• Korean Journal of Organic Agriculture
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• v.25 no.2
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• pp.345-355
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• 2017

This study was conducted to evaluate rice seed disinfection efficacy of loess-sulfur for the suppression of Bakanae disease caused by Fusarium fujikuroi. Rice seeds were treated at different concentrations of loess-sulfur, soaking time and temperature, and combination of hot-water treatment. Rice cultivar, Shindongjin harvested from Bakanae disease-infested area in 2015, was used. Loess-sulfur was treated as follows; concentration of undiluted solution, 2%, 1% and 0.5%; soaking time of 24 and 48 hours; treatment temperature of $20^{\circ}C$ and $30^{\circ}C$; hot water treatment or not. Optimal conditions of rice seed disinfection were selected soaking time of 48 hours and the suspension of 0.5% and 1% loess-sulfur by investigating seed germination and isolation frequency of Fusarium spp. on Komada agar medium in vitro, and were established 3 disinfection conditions as hot water ($60^{\circ}C$, 10 min.) + 1% loess-sulfur ($20^{\circ}C$, 48 hours), 1% loess-sulfur only ($30^{\circ}C$, 48 hours) and 1% loess-sulfur only ($20^{\circ}C$, 48 hours) through additional test in greenhouse. Above 3 conditions were verified by rice seedling box and paddy field test in the way of investigating Bakanae diseased plants (%) and healthy plants (%). Consequently, most effective rice seed disinfection conditions on Bakanae disease were combination of hot water and 1% loess-sulfur and loess-sulfur only at $30^{\circ}C$. Furthermore, treatments with these conditions showed control value of 100% were maintained from seedling to the heading stage in the field. However, treatment of 1% loess-sulfur only at $20^{\circ}C$ showed low control value of 78.2% in paddy field. Hot water only treatment turned out to be an effective disinfection method when conducted thoroughly with $60^{\circ}C$, 10 min. However, it was thought additional soaking process with loess-sulfur after hot water treatment served more high control effect against Bakanae disease when rice seeds were disinfected on a large scale. This results expected rice seed disinfection with loess-sulfur were effectively and easily usable method if farmers had only one of either hot water-disinfector or seed-disinfector. In addition, loess-sulfur is well-known to farmers, simple to manufacture method and cheap.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.52 no.2
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• pp.162-168
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• 2007

Compatible and incompatible interactions of near-isogenic lines containing one of Xa1, Xa3, and Xa7 resistance genes with Japanese bacterial blight isolates (T7174, T7147, and T7133) were examined in order to determine the variation of bacterial blight resistance and the stability of resistance gene. IRBB 101 line having a Xal gene was compatible (host susceptible) with T7147 and T7133 isolates but incompatible (host resistant) with T7174 isolate at all the tested rice growth stages. IRBB 103 line having a Xa3 gene was susceptible or moderately resistant to the three isolates at seedling and maximum tillering stage but resistant at heading stage. IRBB 101 line having a Xa7 gene was semi-compatible with the three isolates at seedling stage but incompatible at the other growth stages. Overall there were clear differences between compatible and incompatible interactions of rice with Xanthomonas oryzae pv. oryzae races. In the mixed inoculations of compatible and incompatible isolates, the lesion length from near-isogenic lines decreased as the ratios of incompatible races increased. When the distinction between compatible and incompatible isolates was unclear, there was almost no variation of lesion length regardless of mixed ratios. The pathogenicity of the mixed races in the incompatible Interactions increased rather than the individual inoculation whereas the lesion length of compatible interactions was similar to that of the individual inoculation. These data indicate the incompatible races inhibit the virulence of a compatible race but compatible races increase the disease occurrence due to incompatible races. Furthermore, IRBB 107 line that showed resistance to all the isolates at all the tested growth stages was considered as a good parent f3r breeding of resistant variety.

• The Korean Journal of Pesticide Science
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• v.19 no.4
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• pp.424-427
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• 2015

Damping-off is a critical disease on ginseng seedling, which caused by the fungal pathogen Rhizoctonia solani. The disease has been prevented by tolclofos-methyl for the last 20 years. However, the tolclofos-methyl usually detected on the harvested roots of 6-year-old ginseng. Herein, we tried to select an alternative pesticide which not only must be safe but also efficiently inhibits the fungal pathogen. Four fungicides (fludioxonil, flutolanil, pencycuron, and thifluzamide) were applied to their inhibition efficacy against the pathogen. In in vitro test, fludioxonil treatment showed 80% inhibition activity for 25 days. Thifluzamide and flutolanil showed the activity for 10 days. Pencycuron showed for 1 days. In addition, the fludioxonil was more effective to control the pathogen comparing to other three fungicides in field. The incidence of damping-off was reduced to 71% by fludioxonil treatment. The level of the fungicide residue in seedling was 0.44 mg/kg, which value will be a negligible level in final products after 5 years. Consequently, the fludioxonil is a conceivable alternative for tolclofos-methyl to cope with R. solani.

• Korean Journal Plant Pathology
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• v.3 no.4
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• pp.252-260
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• 1987

Incidence of lettuce drop was observed throughout the growing season in the vinylhouse at the southern part of Korea, Kimhai. Occurrence of this disease was especially severe at the seedling stage. Number of sclerotia in surface soil $(30\times30\times5cm)$ was 22.0 at the seedling stage, and 5.3 at harvest in the infected area. Temperature for mycelial growth ranged from 5 to $30^{\circ}C$ with optimum temperature at $25^{\circ}C$. Sclerotia were formed fewer at low temperature, but their size was larger resulting in heavier dry weight than that at high temperature. The apothecia were formed from the sclerotia that were buried in March, April and September upto 3cm soil depth, but formed from those buried only 1 em soil depth in October. Sclerotia buried in June and December did not form apothecia regardless of soil depth by 90 days. The sclerotia buried in the 5cm of soil depth did not form apothecia. Sclerotia that were embedded in wet or flooded soil at $25^{\circ}C$ and $30^{\circ}C$ for 5 weeks lost their viability. Infection of lettuce was possible with mycelia originated from sclerotia on autoclaved lettuce plant fragments. The fungus was pathogenic on 25 plant species in 8 families in artificial inoculation tests. Lettuce seedlings appeared to be infected by airborne ascospore originated from sclerotia on crops and weeds around paddy fields, because sclerotia existing in soil might perish under long flood conditions during rice cultivation.

• Research in Plant Disease
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• v.22 no.3
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• pp.208-212
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• 2016

During the nursery seedlings stage at Muan in 2013, moisture and temperature conditions were favorable for the occurrence of onion downy mildew. Several fungicides were evaluated for controlling onion downy mildew at the stage of seedling. The disease incidence of the untreated control was 51.1%, which was sufficient to evaluate the fungicide efficacy for the control of onion downy mildew. Incidence at the mancozeb treatment (MAN treatment) was 4.4% and it was the highest control value of 91.4%. Incidence at the various fungicides treatment (MIX treatment) consisted of amectotradin plus dimethomorph, floupicolide plus propamocarb HCl, or dimethomorph plus pyraclostrobin was 10.0%, and the control value of the MIX treatment was 80.4%. Among the tested fungicides, amectotradin plus dimethomorph (AME plus DIM treatment) was selected and treated. Incidence of AME plus DIM treatment was 12.2%. There was statistically significant difference among the three different treatments and the untreated control. These results suggest that the application of fungicides on onion nursery seedlings was effective to control the onion downy mildew.

• Korean Journal of Medicinal Crop Science
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• v.6 no.4
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• pp.277-285
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• 1998

Antifungal activity on major seedborne diasease of crops was screened by the treatment of the extracts from 50 medicinal plants in vitro and in vivo. The extracts of garlic and taxus, Rheum undulatum, Achiranthes japonica, Glycyrrhiza uralensis, Oenothera lamar kiana treated with the blotting filter paper and water agar methods inhibited the growth of Pyricularia oryzae, Alternaria sesamicola, Colletotrichum gloeosporioides, and Alternaria brassicicola among the tested plants. Antifungal activities on infected seeds by soaking methods were shown even at the dilution of the extracts by 10 times. The activity was the highest in soaking seeds at $25^{\circ}C$ for 24 hours. The effect of plant extract on seed germination was not significant as compared with untreated seed. However, early growth of seedling was increased by the treatment of extracts. The extract of taxus slightly inhibited the seed germination of radish and chinese cabbage but those of Achirunthes japonica, Glycyrrhiza uralensis and Oenthfera lamarkiana showed severe damage on the seed germination and early growth of seedling.

• The Korean Journal of Mycology
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• v.43 no.4
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• pp.253-259
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• 2015

Anthracnose caused by Collectotrichum acutatum is the most devastating disease of pepper plants in Korea. In this study, we evaluated the effect of selected antagonistic bacteria on control of anthracnose and plant growth promotion of pepper plants under field conditions. Four different bacterial isolates used in the current study were isolated from the pepper rhizosphere (GJ01, GJ11) and tidal flat (LB01, LB14) in previous studies. Four bacterial isolates, together with a control strain (EXTN-1), showed antifungal activity against C. acutatum in a dual culture assay. To test for plant growth promotion effect, seedling vigor index and growth parameters of pepper were measured under field condition. As a result, all four bacterial isolates were effective for improving plant growth promotion. The strain GJ01 was the most effective in improving the seedling vigor on pepper, but the strain GJ11 in increasing the pepper fruit yield. The incidence of anthracnose was inhibited in the range of 63.2~72.5% by treatment of four bacterial isolates. The current study indicated that the four bacterial isolates could be used as potential biological control agents of anthracnose disease of pepper.

• Research in Plant Disease
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• v.30 no.2
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• pp.124-130
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• 2024

Leaf blight caused by Stemphylium vesicarium is one of the most important fungal diseases of garlic (Allium sativum L.) worldwide, which results in a reduction of quality and yield. The breeding of resistant cultivars is an efficient approach to decrease the use of chemical fungicides and minimize crop losses. In this study, to find the resistant garlic resources against S. vesicarium, we evaluated the resistance degree of 20 garlic germplasms. To do this, garlic seedlings at four-leaf stage were rubbed with nonabsorbent cotton and then inoculated with spore suspension (3.0×10⁵ spores/ml of potato dextrose broth) of S. vesicarium by spray method. Three to seven days after inoculation, the infected leaf area (%) of garlic seedling was measured. 'Daeseo' and 'Namdo' were included as susceptible and resistant control cultivars, respectively. After 3 to 7 days of incubation, the infected leaf area (%) of garlic seedling was measured. Our results showed that IT245512, IT245528, and IT244068 lines exhibited the highest resistance against S. vesicarium, whereas IT257134 and IT253043 lines were more susceptible than the susceptible cultivar 'Daeseo'. Based on the results, the resistant genetic resources selected in this study can be used a basic material for resistant garlic breeding system against leaf blight.

• Research in Plant Disease
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• v.16 no.1
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• pp.41-47
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• 2010

A total of 10,753 oligotrophic bacteria were isolated from the cultivated soils of red-pepper infected by Phytophthora blight disease in various regions of Korea (Chungju, Anmyon, Taean, Andong, Eumsung and Goesan). Seven bacteria isolates among these collected resources were selected by the first screening of in vitro antagonistic assay against major several plant pathogenic fungi including Phytophthora capsici. Finally, strain 7F was selected by pot assay for a possible biological control agent against Phytophthora blight disease of pepper seedling in the greenhouse. Strain 7F was identified as Bacillus subtilis on the basis of its 16S rDNA sequence analysis and as standardized biochemical characteristics assay kits such as API20 NE. In the experiment of P. capsici zoospore infected red-pepper on the pot test, infection rate of red-pepper with nonetreatment to Phytophthora blight disease was 87%, while the rate was only 6% in the pot treated with strain 7F. This result indicated that the Bacillus subtilis strain 7F will be useful as a potential biocontrol agent for Phytophthora blight disease of red-pepper.

• Korean Journal of Weed Science
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• v.17 no.4
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• pp.362-367
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• 1997

A field experiment was conducted to determine an optimum control time of water foxtail(Alopecurus aequalis var. amurensis Ohwi), a most troublesome weed, in no-tillage dry seeded rice. Paraquat, a non-selective herbicide, was applied at 1.5 days interval from March 15 to May 15 at a concentration of 3,000ml per hectar and its control efficacy to A. aequalis was recorded before and after seed sowing. In addition. other characters such as decayed injury of A. aequalis to rice seedling, and its influence of seedling stand were also investigated in relation to rice grain yield. Dry weight of A. aequalis was rapidly increased with delay in control time from 42g/$m^2$at March 15 to 237g/$m^2$ at May 15. The amount of its regrowth at seeding time was highest with 68.3g, when paraquat was applied at March 15, then decreased thereafter and it was less than 6.2g when paraquat was applied after April 15 which indicates above 98% control rate. The control rate of A. aequalis, at 30 days after paraquat application way likewise similar to that the seeding time. Rice seedling stands in the plot treated with paraquat before April 15 were not affected by decayed injury of A. aequalis while decayed injury of 3 to 4 degree for those after April 30 application was noted. Dwarf virus disease on rice seedling due to occurrence of A. aequalis was not observed when A. aequalis was controled from March 30 to May 15 while it was occurred in the plot of March 15 application and the untreated control. The control plot of A. aequalis at April 15 had the highest grain yield with 4.79ton/10a. Based on control rate of A. aequalis, seedling stands of rice, virus disease, and rice grain yield, the most suitable control time of A. aequalis in no-tillage dry seeded rice is considered to be about April 15.