• The Plant Pathology Journal
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• v.21 no.2
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• pp.87-92
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• 2005

The structural differences between healthy and diseasedpanicle necks caused by Pyricularia oryzae were observed using electron-microscope. In the diseased panicle neck, the infection hyphae of the rice blast pathogen grew through the sclerenchymatous fiber tissue and reached to the central internal lacuna. Since the pathogen grew through the sclerenchymatous fiber tissues, the vascular bundle composed with xylem and phloem had been destroyed and finally the nutrients from the leaf and stem were not able to be transported into the grains. Infection of panicle base by the blast pathogen until 20 days after heading caused more than 50% of yield loss in both Jinmibyeo and Chucheongbyeo. There was a positive correlation between incidence of the panicle blast and rice yield losses. The regression equations between incidence of the panicle blast and yield losses were y= -3.61+496.7 ($R^2$=0.70) in Jinmibyeoand y=-3.93+520.2 ($R^2$=0.82) in Juanbyeo. The panicleblast caused deterioration of grain quality. Healthy grain rate was reduced by increase of panicle blast infection.

• The Plant Pathology Journal
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• v.39 no.1
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• pp.136-140
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• 2023

Rice panicle blast is one of the most serious diseases threatening stable rice production by causing severe damage to rice yields and quality. The disease is easy to occur under low air temperature and frequent heavy rainfall during the heading season of rice. In 2021, a rice panicle blast severely occurred in the Jeonbuk province of Korea. The incidence area of panicle blast accounted for 27.7% of the rice cultivation area of Jeonbuk province in 2021, which was 13.7-times higher than in 2019 and 2.6-times higher than in 2020. This study evaluated the incidence areas of rice panicle blast in each region of Jeonbuk province in 2021. The weather conditions during the heading season of rice, mainly cultivated rice cultivars, and the race diversity of the Jeonbuk isolates were also investigated. It will provide important information for the effective control of the rice panicle blast.

• Research in Plant Disease
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• v.21 no.2
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• pp.103-106
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• 2015

Isolates of the rice blast fungus show a range of tissue-specificities infecting leaves, nodes, neck and panicles. Although neck and panicle blast cause significantly greater yield losses than the leaf blast, virulence tests of the blast isolates have been performed only rice leaves instead of neck and panicles. In this study, we have developed a virulence test method for neck and panicle blast. We selected three representative isolates from each of leaf, neck, and panicle blast. We observed that severe disease lesions developed on the neck and the panicles when the infected rice plants were incubated in a dew chamber for 48 h instead of 24 h when tested on leaves. Unlike the leaf blast, a typical lesion on the neck and panicles appeared after 14 days post-infection as opposed to 7 days with leaf blast. This method will be applied to examine tissue-specificity of the rice blast fungus isolates.

• Korean journal of applied entomology
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• v.19 no.4 s.45
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• pp.203-211
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• 1980

The pattern of blast disease incidence of Tonsil-line rice varieties derived from the cross between Indica and Japonica type was quite different from that of Japonica-type rice varieties. The former showed discontinuity between the incidence of leaf blast and panicle blast; the incidence .of leaf blast was slight, while that of panicle blast was very severe. Different level of nitrogen fertilizer applied influenced significantly the incidence of leaf blast but influenced slightly the incidence of panicle blast of Tongil-line rice varieties. The infection percentage of panicle blast of Tongil-line rice varieties was about $90\%$ and most of them were infected in leaf sheaths during booting stage, but infection of panicle blast of Japonica-type rice varieties in leaf sheaths during booting stage was very low, only about $3\%$. Infection route of panicle blast in leaf sheaths during booting stage, microflora in leaf sheaths, and specific susceptibility of young panicle to blast disease were investigated in the epidemiological point of view.

• Korean Journal of Agricultural Science
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• v.11 no.1
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• pp.61-67
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• 1984

In an attempt to obtain a basic information to develop methods of an effective chemical control and disease forecasting of panicle blast of rice, effects of conidial number of the causal fungus, Pyricularia oryzae, collected in different periods and the rate of leaf blast occurrence on the occurrence of panicle blast were investigated. Conidial number the fungus collected in 5 days before and after heading date were closely related with panicle blast occurrence. But no relationship was obtained between the occurrence rate of leaf blast and that of panicle blast. Considering the incubation period of the disease, we presume that the most effective application periods of chemicals are 5-10 days and 10-15 days before heading, when immediate effective chemicals and slow effective chemicals are applied, respectively.

• The Plant Pathology Journal
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• v.16 no.3
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• pp.147-150
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• 2000

Sporulation patterns of rice blast fungus were studied at relatively later stages of leaf blast and neck blast seasons in Icheon, Korea. This experiment was done by detaching lesion-bearing leaves and panicle bases. The number of conidia remaining on the leaf blast lesions of different cultivars from Jul 20 to Jul 23 ranged from 3,640 to 82,740 spores. More conidia were observed on the adaxial surface because they were released from abaxial surface. After heading, sporulation was observed from the lesions on the flag leaves but the number of spores was less than in the late July. Detached panicle bases or uppermost internodes infected by Pyricularia grisea produced abundant amount of conidia. Among these panicle bases, 30.1 mm size lesion recorded the highest count of 244,560 spores. When we compared the sporulation amount using the KY-type spore trap, more conidia were recorded from intact lesions than from the lesions which removed conidia and conidiophore The ratio of conidia release against total sporulation ranged from 20.5%-25.0% for leaf blast and 8.2%-25.3% in the neck blast. Effective inoculum potential was also discussed.

• Korean Journal Plant Pathology
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• v.11 no.4
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• pp.338-343
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• 1995

Incidence of blast caused by Pyricularia grisea on five new cultivars and four elite lines (C/L) of rice was investigated at different locations, Icheon, Chuncheon, Jecheon and Naju, 1992 to 1994. Disease indices of leaf blast on the tested C/L except Juanbyeo and Keumnambyeo ranged from 0 to 6 in the blast nursery. Under the field conditions, percentages of diseased leaf area of Kuemnambyeo were 6.5% in Jecheon and 2.8% in Icheon in 1993. The incidence of panicle blast on the C/L except Suweon 394 and Milyang 117 differed depending on the locations and years. In case of Unjangbyeo, panicle blast was rarely observed n the fields in Icheon and Naju, but the disease incidences were 21.8% in Jecheon in 1993 and 16.4% in Chuncheon in 1994. Race distribution of the blast fungus was variable according to the locations. The major race in the Jecheon site was KI-197, which was recently identified.

• Korean Journal of Agricultural Science
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• v.12 no.2
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• pp.356-369
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• 1985

In Korea, inevitable researches for the blast control exactly started from 1927 by the organization of Office of Rural Development with the local extensive outbreak of panicle blast at Jeonlla Buk-Do Province in 1926. At present, the rice blast is still one of the most destructive and widespread diseases in spite of considerable contributions by rice scientists, particularly plant pathologists during last 55 years in Korea. Rice blast control and management are very difficult because of the marked variability in pathogenicity of the blast fungus. From the results obtained through the disease surveys during last 70 years, different 3 prevalence type of blast such as bimodal leaf-blast type, bimodal panicle-blast type and bimodal continual blast type were recognized. In generally speaking, pattern of blast outbreak is said to be characterized by severe outbreak of panicle blast after slight outbreak of leaf blast with discontinuity between leaf and panicle blast. So we have to pay much attention for successful management of panicle blast giving direct influence to rice yield. Main factors induce blast epidemic were pointed out to be breakdown of the disease resistance, nutritional unbalance such as excess application of nitrogen, delay of transplantation and longspell of rain fall by extensive surveys and researches on blast during last 70 years in Korea. The fact some of Japonica varieties such as Kokuryomiyako, Tamanishiki, Ginbozu and Pungok belong to varietal group A had been cultivated with extensive acrage over 30 years in this country should be mentioned by Korean rice scientists. Differences in field resistance between varieties in the same group are detectable and apparently small but sometimes epidemiologically significant differential effects may be found out in case of blast. Much more attention should be payed to accumulate the knowledges on field resistance for successful management of blast. Excess application of nitrogen is more effective to outbreak of panicle blast than that of leaf blast of IR varieties. In comparatively low level application of nitrogen infection rate of panicle blast of IR varieties is considerably high. Low temperature effects on outbreak of blast is very great. It results in remarkable increase of the inoculum potential on the leaf lesions and infection of panicle blast in leaf sheathes of IR varieties during the booting stage. In economic point of view, it is concluded that 5 times sprays of effective fungicides including 3 times before and 2 times after heading is good enough to control blast. We have experienced no one of control measures for blast is superior to all others. The integrated control measures was established as guideline of blast control around 1950 in Korea. This guideline must be helpful for rice growers as long as rice growing continue.

• Korean journal of applied entomology
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• v.22 no.4 s.57
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• pp.277-282
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• 1983

Number and percentage of diseased area of leaf blast lesions formed on different leaf location were mostly distributed from the flag leaf(n-1) to the 3rd leaf from the top(n-3) in Tongil line rice varieties and on the 2nd leaf from the top(n-2) in Japonica type rice varieties. Especially leaf lesions of Nopung which was more susceptible to leaf blast among Ton1 line rice varieties were mostly distributed on flag leaf. Relation between the degree of lesion distribution and level of fertilizer was more clear with an increase of fertilizer quantity. Leaf blast lesions of rice varieties were generally distributed from the flag leaf to the with leaf from the top but mainly those at flag leaf and the 2nd leaf from the top were found to be most responsible for inoculum source of panicle blast after booting stage. Increase of the conidia formation was resulted from fluctuation of temperature$(24^{\circ}C\~16^{\circ}C)$ in low temperature range after booting stage and many inoculum sources were supplied on panicles until the end of September without impeding dispersal from leaf blast lesions as an inoculum source of panicle blast.

• Korean Journal Plant Pathology
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• v.11 no.3
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• pp.238-244
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• 1995

Severity of panicle blast disease on the leading cultivars of rice was investigated at nine locations of Korea during summer in 1993 with frequent raining and low temperature conditions. Incidence of panicle blast was 26% on Jinmibyeo, 23% on Chuncheongbyeo and 40% on Odaebyeo. Race distribution of Pyricularia grisea was examined from 1993 to 1994. A total of 1,098 isolates of the fungus obtained from the blast nurseries and framers; fields were screened using Korean differential varieties. Twenty one races were identified in 1993 and 19 races in 1994. KI-181, KJ-103, KJ-104, KI-241 and KI-209 were identified as new races, and KJ-301 (15%), KJ-201 (13%), KJ-105 (12%) and KI-409 (12%) were major races during 1993 and 1994. Race KI-197, which has a wide spectrum of virulence on rice cultivars, was isolated in a ratio of 8.3% and evenly distributed in the whole country. Some of the major and newly identified races during 1993∼1994 were used for spray-inoculation on leading cultivars and differential varieties in a greenhouse. We found that most of the cultivars were resistant to the major races, KJ-301 and KI-409, but were very susceptible to the new races, KI-241, KI-209, KI-181 and KJ-103.