochemical and physiological tests, as well as Biolog system. The results obtained for pathogenicity, Biolog analysis, and molecular data corresponded with those for P. carotovorum subsp. carotovorum. To our knowledge, this is the first report of the presence of P. carotovorum on O. japonica in Korea. References: (1) C.-H. Kim et al. Kor. J. Med. Crop Sci. 11:31, 2003. (2) N. W. Schaad et al. Erwinia Soft Rot Group. Page 56 in: Laboratory Guide for Identification of Plant Pathogenic Bacteria. 3rd ed. N. W. Schaad et al. eds. American Phytopathological Society, St. Paul. MN, 2001. (3) W. G. Weisburg et al. J. Bacteriol. 173:697, 1991.

scholarly journals First Report of Bacterial Leaf Spot Caused by Pseudomonas syringae pv. aptata on Swiss Chard, Beta vulgaris subsp. vulgaris, in Arizona

Plant Disease ◽  
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.

scholarly journals First Report of a Leaf Spot of Radermachera sinica in China Caused by Bacillus megaterium

Plant Disease ◽  
2014 ◽  
Vol 98 (10) ◽  
pp. 1425-1425 ◽  
Author(s):  
Y. L. Li ◽  
Z. Zhou ◽  
Y. C. Yuan ◽  
J. R. Ye
Keyword(s):  
16S Rdna ◽  
Bacillus Megaterium ◽  
Leaf Spot ◽  
Disease Incidence ◽  
Bacterial Suspension ◽  
Distilled Water ◽  
Biochemical Tests ◽  
16S Rdna Gene ◽  
First Report ◽  
Rdna Gene

Radermachera sinica is widely planted as an ornamental plant in homes, offices, and malls in China. A leaf spot of R. sinica occurred in Luoyang, China, from 2013 to 2014. Lesions mostly occurred in wounds and were irregular with light brown centers and purple borders. One or more lesions on a leaf sometimes covered the entire blade. Eighty plants were surveyed in Luoyang, with disease incidence of 17%. Five millimeter pieces from the borders of lesions were surface-disinfected with 75% ethanol for 30 s, 1% sodium hypochlorite for 5 min, washed three times in sterilized distilled water, placed on nutrient agar (NA) medium at 25°C in darkness, and incubated for 24 to 48 h. Four white, round, smooth, and shiny colonies were selected for further identification. All strains were gram-positive, aerobic rods with many peritrichous flagella, and could grow in medium containing 5% NaCl. The strains were positive for catalase, starch hydrolysis, liquefaction of gelatin, reduction of nitrate, acid production from glucose, mannitol, maltose, lactose, xylose, and pectinose. The strains were positive for phenylalanine deaminase, decomposition of tyrosine, and utilization of citrate. The strains were identified by biochemical tests as Bacillus megaterium (1). To confirm pathogenicity, the strains were grown on NA for 48 h and suspended in sterile distilled water to produce a suspension with a final concentration of 108 CFU/ml. Healthy leaves of biennial R. sinica plants were sterilized with 75% ethanol and washed three times with sterilized distilled water. Fresh wounds were made with a sterile needle on the healthy leaves. Each of four strains was tested by spray inoculation with a bacterial suspension on three leaves. Sterile distilled water was used as negative control. Plants were enclosed in plastic bags and placed in a growth chamber at 28°C with 80% relative humidity. After 5 days, water-soaked lesions were observed. Two weeks later, lesions 4 mm in diameter turned light brown with purple borders, and most of lesions occurred in puncture wounds. Symptoms similar to those observed on field plants developed on all inoculated leaves, while no symptoms appeared on the control leaves. B. megaterium was re-isolated from the lesions of inoculated leaves, but not from the control leaves. To confirm the bacterial identification, PCR was performed on the 16S rDNA gene with P1/P2 (P1: CAGAGTTTGATCCTGGCT, P2: AGGAGGTGATCCAGCCGCA) (2) and 1,463 bp of the 16S rDNA gene (GenBank Accession No. KJ789369) showed 100% sequence identity to B. megaterium DSM 319 (NC_014103.1). To our knowledge, this is the first report of a leaf spot of R. sinica caused by B. megaterium in China as well as anywhere in the world. References: (1) P. Vos et al. Bergey's Manual of Systematic Bacteriology. Vol 3: The Firmicutes. Springer, 2009. (2) W. G. Weisbury et al. J. Bacteriol. 173:697, 1991.

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