• 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 Plant Pathology
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• v.13 no.2
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• pp.79-84
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• 1997

Incidence of rice blast on new rice cultivars and elite lines was observed from 194 to 1996 in Icheon, Chuncheon, Jecheon and Naju areas. The observations were made in the nuseries and in the fields. In the nurseries, only cultivars Daesanbyeo and Hyangmibyeo 2 showed moderate levels of resistance to leaf blast, with the disease index 0 to 6. From the field observations, it was found that cultivars Hyangmibyeo 2 and Suwon 414 were highly resistant to leaf blast, but susceptible to neck blast. the fields, leaf blast was not observed. In general, there was great yearly and regional variation in the incidence of neck blast within the same cultivars, some times ranging from 0 to 100% of incidence. However, the range of fluctuation in the disease incidence were relatively small in the cultivars Daejinbyeo (0∼17.5%), Daesanbyeo (0∼4.0%), Donganbyeo (0∼21.4%) and Hwasambyeo (0∼13.9%). Hyangmibyeo 2 and Seojinbyeo were rarely infected with neck blast in Chuncheon and Naju all of the years, the same cultivars were severely infested with neck blast; 45.1 and 45.5%, respectively, in Jecheon in 1995. The occurrence of different races of rice blast fungus were different at different areas. However, it was found that in Icheon, Chuncheon, Jecheon and Naju areas, the dominant races were KI-409, KJ-201 and KJ-301.

• Korean Journal Plant Pathology
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• v.14 no.5
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• pp.496-501
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• 1998

Incidence of rice blast on new rice cultivars and elite lines was observed from 1995 to 1997 in Icheon, Chuncheon, Jecheon and Naju areas. The observation was made in the nurseries and fields. In the nurseries, three cultivars Grubyeo, Sangjuchalbyeo and Suwon 414 showed moderate levels of resistance to leaf blast, with the disease index 0 to 5. From the field observation, it was found that cultivars Heugjinjubyeo and Unbong 18 were highly resistant to leaf blast, but susceptible to neck blast. In general, there was a great variation yearly and regionally in the incidence of neck blast within the same cultivar, ranging from 0 to 100%. However, the range of neck blast infection was relatively narrower in the cultivars Yunghaebyeo (0∼2.4%) and Suwon 414 (0∼2.2%) during observation period. Races of rice blast fungus were variable at different areas. Among them dominant races were KI-409, KJ-201 and KJ-301.

• Korean Journal of Agricultural Science
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• v.6 no.2
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• pp.97-104
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• 1979

The present study was attempted to find out the effects of different fertilizer levels on the process and pattern of blast epidemic of Milyang 23 which is a variety belong to Tongil-line of rice and very susceptible to new races of the blast fungus. The results obtained from the study are as follows. In general, the plant become more susceptible to blast with increase of fertilizers applied and there is a close relationship between the incidence of blast and levels of fertilizer. Such a relationship appears more clearly in case of the incidence of leaf blast while it is not so clear in case of the incidence of node blast and neck blast. In spite of low level of fertilizer, both of node and neck blast occur considerably and the difference compared with that of high level of fertilizer is not so great. Therefore, the disease escaping in the node or the neck of panicle by regulation of fertilizer level may be impossible. And also forecasting of the neck blast by estimate of the incidence of leaf blast is very difficult because of discontinuity of the incidence of blast on the leaf and the node.

• Korean Journal of Agricultural Science
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• v.12 no.2
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• pp.206-241
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• 1985

Attempts to search infection period, infection speed in the tissue of neck blast of rice plant, location of inoculum source and effects of several conditions about the leaf sheath of rice plants for neck blast incidence have been made. 1. The most infectious period for neck blast incidence was the booting stage just before heading date, and most of necks have been infected during the booting stage and on heading date. But $Indica{\times}Japonica$ hybrid varieties had shown always high possibility for infection after booting stage. 2. Incubation period for neck blast of rice plants under natural conditions had rather a long period ranging from 10 to 22 days. Under artificial inoculation condition incubation period in the young panicle was shorter than in the old panicle. Panicles that emerged from the sheath of flag leaf had long incubation period, with a low infection rate and they also shown slow infection speed in the tissue. 3. Considering the incubation period of neck blast of rice plant, we assumed that the most effective application periods of chemicals are 5-10 days for immediate effective chemicals and 10-15 days for slow effective chemicals before heading. 4. Infiltration of conidia into the leaf sheath of rice plant carried out by saturation effect with water through the suture of the upper three leaves. The number of conidia observed in the leaf sheath during the booting stage were higher than those in the leaf sheath during other stages. Ligule had protected to infiltrate of conidia into the leaf sheath. 5. When conidia were infiltrated into the leaf sheath, the highest number of attached conidia was observed on the panicle base and panicle axis with hairs and degenerated panicle, which seemed to promote the infection of neck blast. 6. The lowest spore concentration for neck blast incidence was variable with rice varietal groups. $Indica{\times}Japonica$ hybrid varieties were infected easily compared to the Japonica type varieties, especially. The number of spores for neck blast incidence in $Indica{\times}Japonica$ hybrid varieties was less than 100 and disease index was higher also in $Indica{\times}Japonica$ hybrid than in Japonica type varieties. 7. Nitrogen content and silicate content were related with blast incidence in necks of rice plants in the different growing stage changed during growing period. Nitrogen content increased from booting stage to heading date and then decreased gradually as time passes. Silicate content increased from booting stage after heading with time. Change of these content promoted to increase neck blast infection. 8. Conidia moved to rice plant by ascending and desending dispersal and then attached on the rice plant. Conidia transfered horizontally was found very negligible. So we presumed that infection rate of neck blast was very low after emergence of panicle base from the leaf sheath. Also ascending air current by temperature difference between upper and lower side of rice plant seemed to increase the liberation of spores. 9. Conidial number of the blast fungus collected just before and after heading date was closely related with neck blast incidence. Lesions on three leaves from the top were closely related with neck blast incidence, because they had high potential for conidia formation of rice blast fungus and they were direct inoculum sources for neck blast. 10. The condition inside the leaf sheath was very favorable for the incidence of neck blast and the neck blast incidence in the leaf sheath increased as the level of fertilizer applied increased. Therefore, the infection rate of neck blast on the all panicle parts such as panicle base, panicle branches, spikelets, nodes, and internodes inside the leaf sheath didn't show differences due to varietal resistance or fertilizers applied. 11. Except for others among dominant species of fungi in the leaf sheath, only Gerlachia oryzae appeared to promote incidence of neck blast. It was assumed that days for heading of varieties were related with neck blast incidence.

• Research in Plant Disease
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• v.10 no.1
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• pp.69-72
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• 2004

The control activity of isoprothiolane and tricyclazole mixed with carbosulfan, and probenazole by the nursery treatment was performed against rice leaf and neck blast caused by Magnaporthe grisea. In the paddy field, three fungicides showed good activities against leaf blast 3 months after nursery treatment. Especially the activity of tricyclazole against leaf blast gradually increased by the laps of time to 85.5％, which was assessed at 6 September,2003. Although the control value of isoprotholane and tricyclazole mixed with carbosulfan against neck blast was 47.5％ and 61.1％, respectively, probenazole showed a very high activity against not only leaf blast but also neck blast, of which that was 91.2％. No phytotoxicity was observed in all the treatments after transplanting rice seedling in the paddy field. Based on these results, three systemic fungicides tested in this study showed such a good potential that they might be used to formulate the nursery treating granule.

• Korean journal of applied entomology
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• v.22 no.4 s.57
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• pp.287-292
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• 1983

Incubation period of rice neck blast was investigated by injection of conidial suspension of Pyricularia oryzae into young panicles inside the flag leaf sheath at booting stage. Eleven to fifteen days were taken for symptom appearance from the date of injection. About two days were taken from conidia germination until infection occurred, the incubation period was determined as nine to thirteen days for the symptom development of neck blast in rice plants.

• Research in Plant Disease
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• v.9 no.2
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• pp.68-71
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• 2003

Correlation between rice yield loss and infection time of neck blast after panicle emergence was analyzed in paddy fields at Icheon in 1999 and 2000. As the neck blast occurred at early heading stage, the yield loss of a early maturity variety, Jinmibyeo, ranged from 83.9% to 81.6%, while it ranged from 44.3% to 33.1% when the disease developed 30 days after heading. The regression equations of yield loss(y) caused by the neck blast infection time(x) in Jinmibyeo were y =1.2717x + 79.523(R2 = 0.9487) and y = 1.6872x + 74.545(R2 = 0.7993) in 1999 and 2000. In a mid-lately maturity variety, Chucheongbyeo, yield loss ranged from 64.9% to 47.8% when the disease developed at early heading stage. While it ranged from 29.1% to 8.9% when the disease occurred 40 days after heading. The regression equations of yield loss caused by the disease in Chucheongbyeo were y= 1.2717x + 79.523($R^2$ = 0.9487) and y = 1.6872x + 74.545(($R^2$ = 0.7993) in 1999 and 2000. Weights of 1,000 rice grains of Jinmibyeo and Chucheongbyeo were also drastically decreased to 38.3% and 57.3%, respectively, compared to healthy control when the disease occurred at early heading stage. However, weights of the two cultivars were 87.6% and 92.9% compared to control when the disease developed after 40 days of heading. Results indicated that there is a highly negative correlation between rice yield loss and infection time of the neck blast.

• 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 of applied entomology
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• v.21 no.1 s.50
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• pp.15-18
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• 1982

The integrated soil improvement practice reduced neck blast incidence by ranging from 6.3 to 59.5 percent compared to control plot. However, effect of integrated soil improvement practice in reducing neck blast incidence was greater in Tongil type cultivars. On the contrary, mean value of plant height of eleven rice cultivars was taller by 6.4cm in the integrated soil improvement plot with 2.3 more tillers than that of control plot. As a result, yield increase of milled rice by metric tons per hectare was 24.1 percent in the integrated soil improvement plot.