A New Disease, Bacterial Leaf Spot of Rape, Caused by Atypical Pseudomonas viridiflava in South Korea.

In March 2007, a bacterial leaf spot of rape (Brassica napus var. oleifera) was observed in fields near Seogwipo City, Jeju Province, South Korea. Symptoms on leaves included white and corky-brown spots and sometimes water-soaked spots on the lower leaf surface. Seven bacterial isolates (BC2495-BC2497 and BC2506-BC2509) were recovered on trypticase soy agar (TSA) from leaf spot lesions surface sterilized in 70% ethyl alcohol for 1 min. Isolates were gram-negative, aerobic rods with one to three flagella. Pathogenicity was evaluated on 2-week-old rape plants by spot and spray inoculation. Bacteria were grown on TSA for 48 h at 25°C. Five microliters of bacterial suspension in sterile distilled water (1 × 105 CFU/ml) were spot inoculated on pinpricked positions of five detached leaves for each isolate. The detached leaves were incubated in a plastic box with high humidity at 20°C. Spot-inoculated surfaces turned white 48 h after inoculation followed by a brownish discoloration. A bacterial suspension in sterile distilled water (100 ml at 1 × 105 CFU/ml) was sprayed onto three plants for each isolate. Plants were maintained in a growth chamber at 20°C and 90% relative humidity. Isolates induced identical symptoms 2 weeks after spray inoculation as those originally observed on rape in the fields. Bacteria were reisolated 18 days after inoculation from diseased lesions surface sterilized in 70% ethyl alcohol for 1 min. Pathogenicity of the reisolated bacteria was confirmed by spot inoculation as described above. No symptoms were noted on detached leaves and intact plants inoculated with sterilized distilled water. Using the Biolog Microbial Identification System, Version 4.2 (Biolog Inc., Hayward, CA), the isolates were identified as Pseudomonas viridiflava with a Biolog similarity index range of 0.52 to 0.72 after 24 h. Results of LOPAT tests (2) of isolates were identical to that of atypical P. viridiflava reported by Gonzalez et al. (1). Levan production and pectolytic activity of the isolates were variable. All isolates were positive for tobacco hypersensitivity and negative for oxidase reaction and arginine dihydrolase production. The 16S rDNA region (1,442 bp) of the isolates (GenBank Accession Nos. HM190218-HM190224; P. viridiflava CFBP2107T = HM190229), amplified by using universal PCR primers, shared 100% sequence identity with atypical P. viridiflava (GenBank Accession No. AM182934) (1). The gyrB sequence (638 bp) from the isolates (GenBank Accession Nos. HM190232-HM190238; P. viridiflava CFBP2107T = HM190239), amplified by using previously reported PCR primers (3), had a distance index value range of 0.029 to 0.031 with that of the P. viridiflava CFBP2107T (=BC2597) as determined by Jukes-Cantor model using MEGA Version 4.1 (4). On the basis of phenotypic characteristics and the sequences, the seven isolates were identified as atypical P. viridiflava. The disease is named "bacterial leaf spot". To our knowledge, this is the first report of bacterial leaf spot of rape caused by atypical P. viridiflava. References: (1) A. J. Gonzalez et al. Appl. Environ. Microbiol. 69:2936, 2003. (2) R. A. Lelliott et al. J. Appl. Bacteriol. 29:470, 1966. (3) H. Sawada et al. J. Mol. Evol. 49:627, 1999. (4) K. Tamura et al. Mol. Biol. Evol. 24:1596, 2007.

Bacterial Spot of Tomato Caused by Xanthomonas perforans, a New Disease in Korea.

In July 2007, a leaf spot was observed on seedlings of tomato (Solanum lycopersicum) in a commercial greenhouse in Sungju County, Korea. Symptoms were dark, circular-to-irregular, water-soaked spots surrounded by chlorotic halos. Affected leaves turned yellow and readily detached. Two bacterial isolates, BC2642 and BC2923, were obtained from leaf lesions. The isolates were gram-negative, aerobic rods with a single flagellum. On peptone sucrose agar, colonies were yellow and raised with smooth margins. Starch and pectate hydrolysis tests were positive. Pathogenicity was confirmed by spraying cell suspensions containing 108 CFU/ml on seedlings of tomato (cv. Seokwang) and hot pepper (Capsicum annuum cv. Daekwang) in a greenhouse maintained at 28 ± 2°C. The isolates induced similar symptoms as those originally observed on tomato and also caused spots and a marginal blight of leaves of pepper 2 weeks after inoculation. No symptoms were noted on the control plants sprayed with sterilized distilled water. The identity of bacteria reisolated from spots on leaves of both plants were confirmed by comparison of patterns of metabolite fingerprints with those from preliminary identification of the isolates using the Biolog Microbial Identification System, version 4.2 (Biolog Inc., Hayward, CA), and reinoculation of the seedlings as above. The 16S rRNA gene (rrs) and the intergenic spacer (IGS) located between the rrs and the 23S rRNA gene, and partial sequences of gyrB were sequenced to aid in the identification of the isolates (1-3). A 2,134-bp fragment of the rrs and IGS regions and 701-bp fragment of the gyrB region from isolates BC2642 and BC2923 were compared with sequences in GenBank. Sequences from both isolates shared 100% similarity to sequences of Xanthomonas perforans (Genbank Accession No. AF123091). On the basis of the sequences and other assays, the two isolates were identified as X. perforans. To our knowledge, this is the first report of bacterial spot of tomato caused by X. perforans in Korea. Nucleotide sequence data reported are available under Accession Nos. GQ461739 and GQ461740 for rrs and IGS of BC2642 and BC2923, respectively, and GQ368187 and GQ380567 for gyrB of BC2642 and BC2923, respectively. An outbreak of this disease in the greenhouse may be due to the use of tomato seeds harvested in foreign countries where spot is known to occur. The disease is expected to have a significant economic impact on tomato culture in Korea. References: (1) J. B. Jones et al. Int. J. Syst. Evol. Microbiol. 50:1211, 2000. (2) N. Parkinson et al. Int. J. Syst. Evol. Microbiol. 59:264, 2009. (3) J. M. Young et al. Syst. Appl. Microbiol. 31:366, 2008.

Analysis of the causes of treatment failure in gamma knife radiosurgery for intracranial arteriovenous malformations.

OBJECT: The authors sought to analyze causes for treatment failure following gamma knife radiosurgery (GKS) for intracranial arteriovenous malformations (AVMs), in cases in which the nidus could still be observed on angiography 3 years postsurgery. METHODS: Four hundred fifteen patients with AVMs were treated with GKS between April 1990 and March 2000. The mean margin dose was 23.6 Gy (range 10-25 Gy), and the mean nidus volume was 5.3 cm3 (range 0.4-41.7 cm3). The KULA treatment planning system and conventional subtraction angiography were used in treatment planning. One hundred twenty-three of these 415 patients underwent follow-up angiography after GKS. After 3 years the nidus was totally obliterated in 98 patients (80%) and partial obliteration was noted in the remaining 25. There were several reasons why complete obliteration was not achieved in all cases: inadequate nidus definition in four patients, changes in the size and location of the nidus in five patients due to recanalization after embolization or reexpansion after hematoma reabsorption, a large AVM volume in five patients, a suboptimal radiation dose to the thalamic and basal ganglia in eight patients, and radioresistance in three patients with an intranidal fistula. CONCLUSIONS: The causes of failed GKS for treatment of AVMs seen on 3-year follow-up angiograms include inadequate nidus definition, large nidus volume, suboptimal radiation dose, recanalization/reexpansion, and radioresistance associated with an intranidal fistula.