• Research in Plant Disease
• /
• v.18 no.4
• /
• pp.324-330
• /
• 2012

This study was conducted to investigate the association of race distribution of Pyricularia oryzae with rice cultivar and location. Races present in a given location were different in cultivars, and the races from a given cultivars were different by location. For precise study of race distribution, it needs to identify isolates by considering cultivation ratio and collection area. There are great differences between the resistant degree in the upland blast nursery and on the resistant degree of the leaf blast and panical blast in the paddy field. The number of virulent races in a rice cultivar was not related with the resistant degree in blast nursery or in paddy field.

• Korean Journal Plant Pathology
• /
• v.3 no.2
• /
• pp.131-136
• /
• 1987

Rates of lesion development over time and disease gradients over distance for blast disease on the two rice varieties, Brazos and M-20 1 were significantly affected by two different cultural conditions, upland and flooded conditions. Flooding rice field plots lowered the rates of lesion increase and flattened the disease gradients for both varieties. Despite absence of statistically significant differences in the rate of lesion increase between four sampled distances from infection focus, rate of lesion development tended to be slightly greater as distance from the infection focus increases. Rate of lesion increase was greater with more susceptible variety M-201 than with Brazos. Disease gradient was steeper for M-201 than for Brazos. As blast disease progressed, disease gradients became flattened regardless of variety due to the infections originated from secondary foci. Between two empirical disease gradient models examined, Kiyosawa & Shiyomi model was fitted better over Gregory model. Rates of blast isopath movement under upland conditions were calculated as approximately 0.2m/day and 0.4 m/day for Brazos and M-201, respectively. The results in this study suggest that differences in varietal resistance to blast could be detected by measuring disease gradient as efficiently as by measuring infection rate.

• Research in Plant Disease
• /
• v.9 no.4
• /
• pp.183-188
• /
• 2003

Correlation between the rice panicle blast and the rice quality and yield was evaluated in field experiments. Results showed that there were high positive correlations between the disease incidence and the rice yield and quality. The correlation coefficients between the disease incidence and the yield of Jinmibyeo, an early maturing cultivar and Juanbyeo, an middle maturing cultivar were $R^2$=0.6518 and $R^2$=0.7977, respectively. As the disease incidence increased weight of 1,000 grains of the two cultivars decreased showing coefficients $R^2$=0.6848 and $R^2$=0.7841, respectively. Percentage of matured grains in healthy plots were 95 and 98%, however, as the disease incidence increased percentage of matured rice grains decreased showing $R^2$=0.4745 in Jinmibyeo and $R^2$=0.703 in Juanbyeo. As the disease increased, rate of the damaged rice also increased, showing $R^2$=0.6607 in Jinmibyeo and $R^2$=0.6706 in Juanbyeo, respectively.

• Korean Journal Plant Pathology
• /
• v.12 no.2
• /
• pp.231-236
• /
• 1996

한국에서 재배되고 있는 벼 품종의 도열별에 대한 지속저항성 품종을 조기에 선발, 보급할 수 있는 방법을 보색하기 위하여 1985년부터 1994년까지 온실 유묘검정, 밭못자리 및 포장검정을 통하여 저항성 정도를 평가하고 재배면적과 재배기간을 참고로 하여 지속저항성 품종을 선발하였다. 도열병에 대한 저항성 품종으로는 다양한 레이스에 침해되면서 개체당 병반수 20개 이내, 밭못자리검정에서는 평균 발병정도 5이하, 본답에서의 잎도열병은 병반면적율 0.5%이하, 이삭도열병 발생은 이병수율 5% 이내로 병발생이 비교적 적은 섬진벼, 팔공벼 및 동진벼를 선발하였고, 지속저항성 품종으로는 재배기간이 10년 이상 유지되면서 재배면적은 전체재배 면적의 20% 이상을 차지하고 있는 품종 중 장기간 동안 저항성을 발현하는 동진벼를 선발하였다.

• Research in Plant Disease
• /
• v.8 no.4
• /
• pp.199-206
• /
• 2002

It was investigated on the relationship of the rice blast epidemics and the real-time meteorological factors, at the experimental paddy field in 1997. Weather factors(temperature, relative humidity, irradiation, precipitation, the direction of wind, wind speed, soil temperature and leaf-wetness, etc) were measured by using the automated weather station. The most influenced weather factor to blast epidemics, was the average max-temp($R^2$= 0.95) during 10 days before leaf blast epidemics, while the least thing was wind speed($R^2$= 0.24). The most potential weather factors correlated with the blast epidemics were T-ave(average temperature), T-max(maximum temperature), RH(Relative Humidity) and RD(Relative Humidity > 90% hrs). A statistics model(the regression equation) of the blast epidemics with the potential weather factors, was established as tallows ; Y = -3410.91 - 23.91 $\times$ T-ave ＋ 28.56 $\times$ T-max ＋ 41.0 $\times$ RH - 3.75 $\times$ RD, ($R^2$= 0.99). (T-ave >= 19$^{\circ}C$, T-max - T-ave >= 5.2$^{\circ}C$ and RH% >= 90.4%). According to the fitness test($\chi$$^2$) of the model, the observed blast disease severity was quite close to those expected.

• The Korean Journal of Pesticide Science
• /
• v.8 no.3
• /
• pp.168-174
• /
• 2004

In a course of the process for a lead optimization of 2-imino-l,3-thiazolines 1 which show a selective in vivo antifungal activity against rice blast, new compounds 2 in which C-5 was substituted by methyl group of the lead compound were synthesized and tested for the biological activity. Bromination of $\beta$-keto ester 7 followed by the reaction with thiourea and hydrolysis gave 2-imino-5-methyl-l,3-thiazoline carboxylic acid 3. Coupling reactions of 3 with aniline derivatives afforded 17 kinds of the corresponding 2-imino-5-methyl-l,3-thiazoline carboxanilides 2. Their in vivo antifungal activity against rice blast was weaker than that of 1, indicating that the in vivo antifungal activity of 2-imino-l,3-thiazolines was affected by the substituent at C-5. These results would be an important data for the molecular design in the lead optimization process of this series.

• Korean Journal Plant Pathology
• /
• v.3 no.2
• /
• pp.93-99
• /
• 1987

Six rice cultivars showing various types of resistance or susceptibility to Pyricularia oryzae in the field were used to study the relationship between susceptibility and contents of carbohydrates, amino acids and phenolics at different plant maturities and leaf ages under controlled environmental conditions. No consistent differences between the susceptible cultivars and adult-plant-resistant cultivars were found in terms of the contents of individual carbohydrates, total amino acids and phenolics in rice leaves throughout the plant development. Only the adult-plant-resistant cultivar Dobong had lower contents of inositol throughout the plant development than the other cultivars. The amounts of sucrose, inositol, glucose, and fructose increased in all tested cultivars at eight leaf stage than those at five leaf stage, but slightly decreased at twelve leaf stage. In contrast, total amino acids and phenolics gradually decreased during plant development. With increasing age of rice leaves, the amounts of total soluble amino acids and phenolics gradually increased in healthy fifth leaf tissues, although there were no significant differences between the cultivars. In particular, a high level of phenolics existed in old fifth leaves of the cultivar Dobong. These results suggest that increased resistance to blast of matured rice plants and old leaves may be the two different phenomina derived from the physiological changes occurring during plant development and leaf senescence, probably functioning differently in P. oryzae development.

• Korean Journal Plant Pathology
• /
• v.3 no.1
• /
• pp.3-7
• /
• 1987

Ethanol-soluble amino acids and phenolics in healthy and blast-infected leaves of the susceptible rice cultivar Nakdong and adult-plant-resistant cultivar Dobong were quantitatively analyzed, At the 3 days after inoculation, the levels of soluble amino acids and phenolics in the infected fifth and eighth leaves of the two cultivars ere similar to those of comparable healthy controls. As blast lesions appeared on the leaves at the 5 days after inoculation, the soluble amino acids and phenolics began to increase. At the 7 days after inoculation, the levels of amino acids and phenolics were about 1.5-3 times more than those in healthy controls at the five-and eight leaf stages. The adult-plant-resistant cultivar Dobong showed higher amounts of soluble amino acids and phenolics in both healthy and infected fifth and eighth leaves than did the susceptible cultivar Nakdong, although Dobong was less infected by Pyricularia oryzae than Nakdong, The pronounced increases in amino acids and phenolics in rice leaves of the cultivar Dobong during the blast infection may play an important role in the expression of adult-plant resistance to blast.

• Research in Plant Disease
• /
• v.29 no.3
• /
• pp.243-250
• /
• 2023

To explore the distribution and the resistance reaction of rice blast pathogens that may occur in North Korea, rice blast pathogens in the North Korean border regions of Dandong and Yeon-gil in China and the North Korean border region of Cheorwon in South Korea were analyzed. In addition, comparative analysis was conducted with rice blast pathogen in Suwon and Jeonju, inland regions of South Korea. Resistance reactions above average were observed in monogenic rice lines (IRBLzt-T, IRBL9-W, IRBL20-IR24, and IRBLta-CP1) in Jeonju, Suwon, and Cheorwon from 2018 to 2020. In Dandong and Yeon-gil, the monogenic lines IRBLz5-CA, IRBL12-M, and IRBL19-A consistently showed resistance reactions for three years. Notably, IRBL19-A exhibited strong resistance. Race distribution analysis in South Korea indicated a shift from KI to KJ dominance from 2018 to 2020, while in the North Korean border regions of Dandong and Yeon-gil, the KI race was dominant in 2021 and 2022. The race distribution of rice blast pathogens in China's North Korean border regions differed significantly from that in South Korea.

• Research in Plant Disease
• /
• v.25 no.4
• /
• pp.164-172
• /
• 2019

Rice blast disease caused by Magnaporthe oryzae is the most important disease of rice in both South and North Korea. Cultivation of disease-resistant cultivar is the best way to prevent this notorious disease, but M. oryzae races have been continuously changed to adapt a new cultivar. Therefore, it is important to get the information about the race and avirulence genes of the pathogen for developing blast-resistant rice cultivar. Since the entrance of North Korea was prohibited, the information about the races of M. oryzae in North Korea border areas and South Korea was collected to get the information about the diversity of rice blast pathogen in North Korea. The disease occurrence on monogenic lines carrying single resistant gene was investigated in Jeonju, Suwon, Cheorwon, Goseong, and Baengnyeongdo in Korea, and Dandong in China. The monogenic lines in Jeonju and Suwon showed diverse ranges of the response, while those in Baengnyeongdo and Dandong showed relatively high resistant responses to rice blast. All the field isolates of M. oryzae were characterized for rice blast races by the Korean differential varieties and screened for known avirulence genes to determine the spatial distribution of avirulence genes and the population of M. oryzae.