• The Plant Pathology Journal
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• v.29 no.4
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• pp.440-445
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• 2013

Balloon flower (Platycodon grandiflorum) is a kind of mountain herbs whose roots have restorative properties and the cultivating acreage of balloon flower has been steadily increasing in Korea. More frequent rain and high amount of rainfalls as a result of climate changes predisposed balloon flower to the outbreaks of root rot at high-density cultivation area in recent years. Root crowns were usually discolored into brown to blackish brown at first and the infected plants showed slight wilting symptom at early infection stage. Severely infected roots were entirely rotted and whole plants eventually died at late infection stage. The overall disease severities of root rot of balloon flower were quite variable according to the surveyed fields in Jeonnam, Gyeongnam and Jeju Provinces, which ranged from 0.1% to 40%. The root rot occurred more severely at the paddy or clay soils than the sandy soils and their severities were much higher at lowland than upland in the same localty. The disease increased with aging of the balloon flower. The causal fungi were identified as Fusarium solani and F. oxysporum on the basis of their mycological characteristics. The optimum temperature ranges of their mycelial growths was found to be $24^{\circ}C$. The pathogenic characters of F. solani and F. oxysporum treated by artificial wounding inoculation on healthy roots of balloon flower revealed that F. solani was more virulent than F. oxysporum. This study identified the causal agents of root rot of balloon flower as Fusarium solani and F. oxysporum, probably for the first time.

• Mycobiology
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• v.29 no.4
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• pp.224-226
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• 2001

Inflorescence of Allium thunbergii was found to be severely infected with Fusarium sp. The flower was covered with the fungus and eventually failed to form seeds. The causal fungus was identified as F. proliferatum(Matsushima) Nirenberg based on the cultural and morphological characteristics. Pathogenicity of the fungus was proved by artificial inoculation onto the healthy plants. This is the first record of this disease from Korea.

• The Plant Pathology Journal
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• v.28 no.2
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• pp.156-163
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• 2012

Stem rots caused by Rhizoctonia solani and Sclerotinia sclerotiorum have been known as devastating diseases in balloon flower plants. Antifungal activities of four fungicides, azoxystrobin, polyoxin B, trifloxystrobin and validamycin A were evaluated in vitro, showing effective suppression with mycelial growth of the fungal isolates on PDA media. Efficacies of the four fungicides were also demonstrated in stem tissues of balloon flower plants against R. solani and S. sclerotiorum. A commercially available Bacillus subtilis strain Y1336 was tested in terms of antagonistic biological control of stem rot disease of balloon flower plants. The bacterial strain revealed its antifungal activities against R. solani and S. sclerotiorum demonstrated by dual culture tests using paper discs and two plant pathogenic fungi on PDA media, as well as by plant inoculation assay, indicating that this antagonistic bacterial strain can be incorporated into disease management program for balloon flower stem rot diseases together with the four chemical fungicides.

• Journal of Microbiology and Biotechnology
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• v.10 no.4
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• pp.435-440
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• 2000

A pathogenic fungus causing balloon flower root rot (Platycodon grandiflorum) was isolated from naturally infected roots. The microbial characteristics of the isolated microorganism were similar to those of Rhizoctonia solani. About 500 bacterial species from field soils were screened for a biological agent against the above-mentioned putative pathogen, and several bacteria with the antifungal activity were isolated. Among them, the isolated JS2 was identified as Pseudomonas aeruginosa. This strain showed a broad spectrum of antifungal activity potentially. When the antifungal substance was purified from a broth culture of JS2, it was identified as 2,4-diacetylphloroglucinol (Phl).

• The Plant Pathology Journal
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• v.16 no.6
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• pp.321-324
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• 2000

season of 2000. The disease infection usually started from flower, peduncle and young fruits, then moved to flower stalk, stem and leaves. At first, the lesions started with water-soaked, rapidly softened, and then the area gradually expanded. In severely affected film house, the rate of infected fruits reached to 28.6%. Numerous sporangiospores were formed on the diseased fruits, flower stalk, stem and leaves. Most of the sporangiospores were appeare to be rapidly dispersed in the air. The mycelia grew on the surface of host and formed stolons. Colonies on potato dextrose agar were cottony at first brownish black at maturity. Sporangia were 125.3${\times}$294.2 ${\mu}$m. globose or sub-globose with somewhat flattened base. White at first the black, many spored, and are never overhanging. Sporangiophores were 2.7-6.8${\times}$12.9-33.9 ${\mu}$m, smooth-walled, non-septate, light brown, simple, long, arising in groups of 3-5 from stolons opposite rhizoids. Sporangiophores were 8.6-21.1${\times}$6.41-1.7 ${\mu}$m, irregular, round, oval, elongate, angular and brownish-black streaked. Columella were 63.8${\times}$140.4 ${\mu}$m. brownish gray, umberella-shaped when dehisced. The causal organism was identified as Rhizopus stolonifer Lind on the basis of the morphological characteristics of the fungus. Rhizopus soft rot on squash (Cucurbita moschata) caused by the fungi has not been previously reported in Korea.

• Horticultural Science & Technology
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• v.19 no.4
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• pp.591-595
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• 2001

This study was conducted to find out the proper chemicals and doses for controlling the bulb disease of Lilium Oriental hybrids 'Capablanca' and 'Marco Polo' cultivars during storage, and to ascertain any disadvantage of the treatment on shoot growth and flower development. Bulbs of 'Casablanca' and 'Marco Polo' cultivars were dipped in some fungicide solutions, including azoxystrobin, benomyl+thiram, and prochloraz, and culture broth of antagonistic bacteria for one hour. The rot was apparently inhibited by azoxystrobin and prochloraz solution dippings and it was not by benomyl+thiram in bulbs produced domestically. To improve physiological integrity, calcium chloride was treated. However, this treatment had no positive effects on bulb rot of lily. When bulbs were dipped in one-fifth of diluted broth. But the bulb rot was inhibited effectively as compared with untreated during storage. Benomyl+thiram and that with calcium inhibited the sprouting in 'Casablanca' and 'Marco Polo' cultivars during cultivation. Calcium and benomyl+thiram treatments decreased growth of leaf and flower but with no statistically significant difference. Other fungicidal materials treated to bulbs showed no effect on vegetative growth and flower quality.

• Research in Plant Disease
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• v.21 no.4
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• pp.334-336
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• 2015

Sclerotium rot on Pulsatilla koreana was observed in the exhibition field of Jinju Agriculture Technology Center in July 2013. The infected plants showed water-soaked, blighted and rotted symptoms. White mycelial mats spread over lesions, and then numerous sclerotia were formed on flower stalk and flower stem near the soil line. The sclerotia were globoid in shape, 1-3 mm in size and white to brown in color. The optimum temperature for mycelial growth and sclerotia formation on PDA was $30^{\circ}C$ and the hyphal width was $4-8{\mu}m$. The typical clamp connections were observed in the hyphae of the fungus grown on PDA. For molecular identification, the complete ITS rDNA sequence of the causal fungus was sequenced and analyzed. On the basis of mycological characteristics, ITS rDNA sequence analysis, and pathogenicity to host plants, this fungus was identified as Sclerotium rolfsii Saccardo. This is the first report of sclerotium rot on Pulsatilla koreana caused by S. rolfsii in Korea.

• Research in Plant Disease
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• v.8 no.1
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• pp.55-58
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• 2002

In July 2001, rotting and shivering flowers of cotton rose (Hibiscus mutabitis) were fecund in the flower beds along the roadsides in Jinju area. The disease first started as water-soaking, dark-green lesions on the petals, and then whole flower was rotted rapidly, Whitish mycelia and monosporous sporangiophore with monosporous sporangiola were formed abundantly on the lesions. Colony appeared as white to pale yellowish brown mycelia on potato dextrose agar medium (PDA). Monosporous sporangiophore was long slender and branched at the apex, each branch bearing a head of sporangiospores. Sporangium was subglobose in shape and was 42.6-114.2$\mu$m in size. Monosporous sporangiola were elliptic, fusiform or ovoid, and brown in color and 12.3~21.6 $\times$8.3~11.6$\mu$m Um in size. Sporangiospores were elliptic, fusiform or ovoid in shape, dark brown or brown in color and 16.3~23.8$\times$8.2~13.6$\mu$m in size, and they had three or more appendages at bipolar end. Zygospores were mostly globose, dark black colored and sized was 46.2-78.4$\mu$min diameter, The fungus grew on PDA between at 15 to 4$0^{\circ}C$, and the optimum temperature was 3$0^{\circ}C$. This is the first report on the flower rot of cotton rose caused by C. cucurbitarum in Korea.

• Research in Plant Disease
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• v.9 no.1
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• pp.25-27
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• 2003

In 2002, a stem rot disease was found on Pansy (Viola tricolor) in several road-side flower beds in Jinju City, Gyeongnam province, Korea. The typical symptoms of the disease were stem rot, crown rot, wilt or blight. Upper parts of the infected stems were mostly blighted. White mycelial mats were spread over lesions and the sclerotia were farmed on the stems near soil line. The sclerotia was globoid or irregular in shape, 1.3~4.2 mm in size, and brown in color, The optimum temperature for fungal growth was about 3$0^{\circ}C$. The typical clamp connections were found in the hyphae of the fungus grown on PDA, and hyphal diameter was 3.9~10.4 ${\mu}{\textrm}{m}$. On the basis of mycological characteristics and pathogenecity test on host plants, the fungus was identified as Sclerotium rolfsii. This is the first report on the stem rot of Viola tricolor caused by Sclerotium rolfsii in Korea.

• The Plant Pathology Journal
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• v.17 no.4
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• pp.231-235
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• 2001

From April to May 1998, Phytophthora rot on pear, which has not been reported in Korea before, became an epidemic in the southeast part of the country under abnormally higher temperature and prolonged rainy days. Average temperature was about $3^{\circ}$ higher than in normal years, and 29 days were rainy during the 2 months in the areas surveyed. Over 1,000 orchards estimated at about 270 ha in 19 cultivation areas were infected by the disease, which occurred on all parts of the tree such as leaves, shoots, branches, stems, and flower clusters. Among 43 isolates collected from various locations and plant parts, 41 were identified as Phytophthora cactorum while 2 were identified as P. cambivora based on their mycological characteristics. The representative isolates revealed strong pathogenicity not only to pear but also to apple and peach. Among 23 pear cultivars tested, 7 were estimated as susceptible, 4 were moderate, and 11 were resistant to the pathogen. Results suggest that Phytophthora disease on pear is a potential threat to pear cultivation when environmental factors are favorable to disease development.