In 2006 and 2007, a new bacterial disease was observed in field-cultivated soybeans in Boeun District and Munkyung City of Korea. The disease caused severe blighting of soybean (Glycine max) leaves. Soybean leaves in fields showed yellowish spots with brown centers. Brown and dead areas of variable size and shape were surrounded by wide, yellow haloes with distinct margins. Spots might coalesce and affected leaves fell readily. Seven bacterial strains were isolated from chlorotic areas of soybean leaves and all produced white colonies on trypticase soy agar. With the Biolog Microbial Identification System, version 4.2, (Biolog Inc., Hayward, CA) all strains and Pseudomonas syringae pv. tabaci CFBP2106T were identified as P. syringae pv. tabaci with a Biolog similarity index of 0.28 to 0.52 and 0.48 after 24 h. Pathogenicity of the strains (three plants per strain) on soybean leaves at the V5 stage (cv. Hwanggeum) was confirmed by rub inoculation with bacterial suspensions (1 × 108 CFU/ml) in sterile distilled water on the lesions cut 1 cm long on the upper side of the leaves with razor blades and by pinprick on 3-week-old leaves of tobacco (Nicotiana tabacum cv. Samsun) in the greenhouse. Wildfire symptoms on the soybean leaves and faint halos on tobacco leaves were observed 4 days after inoculation. The identification of reisolated bacterial strains was confirmed with the metabolic fingerprintings on Biolog. LOPAT tests (1) and phenotypic characteristics (3) of the strains were similar to those of the CFBP2106T. Colonies were levan positive, oxidase negative, potato soft rot negative, arginine dihydrase negative, and tobacco hypersensitivity negative. All strains were gram-negative, aerobic rods with a polar flagellum. Strains were negative for esculin hydrolysis, gelatin liquefaction, urea production, accumulation of poly-β-hydroxy butyrate, starch hydrolysis, ornithine dihydrolase, lysine dihydrolase, growth at 37°C, utilization of geraniol, benzoate, cellobiose, sorbitol, trehalose, l-rhamnose, and adonitol. Positive reactions were catalase and arbutin hydrolysis, utilization of sorbitol, d-arabinose, and dl-serine. The strains were variable in utilization of mannitol, sucrose, and d-arabinose. The 1,472-bp PCR fragments of strains, BC2366 (GenBank Accession No. FJ755788) and BC2367 (No. FJ755789) was sequenced using 16S rDNA universal primers (2). The sequences shared 100% identity with the analogous sequences of P. syringae pv. glycenea (GenBank Accession No. AB001443) available in NCBI databases. Based on the phenotypic, genetic, and pathological characteristics, all strains were identified as P. syringae pv. tabaci. To our knowledge, this is the first report of P. syringae pv. tabaci causing wildfire on soybean in Korea. References: (1) R. A. Lelliott et al. J. Appl. Bacteriol. 29:470, 1966. (2) I.-S. Myung et al. Plant Dis. 92:1472, 2008. (3) N. W. Schaad et al., eds. Laboratory Guide for Identification of Plant Pathogenic Bacteria. 3rd ed. The American Phytopathological Society, St. Paul, MN, 2001.
In 2007, a new bacterial disease was observed in greenhouse-cultivated cherry tomatoes in Cheorwon and Iksan provinces, Korea. The disease caused severe wilt of tomatoes (Solanum lycopersicum cv. Koko). Infected young petioles were curled downward. Margins of the leaves rolled upward and whole leaves were distorted. Stem cankers had reddish or dark brown cavities. Vascular tissues in stems cut longitudinally were brown to deep brown, but no bird's eye lesions were observed. Eight bacterial strains recovered from the stems of wilted tomatoes produced yellow colonies on nutrient broth-yeast extract agar and pink colonies on triphenyl tetrazolium chloride. Pathogenicity of the strains (three plants per strain) on 18-day-old tomatoes (cv. Koko) was confirmed by clip inoculation of petioles of second leaves and spray inoculation with bacterial suspensions (1 × 108 CFU/ml) in sterile distilled water. Wilt and canker symptoms were observed 2 weeks after inoculation. Symptoms produced by both inoculation methods were systemic and localized. Clip inoculation of tomatoes resulted in wilt, defoliation, and open stem cankers, whereas small, white spots (2 to 3 mm in diameter) and sometimes water-soaked, dark brown-to-black lesions on the leaf margins were observed with spray inoculation. Bacteria were reisolated from stems and leaves of the inoculated plants and their identities confirmed by direct PCR using specific primer set CMM5/CMM6 (1). No symptoms were observed on negative control plants inoculated with sterile water. All strains were gram-positive aerobic rods with no polar flagella. Strains were positive for esculin hydrolysis, gelatin liquefaction, H2S production from peptone, utilization of citrate and succinate, and acid from d(+)mannose and negative for starch hydrolysis, casein hydrolysis, methyl red reaction, acid from inulin, mannitol, d(+)-melezitose and d(–)sobitol, and utilization of acetate, formate, lactate, propionate, and ribose. Identification as C. michiganensis subsp. michiganensis was confirmed using 16S rDNA universal primers fD1 and rP2 (4) and internal primers (3). The 1,439-bp PCR fragment of strain BC2643 was sequenced (GenBank Accession No. EU685335) and compared with reference C. michiganensis subspecies strains in GenBank: AM410696 (C. michiganensis subsp. michiganensis), AM410693 (C. michiganensis subsp. tessellarius), AM410697 (C. michiganensis subsp. nebraskensis), AM410694 (C. michiganensis subsp. sepedonicus), and AM410695 (C. michiganensis subsp. insidiosus). The sequence had a similarity index of 0.999 calculated by Juke-Cantor model (2) with the 16S rRNA sequence of C. michiganensis subsp. michiganensis (AM410696). The fragment size of eight strains amplified by PCR using CMM5/CMM6 (1) was identical to that of the C. michiganensis subsp. michiganensis reference strain KACC20122. On the basis of the physiological, genetic, and pathological characteristics, all strains were identified as C. michiganensis subsp. michiganenesis. To our knowledge, this is the first report of C. michiganensis subsp. michiganenesis causing bacterial canker on tomato in Korea. References: (1) J. A. Dreier et al. Phytopathology 85:464, 1995. (2) S. Kumar et al. Brief. Bioinform. 5:50, 2004. (3) S. W. Kwon et al. Int. J. Syst. Bacteriol. 47:1061, 1997. (4) W. G. Weinsburg et al. J. Bacteriol. 173, 697, 1991.
Background: Forecasting bud physiologic conditions can help ‘Fuji’ apple farmers manage their orchards more efficiently. Being able to determine the nature of a bud before bud burst is one such forecast that could be of use to these ‘Fuji’ growers. The aim of this research project was to determine if a device, a visible/near-infrared spectrometer, could be employed to determine whether a bud is a flower or non-flower bud without destroying the bud. Methods: Experiments were conducted on buds taken from a ‘Fuji’ apple tree, beginning on January 29 through to March 31, 2021, three days before bud burst. The data from the visible/near-infrared spectrometer clarified whether a bud was a flower or a non-flower bud. The Spectro data Classification Learner App proved to be an accurate classification method to analyze flower and non-flower bud Spectro data. Result: Three days before bud burst, the chlorophyll content levels of the non-flower buds were markedly higher (P≤0.05) than those of the flower bud, which explains why the visible border of the near-infrared spectrometer might have been changed by the chlorophyll content of buds. The visible and near-infrared bands of the buds showed that the Spectro data of the non-flower buds were higher than those of the flower buds when measurements were made three days before bud burst. Three days before bud burst Cubic KNN of KNN classifier analyzed flower and non-flower buds smoothly. Spectro data were labeled as accuracy 75.9%, sensitivity 86% and specificity 67%. The results that were obtained suggest that farmers could use a visible/near-infrared spectrometer to identify flower and non-flower buds in their orchards, without damaging the buds, three days before bud burst.
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