• Research in Plant Disease
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• v.20 no.1
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• pp.50-53
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• 2014

Rhizopus soft rot of lily (Lilium longiflorum) caused by Rhizopus oryzae was observed in the experimental field in Taean Lily Experiment Station in Korea, 2012. The typical symptoms were water-soaked lesions on bottom stem and leaf rot. The lesion rapidly expanded and the plant was softened totally. The fungus grew vigorously at an optimum temperature ($25^{\circ}C$) and brownish colony and black sporangia were formed on potato dextrose agar medium. Sporangiophores formed on end of sporangia were sub-globose, brownish and $6-10{\mu}m$ in size. Sporangia were globose, blackish and $87-116{\mu}m$ in size. Sporangiospores were irregularly oval and sub-globose, brownish $4-8{\mu}m$ in size. On the basis of mycological characteristics, analyzing sequences of internal transcribed spacer region of ribosomal DNA, and pathogenicity test on host plants, the causal fungus was identified as R. oryzae. This is the first report of Rhizopus soft rot on lily caused by R. oryzae in Korea.

• Research in Plant Disease
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• v.12 no.3
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• pp.153-157
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• 2006

In 2005, average temperature was lower, and average rainfall was less than those of previous year. The diseases of rice, barley, pepper, chinese melon, apple and oriental pear were surveyed. Bacterial blight, bacterial grain rot, and panicle disease of rice, black rot of pear, and white rot and bitter rot of apple were severe. Especially, brown rot of rice occurred four times higher than those of previous year. Panicle blight of rice increased about 3 times, compared with the previous year, presumed that the higher rainy days, rainfall and RH promoted spread of the fungal pathogens to panicles of rice. The diseases of rice leaf blast, sudden wilt syndrome, downy mildew and powdery mildew of chinese melon in plastic greenhouse, and virus diseases of hot pepper occurred distinctly less than those of the previous year. Another diseases surveyed occurred similar or less.

• Research in Plant Disease
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• v.13 no.1
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• pp.66-70
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• 2007

During 1997 and 1998, a new disease of lettuce (Lactuca sativa) was observed on greenhouse-grown plants in Kwangju and Kwangmyung. Lesions on leaves were irregular, small, pale green to black, water-soaked, and 2 to 5 mm in diameter, Coalescing lesions sometimes caused defoliation of older leaves. Isolations made from diseased leaves on yeast extract dextrose calcium carbonate agar yielded nearly pure cultures of a yellow pigmented bacterium typical of a xanthomonad. Two bacterial strains (SL0246 and SL1352) were purified and used for further tests. Pathogenicity of strains was confirmed on 5-week-old lettuce plants injected with bacterial suspensions containing $10^8$ cfu/ml of phosphate buffered saline. The representative Xanthomonas strains isolated from lettuce were compared with a reference strain X. campestris pv, vitians for fatty acid profiles and metabolic fingerprints using GN2 microplate, showing that all outcomes were indistinguishable between the representative and reference strains. This is the first report of bacterial leaf spot and dry rot of lettuce in Korea.

• Research in Plant Disease
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• v.12 no.2
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• pp.69-74
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• 2006

Basal rot of freesia caused by a Sclerotium sp. occurred at Incheon areas. Incidence of the disease reached up to 45% and averaged 17.0% in the fields. Typical symptoms consisted of sheath dry and leaf blight due to rots on basal leaves. The causal fungus was identified as Sclerotium sp. based on following mycological characteristics. The fungus formed sclerotia on cultural media and plant tissues, but did not produce asexual spores. On cultural medium, aerial mycelia of the fungus changed color from white to clay with cultural age and smelled musty odor. Numerous irregular and elliptical black microsclerotia of the fungus were formed on potato dextrose agar (PDA) after 5 days of incubation at $25^{\circ}C$ and sized $115{\sim}200{\times}95{\sim}150 (av. 145{\sim}126.5){\mu}m$. The fungus grew at $10{\sim}32^{\circ}C$ and $pH 4.0{\sim}8.5$. However, the optimal temperature and pH for mycelial growth of the fungus were $24^{\circ}C$ and 5.5 respectively. The isolate showed present pathogenicity to not only freesia but gladiolus in the pathogenicity test, and the symptoms were similar to those observed in the fields. Basal rot of freesia caused by Sclerotium sp. is firstly reported in Korea.

• Korean journal of applied entomology
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• v.20 no.3 s.48
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• pp.135-145
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• 1981

Vegetables including Chinese cabbage and radish have been grown in alpine areas such as Muju, Namweon, Jinan and Jangsu during the shortage period of vegetables. The incidence of various diseases, environmental factors such as temperatures and rainfalls, and aphid populations as virus vector were observed at 10-day intervals from July to September in those areas. Disease incidence showed no significant difference among locations. Major diseases in Chin ese cabbage were bacterial soft rot, white spot, downy mildew, mosaic virus, Alternaria leaf spot and Fusarium seedling blight. Major diseases in radish were virus, white rust, black rot, root rot, leaf spot and Fusarium seedling blight. Disease incidence reached peak on Aug. 20 with $27\%$ infection in radish and with $20\%$ infection in Chinese cabbage during the growing season, and declined thereafter. Percentage of infection in each growth stage showed $25\%$ at root thickening stage and $26\%$ at the harvest time in radish; and the head formation stage, $24\%$ at the harvest time. The data indicate that disease incidence in radish increased rapidly at late growing stage and progressively increased in Chinese cabbage Seedling blight caused by Fusarium sp. and root rot caused by Aphanomyces sp. were also observed in those areas. Cool and wet weather appeared to be favorable for disease incidences during the rainy period of growing season although average temperature was about $25^{\circ}C$. Populations of aphids were lower in the alpine vegetable growing area than that of flat areas. Aphids as virus vectors from total aphids collected were $73.5\%$ or 289 virus vectors /993 total aphids in Namweon and $18.1\%$ or 31 virus vectors/171 total aphids in Muju. The most prerevalent species of aphids was Myzus persicae Sulz.

• Research in Plant Disease
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• v.17 no.1
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• pp.95-98
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• 2011

This research was carried out to selection of desirable cultivar for organic cultivation of carrot in Korea. The assay of disease resistance, insect tolerance and rate of bolting were investigated on 32 cultivars of genetic resources of carrot. This experiment was carried out at experimental field and greenhouse of Gangneung-Wonju National University. 'PI 223360' was resistant against powdery mildew. Ten cultivars including 'Oxheart Carrot Heirloom' were moderately resistant, 22 cultivars including 'Long Impeator #58' were susceptible to powdery mildew. Although there was no resistant cultivar against black rot and leaf blight, our results showed that several cultivars have moderate resistance. Thirteen cultivars including 'Oxheart Carrot Heirloom' were having insect (Erythroplusia pyropia) tolerance and 'SA 102' and 'Scarlet Keeper Carrot Rare' were susceptible. According to the investigation of bolting, 6 cultivars including 'Hongsim Ouchon Carrot' were early bolting and 4 cultivars including 'Japanese Imperial Long Carrot' were moderate bolting. Other cultivars were identified as late bolting. From above results, we confirmed that 'Oxheart Carrot Heirloom' was suitable cultivar for organic cultivation among 32 genetic resources of carrot.

• Asian Journal of Turfgrass Science
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• v.24 no.1
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• pp.9-15
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• 2010

During 2008~2009 winter season, yellow patch and gray snow mold occurred on turfgrass plants in golf courses in Kangwon and Jeonbuk provinces, respectively. The fungi associated with the diseases were identified as Rhizoctonia cerealis Van der Hoeven and Typhlua incarnata Lasch ex Fr., based on the morphological characteristics of hyphae and sclerotia. R. cerealis and T. incarnata were pathogenic to most turfgrass and crop species tested. R. cerealis infected crown, stem and leaf tissue of the host plants, and the symptom was light yellow circular patch. Individual infected leaf near the margin of patch developed red color first and finally turn brown. The symptoms caused by gray snow mold pathogen are water-soaked spots, and became a watery soft rot. Infection parts became yellow and then turned brown followed by death of the whole plant. White mycelia were developed on higher petioles, leaves, and on soil where these plant parts lay, and black sclerotia of variable size and shape formed in the mycelial mass. All isolates tested were pathogenic on most turfgrass and crop plants, and significantly different in aggressiveness. Disease severity increased with longer snow cover days on target plants, suggesting that disease severity was expressed over snow cover days. There were significant differences in disease severity among the graminious species, and among cultivars within each species, indicating varying levels of susceptibility to R. cerealis and T. incarnata.

• Korean Journal of Agricultural Science
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• v.12 no.2
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• pp.191-198
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• 1985

Sixty one commercial seed samples of three cruciferous vegetable crops were examined for seed-borne Alternaria spp. by deep freezing blotter method. Alternaria raphani, A. brassicicola and A. brassicae were detected from 7, 6 and 1 seed samples of chinese cabbage out of 20 with average infection ratio of 3.8, 1.8 and 0.5, respectively. A. raphani and A. brassicae were detected from 11 and 2 seed samples of radish out of 38 with average infection ratio of 7.2 and 1.0, respectively. A. brassicicola was detected from 3 samples of cabbage seed with average infection ratio of 21.8. Most of the Alternaria spp. detected were recovered from the seed coat and caused seed rot and seedling infections. A. brassicicola was recovered from the embryos of radish, chinese cabbage and cabbage in low infections and A. raphani was recovered from the embryos of radish. In inoculation experiments, A. brassicicola, A. brassicae and A. raphani produced black leaf spots on old leaves of three creciferous vegetable crops and the spots gradually increased in size appearing gray to light brown lesions which later coalesce and caused defoliation.

• Research in Plant Disease
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• v.17 no.2
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• pp.148-154
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• 2011

This study was conducted to control the seed borne pathogens (Alternaria spp.) of carrot and to examine the seed germination rate by using 13 environment friendly agricultural materials instead of conventional chemicals for organic cultivation. The growth inhibiting effects on pathogens showed the different responses according to each agricultural material and effective 7 materials against seed borne pathogens were selected. Among 7 materials, the carrot seeds sterilized with plant extracts, Tanger Stop and Land Saver were not germinated at all. The germination rate of seeds sterilized with other materials showed the similar levels with reference chemical (Benlate-T) and non-treated seeds. Infection rates of seeds sterilized with seaweed extract, Bellopper for controlling A. radicina and plant extract, Ssial-100 for A. dauci were similar or low infection rate compared with reference chemical. The germination rate and root length of seeds sterilized with Bellopper and Ssial-100 was similar or superior to those of chemical sterilized seeds. The optimal condition seemed to be a little bit different depending on the concentration of materials. As a result, the sterilization of carrot seeds by using the environment friendly materials could be effectively utilized as a technology to inhibit the infection of seed-borne pathogens.

• Korean Journal of Breeding Science
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• v.43 no.3
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• pp.172-176
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• 2011

'Suan' is a new $F_1$ hybrid variety of rapeseed (Brassica napus L.) with early maturing and high oleic acid. This hybrid variety was bred by the cross between Mokpo-CGMS (male sterile line) and 8516-B-5-6-5-3 (restore line) for the production of bio-diesel and edible oil in 2006. 'Suan' has green and parted leaf, yellowish flower, and black seed coat. 'Suan' is more tolerant to lodging and stem rot compared to 'Sunmang', check variety. The ripening date of 'Suan' is June 2nd which is 6 days earlier than 'Sunmang'. Yield trials were conducted from 2006 to 2007 and regional adaptation trials were examined at five locations each in 2008 and 2009. The average seed yield of regional adaptation trials was 381 kg/10a that was 4% higher than that of 'Sunmang'. Total oil content of 'Suan' was 44.3%. Oleic acid content was 68.3%, which is 5.2% higher than 'Sunmang' but, erucic acid was not detected. Total glucosinolate content was 2.31 mg/g. Therefore, this variety is recommended as a leading variety at southwestern area including Jeonnam, Jeonbuk and Kyongnam provinces of South Korea.