scholarly journals First Report of Black Rot on Arugula Caused by Xanthomonas campestris pv. campestris in Argentina

Plant Disease ◽  
2008 ◽  
Vol 92 (6) ◽  
pp. 980-980 ◽  
Author(s):  
A. M. Romero ◽  
R. Zapata ◽  
M. S. Montecchia
Keyword(s):  
Xanthomonas Campestris ◽  
Pathogenic Bacteria ◽  
Biochemical Characterization ◽  
Bacterial Suspension ◽  
Black Rot ◽  
Strictly Aerobic ◽  
First Report ◽  
Plastic Bags ◽  
Water Plants ◽  
Xanthomonas Campestris Pv Campestris

During the fall of 2005, arugula (Eruca sativa Mill.) plants grown in experimental field plots in Buenos Aires, Argentina presented V-shaped necrotic lesions on leaf margins and blackened veins with broad yellow halos, followed by leaf necrosis. At flowering, 96% of the plants were affected with 27% of the leaves with symptoms. Yellow, round, mucoid, convex, bacterial colonies were isolated from several leaves on yeast dextrose chalk agar. Two strains were further studied. Xanthomonas campestris pv. campestris Xcc8004 was used as a control. Strains were gram negative, rod shaped, strictly aerobic, catalase-positive, oxidase and urease-negative, hydrolyzed starch, gelatine and aesculin, and did not reduce nitrate (2). Pathogenicity was tested by spraying 10 3-week-old arugula plants with either a bacterial suspension (107 CFU/ml) or sterile water. Plants were placed in plastic bags for 72 h after inoculation. All inoculated plants showed necrotic lesions enlarging from the margin of the leaves 7 days after inoculation. No lesions were observed on control plants. On the basis of biochemical characterization (2) and genomic fingerprints generated by BOX-PCR (1), the pathogen was identified as X. campestris pv. campestris. To our knowledge, this is the first report of X. campestris pv. campestris causing black rot on arugula in Argentina. References: (1) J. L. Rademaker et al. Int. J. Syst. Evol. Microbiol. 50:665, 2000. (2) N. W. Schaad et al. Laboratory Guide for Identification of Plant Pathogenic Bacteria. 3rd ed. The American Phytopathological Society, St. Paul, MN, 2001.

scholarly journals First Report of Acidovorax avenae subsp. avenae Causing Bacterial Leaf Stripe of Strelitzia nicolai

Plant Disease ◽  
2011 ◽  
Vol 95 (11) ◽  
pp. 1474-1474 ◽  
Author(s):  
T. E. Seijo ◽  
N. A. Peres
Keyword(s):  
Pathogenic Bacteria ◽  
Fatty Acid Analysis ◽  
South Florida ◽  
Metabolic Phenotype ◽  
Bacterial Suspension ◽  
Rrna Gene ◽  
First Report ◽  
Plastic Bags ◽  
Young Leaves ◽  
Symptomatic Tissue

White bird of paradise (Strelitzia nicolai Regel & K. Koch) is a commonly grown ornamental in central and south Florida. Each summer of 2004 to 2007, a reoccurring disease was observed at a commercial nursery in central Florida. Diseased plants had brown, necrotic stripes between the lateral leaf veins, which usually appeared along the midvein and spread toward the leaf edge. Lesions developed on the youngest leaves as they emerged from the central whorl. During 2004 and 2005, 20 symptomatic leaves were sampled. A white, nonfluorescent bacterium was consistently isolated from symptomatic tissue. It induced a hypersensitive response (HR) on tomato, grew at 41°C, and was identified as a Acidovorax sp. based on fatty acid analysis and as Acidovorax avenae subsp. avenae by Biolog metabolic phenotype analysis (similarity 0.76 to 0.86). A partial 16S rRNA gene sequence (1,455 bp) (Accession No. EF418616) was identical to four sequences in the NCBI (National Center for Biotechnology Information) database: one from A. avenae subsp. avenae and three from A. avenae of undetermined subspecies. To confirm pathogenicity, a bacterial suspension (O.D590 = 0.1) was applied to fill the central whorl (~0.5 to 1 ml) of potted S. nicolai. Plants were incubated for 7 to 10 days inside plastic bags at ambient temperature. Plants were inoculated individually with five strains of A. avenae subsp. avenae, four from S. nicolai, and one from corn (ATCC19860). Two to nine plants per strain were inoculated in each experiment. All strains were tested at least twice and noninoculated control plants were included. Symptoms were reproduced on the emerging leaf of 50 to 100% of inoculated plants with all five A. avenae subsp. avenae strains. No symptoms were observed on the controls. The bacteria recovered from symptomatic tissue were confirmed to be A. avenae subsp. avenae. Corn seedlings were inoculated as described above, except that entire seedlings were sprayed. Water-soaked lesions along the length of older leaf blades developed in 4 to 7 days. Only the corn strain was pathogenic (>80% of seedlings symptomatic), indicating host specificity. To our knowledge, this is the first report of A. avenae subsp. avenae infecting S. nicolai. In 1971, Wehlburg (2) described the same symptoms on orange bird of paradise (S. reginae) as being caused by a nonfluorescent Pseudomonas sp. This report likely describes the same disease since the published description is consistent with symptoms caused by A. avenae subsp. avenae. The pathogen reported by Wehlburg (2) had one polar flagellum, reduced nitrate, produced oxidase and a HR, and utilized arabinose, but not sucrose or arginine, characteristics consistent with those of A. avenae subsp. avenae (1). The only difference was A. avenae subsp. avenae has a delayed positive starch hydrolysis (1), whereas Welhburg's strain was negative. This disease occurs mainly on young leaves when plants receive daily overhead irrigation. Incidence can be as high as 40%, occasionally causing mortality, but even mild symptoms affect appearance and reduce marketability as an ornamental. References: (1) N. W. Schaad et al. Laboratory Guide for Identification of Plant Pathogenic Bacteria. 3rd ed. The American Phytopathological Society, St. Paul, MN, 2001. (2) C. Wehlburg. Plant Dis. Rep. 55:447, 1971.

scholarly journals First Report of Xanthomonas campestris pv. campestris Causing Marginal Leaf Necrosis of Arugula (Eruca vesicaria subsp. sativa) in Serbia

Plant Disease ◽  
2021 ◽  
Author(s):  
Andjelka Prokić ◽  
Tamara Marković ◽  
Jelena Menković ◽  
Milan Ivanovic ◽  
Aleksa Obradoviċ
Keyword(s):  
Xanthomonas Campestris ◽  
Disease Incidence ◽  
Positive Control ◽  
Negative Control ◽  
Accurate Information ◽  
Strictly Aerobic ◽  
Distilled Water ◽  
Tetrazolium Chloride ◽  
First Report ◽  
Xanthomonas Campestris Pv Campestris

Arugula (Eruca vesicaria subsp. sativa (Miller) Thell., syn. Brassica eruca L.), is an annual cruciferous crop that is increasingly grown for fresh consumption in Serbia. In November 2018, a few detached leaves of cultivated arugula originating from a local producer, showing necrotic lesions, were observed in a fresh vegetable market in Belgrade, Serbia. Information about the disease incidence and severity was not available. Intensity of the observed symptoms was low, but it could be a consequence of the produce quality selection for the market. The leaves developed irregular chlorotic lesions starting from the leaf edge, and tissue within some of them turned dark brown and necrotic (Fig. 1a). From the lesions on different leaves, smooth, bright yellow pigmented, round and opalescent bacterial colonies were isolated on nutrient agar (NA) medium after 72 h of incubation at 26°C. Six bacterial isolates, obtained from three leaf subsamples which induced hypersensitive reaction in tobacco leaves (Nicotiana tabacum L. cv. Samsun), were selected for further studies. On yeast - dextrose – CaCO3 medium, the strains formed characteristic creamy yellow, mucoid, opaque and convex colonies. All isolates were Gram-negative, strictly aerobic, non-fluorescent and catalase positive, did not produce oxidase nor arginine dehydrolase, and did not show pectynolitic activity on potato tuber slices. They hydrolyzed starch, gelatine and esculin, used glucose and sucrose, but not arabinose as a carbon source, and did not reduce nitrates. They grew at 36°C, and tolerated 5% NaCl and 0.02% triphenyl-tetrazolium chloride (Lelliott and Stead, 1987). These growth characteristics were similar as for the reference Xanthomonas campestris pv. campestris (Xcc) strain KFB 105, used in all tests as a positive control (Obradović et al., 2000). The isolates were further characterized by polymerase chain reaction (PCR) using primers DLH120/DLH125, specific for the hrpF gene region of X. campestris according to Berg et al. (2005). Specific DNA fragment of 619 bp was amplified for all tested isolates. Amplification and partial sequencing of the gyrB gene of four isolates was performed using set of primers described by Parkinson et al. (2007). All obtained partial gyrB sequences were identical to each other. According to BLAST analysis (GenBank Acc. Nos. MW508894 - MW508897) they shared 100% of sequence identity with different Xcc strains and 99.5 % with the X.c. pv. raphani pathotype strain, deposited in the NCBI GenBank database. Pathogenicity of the isolates was tested by spraying leaves of 3-week old E. sativa seedlings grown in a commercial potting mix in a greenhouse, with a 24 h-old bacterial culture suspended in sterile distilled water (107 CFU/ml). Xcc strain KFB 105 was used as positive and sterile distilled water as negative control. Inoculated plants were incubated under plastic bags for 48 h and further maintained in a greenhouse at approx. 28°C. On inoculated plants, chlorotic lesions, spreading from the leaf margins, further coalescing into irregular, V-shaped tissue necrosis associated with blackening of veins, developed up to two weeks after inoculation (Fig. 1b, c). The colonies reisolated from symptomatic leaves were identified using PCR, as described above. Based on studied characteristics, all six isolates associated with arugula leaf lesions in Serbia belong to a clonal population. They were identified as X. campestris pv. campestris, the causal agent of black rot, a major disease affecting crucifers, including arugula worldwide (Romero et al., 2008; Rosenthal, et al., 2018). So far, it has been described on Brassica oleracea and B. napus in Serbia (Obradović et al., 2001; Popović et al., 2019). This is the first report of Xcc infecting arugula in this country. The severity of the symptoms developed on artificially inoculated plants indicated significant potential of the pathogen to affect arugula crop in conditions favoring infection. Being a minor crop, accurate information about severity of arugula diseases in Serbia is not available. Lack of crop rotation and close proximity of other Xcc host species on a farm could contribute to further spreading of this problem. Follow up of this arugula disease should reveal the distribution, population structure and genetic diversity of Xcc strains affecting this crop in Serbia.

scholarly journals First Report of Black Rot of Cauliflower and Kale Caused by Xanthomonas campestris pv. campestris in Yugoslavia

Plant Disease ◽  
1999 ◽  
Vol 83 (10) ◽  
pp. 965-965 ◽  
Author(s):  
A. Obradović ◽  
M. Arsenijević
Keyword(s):  
Xanthomonas Campestris ◽  
Pathogenic Bacteria ◽  
Black Rot ◽  
Triphenyl Tetrazolium Chloride ◽  
American Phytopathological Society ◽  
Tetrazolium Chloride ◽  
Gram Negative ◽  
First Occurrence ◽  
Dark Green ◽  
Xanthomonas Campestris Pv Campestris

In Yugoslavia, Xanthomonas campestris pv. campestris was isolated from forage kale in 1964 and cabbage in 1997 (1). Recently, the incidence and severity of black rot symptoms on cabbage, cauliflower, and kale have increased. Gram-negative, rod-shaped, motile bacteria were isolated from the diseased leaf and vascular tissues of cauliflower and kale plants collected from 1995 to 1998. The isolates formed yellow, convex, mucoid colonies on yeast dextrose chalk medium, metabolized glucose oxidatively, grew at 37°C, hydrolyzed gelatin and esculin, produced acids from d-arabinose, glucose, sucrose, and trehalose, and did not reduce nitrates. They were nonfluorescent, amylolytic and pectolytic, oxidase negative and catalase positive, and tolerant to 5% NaCl but not to 0.1% triphenyl tetrazolium chloride. Koch's postulates were completed by injecting bacterial suspensions (108 CFU/ml) into leaf petioles of cabbage, cauliflower, and kale seedlings (2- to 3-leaf stage). Dark green watersoaking of petioles and leaf veins followed by yellowing and collapse of inoculated plants was observed after 3 to 5 days. When compared with published information (2), the isolates were identified as X. campestris pv. campestris. This is the first occurrence of this bacterium in cauliflower and kale in Yugoslavia. References: (1) O. Jovanovic et al. Plant Prot. Belgrade 221:175, 1997. (2) N. W. Schaad. 1988. Laboratory Guide for Identification of Plant Pathogenic Bacteria. 2nd ed. The American Phytopathological Society, St. Paul, MN.

scholarly journals First Report of Bacterial Blight of Four O'Clock (Mirabilis jalapa), Caused by Xanthomonas campestris in California

Plant Disease ◽  
2003 ◽  
Vol 87 (7) ◽  
pp. 874-874 ◽  
Author(s):  
S. T. Koike ◽  
H. R. Azad
Keyword(s):  
Xanthomonas Campestris ◽  
Pathogenic Bacteria ◽  
Carbon Sources ◽  
The United States ◽  
Black Rot ◽  
First Report ◽  
Landscape Plant ◽  
Leaf Spots ◽  
Initial Symptoms ◽  
Mirabilis Jalapa

Four o'clock (Mirabilis jalapa) is an ornamental used in California as a landscape plant. In 2000 and 2001, four o'clock transplants produced in commercial greenhouses in coastal California were severely affected by a foliar disease. Initial symptoms were small (2 to 5 mm diameter), angular, water-soaked leaf spots that often developed first on leaf edges. Spots enlarged, rapidly turned brown to dark brown, coalesced, and caused transplants to take on a blighted appearance. When leaf spots were macerated and streaked onto sucrose-peptone agar, a yellow, mucoid bacterium was consistently isolated. Based on morphological, physiological, and biochemical characteristics, we identified the bacterium as Xanthomonas campestris (2). Furthermore, Biolog GN profiles identified five Mirabilis strains as X. campestris pv. campestris with similarity values of 79.7 to 87.6%. Fatty acid analyses identified them as the same pathovar with similarity values of 75.8 to 82.1%. These strains also used cellobiose and arabinose as carbon sources and produced acid from arabinose, which are characteristic features for this pathovar. Pathogenicity was demonstrated by growing inocula of six strains in nutrient broth shake cultures for 48 h and misting 30 ml of the broth cultures (106 CFU/ml) on sets of 12 potted four o'clock plants. Control plants were misted with sterile broth. After inoculation, plants were incubated in a dew chamber (100% relative humidity at 18°C) for 24 h then maintained in a greenhouse (24 to 26°C). After 7 to 10 days, leaf spots similar to those originally observed developed on all inoculated plants. Bacteria reisolated from these plants were characterized and found to be the same as those used for inoculation. Control plants remained symptomless. Because of the biochemical similarity between Mirabilis strains and the black rot pathogen of crucifers (X. campestris pv. campestris), we inoculated sets of six cauliflower (Brassica oleracea var. botrytis cv. White Magic) plants with five Mirabilis strains and two X. campestris pv. campestris strains using the same method. After 14 days, cauliflower plants inoculated with Mirabilis strains were symptomless, while plants inoculated with the black rot pathogen developed symptoms typical of this disease. X. campestris was only reisolated from the cauliflower plants inoculated with the crucifer strains. Because the four o'clock transplants from the commercial greenhouse were produced in close proximity to vegetable hosts of other Xanthomonas pathogens, we inoculated pepper (Capsicum annuum), tomato (Lycopersicon esculentum) and four o'clock transplants with four Mirabilis strains using the method described. The four o'clock strains failed to cause any disease on pepper and tomato but resulted in typical leaf spots on four o'clock. Bacteria reisolated from four o'clock plants and characterized were the same as the original strains. All inoculation experiments were repeated and results were the same. To our knowledge, this is the first report of X. campestris on four o'clock in California and the United States. Occurrence of this disease on direct-seeded plants in enclosed greenhouses provides circumstantial evidence that the pathogen might be seedborne. This pathogen may be related to the Xanthomonas sp. reported on four o'clock in India (1). Reference: (1) J. C. Durgapal and B. M. Trivedi. Curr. Sci. 45:111, 1976 (2) N. W. Schaad et al. Laboratory Guide for Identification of Plant Pathogenic Bacteria, 3rd ed. The American Phytopathological Society, St. Paul, MN, 2001.

scholarly journals First Report of Xanthomonas campestris pv. campestris as the Causal Agent of Black Rot on Oilseed Rape (Brassica napus) in Serbia

Plant Disease ◽  
2013 ◽  
Vol 97 (3) ◽  
pp. 418-418 ◽  
Author(s):  
T. Popović ◽  
J. Balaž ◽  
M. Starović ◽  
N. Trkulja ◽  
Ž. Ivanović ◽  
...  
Keyword(s):  
Oilseed Rape ◽  
Xanthomonas Campestris ◽  
Reference Strain ◽  
Positive Control ◽  
Control Treatment ◽  
Bacterial Suspension ◽  
Bacterial Strains ◽  
16S Rdna Sequence ◽  
Plastic Bags ◽  
Xanthomonas Campestris Pv Campestris

In September 2010, leaves of oilseed rape (Brassica napus L.) with v-shaped, necrotic lesions on the leaf margins surrounded by yellow halos were collected. Symptoms were observed on the domestic cultivar Slavica (IFVC, Novi Sad) located in the Bačka region, Vojvodina, Serbia, from a 3-ha field. Average disease incidence on 3-month-old plants was 45% (15 to 75%). Diseased leaves were rinsed in sterilized distilled water (SDW) and dried at room temperature for isolations. Leaf sections taken from the margin of necrotic leaf tissue were macerated in SDW and the extract was streaked onto yeast extract-dextrose-calcium carbonate (YDC) agar. Plates were incubated at 28°C for 3 days. Colonies were yellow, translucent, circular, and raised. Ten representative strains tested further were all gram-negative, catalase-positive, and oxidase-negative. The partial 16S rDNA sequence of a representative strain, TUr1, was amplified using primers fD1 and rD1 (2), and determined using the IMGGI SeqService facility in Belgrade. The 1,510-bp 16S rDNA sequence of TUr1 was compared to that of known strains in the NCBI GenBank database, and showed greatest similarity with that of Xanthomonas campestris pv. campestris (Xcc) strains ATCC 33913 and B100 (99% homology). Pathogenicity of 10 strains grown for 48 h on YDC at 28°C was completed using each of three methods: spraying a bacterial suspension (108 cfu/ml) onto the leaf surfaces of oilseed rape plants, stabbing the major veins of each of the first two true leaves with the tip of a sterile toothpick that had been dipped into a colony of the appropriate strain, and immersing cotyledons of the plants into a bacterial suspension (108 cfu/ml). All three tests were performed on 4-week-old oilseed rape plants of the cultivar Slavica. SDW was used for the negative control treatment for each method of inoculation. Reference strain Xcc NCPPB 1144 was used as a positive control treatment. Tests plants (two for each method of inoculation and each bacterial strain or control treatment) were maintained in a greenhouse at 25 ± 1°C and 80% relative humidity by keeping the plants in plastic bags. Two control plants for each of the negative and positive control treatments for each inoculation method were also enclosed in separate plastic bags. The bacterial strains and reference strain caused yellow lesions on inoculated plants that turned necrotic starting about 7 days after inoculation (DAI). The spots coalesced within 21 DAI to form necrotic areas. Plants inoculated with SDW remained symptomless. Reisolations were done onto YDC as described above. Reisolated strains showed the same colony morphology as described above. The bacterial strains grew at 35°C; produced levan from sucrose, hydrogen sulfide, and indole; did not reduce nitrate; hydrolyzed Tween 80; starch, gelatin, and aesculin; did not show tolerance to 0.10 and 0.02% triphenyl-tetrazolium chloride; and produced acid from d-arabinose, arginine, dulcitol, galactose, d-glucose, maltose, mannose, sorbitol, sucrose, and xylose (1). All strains tested by Plate Trapped Antigen-ELISAs (ADGEN Phytodiagnostics, Neogen Europe Ltd., Scotland) reacted with Xcc-specific polyclonal antibodies. Based on these tests, the strains were identified as Xcc. To our knowledge, this is the first report of this pathogen causing black rot of oilseed rape in Serbia. References: (1) T. B. Adhikariand and R. Basnyat. Eur. J. Plant Pathol. 105:303, 1999. (2) W. G. Weisburg et al. J. Bacteriol. 173:697, 1991.

scholarly journals Recent Outbreaks of Black Rot of Brassicas Caused by Xanthomonas campestris pv. campestris in Southern Mozambique

Plant Disease ◽  
2009 ◽  
Vol 93 (11) ◽  
pp. 1218-1218
Author(s):  
J. Bila ◽  
A. M. Mondjana ◽  
E. G. Wulff ◽  
C. N. Mortensen
Keyword(s):  
Xanthomonas Campestris ◽  
Pathogenic Bacteria ◽  
Identification System ◽  
Black Rot ◽  
Microbial Identification ◽  
Brassica Spp ◽  
Brassica Crop ◽  
Leaf Tissues ◽  
Pathogenicity Tests ◽  
Xanthomonas Campestris Pv Campestris

In August and September of 2007, black rot symptoms were observed on seedbed and field plants of Brassica spp. grown in the southern districts of Boane, Mahotas, and Chòkwé in Mozambique. One hundred eighty-two cabbage-growing households were evaluated for the incidence of Xanthomonas campestris pv. campestris. Five Brassica cultivars, Glory F1, Glory of Enkhuizen, Copenhagen Market, Starke (Brassica oleracea pv. capitata L.), and Tronchuda (B. oleracea L. var. costata DC) were grown in the areas for several years. The hybrid Glory F1 was the most popular grown cultivar in the surveyed areas. In the Boane district, the highest incidence of black rot was recorded on Copenhagen Market (70%), Starke (67.9%), and Glory F1 (67.3%). In Chòkwé, Tronchuda (Portuguese kale) was the least affected Brassica crop. Water-soaked lesions starting at the edge of leaves with typical V-shaped necrotic lesions and vein discoloration were the most commonly observed symptoms. When examined with a microscope, cut edges of symptomatic stem and leaf tissues consistently exhibited bacterial streaming. The bacteria were isolated from commercial seed and field-grown plants on semiselective agar media (2). Forty-six X. campestris pv. campestris strains that were gram negative, aerobic, starch positive, nitrate negative, and oxidase negative or weakly positive (3) were further identified on the basis of ELISA (Agdia Inc., Elhart, IN), GN Biolog Microbial Identification System, version 4.2 (Biolog Inc., Hayward, CA), and PCR-specific primers (1). Pathogenicity tests were conducted by pin inoculating two upper leaves of cabbage (cv. Wirosa) in the 2- to 3-leaf stage with bacterial growth from 24-h-old agar cultures (2). Black rot symptoms developed on nearly all inoculated plants within 7 to 14 days. No symptoms were observed on control plants inoculated with a sterile pin without bacterial inoculum. The severity of black rot of Brassica spp. in three important farming districts caused significant losses in Mozambique. References: (1) T. Berg et al. Plant Pathol. 54:416, 2005. (2) S. J. Roberts and H. Koenraadt. Page 1 in: International Rules for Seed Testing: Annexe to Chapter 7 Seed Health Methods. ISTA, 2007. (3) N. W. Schaad et al. Laboratory Guide for Identification of Plant Pathogenic Bacteria. 3rd ed. The American Phytopathological Society, St. Paul, MN, 2001.

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 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.

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