scholarly journals First Report of Pseudomonas syringae pv. coriandricola Causing Bacterial Leaf Spot on Carrot, Parsley, and Parsnip in Serbia

Plant Disease ◽  
2015 ◽  
Vol 99 (3) ◽  
pp. 416-416 ◽  
Author(s):  
T. Popović ◽  
Ž. Ivanović ◽  
M. Ignjatov ◽  
D. Milošević
Keyword(s):  
Pseudomonas Syringae ◽  
Leaf Spot ◽  
Bacterial Suspension ◽  
Pathogenicity Test ◽  
Distilled Water ◽  
Bacterial Leaf Spot ◽  
Koch’S Postulates ◽  
First Report ◽  
Vegetable Farm ◽  
Koch's Postulates

During the spring of 2014, a severe leaf spot disease was observed on carrot (Daucus carota), parsley (Petroselinum crispum), and parsnip (Pastinaca sativa) on a 0.5-ha vegetable farm in Vojvodina Province, Serbia. The disease appeared under wet and cool conditions with 5 to 25% of plants infected for each of the three crops. Symptoms were characterized as brown angular leaf spots, ~2 mm in diameter, often limited by veins. Collected symptomatic leaves were rinsed and dried at room temperature, and leaf sections taken from the margin of necrotic tissue were macerated in sterile phosphate buffer and streaked onto nutrient agar with 5% (w/v) sucrose (NAS). After isolation, whitish, circular, dome-shaped, Levan-positive colonies consistently formed. Five strains from each host (carrot, parsley, and parsnip) were used for further study. Strains were gram-negative, aerobic, and positive for catalase and tobacco hypersensitive reaction but negative for oxidase, rot of potato slices, and arginine dihydrolase. These reactions corresponded to LOPAT group Ia, which includes Pseudomonas syringae pathovars (3). Repetitive extragenic palindromic sequence (Rep)-PCR fingerprint profiles using the REP, ERIC, and BOX primers (4) were identical for all strains. Sequence typing of the housekeeping genes gyrB and rpoD (1) was performed for three representative strains (one from each host). Sequences were deposited in the NCBI GenBank database as accessions KM979434 to KM979436 (strains from carrot, parsnip, and parsley, respectively) for the gyrB gene and KM979437 to KM979439 (strains from parsnip, parsley and carrot, respectively) for the rpoD gene. Sequences were compared with pathotype strain Pseudomonas syringae pv. coriandricola ICMP12471 deposited in the Plant Associated and Environmental Microbes Database ( http://genome.ppws.vt.edu/cgi-bin/MLST/home.pl ). BLAST analysis revealed 100% homology for gyrB and 99% homology for rpoD. Pathogenicity was tested with five representative strains from each host on four-week-old plants of carrot (cv. Nantes), parsley (cv. NS Molski), and parsnip (cv. Dugi beli glatki) using two methods: spraying the bacterial suspension (108 CFU ml−1) on the leaves until runoff (5) and injecting the bacterial suspension into leaves with a hypodermic syringe (2). Four plants were used per strain and method. Sterile distilled water was applied as a negative control treatment for each plant species. All plants were kept in a mist room with 100% humidity for 4 h, then transferred to a greenhouse at 25°C and 80% relative humidity and examined for symptom development over a period of three weeks. For all strains, inoculated leaves first developed water-soaked lesions on the leaves 5 to 7 days after inoculation (DAI); 14 DAI lesions became dark brown, often surrounded by haloes. No symptoms were observed on control plants inoculated with sterile distilled water. For fulfillment of Koch's postulates, re-isolations were done onto NAS. Re-isolated bacteria were obtained from each inoculated host and confirmed to be identical to the original isolates using the LOPAT tests and Rep-PCR fingerprinting profiles. Based on the pathogenicity test accompanied by completion of Koch's postulates, sequence analysis, and bacteriological tests, the strains were identified as P. s. pv. coriandricola. To our knowledge, this is the first report of bacterial leaf spot of carrot, parsley, and parsnip in Serbia. It may present a threat to production due to quality requirements for fresh market. References: (1) P. Ferrente and M. Scortichini. Plant Pathol. 59:954, 2010. (2) M. Gupta et al. Plant Dis. 97:418, 2013. (3) R. A. Lelliott et al. J. Appl. Bacteriol. 29:470, 1966. (4) F. J. Louws et al. Appl. Environ. Microb. 60:2286, 1994. (5) X. Xu and S. A. Miller. Plant Dis. 97:988, 2013.

scholarly journals First Report of a Leaf Spot Disease of Tobacco Caused by Pseudomonas cichorii in China

Plant Disease ◽  
2021 ◽  
Author(s):  
Dayu Lan ◽  
Fangling Shu ◽  
Yanhui Lu ◽  
Anfa Shou ◽  
Wei Lin ◽  
...  
Keyword(s):  
Pseudomonas Syringae ◽  
Leaf Spot ◽  
Leaf Spot Disease ◽  
Pathogenicity Test ◽  
Pseudomonas Cichorii ◽  
Koch’S Postulates ◽  
First Report ◽  
Initial Symptoms ◽  
Wide Range ◽  
Koch's Postulates

Tobacco (Nicotiana tabacum L.), one of the chief commercial crops, is wildly cultivated worldwide. In June 2020 and 2021, an unknown bacterial leaf spot on tobacco was found in Hezhou and Hechi City, Guangxi, China. 30% of the tobacco were affected and the rate of diseased leaves reached about 10% in the field under high temperature and rainstorm. The disease mainly damaged the middle and top leaves of tobacco plants at vigorous growing stage. The initial symptoms were water-soaked spots on the frontal half of a leaf, and then expanded into circular to irregular spots with a yellow halo at the edge. The spots mostly appeared dark brown at high air humidity, while yellow brown at low humidity and exhibited a concentric pattern. In severe cases, the lesions coalesced and the whole leaf was densely covered with lesions, resulting in the loss of baking value. A bacterium was consistently isolated from diseased leaf tissues on nutrient agar (NA). Growth on NA was predominantly grayish white circular bacterial colonies with smooth margins, and the bacterium is rod-shaped, gram-negative and fluorescent on King’s B medium. Seven isolates (ND04A-ND04C and ZSXF02-ZSXF05) were selected for molecular identification and pathogenicity tests. Genomic DNA of the bacterium was extracted and the housekeeping gene of cts (encoding citrate synthase) was amplified with the primers cts-Fs/cts-Rs (forward primer cts-Fs: 5’-CCCGTCGAGCTGCCAATWCTGA-3’; reverse primer cts-Rs: 5’-ATCTCGCACGGSGTRTTGAACATC-3’) (Berge et al. 2014; Sarkar et al. 2004). 409-bp cts gene sequences were deposited in the GenBank database for seven isolates (accession no. OK105110-OK105116). Sequence of seven isolates shared 100% identity with several Pseudomonas cichorii strains within the GenBank database (accession no. KY940268 and KY940271), and the phylogenetic tree of cts genes of the seven isolates clustered with the phylogroup 11 of Pseudomonas syringae (accession no. KJ877799 and KJ878111), which was classified as P.cichorii. To satisfy Koch’s postulates, a pathogenicity test was tested by using a needle to dip a suspension of the bacterium (108 CFU/ml) and pricking three holes in the tobacco leaf. The control plants leaves were needled with sterile water. Each tobacco plant was inoculated with three leaves, and the test was repeated three times. All plants were placed in transparent plastic boxes and incubated in a greenhouse at 25 ± 3°C. The water-soaked spots appeared 24h after inoculation and quickly expanded through leaf veins. Three days after inoculation, all the inoculated leaves showed symptoms similar to those observed in the field. Control plants remained healthy. Only P. cichorii was successfully re-isolated from the lesions, confirming Koch’s postulates. Pseudomonas cichorii can infect eggplant, lettuce, tomatoand other crops, and has a wide range of hosts (Timilsina et al. 2017; Ullah et al. 2015). To our knowledge, this is the first report of P. cichorii causing leaf spot on tobacco in China.

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 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 Xanthomonas campestris pv. campestris as the causal agent of necrotic leaf spot in Phaseolus vulgaris at Puebla, Mexico

Plant Disease ◽  
2021 ◽  
Author(s):  
Conrado Parraguirre-Lezama ◽  
Omar Romero Arenas ◽  
Maria de los Angeles Valencia de Ita ◽  
Antonio Rivera ◽  
Nemesio Villa-Ruano ◽  
...  
Keyword(s):  
Leaf Spot ◽  
Xanthomonas Campestris ◽  
Casamino Acid ◽  
Bacterial Suspension ◽  
Pathogenicity Test ◽  
Distilled Water ◽  
Tetrazolium Chloride ◽  
First Report ◽  
Bean Plants ◽  
Xanthomonas Campestris Pv Campestris

Beans are the most cultivated legume in the world. In Mexico, it is the second most important crop after corn (FAO 2020; SIAP 2020). Bean plants “Flor de Mayo M38” variety were affected by a foliar disease during the agricultural cycle 2019 in Puebla-Mexico (19°02'46.6" LN and 98°05'15.6" LO). Necrotic V- shaped lesions were observed on the margins of the leaves surrounded by yellow halos followed by foliar necrosis, affecting 40% of the crop. In Mexico this variety of cultivars is in great demand for local consumption and generates income in foreign currency (Castellanos et al. 1997). Sampling was carried out on 50 plants “Flor de Mayo M38” variety, with necrotic leaf symptoms from ten plots of one hectare. Samples were cut into pieces (5 mm), disinfested with 1% hypochlorite 3 min, and washed with sterile distilled water. Subsequently, samples were dried on sterile paper and placed on Petri plates containing yeast extract calcium carbonate dextrose agar (YDC) medium and kept at 36°C for 3 days. Colonies of ten typical bacteria isolated from all symptomatic plants were Gram (-), small and uniform in size with rounded edges, yellow, convex with entire borders and mucoid appearance on YDC. Bacteria did not grow on 0.1% triphenyl tetrazolium chloride amended casamino acid, peptone, and glucose medium (CPG). Biochemical tests showed that isolates did not reduce nitrate to nitrites, had positive catalase and starch hydrolysis, while the Kovac oxidase test was negative (Schaad and White 1974). Genus identity of the representative isolate Xcf1-APJR, was confirmed by 16S rRNA encoding gene partial sequencing, using universal primers 518F (5'-CCAGCAGCCGCGGTAATACG-3') and 800R (5′-TACCAGGGTATCTAATCC-3′) (Halim et al. 2020). BLASTn alignments against the nucleotide collection were 100% identical to Xanthomonas sequences including Xanthomonas campestris pv. campestris strains NZ_AP019684.1, CP025750.1, and MN108237.1. The 1,418 bp sequence was deposited in the GenBank database under accession number MT645246. The identification of species/pathovar was accomplished by serological methods using a polyclonal antiserum specific for X. campestris pv. campestris (Popovic ́ et al. 2013) with the DAS-ELISA commercial kit (catalog number 07122C/096, LOEWE Biochemica GmbH, Germany). The pathogenicity test was carried out on 50 healthy bean plants from the "Flor de Mayo M38" variety. Bacterial culture incubated at 28°C for 48 h in YDC medium was used to prepare the bacterial suspension (108 CFU mL-1). The first two lower leaves of 30-day-old plants were inoculated by sprinkling. Ten plants sprayed with sterile distilled water were used as negative control. All plants were kept for 20 days in greenhouse at 18-26°C and relative humidity of 60%. After seven days, chlorotic lesions developed on all inoculated plants that became necrotic from 14 days after inoculation (dai). Necrotic leaf spots merged at 14 dai to form necrotic areas of more than 20 mm in diameter, reaching total necrosis of the leaf tissue at 20 dai and were similar to the symptoms observed in the field. Koch's postulates were confirmed by the reisolation of Xcf1-APJR strain, which presented the same colony morphology, partial sequence, and polyclonal specific detection. This is the first report of this pathogen causing necrotic leaf spot in beans from the "Flor de Mayo M38" variety in Puebla-Mexico. The author(s) declare no conflict of interest. References: FAO. 2020. FAOSTAT. Food and Agriculture Data. http://www.fao.org/faostat/en/#home/. SIAP. 2020. Atlas Agroalimentario. https://www.gob.mx/siap/. Castellanos, J. Z., et al. 1997. Arch. Latinoam. Nutr. 47:163. Schaad, N. W., and White, W. C. 1974. Phytopathology. 64:876. https://doi.org/10.1094/Phyto-64-876 Halim, R. A., et al. 2020. HAYATI J. Biosciences. 27:215. https://doi.org/10.4308/hjb.27.3.215 Popovic ́, T., et al. 2013. Plant Dis. 97:418. https://doi.org/10.1094/PDIS-05-12-0506-PDN

scholarly journals First Report of Leaf Spot Caused by Didymella americana on Cassia nomame in China

Plant Disease ◽  
2021 ◽  
Author(s):  
Weiming Sun ◽  
Lina Feng ◽  
Xiaolei Wen ◽  
Bojia Han ◽  
Danrun Xing ◽  
...  
Keyword(s):  
Sequence Analysis ◽  
Leaf Spot ◽  
Disease Incidence ◽  
Morphological Characteristics ◽  
Rrna Gene ◽  
Pathogenicity Test ◽  
Koch’S Postulates ◽  
First Report ◽  
Initial Symptoms ◽  
Koch's Postulates

Cassia nomame (Sieb.) Kitagawa is an annual plant in the Leguminousae family. The aerial parts of C. nomame have been used as tonic and diuretic in Korea and Japan (Syed et al. 2019). A leaf spot was observed on the leaves of a 1-year-old C. nomame landrace in Changli County (39.42°N, 119.10°E), Qinhuangdao City, Hebei Province during August to October in 2018. In many fields (n≥3), the disease incidence over 80% in the middle and late stage of plant growth. Symptoms on leaves in one field began with many small, dark necrotic spot lesions. Later, the lesions spread to round-to-oval, slightly sunken in the center, and large necrotic patches with indefinite margins. Finally, lesions coalesced and resulted in defoliation. Lesions were occasionally observed on the pods. Symptoms on the pods were initially small, dark spots and then expanded to large necrotic patches with irregular edges. Symptomatic tissues (n=32) from pods and leaves were cut into 3 to 8 mm2 squares, surface disinfested with 75% ethanol for 10 s, rinsed with sterile distilled water, then placed on potato dextrose agar (PDA) at 28℃. After 3 days, ten isolates with consistent characteristics were obtained with a frequency 52.6%. The isolates on PDA were round, initially pale and had little aerial mycelium, gradually turned olive green and had dense wool-like dense aerial mycelia after 3 days. Conidia were hyaline, smooth, solitary, and elliptical. The conidia measured 5.4 to 8.2 μm × 2.5 to 3.8 μm (n=50), and has two oil bodies positioning at opposite poles. Pigmented chlamydospores were spherical or nearly pear-shaped, and solitary. Black fructifications (pycnidia) were produced profusely on PDA after subculture for 3 days. All the isolates were similar to Didymella sp. in morphology (Aveskamp et al. 2009). Choice three isolates YSGUO8 YSGGUO8-a and YSGGUO8-b to be further characterized by sequencing of the internal transcribed spacer (ITS), actin gene, and 28S large subunit of the nuclear rRNA gene (LSU) (Zhang et al. 2017). The sequences of three strains (MK836417 MZ484072 and MZ484073 for ITS, MK837604 MZ593675 and MZ593676 for actin, MK843781 MZ836208 and MZ836207 for LSU, respectively) showed 99% to 100% similarity with Didymella americana K-004 (KY070279 for ITS,KY070285 for LSU), Phoma americana CBS 256.65 (FJ426973 for ITS, FJ426871 for actin, MH870196 for LSU) and P. americana CBS 185.85 (FJ426972 for ITS, FJ426870 for actin, GU237990 for LSU) in GenBank. The fungi were identified as D. americana (formerly P. americana or Peyronellaea americana) on the basis of morphological characteristics and sequence analysis. A pathogenicity test was conducted with three times on 1-year-old C. nomame strain at the 4 to 6 compound leaf stage. Conidia were obtained from 7-day-old PDA cultures grown at 28℃ with a 12-h photoperiod. Koch’s postulates were fulfilled by spray inoculating ten healthy young plants with 106 conidia per milliliter of D. americana strain YSGUO8, and sterile water as the control. After inoculation, the plants were managed at 28℃, 60% relative humidity and a 12-h photoperiod. After 5 to 8 days, the inoculated leaves developed small and dark spots lesions similar to those observed on the leaves with initial symptoms in the field. The control leaves remained symptomless. The same fungi were re-isolated from infected leaves by morphology observation and sequence analysis, confirming Koch's postulates. D. americana has caused leaves spot on Table Beet in New York (Vaghefi et al. 2016). To our knowledge, this is the first report of D. americana causing leaf spot of C. nomame in China.

scholarly journals Bacterial Leaf Spot of Onion Caused by Pseudomonas syringae pv. porri, a New Disease in Korea

Plant Disease ◽  
2011 ◽  
Vol 95 (10) ◽  
pp. 1311-1311 ◽  
Author(s):  
I.-S. Myung ◽  
J. H. Joa ◽  
H. S. Shim
Keyword(s):  
Pseudomonas Syringae ◽  
Leaf Spot ◽  
Reference Strain ◽  
Leaf Surface ◽  
Bacterial Suspension ◽  
Distilled Water ◽  
Bacterial Leaf Spot ◽  
Rpod Gene ◽  
Allium Cepa L ◽  
Spray Inoculation

In April 2007, a bacterial leaf spot of onion (Allium cepa L.) was observed in fields of Namjeju, Jeju Province in Korea with incidence varying from 95 to 100%. Symptoms on leaves included leaf blight and white and brown spots on the leaf surface. Eight bacterial isolates were recovered on trypticase soy agar (TSA) from leaf spot and blight lesions that were surface sterilized in 70% ethanol for 1 min. The isolates were fluorescent on King's B agar and gram-negative, aerobic rods with one to three polar flagella. All isolates belonged to P. syringae (LOPAT) group Ia (+, −, −, −, +) (1). The gyrB, rpoD (2), and rpoB regions (4) of the isolates and reference strain Pseudomonas syringae pv. porri CFBP 1908PT (=BC2583) were partially sequenced using reported primers (2,4). The rpoB region (1,119 bp) of the isolates (GenBank Accession Nos. JF719311–JF719318 for rpoB) shared 100% identity with P. syringae pv. porri CFBP 1908PT (GenBank Accession No. JF719319). Phylogenetic analysis based on partial sequences of the gyrB (660 bp) and rpoD (590 bp) loci of Pseudomonas spp. available in the GenBank (2,4), the reference strain P. syringae pv. porri CFBP 1908PT, and the field isolates was conducted using Jukes-Cantor model in MEGA Version 4.1 (3). The isolates and reference strain P. syringae. pv. porri CFBP 1908PT clustered in one group (GenBank Accession Nos. JF719293–JF719300 for gyrB; JF719302–JF719309 for rpoD). On the basis of phenotypic and pathological characteristics and the sequences, the eight isolates were identified as P. syringae pv. porri. Pathogenicity was evaluated on 3-week-old onion plants (cv. Marushino 330) by spot and spray inoculation. Bacteria were grown on TSA for 24 h at 28°C. Five microliters of bacterial suspension in sterile distilled water (1 × 106 CFU/ml) were spot inoculated on pinpricked positions of five leaves for each isolate and incubated in humid plastic boxes at 27°C. Spot-inoculated surfaces turned white 2 days after inoculation, followed by brownish discoloration. A bacterial suspension in sterile distilled water (100 ml at 1 × 106 CFU/ml) was sprayed onto three plants for each isolate. Plants were maintained in a greenhouse at 18 to 27°C and 80% relative humidity. Isolates induced identical symptoms on all inoculated plants 2 weeks after spray inoculation as those originally observed on onion in the fields. Bacteria were reisolated 3 weeks after inoculation from diseased lesions surface sterilized in 70% ethanol for 1 min and the identity of the reisolated bacteria confirmed by analyzing the sequences of rpoD gene (2). No symptoms were noted on intact plants inoculated with sterilized distilled water. To our knowledge, this is the first report of bacterial leaf spot of onion caused by P. syringae pv. porri in Korea. The disease is expected to have a significant economic impact on onion culture in the fields of Jeju Province in Korea. References: (1) R. A. Lelliott et al. J. Appl. Bacteriol. 29:470, 1966. (2) H. Sawada et al. J. Mol. Evol. 49:627, 1999. (3) K. Tamura et al. Mol. Biol. Evol. 24:1596, 2007. (4) L. Tayeb et al. Res. Microbiol. 156:763, 2005.

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 Pseudomonas syringae pv. aptata Causing Bacterial Leaf Spot on Sugar Beet in Serbia

Plant Disease ◽  
2015 ◽  
Vol 99 (2) ◽  
pp. 281-281 ◽  
Author(s):  
V. Stojšin ◽  
J. Balaž ◽  
D. Budakov ◽  
Slaviša Stanković ◽  
I. Nikolić ◽  
...  
Keyword(s):  
Sugar Beet ◽  
Pseudomonas Syringae ◽  
Leaf Spot ◽  
Leaf Surface ◽  
Negative Control ◽  
Gyrb Gene ◽  
Bacterial Suspension ◽  
Bacterial Strains ◽  
Gene Sequences ◽  
Bacterial Leaf Spot

A severe bacterial leaf spot was observed during June and July 2013 on commercial cultivars of sugar beet (Beta vulgaris var. saccharifera) in the Vojvodina Province of Serbia. Serbia is a major sugar beet production area in southeastern Europe, with 62,895 ha and 3 million tons of sugar beet yield in 2013. A foliar leaf spot observed in 25 commercial sugar beet fields surveyed ranged from 0.1 to 40% severity. Symptoms were characterized as circular or irregular, 5- to 20-mm diameter, white to light brown necrotic spots, each with a dark margin. Diseased leaves were rinsed in sterilized, distilled water (SDW) and dried at room temperature, and leaf sections taken from the margin of necrotic tissue were macerated in SDW. Isolations from 48 symptomatic leaves onto nutrient agar with 5% (w/v) sucrose (NAS) produced bacterial colonies that were whitish, circular, dome-shaped, and Levan-positive. Representative isolates (n = 105) were Gram negative; aerobic; positive for catalase, fluorescence on King's medium B, and tobacco hypersensitivity; and negative for oxidase, potato rot, and arginine dehydrolase. These reactions corresponded to LOPAT group Ia, which includes Pseudomonas syringae pathovars (2). Repetitive extragenic palindromic sequence (rep)-PCR was used for genetic fingerprinting the isolates using the REP, ERIC, and BOX primers. Twenty-five different profiles were obtained among the strains. From each profile group, one representative strain was sequenced for the gyrB gene (1). Four heterogenic groups were observed, and representative gyrB gene sequences of each group were deposited in the NCBI GenBank (Accession Nos. KJ950024 to KJ950027). The sequences were compared with those of pathotype strain P. syringae pv. aptata CFBP 1617 deposited in the PAMDB database; one strain was 100% homologous, and the other three were 99% homologous. To fulfill identification of the Serbian sugar beet isolates, gltA and rpoD partial gene sequences were determined (1), and the sequences were deposited as Accession Nos. KM386838 to KM386841 for gltA and KM386830 to KM38683033 for rpoD. The sequences were 100% homologous with those of pathotype strain CFBP 1617. Pathogenicity of each of four representative bacterial strains was tested on 3-week-old plants of the sugar beet cultivars Marinela, Serenada, and Jasmina (KWS, Belgrade, Serbia) and Lara (NS Seme, Novi Sad, Serbia) by atomizing a bacterial suspension of ~106 CFU/ml of the appropriate isolate onto the abaxial leaf surface of three plants per cultivar until water-soaking of the leaf surface was observed. Three plants of each cultivar atomized similarly with P. syringae pv. aptata CFBP 2473 and SDW served as positive and negative control treatments, respectively. Inoculated plants were kept in a clear plastic box at 80 to 100% RH and 17 ± 1°C and examined for symptom development over 3 weeks. For all test isolates and the control strain, inoculated leaves first developed water-soaked lesions 7 days after inoculation (DAI). By 10 to 14 DAI, lesions were necrotic and infection had spread to the petioles. By 21 DAI, wilting was observed on more than 50% of inoculated plants. Negative control plants were symptomless. Bacteria re-isolated onto NAS from inoculated leaves had the same colony morphology, LOPAT results, and gyrB partial gene sequences as described for the test strains. No bacteria were re-isolated from negative control plants. Based on these tests, the pathogen causing leaf spot on sugar beet in Serbia was identified as P. syringae pv. aptata. References: (1) P. Ferrente and M. Scortichini. Plant Pathol. 59:954, 2010. (2) R. A. Lelliott et al. J. Appl. Bacteriol. 29:470, 1966.

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