• Korean Journal Plant Pathology
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• v.13 no.4
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• pp.232-238
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• 1997

Culture conditions affecting mycelial growth and sporulation of P. theae, SP2, SP3 and P. longiseta which causing leaf blight on oriental persimmon leaf blight have been investigated. The optimum temperature for the mycelial growth and sporulation on potato dextrose agar was $25{\sim}30^{\circ}C$ in all the fungi, but was inhibited and finally arrested at 10 and $30^{\circ}C$. The optimum pH for mycelial growth and sporulation were ranged at pH 4.5~5.0 and 5.0~6.0 in all the fungi. Lenonian agar, potato sucrose agar and oatmeal medium were good culture media for the mycelial growth and sporulation of all the fungi. The effective sources of nitrogen and carbon for the mycelial growth were tryptone, glycine, starch, dextrose, galactose and lactose. Glutamic acid, peptone and tryptone were good nitrogen sources for sporulation of the fungi. Sucrose, starch and galactose were also good carbon sources for sporulation. Generally, vitamins had no effect on mycelial growth and sporulation. The pH of the potato dextrose broth inoculated with SP2, SP3 and P. theae and P. longiseta was changed from 7.0 to 4.5~4.7 and 5.0~5.4 after incubating for 10 days, respectively. But, the initial pH of the medium adjusted to 5.0 was lowered to 4.5~4.7 after incubating for 10 days.

• Research in Plant Disease
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• v.17 no.1
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• pp.78-81
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• 2011

Soft rot caused by Rhizopus oryzae occurred on unshiu orange (Citrus unshiu Marc.) sampled from commercial markets in Jinju, Korea, 2010. The first symptom of soft rot on orange is a water-soaked appearance of the affected tissue. The infected parts later disintegrated into a mushy mass of disorganized cells followed by rapid softening of the diseased tissue. The lesion on orange was rapidly softened and rotted, then became brown or dark brown. Optimum temperature for mycelial growth of the causal fungus on potato dextrose agar was $30^{\circ}C$ and growth was still apparent at $37^{\circ}C$. Sporangiophores were $6{\sim}20\;{\mu}m$ in diameter. Sporangia were globose and $40{\sim}200\;{\mu}m$ in size. The color of sporangia was brownish-grey to blackish-grey at maturity. Sporangiospores were sub-globose, brownish- black streaked and $4{\sim}10\;{\mu}m$ in size. Columella were globose to sub-globose and $85{\sim}120\;{\mu}m$ in size. On the basis of mycological characteristics, pathogenicity test, and the ITS sequence analysis, the causal fungus was identified as Rhizopus oryzae. To our knowledge, this is the first report of soft rot caused by R. oryzae on unshiu orange 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.8 no.1
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• pp.63-65
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• 2002

Red spot disease was found on broad bean (Vicia faba) in several farmer's field located in Changseon-myon, Namhae-gun, Gyeongnam provice in Korea. The typical symptoms of the disease were appeared on leaves and stems. The infection rates of the disease in the surveyed area were ranged from 16.4 to 84.6%. Lesions on the leaves were round with 1~4.2 mm in size and on the stem were narrow long fusiform with 1~15 mm in size. Conidia and conidiaphores were not readily farmed on PDA, however, a few conidia were formed on PDA added in extracts of 10 g of broad bean leaves. Conidia were light yellow green in color, globose or obovoid in shape, and 10~24$\times$8~22 $\mu$m in size. Conidiophores were cylindrical in shape, light brown in color and 3.6~12.8 $\mu$m in wide. Sclerotia of the fungus were readily formed in artificial media such as PDA. They were ellipsoid to irregular in shape, 1.2~11.8 mm in size and dark in color, The optimum temperature far growth of the fungus was about 2$0^{\circ}C$. On the basis of mycological characteristics, the fungus was identified as Botrytis fabae. This is the first report on the red spot of broad bean caused by Botrytis fabae in Korea.

• Research in Plant Disease
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• v.11 no.2
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• pp.146-151
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• 2005

A new bacterial disease of sesame(Sesamum indicum) was observed on field-grown plants in Suwon, Hongchun and Yeonchun in 2000. Leaf symptoms initially appeared as water-soaked spots that gradually enlarged, became necrotic and were often bordered by a small zone of lemon yellow tissue. In the case of severe infection, dead leaves were defoliated. 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 were purified and used for farther tests. Pathogenicity of strains was confirmed on 3-week-old sesame plants sprayed with bacterial suspensions containing $10^{8}cfu/ml$ of phosphate buffered saline. The Biolog and fatty acid analyses of the two strains(SL3451 and SL3476) 1mm sesame leaf blight showed that they could be identified as ft campestris pv. sesami because of their high similarity to the tester strain(X. campestris pv. sesami LMG865) with a match probability of $100\%$. The bacterium grew well between 18 and 36$^{\circ}C$, but optimum temperature was $27^{\circ}C$ on LB broth. This is the first report of bacterial blight of sesame in Korea. Symptoms of bacterial blight of sesame are difficult to differentiated with those of bacterial leaf spot caused by Pseudomonas syringae pv. sesami.

• Research in Plant Disease
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• v.11 no.2
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• pp.158-161
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• 2005

Stenotrophomonas maltophilia BW-13 is a potent biocontrol agent to control crisphead lettuce bottom rot caused by Rhizoctonia solani. To define the optimum conditions for the mass production of the S. maltophilia BW-13, we have investigated optimum culture conditions and effects of various carbon sources on the bacterial growth. The optimum initial pH and temperature were determined as pH $6.0\~7.0 and $35^{\circ}C$, respectively. For the selection of effective carbon source for the mass production, we tested the low molecular carbon sources such as sucrose, glucose, lactose, maltose, manose and the high molecular carbon source such as dough conditioner, rice bran, corn starch, sweet potato starch. As the results, the addition of dough conditioner in a basal medium ($1.25\%\;K_{2}HPO_4,\;0.38\%\;KH_{2}PO_4,\;0.01\%\;MgSO_4{\cdot}7H_{2}O,\;0.5\%\;Yeast extract$) was able to achieve higher cell density and the antifungal activity than others. Therefore, the basal medium containing $3\%$ dough conditioner (named as dough conditioner medium) was finally selected the optimized media for the mass production of BW-13 strain.

• Research in Plant Disease
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• v.13 no.1
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• pp.57-60
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• 2007

A rhizopus soft rot caused by Rhizopus stolonifer occurred sporadically on grape in orchard in Gyeongsang-nam-do Agricultural Research and Extension Services and in Wholesale Market of Agricultural Products in Jinju city. The infected fruits were rapidly water-soaked, softened and eventually rotted, and the symptoms were initiated from wounds or cracks occurred at harvest time. Sporangiophores were $850{\sim}1,800{\mu}m$ in length and $12{\sim}23{\mu}m$ in width. Sporangia were globose or hemispheric and $80{\sim}190{\mu}m$ in size. The color of sporangia was white and cottony at first and gradually to brownish black, bearing abundant spores when it matured. Columella were hemispheric and $70{\sim}95{\mu}m$ in size. Sporangiospores were irregular round or oval, brownish-black streaked and $8{\sim}22{\times}6{\sim}10{\mu}m$ in size. The optimum temperature for mycelial growth of the fungus on PDA was 25$^{\circ}C$. On the basis of mycological characteristics and pathogenicity to grape (Vitis vinifera), the causal fungus was identified as Rhizopus stolonifer (Ehrenberg ex. Fr,) Lind. This is the first report of Rhizopus soft rot by R. stolonifer on grape (V. vinifera) in Korea.

• Research in Plant Disease
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• v.13 no.2
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• pp.104-109
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• 2007

Pink root disease of onion, a known worldwide constraint upon onion production, significantly reduces crop levels in the main Korea cultivation area. In order to examine the effect of flooding on incidence of pink root disease caused by Pyrenochaeta terrestris and on onion growth and on populations of soil fungi, field experiments were conducted during two seasons, 2003/04 and 2004/05 at Onion Research Institute. Populations of soil fungi from fields were assayed on selective media. Flooding treatment was effective in reducing populations of P. terrestris, Pythium spp., and Rhizoctonia sp. in soil; fungal populations in soils flooded for 90 days were reduced to 1/2 to 1/3 of those in non-flooded soils. In nursery bed, protective activities of soils flooded for over 60 days were 93.5 to 99.2% and their pink root incidences were less than 5%, which were 1/11 to 1/18 of that in control. Increased yield of onion bulbs was associated with control of soil borne pathogenic fungi by flooding treatments. As flooding period was prolonged, bulb grade showed the tendency to increase. Soil flooding for over 60 days resulted in effective disease control, facilitated accurate planning of plant population in the field, extension of the growing-season and consequently higher yields of better quality.

• Research in Plant Disease
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• v.13 no.2
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• pp.110-114
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• 2007

Anthracnose fungus was most pathogenic on soybean sprout, of the fungi and bacteria isolated from rotten sprout on market. Bacterial strains associated were not virulent. Dry heat (DHT) applied even as high as $65^{\circ}C$ for 30min. was not effective enough to eliminate the artificially inoculated Colletotrichum gloeosporioides propagules from seedllots. Hot water immersion treatment (HWT), at elevated temperature of $55^{\circ}C$ for 20 min, did eliminate the pathogen but reduced seed germinating and retarded sprout growth: Seed germination was practically acceptable when the seedlots were exposed to at $55^{\circ}C$ for 5 min, but about 20% anthracnose propagules survived. Accordingly, we have optimized the HWT scheme for 5 min at $60^{\circ}C$. This scheme was validated, at small to large scale production system, that surely rule out the possible carry over of the bacterial contaminant from seedlots. This result should improve the shelf-life of soybean sprout on the market.

• Research in Plant Disease
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• v.14 no.3
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• pp.201-204
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• 2008

We've been involved in collection and domestication of Agrimonia pilosa from 2005 to 2007. We observed agrimony powdery mildew caused by Sphaerotheca aphanis. The powdery mildew developed twice a year, in May to June and mid August to September on whole plants of A. pilosa plants, that is, leaves, stem and floral part. We sprayed the Cooking Oil & Yolk mixture (COY) to control the agrimony powdery mildew. When COY was single-sprayed to control agrimony powdery mildew, its control value was 26.9%. However when it was double-sprayed and triple-sprayed at seven days interval, its control value increased up to 80.8 and 82.7%, respectively. Upon the first spray, symptoms of powdery mildew disappeared within three days and suppressive effect of COY was persisted for only seven days. Thereafter, powdery mildew was relapsed to develop. However, on double to triple sprays, powdery mildew was suppressed more than 28 days after final treatment. Therefore, it is concluded that double spray of COY at seven days interval can control effectively agrimony powdery mildew.