Report Of Bacterial Leaf Blight Research Articles

First report of bacterial leaf blight on tea: an emerging threat to the Indian tea industry

First report of bacterial leaf blight on tea: an emerging threat to the Indian tea industry

First Report of Bacterial Leaf Blight caused by Enterobacter asburiae on Sorghum in Jiangsu Province, China.

Sorghum (Sorghum bicolor [L.] Moench) is a major cereal crop in China, with a planting area of more than 674666 ha in 2021. In August 2022, bacterial leaf blight symptoms were observed on sorghum plants grown in a field in Huai'an (119.30437 ºE, 33.999644 ºN), in Jiangsu Province (Fig. 1). To determine the causal agent, four symptomatic leaves from different plants were surface sterilized with 75% (v/v) ethanol for 1 min and washed three times with ddH2O. The surface-sterilized plant tissues were cut into small pieces (4 × 4 mm in size) and cultured on Nutrient Agar (NA) plates at 28ºC for 24 h. To obtain pure cultures, these colonies were transferred to fresh NA plates by using the conventional streak plate method. The purified bacterial cells were rod-shaped, from 1.14 to 1.66 μm long, and from 0.61 to 0.86 μm wide (number of observations = 31) (Fig. 2). Three isolates were used for further characterization. The Gram stain test indicated that the three isolates were Gram negative. 16S rRNA (27F/1492R primers) and gyrB (UP1/Up2r) genes were amplified and sequenced (Marchesi et al. 1998; Yamamoto and Harayama 1995). The obtained 16S rRNA (0R143361-0R143363) and gyrB sequences (0R146993-0R146995) were submitted to GenBank. The 16S rRNA sequences of the three isolated strains showed over 98% identity (1447/1462, 1438/1462 and 1443/1460 bp) to the E. asburiae reference strains ENIPBJ CG1, CAV1043 and 1808 013 (CP014993.1, CP011591.1 and AP019632.1, respectively). Similarly, the gyrB sequences of the three strains showed 98% identity (1103/1129, 1105/1129 and 1108/1129 bp) to the same E. asburiae reference strains. Four-week-old sorghum plants were used in the pathogenicity tests. A phylogenetic tree was constructed with reference strains (Hoffmann et al., 2005). The healthy leaves were inoculated with bacterial suspensions of the three bacterial isolates (OD600 = 0.6~1.0) using the leaf cutting method (Kauffman et al. 1973). For the control group, sterilized ddH2O was used. Each isolate was inoculated in three healthy plants. Inoculated plants were incubated at 28ºC and 75% humidity with alternating 12-h light and 12-h dark cycles with a photon flux density of 200 mmol/m2/s. After 10 days, bacterial leaf blight symptoms were observed in all the inoculated leaves. The inoculated leaves showed severe browning near the inoculation site (1-2 cm), and advanced yellowing from 2 to 7 cm from the inoculation site, while no symptoms were found in control group. The pathogen was recovered from the infected leaves, and its identity was confirmed by 16S rRNA/gyrB sequencing and morphological analysis, fulfilling Koch's postulates (Fig 2). To our knowledge, this is the first report of E. asburiae causing bacterial leaf blight on sorghum worldwide. This species is a well-known pathogen of humans that can cause nosocomial infections (Markovska et al. 2019; Zhu et al. 2017). Recently, E. asburiae was identified as the causal agent of bacterial blight on rice and tuber rot on radish (Wang et al. 2023; Yu et al. 2021). The emergence E. asburiae as a plant pathogen may be produced by the numerous resistant strains reported during recent years. Pantoea ananatis has been reported as a common companion pathogen of E. asburiae (Xue et al. 2021). This report will help to better understand the host promiscuity of E. asburiae and reveals a new pathogen that affects sorghum production in China. This study also serves as a basis for future studies to develop management strategies and cultivation for the disease to prevent sorghum yield loss. As far as we know, no control method for the management of this new plant pathogen was reported to date, which highlights the potential hazard of this discovery. Reference Hoffmann, H., et al. 2005. Syst. Appl. Microbiol. 28:196. Kauffman, H. E., et al. 1973. Plant Dis. Rep. 57:537. Marchesi, J. R., et al. 1998. Appl. Environ. Microbiol. 64:795. Markovska, R., et al. 2019. Infect. Dis. 51:627. Wang, R., et al. 2023. Plant Dis. in press. https://doi.org/10.1094/PDIS-11-22-2650-PDN Xue, Y., et al. 2021. Plant Dis. 105:2078. Yamamoto, S., et al. 1995. Appl. Environ. Microbiol. 61:1104. Yu, L., et al. 2021. Plant Dis. 106:310. Zhu, B., et al. 2017. J. Glob. Antimicrob. Resist. 8:104.

First report of bacterial leaf blight of rice caused by Sphingomonas sp. in Southern Karnataka, India

Bacterial leaf blight disease is a major biotic constraint of rice cultivation distributed widely in Asia including India. During the survey (Kharif 2019) in southern Karnataka bacterial leaf blight severity ranged from 30-55% was recorded from maximum tillering onwards till the dough stage. The symptoms observed were water-soaked stripes from the tip of the leaves to white wavy margins along one or both the edges turning yellowish white and later became straw-colored and finally dries out. Symptomatic blight disease samples were collected from the field and the causal organism was isolated on nutrient agar medium following colony morphology and biochemical characteristics was studied. The isolates were isolated and tested for pathogenicity on variety Jyothi under glass house condition. DNA fingerprinting of 16SrDNA and nucleotide blast analysis of the seventeen isolates sequenced, five showed 97-100% sequence identity with Sphingomonas panni, Sphingomonas paucimobilis, and Sphingomonas sp. and rest of twelve matched to Xanthomonas oryzae and Pantoea sp.

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

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.

First Report of Bacterial Leaf Blight of Strawberry Caused by Pantoea ananatis in Nova Scotia, Canada

HomePlant DiseaseVol. 104, No. 1First Report of Bacterial Leaf Blight of Strawberry Caused by Pantoea ananatis in Nova Scotia, Canada PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of Bacterial Leaf Blight of Strawberry Caused by Pantoea ananatis in Nova Scotia, CanadaSruti Bajpai, Pushp Sheel Shukla, Mohd Adil, Samuel Asiedu, Kris Pruski, and Balakrishnan PrithivirajSruti BajpaiMarine Bio-products Research Laboratory, Dalhousie University, Department of Plant, Food and Environmental Sciences, Truro, NS, CanadaSearch for more papers by this author, Pushp Sheel ShuklaMarine Bio-products Research Laboratory, Dalhousie University, Department of Plant, Food and Environmental Sciences, Truro, NS, CanadaSearch for more papers by this author, Mohd AdilMarine Bio-products Research Laboratory, Dalhousie University, Department of Plant, Food and Environmental Sciences, Truro, NS, CanadaSearch for more papers by this author, Samuel AsieduDalhousie University, Department of Plant, Food and Environmental Sciences, Truro, NS, CanadaSearch for more papers by this author, Kris PruskiDalhousie University, Department of Plant, Food and Environmental Sciences, Truro, NS, CanadaSearch for more papers by this author, and Balakrishnan Prithiviraj†Corresponding author: B. Prithiviraj; E-mail Address: bprithiviraj@dal.cahttp://orcid.org/0000-0002-9822-5261Marine Bio-products Research Laboratory, Dalhousie University, Department of Plant, Food and Environmental Sciences, Truro, NS, CanadaSearch for more papers by this author AffiliationsAuthors and Affiliations Sruti Bajpai1 Pushp Sheel Shukla1 Mohd Adil1 Samuel Asiedu2 Kris Pruski2 Balakrishnan Prithiviraj1 † 1Marine Bio-products Research Laboratory, Dalhousie University, Department of Plant, Food and Environmental Sciences, Truro, NS, Canada 2Dalhousie University, Department of Plant, Food and Environmental Sciences, Truro, NS, Canada Published Online:11 Nov 2019https://doi.org/10.1094/PDIS-05-19-1042-PDNAboutSectionsSupplemental ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat Strawberry is an economically important crop, and its productivity is challenged owing to pathogen infestation. During the 2017 cropping season, leaf blight-like symptom was observed in commercial fields of strawberry (cultivar Florida Radiance) near Great Village, Nova Scotia, Canada (N 45°24′46″, W 63°34′03″). Small pieces of symptomatic leaf from 10 different plants, collected from different sites, were surface sterilized with 2.5% Clorox and placed on nutrient agar (NA) medium. After incubation at 28°C for 48 h, slimy yellow bacterial colonies were observed near the edges of the plated leaf pieces. The colonies were restreaked on NA plates to obtain single colonies. The isolated bacteria were gram-negative, yellow pigmented, utilized citrate as a carbon source, catalase and indole positive, oxidase negative, and grew on MacConkey glucose agar. Phylogenetic analysis of the partial sequencing of the amplified 16S rDNA with the primers (16F27, AGAGTTTGATCMTGGCTCAG; and 16R519, GTATTACCGCGGCTGCTG) revealed that bacteria were in close proximity to the 16S rDNA of Pantoea ananatis (KX656222.1). This isolate was designated as P. ananatis FANS-17-1, and a partial 16s sequence was submitted to NCBI (MH790888). The isolate’s identity was further confirmed by multilocus gene sequence analysis (Stice et al. 2018) by amplifying gyrB (MH845177), fusA (MH845176), and rpoB (MH880819) from FANS-17-1. To confirm Koch’s postulates, pathogenicity tests were conducted in a glasshouse under controlled environmental conditions (25°C, natural daylight conditions). Ten 1-month-old strawberry (cultivar Florida Radiance) plants were sprayed with a cell suspension of P. ananatis (1 × 106 CFU/ml) on both surfaces of leaves. Plants sprayed with water served as a control. Strawberry plants were irrigated with 200 ml per pot of 1 g/liter solution of 20-20-20 NPK once every 15 days. All plants were covered with transparent plastic bags to maintain humidity. The experiment was repeated three times. After 48 h, the bags were removed. In all the plants, initially disease appeared as water-soaked lesions on the abaxial leaf surface that later turned necrotic. After 21 days, chlorosis spread throughout leaves, and plants succumbed to infection. Disease symptoms were not observed in control plants. The pathogen was reisolated from the symptomatic leaves and was confirmed as P. ananatis using morphological, biochemical, and molecular analyses as described above. To confirm the pathogenicity of the bacteria, we tested the pathogenicity of 10 additional isolates, and all isolates produced similar symptoms. Disease symptoms caused by P. ananatis are host dependent, including leaf spots, blotches, dieback, bulb rot, and fruit rot (Walterson and Stavrinides 2015). P. ananatis has been reported to cause leaf blight in onion and rice (Mondal et al. 2011; Schwartz and Otto 2000). To our knowledge, this is the first report of P. ananatis causing leaf blight in strawberry in Nova Scotia, Canada. This report expands the host range of P. ananatis and highlights the importance of the bacteria as a plant pathogen. Further, the report will help the strawberry industry in Nova Scotia to better manage the disease now that the etiology is known.The author(s) declare no conflict of interest.

First Report of Bacterial Leaf Blight of Rice Caused by Xanthomonas oryzae pv. oryzae in Benin

First Report of Bacterial Leaf Blight of Rice Caused by <i>Xanthomonas oryzae</i> pv. <i>oryzae</i> in Benin

First report of bacterial leaf blight on cosmos (Cosmos bipinnatus Cav.) caused by Pseudomonas cichorii in Japan

Since 2006, a commercial grower in Japan has noted a leaf blight symptom on potted cosmos plants grown in a field. In August 2012, a Pseudomonas-like bacterium was isolated from the symptomatic leaves and found to cause the same symptom on cosmos seedlings after inoculation. On the basis of bacteriological and phylogenetic analyses, the causative bacterium was identified as Pseudomonas cichorii. This is the first report of bacterial leaf blight on cosmos caused by P. cichorii in Japan.

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

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.

First report of bacterial leaf blight of jute (Corchorus capsularis L.) caused by Xanthomonas campestris pv. capsularii in India

Xanthomonas campestris pv. capsularii causing blight on jute (Corchorus capsularis) leaves was reported for the first time in India. The symptom of the disease initially observed was appearance of small angular brown leaf spots and later as blighted areas on leaf lamina. The disease-causing pathogen was isolated and identified on the basis of its colony morphology, PCR, sequencing and subsequent BLASTn analysis.

Bacterial leaf blight of sweet pepper (Capsicum annuum) caused by Pseudomonas cichorii in Japan

Sweet peppers (cv. Tosajishi beauty) with leaf blight symptoms were observed in Kochi Prefecture, 2003. Initially, small spots formed on leaves, and later enlarged to brown to dark brown spots, and eventually blighted leaves fell. Several bacteria that caused the same symptoms were isolated and subsequently reisolated. These bacteria were identified as Pseudomonas cichorii on the basis of bacterial characteristics and the 16S rRNA gene sequence. This is the first report of bacterial leaf blight in the sweet pepper in the world.

First Report of Bacterial Leaf Blight on Broccoli and Cabbage Caused by Pseudomonas syringae pv. alisalensis in South Carolina.

In May of 2009, leaf spot and leaf blight symptoms were observed on broccoli (Brassica oleracea var. italica) and cabbage (B. oleracea var. capitata) on several farms in Lexington County, the major brassica-growing region of South Carolina. Affected areas ranged from scattered disease foci within fields to entire fields. Initial infection symptoms on leaves of both crops included circular and irregular-shaped necrotic lesions that were 3 to 10 mm in diameter, often with yellow halos and water soaking. As the disease progressed, the lesions tended to coalesce into a general blight of the entire leaf. Diseased leaves from both broccoli and cabbage were collected from each of four fields at different locations in the county. Leaves were surface disinfested, macerated in sterile distilled water, then aliquots of the suspension were spread on King's medium B (KB) agar. All samples produced large numbers of bacterial colonies that fluoresced blue under UV light after 24 h of growth. In total, 23 isolates (13 from broccoli and 10 from cabbage) were collected. These isolates were gram negative, levan production positive, oxidase negative, pectolytic activity negative, arginine dihydrolase negative, and produced a hypersensitive response on tobacco, thus placing them in the Pseudomonas syringae LOPAT group (2). Two broccoli and two cabbage isolates were selected at random and tested for pathogenicity to cabbage cv. Early Jersey Wakefield, broccoli cv. Decicco, turnip cv. Topper, broccoli raab cv. Spring, collard cv. Hi-Crop, and oat cv. Montezuma in greenhouse tests. Bacteria were grown on KB agar for 24 h and a bacterial suspension was prepared and adjusted to an optical density of 0.1 at 600 nm. Three-week-old plants were spray inoculated to runoff and held at 100% relative humidity for 12 h after inoculation, prior to return to the greenhouse bench (4). P. syringae pv. maculicola strain F18 (4) and the pathotype strain of P. syringae pv. alisalensis BS91 were included as controls, along with a water-inoculated negative control. Plants were evaluated at 14 days postinoculation. The four unknown bacterial isolates and BS91 were pathogenic on all brassica plants tested, as well as on oat. In contrast, the P. syringae pv. maculicola strain F18 was not pathogenic on broccoli raab or oat. Symptoms produced by all isolates and strains tested were similar to those observed in the field. No symptoms were observed on water-inoculated plants. Comparative repetitive sequence-based (rep)-PCR DNA analysis using the BOXA1R primer (3) resulted in a DNA banding pattern of each of the isolates from the South Carolina fields (23 isolates), as well as those reisolated from inoculated plants, that was identical to P. syringae pv. alisalensis BS91 and differed from the P. syringae pv. maculicola F18 strain. On the basis of the rep-PCR assays and the differential host range (1), the current disease outbreak on broccoli and cabbage in South Carolina is caused by the bacterium P. syringae pv. alisalensis. Broccoli is a relatively new, albeit rapidly expanding, production vegetable in South Carolina; this disease may represent a limiting factor to future production.

First report of bacterial leaf blight of white-flowered calla lily caused by Xanthomonas campestris pv. zantedeschiae in Taiwan

First report of bacterial leaf blight of white-flowered calla lily caused by Xanthomonas campestris pv. zantedeschiae in Taiwan