scholarly journals First Report of Acidovorax avenae subsp. citrulli as the Causal Agent of Bacterial Leaf Blight of Betelvine in Taiwan

Plant Disease ◽  
2010 ◽  
Vol 94 (8) ◽  
pp. 1065-1065 ◽  
Author(s):  
W.-L. Deng ◽  
T.-C. Huang ◽  
Y.-C. Tsai
Keyword(s):  
Leaf Blight ◽  
Causal Agent ◽  
Bacterial Leaf Blight ◽  
Bacterial Suspension ◽  
Identification System ◽  
Distilled Water ◽  
First Report ◽  
Microbial Identification ◽  
Sequence Identity ◽  
Disease Free

In November 2008, betelvines (Piper betle L., Piperaceae) exhibiting leaf blight symptoms were observed in central Taiwan. Infections resulted in a 30 to 70% loss of leaf yield in the investigated betel leaf-producing facilities. Symptoms began with small, necrotic, water-soaked spots that progressed to circular to irregularly shaped brown lesions, 5 to 10 mm in diameter, with chlorotic halos on leaves; some lesions started from the edge of leaves and later fused to form dried, necrotic margins. Bacteria-like streaming fluid was visible from the edges of freshly cut lesions at the junctions of chlorotic and necrotic leaf tissues when observed with a light microscope at ×100. When the streaming fluid was streaked onto King's medium B (3), a slow-growing, gram-negative, nonfluorescent bacterium was identified from the whitish colonies that consistently developed on the medium. Five bacterial isolates from three lesions were characterized with fatty acid methyl ester analysis (Agilent Technologies, Santa Clara, CA) and Sherlock Microbial Identification System (Microbial IDentification Inc., Newark, DE), and for each isolate, the bacterium was confirmed as Acidovorax avenae subsp. citrulli with a similarity index >0.70. In addition, the Biolog system (Biolog, Hayward, CA) and 16S ribosomal RNA sequence identity comparison were performed to confirm that the five betelvine-isolated bacteria were A. avenae subsp. citrulli based on a similarity of 0.54 with Biolog and 99% sequence identity for 16S rRNA gene. Koch's postulates were fulfilled by infiltrating a bacterial suspension of 3 × 105 CFU/ml into 40 leaves of four greenhouse-grown, disease-free, mature betelvine plants. After inoculation, plants were kept in a humidified greenhouse at 28°C to favor symptom development and symptoms similar to those observed in the greenhouse were evident at 7 days post inoculation (dpi) on all bacterium-infiltrated leaves. Control leaves infiltrated with distilled water remained symptomless. Bacteria showing morphological and biochemical similarities (2) to the ones used for inoculation were isolated from all of the inoculated betelvine leaves. In addition, a bacterial suspension at 3 × 108 CFU/ml was sprayed at the amount of 5 ml per plant onto 6 to 10 plants each of 4-week-old disease-free seedlings of watermelon (Citrullus lanatus (Thunb.) Matsum & Nakai, cv. Empire No. 2), oriental sweet melon (Cucumis melo L. var. saccharinus Naudin, cv. Silver Beam), and waxgourd (Benincasa hispida (Thunb.) Cogn., cv. Cheerer) for bioassays, and the inoculated seedlings were enclosed in plastic bags for 36 h at 28°C. Water-soaked lesions were observed on leaves of watermelon and waxgourd at 2 dpi and on sweet melon at 4 dpi on all inoculated plants but not on distilled water-sprayed control plants, indicating that A. avenae subsp. citrulli strains from betelvine could also infect melon plants. A. avenae subsp. citrulli was previously identified as the causal agent of bacterial fruit blotch on melon and bitter gourd in Taiwan (1). To our knowledge, this is the first report that A. avenae subsp. citrulli can naturally infect betelvine, a noncucurbit crop, to elicit bacterial leaf blight disease. References: (1) A.-H. Cheng and T.-C. Huang. Plant Pathol. Bull. 7:216, 1998. (2) J. B. Jones et al. Page 121 in: Laboratory Guide for Identification of Plant Pathogenic Bacteria. 3rd ed. The American Phytopathological Society, St. Paul, MN, 2001. (3) E. O. King et al. J. Lab. Clin. Med. 44:301, 1954.

scholarly journals First report of bacterial leaf blight caused by Xanthomonas hortorum pv. carotae on carrots in Spain

Plant Disease ◽  
2021 ◽  
Author(s):  
José Luis Palomo Gómez ◽  
Maria Shima ◽  
Adela Monterde ◽  
Inmaculada Navarro ◽  
Silvia Barbé ◽  
...  
Keyword(s):  
Sequence Analysis ◽  
Xanthomonas Campestris ◽  
Negative Control ◽  
Leaf Blight ◽  
Bacterial Leaf Blight ◽  
Pcr Analysis ◽  
Bacterial Suspension ◽  
Rrna Gene ◽  
Distilled Water ◽  
First Report

In September 2019, symptoms resembling those of bacterial leaf blight were observed on carrot plants (Daucus carota L. subsp. sativus Hoffm.) cv. Romance cultivated in commercial plots in Chañe (Segovia), Spain. Symptoms were observed in two plots surveyed representing three hectares, with an incidence greater than 90%, and also in some plots in other nearby municipalities sown with the same batch of seeds. The lesions observed at the ends of the leaves were initially yellow that develop dark brown to black with chlorotic halos on leaflets that turned necrotic. Yellow, Xanthomonas-like colonies were isolated onto YPGA medium (Ridé 1969) from leaf lesions. Two bacterial isolates were selected and confirmed by real-time PCR using a specific primer set for Xanthomonas hortorum pv. carotae (Temple et al. 2013). All isolates were gram-negative, aerobic rods positive for catalase, able of hydrolyzing casein and aesculin and growing at 2% NaCl, while were negative for oxidase and urease tests. Sequences of 16S rRNA gene showed 100% similarity with Xanthomonas campestris, X. arboricola, X. gardneri, X. cynarae strains (GenBank accession numbers: MW077507.1 and MW077508.1 for the isolates CRD19-206.3 and CRD19-206.4, respectively). However, the resulting phylogeny of multilocus sequence analysis (MLSA) of a concatenation of the housekeeping genes atpD, dnaK, and efp (Bui Thi Ngoc et al. 2010), by using neighbour-joining trees generated with 500 bootstrap replicates, grouped the two isolates with the X. hortorum pv. carotae M081 strain (Kimbrel et al. 2011) (GenBank accession numbers: MW161270 and MW161271 for atpD for the two isolates, respectively; MW161268 and MW161269 for dnaK; MW161272 and MW161273 for efp). A pairwise identity analysis revealed a 100% identity between all three isolates. Pathogenicity of the isolates was tested by spray inoculation (Christianson et al. 2015) with a bacterial suspension (108 CFU/ml) prepared in sterile distilled water at 3 to 4 true-leaf stage (six plants per isolate). Sterile distilled water was used as negative control. The inoculated plants were incubated in a growth chamber (25°C and 95% relative humidity [RH]) for 72 h, and then transferred to a greenhouse at 24 to 28°C and 65% RH. Characteristic leaf blight symptoms developed on inoculated carrot plants, while no symptoms were observed on the negative control plants 20 days after inoculation. The bacterium was re-isolated from symptomatic tissue and the identity confirmed through PCR analysis. Based on PCR, morphological and phenotypic tests, sequence analysis, and pathogenicity assays, the isolates were identified as X. hortorum pv. carotae. To our knowledge, this is the first report of bacterial leaf blight of carrot caused by X. hortorum pv. carotae in Spain, and the first molecular and pathological characterization. It is important to early detect this pathogen and take suitable measures to prevent its spread, since it could cause yield losses for a locally important crop such as carrot.

scholarly journals First Report of Fire Blight Disease on Blackberry in Turkey

Plant Disease ◽  
2012 ◽  
Vol 96 (12) ◽  
pp. 1818-1818
Author(s):  
K. K. Bastas ◽  
F. Sahin
Keyword(s):  
Disease Incidence ◽  
Acid Methyl Ester ◽  
Negative Control ◽  
Culture Collection ◽  
Bacterial Suspension ◽  
Identification System ◽  
Distilled Water ◽  
Bacterial Strains ◽  
First Report ◽  
Microbial Identification

During 2008 and 2009, a new disease on blackberry (Rubus fruticosus cv. Chester) causing leaf and shoot blight and cankers with brown discoloration of necrotic tissues on mature branches was observed in Isparta and Konya provinces of Turkey. Disease incidence was estimated to be 4% for the two years. Isolations were made from lesions on leaves and shoots on nutrient sucrose agar (NSA) medium. Bacteria consistently isolated from the diseased tissues were identified on the basis of biochemical, physiological (2), and molecular tests (1). Eleven representative bacterial strains were gram-negative, rod-shaped, mucoid, fermentative, yellow-orange on Miller and Scroth (MS) medium, positive for levan formation and acetoin production, no growth 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. Two reference strains of Erwinia amylovora (EaP28 and NCPPB 2791) obtained from the culture collection unit of Selcuk University were used as positive controls. All strains induced a hypersensitive response in tobacco (Nicotiana tobaccum cv White Burley) 24 h after inoculation with a 108 CFU/ml bacterial suspension in water. All strains were identified as E. amylovora using the species-specific primers set A/B (1), which amplified a 1-kb DNA fragment in PCR, and 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 confirmed by injecting bacterial suspensions (108 CFU/ml–1) in sterile distilled water into the shoot tips of 2-year-old R. fruticosus cv. Chester and the first blighting symptoms were observed on leaves within 3 days and also 10 days later after inoculation on shoots. Sterile distilled water was used as a negative control. No symptoms were observed on control plants. All tests were repeated three times. The bacterium was reisolated from inoculated plants and identified as. E. amylovora. To our knowledge, this is the first report of E. amylovora on blackberry in Turkey. Phytosanitary measures are needed to prevent any further spread of the bacterium to new blackberry areas. References: (1) S. Bereswill et al. App. Environ. Microbiol. 58:3522, 1992. (2) A. L. Jones and K. Geider. Lab. Guide for Identification of Plant Pathological Bacteria, 40, 2001.

scholarly journals First Report of Bacterial Leaf Blight of Carrot Caused by Xanthomonas hortorum pv. carotae in Korea

Plant Disease ◽  
2014 ◽  
Vol 98 (2) ◽  
pp. 275-275 ◽  
Author(s):  
I.-S. Myung ◽  
M.-J. Yoon ◽  
J.-Y. Lee ◽  
G.-D. Kim ◽  
M.-H. Lee ◽  
...  
Keyword(s):  
Sequence Analysis ◽  
Negative Control ◽  
Leaf Blight ◽  
Gyrb Gene ◽  
Bacterial Leaf Blight ◽  
Distilled Water ◽  
First Report ◽  
Rpod Gene ◽  
Phenotypic Tests ◽  
Hydrolysis Of

In December 2012, symptoms of typical bacterial leaf blight were observed on carrot plants (Daucus carota L. subsp. sativus) cultivated in commercial fields in Kujwa, Jeju, Korea. The disease was detected in 40% of 50 fields surveyed with an incidence of 10% on average. The bacterial leaf blight lesions on leaf blades were elongated, dark brown to black with water-soaked edges and chlorotic halos. Lesions were also crescent-shaped to V-shaped on leaflets. Four bacterial isolates were recovered on trypticase soy agar from leaf lesions that were surface-sterilized in 70% ethyl alcohol for 20 s. Identity of the isolates was confirmed by PCR product (1,266-bp) using a specific primer set for Xanthomonas hortorum pv. carotae (Kendrick 1934) Vauterin et al. 1995, XhcPP03 (1). All isolates were gram-negative, aerobic rods with a single polar flagellum. Isolates were positive for catalase and negative for oxidase. In phenotypic tests for differentiation of Xanthomonas (2), the isolates positive for mucoid growth on yeast extract-dextrose-calcium carbonate agar, growth at 35°C, hydrolysis of esculin, protein digestion, alkaline in litmus milk, acid production from arabitol, and utilization of glycerol and melibiose. The isolates were negative for growth on SX medium, hydrolysis of starch, and ice nucleation. The gyrB gene (863 bp) and the rpoD gene (870 bp) were sequenced to aid identification of the original isolates using published PCR primer sets, Xgyr1BF/Xgyr1BR and XrpoD1F/XrpoD1R (4), respectively. Sequences of the gyrB gene (GenBank accessions KC920729 to KC920732) from the carrot isolates shared 100% sequence identity with that of the X. hortorum pv. carotae strain NCPPB 425 (EU285243). In phylogenetic analyses based on the partial sequences of the gyrB and the rpoD genes for Xanthomonas spp. available at NCBI (4), and sequences of the carrot isolates (KC920734 to KC920737 for rpoD gene) using the Neighbor-joining method in MEGA Version 5.1 (3), the isolates were clustered in the X. hortorum-cynarae-garnderi group. Pathogenicity of the isolates was tested by spray inoculation with a bacterial suspension (106 CFU/ml) prepared in sterile distilled water at 6 to 7 true-leaf stage (three plants per isolate). Sterile distilled water was used as negative control. The inoculated plants were incubated in a growth chamber (25°C and 95% relative humidity [RH]) for 15 hr, and then transferred to a greenhouse at 24 to 28°C and 65% RH. Characteristic leaf blight symptoms developed on inoculated carrot plants, while no symptoms were observed on the negative control plants 14 days after inoculation. The bacterium was re-isolated from symptomatic tissue and the identity confirmed through gyrB gene sequence analysis (4). Based on PCR, morphological and phenotypic tests, sequence analysis, and pathogenicity assays, the isolates were identified as X. hortorum pv. carotae. To our knowledge, this is the first report of bacterial leaf blight of carrot caused by X. hortorum pv. carotae in Korea. The detection of this pathogen could have a significant economic impact due to yield losses from disease development. Consolidation of quarantine inspection on imported carrot seeds needs to control an outbreak of the disease. Crop rotation and plowing are recommended to reduce incidence of the disease in the infested fields. References: (1) J. A. Kimbrel et al. Mol. Plant Pathol. 12:580, 2011. (2) N. W. Schaad et al. Page 189 in: Laboratory Guide for Identification of Plant Pathogenic Bacteria. 3rd ed. N. W. Schaad et al., eds. The American Phytopathological Society, St. Paul, MN, 2001. (3) K. Tamura et al. Mol. Biol. Evol. 28:2731, 2011. (4) J. M. Young et al. Syst. Appl. Microbiol. 31:366, 2008.

scholarly journals First Report of New Bacterial Leaf Blight of Rice Caused by Pantoea ananatis in Southeast China

Plant Disease ◽  
2021 ◽  
Author(s):  
Lin Yu ◽  
Changdeng Yang ◽  
Zhijuan Ji ◽  
Yuxiang Zeng ◽  
Yan Liang ◽  
...  
Keyword(s):  
Oryza Sativa L ◽  
Sequence Similarity ◽  
Disease Incidence ◽  
Leaf Blight ◽  
Bacterial Leaf Blight ◽  
Bacterial Suspension ◽  
Rrna Gene ◽  
Pantoea Ananatis ◽  
Southeast China ◽  
First Report

In autumn 2020, leaf blight was observed on rice (Oryza sativa L., variety Zhongzao39, Yongyou9, Yongyou12, Yongyou15, Yongyou18, Yongyou1540, Zhongzheyou8, Jiafengyou2, Xiangliangyou900 and Jiyou351) in the fields of 17 towns in Zhejiang and Jiangxi Provinces, China. The disease incidence was 45%-60%. Initially, water-soaked, linear, light brown lesions emerged in the upper blades of the leaves, and then spread down to leaf margins, which ultimately caused leaf curling and blight during the booting-harvest stage (Fig. S1). The disease symptoms were assumed to be caused by Xanthomonas oryzae pv. oryzae (Xoo), the pathogen of rice bacterial blight. 63 isolates were obtained from the collected diseased leaves as previously described (Hou et al. 2020). All isolates showed circular, smooth-margined, yellow colonies when cultured on peptone sugar agar (PSA) medium for 24h at 28℃. The cells were all gram-negative and rod-shaped with three to six peritrichous flagella; positive for catalase, indole, glucose fermentation and citrate utilization, while negative for oxidase, alkaline, phenylalanine deaminase, urease, and nitrate reductase reactions. 16S rRNA gene sequence analysis from the 6 isolates (FY43, JH31, JH99, TZ20, TZ39 and TZ68) revealed that the amplified fragments shared 98% similarity with Pantoea ananatis type strain LMG 2665T (GenBank JFZU01) (Table S3). To further verify P. ananatis identity of these isolates, fragments of three housekeeping genes including gyrB, leuS and rpoB from the 6 isolates were amplified and sequenced, which showed highest homology to LMG 2665T with a sequence similarity of 95%-100% (Table S3). Primers (Brady et al. 2008) and GenBank accession numbers of gene sequences from the 6 isolates are listed in Table S1 and Table S2. Phylogenetic analysis of gyrB, leuS and rpoB concatenated sequences indicated that the 6 isolates were clustered in a stable branch with P. ananatis (Fig. S2). Based on the above morphological, physiological, biochemical and molecular data, the isolates are identified as P. ananatis. For pathogenicity tests, bacterial suspension at 108 CFU/mL was inoculated into flag leaves of rice (cv. Zhongzao39) at the late booting stage using clipping method. Water was used as a negative control. The clipped leaves displayed water-soaked lesions at 3 to 5 days after inoculation (DAI); then the lesion spread downward and turned light brown. At about 14 DAI, blight was shown with similar symptoms to those samples collected from the rice field of Zhejiang and Jiangxi provinces (Fig. S1). In contrast, the control plants remained healthy and symptomless. The same P. ananatis was re-isolated in the inoculated rice plants, fulfilling Koch’s postulates. In the past decade, P. ananatis has been reported to cause grain discoloration in Hangzhou, China (Yan et al. 2010) and induce leaf blight as a companion of Enterobacter asburiae in Sichuan province, China (Xue et al. 2020). Nevertheless, to the best of our knowledge, this is the first report of P. ananatis as the causative agent of rice leaf blight in southeast China. This study raises the alarm that the emerging rice bacterial leaf blight in southeast China might be caused by a new pathogen P. ananatis, instead of Xoo as traditionally assumed. Further, the differences of occurrence, spread and control between two rice bacterial leaf blight diseases caused by P. ananatis and Xoo, respectively need to be determined in the future.

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

Plant Disease ◽  
2014 ◽  
Vol 98 (1) ◽  
pp. 153-153 ◽  
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.

scholarly journals First Report of Crown Gall, Caused by Agrobacterium tumefaciens on Soapberry (Sapindus delavayi) in China

Plant Disease ◽  
2013 ◽  
Vol 97 (5) ◽  
pp. 685-685
Author(s):  
Y. J. Wang ◽  
Y. Y. He ◽  
Z. Xie ◽  
L. Q. Zhang
Keyword(s):  
Agrobacterium Tumefaciens ◽  
16S Rdna ◽  
Crown Gall ◽  
Maximum Parsimony Analysis ◽  
Bacterial Suspension ◽  
Identification System ◽  
Distilled Water ◽  
Bacterial Identification ◽  
Poor Growth ◽  
First Report

Soapberry (Sapindus delavayi (Franch.) Radlk.,) plants are widely grown as shade trees in the subtropical to tropical regions of China. In July 2011, large, aerial galls were observed on the above-ground trunks of 5-year-old soapberry plants in two commercial nursery gardens located in Zhejiang Province. Disease incidence was estimated to be 75%. The galls varied in weight from 2 to 24 g and in texture from soft and spongy to hard, and in some cases, the galls completely girdled the trunk. The trees with galls exhibited poor growth compared with healthy trees. Isolations from the grinded and macerated galls yielded nearly pure white, circular, and glistening bacterial colonies on Roy Sauer medium (2). Six random colonies from different galls were selected for bacterial identification, and showed the same morphological, physiological, and biochemical characters and 16S rDNA sequences. All six isolates (isolate SD01 to SD06) were gram negative, rod-shaped bacteria. Carbon source utilization testing with the Biolog GN Bacterial Identification System (version 3.50) confirmed the bacteria as Agrobacterium tumefaciens with a similarity of 0.90. The most-parsimonious tree from the maximum parsimony analysis (PHYLIP package, version 3.68, 500 replicates) of bacterial 16S rDNA gene sequences showed that A. tumefaciens SD01 (GenBank Accession No. JX997939) clustered phylogenetically most closely (99.5% similarity) with A. tumefaciens C58 (AE007870.2). Pathogenicity was confirmed by injecting 3- to 5-week old tomato and sunflower plants and 2-year-old soapberry with approximately 5 μl of the bacterial suspension (108 CFU/ml) in sterile, distilled water. Sterile distilled water was used as a negative control. Ten plants of each treatment were inoculated. Inoculated plants were then transferred to a greenhouse at 25°C. Typical tumors developed at the inoculation sites on tomatoes and sunflower plants 3 weeks after inoculation and on soapberry 6 weeks after inoculation. No symptoms were observed on the control plants. The bacteria that were readily reisolated from the inoculated plants exhibited the same morphological, physiological characters and 16S rDNA sequence as the original culture and were confirmed as A. tumefaciens, fulfilling Koch's postulates. A. tumefaciens is endemic to China and has a very wide host range (1). However, crown gall of soapberry has never been found in China and other countries. To our knowledge, this is the first report of A. tumefaciens on soapberry plants in China. References: (1) M. A. Escobar and A. M. Dandekar. Trends Plant Sci. 8:380, 2003. (2) L. W. Moore et al. Page 17 in: Laboratory Guide for Identification of Plant Pathogenic Bacteria. 3rd ed. N. W. Schaad et al., eds. The American Phytopathological Society, St. Paul, MN, 2001.

scholarly journals First Report of Leaf Blight on Saposhnikovia divaricata by Pseudomonas viridiflava in Gansu, China

Plant Disease ◽  
2015 ◽  
Vol 99 (2) ◽  
pp. 281-281 ◽  
Author(s):  
Y. Wang ◽  
C. Y. Zeng ◽  
X. R. Chen ◽  
C. D. Yang
Keyword(s):  
16S Rdna ◽  
Leaf Blight ◽  
Gansu Province ◽  
Rdna Sequence ◽  
Bacterial Suspension ◽  
Distilled Water ◽  
16S Rdna Sequence ◽  
First Report ◽  
Saposhnikovia Divaricata ◽  
The Impact

Saposhnikovia divaricata (Turcz) Schischk, a perennial plant in the Umbelliferae, is widely cultivated in north China. As a traditional Chinese medicine, it can be used to cure colds and rheumatism (1). During disease surveys on medicinal plants in August 2010, a bacterial leaf blight was discovered with a general incidence of 40 to 60% on S. divaricata farms in Longxi, Weiyuan County in Gansu China. In young plants, tiny yellow-white points were visible on the backs of the leaves. They then expanded to 2- to 3-mm oil-soaked lesions; leaves appeared crimped and deformed. Later the leaves shriveled; black-brown oil-soaked lesions appeared on the vein and the tissue around it; and black streaks appeared on the stems. Ten diseased leaf and stem tissues were cut into 4- to 5-mm squares, surface-sterilized in 1% sodium hypochlorite for 1 min, rinsed three times, and macerated for 5 min in sterilized distilled water. They were then streaked onto nutrient agar (NA) medium and incubated at 28°C for 3 days. Colonies on NA were round, smooth, translucent, and yellowish green. They were Gram negative and induced a hypersensitive response on tobacco (Nicotiana tabacum L.) leaves. The strain was positive for gelatin, catalase, oxidase, and utilization of glucose and saccharose. Pathogenicity tests were performed by spraying bacterial suspension containing 107 CFU/ml on six leaves of three healthy potted S. divaricata plants and injecting it into another six leaves on three plants. Plants inoculated with sterile distilled water alone served as controls. They were placed in a growth chamber at 25°C and bagged for 24 h to maintain >95% humidity. Thirty-six hours after inoculation, the inoculated leaves appeared water-soaked; 10 days later, the symptoms were apparent on leaves and the plant wilted. The negative control appeared normal. Finally, Koch's postulates were verified by re-isolating P. viridiflava from the leaves with typical blight. The genomic DNA of the isolate was extracted, and the partial 16S rDNA sequence was amplified with a universal bacterial primer set (27f and 1492r) (2). The sequence was deposited in GenBank as KM030291. BLAST search yielded 99% identity with P. viridiflava strains, including the strains KNOX209 (AY604847), RMX3.1b (AY574911), ME3.1b (AY574909), and UASWS0038 (AY919300). Based on the symptoms, colony morphology, biochemical tests, and 16S rDNA sequence identity, the pathogen was identified as P. viridiflava. To our knowledge, this is the first report of leaf blight of S. divaricata by P. viridiflava in Gansu province of China. In Jilin province, the same disease was reported in 2008 (3). The impact of P. viridiflava on S. divaricata production is not yet known. References: (1) Committee of China Pharmacopoeia. Pharmacop. People's Repub. 1:102, 2005. (2) C. Morenol et al. Microbiology 148:1233, 2002. (3) W. Xue. Dissertation. Jilin Agric. Univ. 1, 2008.

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

Plant Disease ◽  
2000 ◽  
Vol 84 (2) ◽  
pp. 201-201 ◽  
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.

scholarly journals First Report of a Leaf Blight of Onion Caused by Xanthomonas spp. in Georgia

Plant Disease ◽  
2003 ◽  
Vol 87 (6) ◽  
pp. 749-749 ◽  
Author(s):  
F. H. Sanders ◽  
D. B. Langston ◽  
J. H. Brock ◽  
R. D. Gitaitis ◽  
D. E. Curry ◽  
...  
Keyword(s):  
Disease Incidence ◽  
Methyl Esters ◽  
Economic Loss ◽  
Leaf Blight ◽  
Identification System ◽  
Sterile Water ◽  
Disease Symptoms ◽  
First Report ◽  
Microbial Identification ◽  
Dry Conditions

In October of 2001 and 2002, a leaf blight was reported affecting Vidalia onion (Allium cepa) cvs. Pegasus and Sweet Vidalia, respectively, in one field each. Lesions on onion seedlings began as a water-soaked, tip dieback that gradually blighted the entire leaf. Symptoms on onion transplants appeared as elongated, water-soaked lesions that typically collapsed at the point of initial infection. In both cases, disease was very severe on seedlings, and disease incidence was 50% or more in both fields. Warm temperatures combined with overhead irrigation and above average rainfall likely enhanced the severity and spread of disease. Disease was not detected on more mature onions once cool, dry conditions occurred later in the season, and no significant economic loss occurred. Seed was tested from seed lots of the aforementioned cultivars and Xanthomonas spp. were not found. Diseased tissue was macerated in sterile, phosphate-buffered saline, and 10 μl of the resulting suspension was streaked on nutrient agar plates. Yellow-pigmented, gram-negative, rod-shaped bacteria were isolated routinely from diseased tissue. Bacteria were catalase-positive, cellulolytic, oxidase-negative, amylolytic, proteolytic, and utilized glucose in an oxidative manner. Analysis of whole cell, fatty acid methyl esters (FAME) using the Microbial Identification System (MIS, Sherlock version 3.1; MIDI, Inc., Newark, DE) identified four representative strains of the bacterium as a pathovar of Xanthomonas axonopodis (similarity indices 0.75 to 0.83). Known Xanthomonas spp. from onion from Colorado and Texas (1,2) had similar FAME profiles when analyzed by the MIDI system. Onion plants were grown under greenhouse conditions for 2 months and inoculated by injecting the base of a quill with 1.0 ml of bacterial suspensions (1 × 107 CFU ml-1) of the Xanthomonas sp. isolated from Georgia, and negative controls were inoculated with 1 ml of sterile water. Disease symptoms developed on plants inoculated with bacterial suspensions in 4 to 7 days and Xanthomonas sp. was isolated from the lesions produced. Disease symptoms occurred when the same suspension was sprayed on onion foliage. No symptoms occurred on plants inoculated with 1 ml of sterile water. To our knowledge, this is the first report of Xanthomonas spp. affecting Vidalia onions. References: (1) T. Isakeit et al. Plant Dis. 84:201, 2000. (2) H. F. Schwartz and K. Otto. Plant Dis. 84:922, 2000.

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