• The Plant Pathology Journal
• /
• v.38 no.1
• /
• pp.46-51
• /
• 2022

Rice blast is the most destructive disease threatening stable rice production in rice-growing areas. Cultivation of disease-resistant rice cultivars is the most effective way to control rice blast disease. However, the rice blast resistance is easy to breakdown within years by blast fungus that continually changes to adapt to new cultivars. Therefore, it is important to continuously monitor the incidence of rice blast disease and race differentiation of rice blast fungus in fields. In 2020, a severe rice blast disease occurred nationwide in Korea. We evaluated the incidence of rice blast disease in Yeoju and compared the weather conditions at the periods of rice blast disease in 2019 and 2020. We investigated the races and avirulence genes of rice blast isolates in Yeoju to identify race diversity and genetic characteristics of the isolates. This study will provide empirical support for rice blast control and the breeding of blast-resistant rice cultivars.

• The Plant Pathology Journal
• /
• v.33 no.2
• /
• pp.103-108
• /
• 2017

World wheat production is now under threat due to the wheat blast outbreak in Bangladesh in early March 2016. This is a new disease in this area, indicating the higher possibility of this pathogen spreading throughout the Asia, the world's largest wheat producing area. Occurrence of this disease caused ~3.5% reduction of the total wheat fields in Bangladesh. Its economic effect on the Bangladesh wheat market was little because wheat contributes to 3% of total cereal consumption, among which ~70% have been imported from other countries. However, as a long-term perspective, much greater losses will occur once this disease spreads to other major wheat producing areas of Bangladesh, India, and Pakistan due to the existing favorable condition for the blast pathogen. The wheat blast pathogen belongs to the Magnaporthe oryzae species complex causing blast disease on multiple hosts in the Poaceae family. Phylogenetic analysis revealed that the Bangladesh outbreak strains and the Brazil outbreak strains were the same phylogenetic lineage, suggesting that they might be migrated from Brazil to Bangladesh during the seed import. To protect wheat production of Bangladesh and its neighbors, several measures including rigorous testing of seed health, use of chemicals, crop rotation, reinforcement of quarantine procedures, and increased field monitoring should be implemented. Development of blast resistant wheat varieties should be a long-term solution and combination of different methods with partial resistant lines may suppress this disease for some time.

• Korean Journal of Agricultural and Forest Meteorology
• /
• v.25 no.4
• /
• pp.245-257
• /
• 2023

The representative crop in the Republic of Korea, rice, is cultivated over extensive areas every year, which resulting in reduced resistance to pests and diseases. One of the major rice diseases, rice blast disease, can lead to a significant decrease in yields when it occurs on a large scale, necessitating early detection and effective control of rice blast disease. Drone-based crop monitoring techniques are valuable for detecting abnormal growth, but frequent image capture for potential rice blast disease occurrences can consume significant labor and resources. The purpose of this study is to early detect rice blast disease using remote sensing data, such as drone and satellite images, along with weather data. Satellite images was helpful in identifying rice cultivation fields. Effective detection of paddy fields was achieved by utilizing vegetation and water indices. Subsequently, air temperature, relative humidity, and number of rainy days were used to calculate the risk of rice blast disease occurrence. An increase in the risk of disease occurrence implies a higher likelihood of disease development, and drone measurements perform at this time. Spectral reflectance changes in the red and near-infrared wavelength regions were observed at the locations where rice blast disease occurred. Clusters with low vegetation index values were observed at locations where rice blast disease occurred, and the time series data for drone images allowed for tracking the spread of the disease from these points. Finally, drone images captured before harvesting was used to generate spatial information on the incidence of rice blast disease in each field.

• Korean Journal Plant Pathology
• /
• v.10 no.1
• /
• pp.47-53
• /
• 1994

Incidences of blast caused by Pyricularia grisea Sacc. on 24 leading cultivars and elite lines of rice were investigated in the fields at Icheon, chuncheon, Jecheon, Naju from 1990 to 1992. In the blast nursery, disease index of leaf blast on Jinmibyeo and Ilpumbyeo were very low as 1 to 3 at Naju, but as high as 6 to 9 at Icheon and other Chuncheon in 1990, but the disease did not occur in other locations and years. The most variable incidence of temporal and spatial leaf blast was observed on Nagdongbyeo, which was 30.6% at Icheon and 2.1% at Chuncheon on 1990, but the disease did not occur at Naju during the investigation. Percentages of diseased panicles on Chucheongbyeo were 11.6% in 1990 and 4.3% in 1992 at Icheon. Odaebyeo and Sobaekbyeo revealed more severe blast occurrences at Chuncheon and Sangju where the elevation was higher than the other places. Regional race distributions of rice blast fungus were more variable at Icheon and Chuncheon than the others.

• The Plant Pathology Journal
• /
• v.37 no.2
• /
• pp.200-203
• /
• 2021

Rice blast caused by the filamentous fungus Magnaporthe oryzae, is arguably the most devastating rice disease worldwide. Development of a high-throughput and reliable field blast resistance evaluation system is essential for resistant germplasm screening, resistance genes identification and resistant varieties breeding. However, the occurrence of rice blast in paddy field is easily affected by various factors, particularly lack of sufficient inoculum, which always leads to the non-uniform occurrence and reduced disease severity. Here, we described a procedure for adequately inducing the occurrence of rice seedling blast in paddy field, which involves pretreatment of diseased straw, initiation of seedling blast for the first batch of spreader population, inducing the occurrence of the second batch of spreader population and test materials. This procedure enables uniform and consistent infection, which facilitates efficient and accurate assessment of seedling blast resistance for diverse rice materials.

• The Plant Pathology Journal
• /
• v.35 no.1
• /
• pp.1-10
• /
• 2019

Wheat blast occurred in Bangladesh for the first time in Asia in 2016. It is caused by a fungal pathogen, Magnaporthe oryzae Triticum (MoT) pathotype. In this review, we focused on the current status of the wheat blast in regard to host, pathogen, and environment. Despite the many efforts to control the disease, it expanded to neighboring regions including India, the world's second largest wheat producer. However, the disease occurrence has definitely decreased in quantity, because of many farmers chose to grow alternate crops according to the government's directions. Bangladesh government planned to introduce blast resistant cultivars but knowledges about genetics of resistance is limited. The genome analyses of the pathogen population revealed that the isolates caused wheat blast in Bangladesh are genetically close to a South American lineage of Magnaporthe oryzae. Understanding the genomes of virulent strains would be important to find target resistance genes for wheat breeding. Although the drier winter weather in Bangladesh was not favorable for development of wheat blast before, recent global warming and climate change are posing an increasing risk of disease development. Bangladesh outbreak in 2016 was likely to be facilitated by an extraordinary warm and humid weather in the affected districts before the harvest season. Coordinated international collaboration and steady financial supports are needed to mitigate the fearsome wheat blast in South Asia before it becomes a catastrophe.

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

• The Plant Pathology Journal
• /
• v.36 no.5
• /
• pp.406-417
• /
• 2020

Early warning services for crop diseases are valuable when they provide timely forecasts that farmers can utilize to inform their disease management decisions. In South Korea, collaborative disease controls that utilize unmanned aerial vehicles are commonly performed for most rice paddies. However, such controls could benefit from seasonal disease early warnings with a lead time of a few months. As a first step to establish a seasonal disease early warning service using seasonal climate forecasts, we developed the EPIRICE Daily Risk Model for rice blast by extracting and modifying the core infection algorithms of the EPIRICE model. The daily risk scores generated by the EPIRICE Daily Risk Model were successfully converted into a realistic and measurable disease value through statistical analyses with 13 rice blast incidence datasets, and subsequently validated using the data from another rice blast experiment conducted in Icheon, South Korea, from 1974 to 2000. The sensitivity of the model to air temperature, relative humidity, and precipitation input variables was examined, and the relative humidity resulted in the most sensitive response from the model. Overall, our results indicate that the EPIRICE Daily Risk Model can be used to produce potential disease risk predictions for the seasonal disease early warning service.

• Journal of Climate Change Research
• /
• v.9 no.2
• /
• pp.133-142
• /
• 2018

Climate change will affect not only the crop productivity but also the pattern of rice disease epidemics in Korea. Impact assessments for the climate change are conducted using various climate change scenarios from many global climate models (GCM), such as a scenario from a best GCM or scenarios from multiple GCMs, or a combination of both. Here, we evaluated the feasibility of using a climate change scenario from the best GCM for the impact assessment on the potential epidemics of a rice leaf blast disease in Korea, in comparison to a multi?model ensemble (MME) scenario from multiple GCMs. For this, this study involves analyses of disease simulation using an epidemiological model, EPIRICE?LB, which was validated for Korean rice paddy fields. We then assessed likely changes in disease epidemics using the best GCM selected for individual agro?climatic zones and MME scenarios constructed by running 11 GCMs. As a result, the simulated incidence of leaf blast epidemics gradually decreased over the future periods both from the best GCM and MME. The results from this study emphasized that the best GCM selection approach resulted in comparable performance to the MME approach for the climate change impact assessment on rice leaf blast epidemic in Korea.

• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.24 no.1
• /
• pp.1-10
• /
• 1979

In order to investigate the causes of epidemic out break of rice blast disease in 1978, investigations were undertaken in respect of climatic conditions, variety, cultural practice and plant pathology. During 1978, especially in August at heading time, it was higher temperature and humidity, higher frequency and amount of rainfall, lower amount of sunshine and solar radiation than less blast infested years. Nitrogen content in rice plant was higher than previous years. Acreage increase of semi-dwarf varieties brought about a result of proportional increase of new blast races which are able to infect the semi-dwarf varieties. It was concluded that those conditions mentioned above might have caused the result of severe neck blast disease in rice varieties in Korea, 1978.