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Blast disease is caused by Magnaporthe grisea (syn. Pyricularia oryzae) firstly reported in 1637 from China. In Nepal it was firstly reported from Thimi, Bhaktapur in 1964. Symptoms of this disease appear in all stages from seedling in nursery to heading in main field, however, the most devastating stages are seedling stage, tillering stage and pan...
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... Blast disease severity is affected by prevailing environmental conditions specifically ambient temperature and humidity (Hunjan & Lore, 2020). Rice and finger millet blast is cased by M. oryzae (Neupane & Bhusal, 2021). Typical blast disease symptoms on leaf include spindle shape lesions with gray middle region and brown margin. ...
... Typical blast disease symptoms on leaf include spindle shape lesions with gray middle region and brown margin. Other symptoms include neck, stem and panicle blast on rice and neck, stem and finger blast on finger millet (Neupane & Bhusal, 2021). Blast disease damages all stages of the crop in rice and in finger millet (Sitther & Gnanamanickam, 1996). ...
Blast disease caused by Magnaporthe sp. is one of the most destructive diseases in cereal crops. Disease infection was studied in farmer fields. Field data was recorded and further information was gathered by interviewing the farmers and agrarian extension officers. Blast infections were assessed in the fields using a standard evaluation system for rice (SES IRRI, 1996). Although symptoms were not observed in seedlings when mature rice fields were infected farmers experienced 100% yield loss. There were no or few leaf symptoms in blast infected mature rice fields yet neck infections were scored as 9 in SES. Unlike rice, leaf blast at seedling stage caused economic losses in finger millet. Mature finger millet fields were susceptible to neck and finger blast. Due to rapid disease development curative fungicide treatment was ineffective in controlling blast. Farmers reported sudden changes in the weather during infections whereby gloomy weather caused a spike in humidity and low temperatures that coincided with the infection. Host susceptibility window synchronized with conducive environments result in severe blast infections therefore, blast disease management needs a coordinated effort and system level interventions whereby control measures and use of resistant germplasm can be combined with climate-based disease predictions to increase the efficiency of disease control.
... Among these, the rice blast disease is reported to have the most devastating effects [4]. The fungus named, Magnaporthe grisea, causes rice blast disease resulting in lesions on the leaves, nodes , and necks which are commonly known as the leaf, node, and neck blast, respectively [5,6]. Since rice blast disease causes devastating effects, rice farmers must be able to detect these diseases so that they can take the next step as soon as possible. ...
Blast is one of the prominent rice diseases. Automictic disease detection can assist farmers to take action timely and accurately. In this experiment, the CNN model has been employed to classify rice disease, especially Blast and Brown Spots. Several pre-trained models have been trained and evaluated on a combined dataset. The dataset was created by capturing images from the field and collecting them from multiple sources. DCGAN has been used to create new synthetic images to enhance the dataset. The obtained result before and after using DCGAN has been compared for determining the improvement of the model performance. The experimental result shows that InceptionResNet V2 outperforms the other pre-trained model after augmenting the images using DCGAN. The InceptionResNet V2 achieved the highest accuracy of 0.911, precision of 0.922, and recall of 0.900 on the combined dataset after the augmentation using DCGAN.
... This is because P. oryzae can infect rice plants from nursery to grain filling. Symptoms caused by the attack of the fungus P. oryzae are in the form of spots on leaves, stem books, panicle necks, and leaf midribs (Bushal, 2021;Cruz and Valent, 2017). In the vegetative phase, there are rhombic spots on the leaves, and in the generative phase, there are neck rot spots. ...
One of the suggested blast disease management approaches is integrated disease control, which combines cultivation practices, resistant cultivars, and fungicide applications as appropriate. Planting resistant varieties are the most cost-effective option, but the resistance is quickly broken down over seasons and areas due to the existence of many races. Planting resistant varieties should therefore be accompanied by other control methods like biological control techniques. Selecting varieties with resistant gene(s) that match the pathogen race in the field is recommended. It is therefore critical to monitor the race composition in the area. This study aimed to determine races of Pyricularia oryzae isolated from different subdistricts in Pinrang, Bone, Maros, and Gowa regencies and the potential of rhizosphere fungal isolates to inhibit the growth of three dominant fungal blast races. Pyricularia oryzae was isolated on rice that showed specific symptoms of blast disease. Blast pathogen was grouped into races using 7 rice differential variety sets: Asahan, Cisokan, IR64, Krueng Aceh, Cisadane, Cisanggarung, and Kencana Bali. Observations were carried out 7 days after inoculation based on the standard evaluation system according to IRRI. The antagonists were isolated from the rhizosphere of healthy rice plants, followed by the dual culture test on Potato Dextrose Agar (PDA). A total of 42 isolates were collected from blast-infected rice, and 14 isolates were obtained from the rice rhizosphere. Based on the reactions of 7 differential varieties, a total of 18 races were determined. Races 000 and 001 were dominated with every 6 isolates, followed by races 003 and 020 with 5 isolates each, and races 033 and 013 with 4 and 3 isolates respectively. The other races were found only every two or single isolate. Dual culture using fungal rhizosphere isolates revealed that five isolates had inhibition above 75% against 3 representative races of P. oryzae. Based on the findings, it is suggested that the variation of P. oryzae races in 4 regencies in South Sulawesi is significantly high, and dominated by 2 races. The five rhizosphere fungal isolates may be used as potential bioagents for the eco-friendly management of rice blast disease.
... All stages of rice growth are threatened by this disease. The pathogen spreads disease to most of the aerial parts of the plant causing lesions on them, including the leaf blade, leaf sheath, collar region, stem, panicle, and grain (hull), and also limits yield potential in disease-prone environments (Neupane & Bhusal , 2020). Globally, blast disease accounts for 70 to 80 % reduction in yield of rice damaging vegetative as well as reproductive stages (Rijal and Devkota 2020). ...
Rice blast (Pyricularia oryzae) is a serious disease which hampers production of rice. The field research was conducted in PMAMP, PIU, Siraha Dhangadimai-10, Kuduwa to evaluate the efficacy of various chemicals against rice blast. The experiment was carried out in Completely Randomized Block Design (RCBD) with 7 treatments (6 chemicals and 1 control) and each treatment was replicated 3 times. Chemicals namely Hexaconazole5%(SC), Carbendazim12%+ Mancozeb 63%(WP), Azoxystrobin 18.2 % + Difenoconazole 11.4% (SC), Thiophonate-Methyl 70%wp, Kasugamycin 2% Wp and Floxystrobin+tubuconazole were used for this experiment. Azoxystrobin18.2 % + Difenoconazole 11.4 % (SC) was recorded as the best chemical followed by Carbendazim12%+Mancozeb 63%WP to control rice blast. The highest disease severity was seen at the control plot. The highest yield was observed in plot with Azoxystrobin+Difenconazole (5.16mt/ha) followed by Carbendazim12%+ Mancozeb 63%WP(5.12mt/ha).
Keywords: Pyricularia oryzae, Disease, Severity, Fungicides, Control, Yield
... The lesion is 1 to 1.5 cm in length, 0.3 to 0.5 cm in width). The resistance variety of rice for this fungus develops the spot but is small in size and does not contain spores (Neupane et al., 2021). Lesions on the leaves coalesce and make leaves wither, mainly found at the seedling as well as tillering phase (Hajimok, 2001). ...
... It is airborne conidia that exist all year round and is responsible for epidemics occurrence throughout the year (Guerber et al., 2006;Raveloson et al., 2018). The low night temperature (15-20ׄ °C), high relative humidity (93-99%), and cloudy weather favor conidia germination, sporulation, and infection (Neupane et al., 2021). Blast development is favored by high nitrogen rates and thick stands which results in high moisture levels, but is most severe under drained or upland conditions. ...
Rice blast is caused by the fungi Magnaporthe oryzae, which belongs to the group Ascomycota. The disease cycle of rice blast begins with the infection of the plant tissue by the spores of the pathogen. The spores can be carried by wind, water, and insects, and can infect the plant at any growth stage, from seedling to the heading stage. Once the spore lands on the plant tissue, they germinate and penetrate the tissue through a specialized structure called appressoria. Inside the plant tissue, the fungus grows and produces lesions that appear as small grayish-white spots on the leaves, collar, neck, and panicle of the plant. Under favorable conditions, the lesions can enlarge rapidly, causing complete crop failure. The epidemiology of rice blasts is influenced by various factors, such as temperature, humidity, rainfall, wind, and varietal susceptibility. The pathogen can survive in the soil and plant debris for several months, providing a potential source of infection for the next crop. Several management strategies have been developed to control rice blasts, including cultural, botanical, nutrient management, biotechnological, and chemical methods. Chemical methods such as fungicides can be used to control the disease, but their use should be judicious to avoid the development of fungicide resistance and environmental pollution.
... Rice blast, caused by pathogenic fungi M. oryzae, is an important fungal disease of rice [52,53]. It has been reported that the loss of rice yield caused by M. oryzae is enough to feed 60 million people every year [54]. ...
Dihydroxynapthalene-(DHN) and L-dihydroxyphenylalanine (L-DOPA) are two types of dominant melanin in fungi. Fungal melanins with versatile functions are frequently associated with pathogenicity and stress tolerance. In rice blast fungus, Magnaporthe oryzae, DHN melanin is essential to maintain the integrity of the infectious structure, appressoria; but the role of the tyrosinase-derived L-DOPA melanin is still unknown. Here, we have genetically and biologically characterized a tyrosinase gene (MoTyr) in M. oryzae. MoTyr encodes a protein of 719 amino acids that contains the typical CuA and CuB domains of tyrosinase. The deletion mutant of MoTyr (ΔMoTyr) was obtained by using a homologous recombination approach. Phenotypic analysis showed that conidiophore stalks and conidia formation was significantly reduced in ΔMoTyr. Under different concentrations of glycerol and PEG, more appressoria collapsed in the mutant strains than in the wild type, suggesting MoTyr is associated with the integrity of the appressorium wall. Melanin measurement confirmed that MoTyr loss resulted in a significant decrease in melanin synthesis. Accordingly, the loss of MoTyr stunted the conidia germination under stress conditions. Importantly, the MoTyr deletion affected both infection and pathogenesis stages. These results suggest that MoTyr, like DHN pigment synthase, plays a key role in conidiophore stalks formation, appressorium integrity, and pathogenesis of M. oryzae, revealing a potential drug target for blast disease control.
... Asibi et al. (2019) reported with long periods of rainy and cloudy conditions, both growth of rice and its resistance to rice blast are weakened. According to some workers (Greer and Webster, 2001;Kapoor et al. 2004;Neupane and Bhusal, 2021), the most suitable conditions for the outbreak of blast fungus are cloudy weather, high relative humidity (93-99 percent), low night temperatures between 15-20°C. ...
... Symptoms of leaf blast typically consist of elongated diamond-shaped lesions with grey or whitish centers and brown or reddish-brown margin . Later, the small spots collapse together, becomes eyeshaped in mature stage and give blistering appearance (Neupane & Bhusal, 2021). Lesion reduces the net photosynthetic rate and impaired the transport of water or nutrients or both and consequently affect the leaf tissues situated near the lesions (Bastiaans, 1991). ...
... When the node of plant is affected, node portion of the culms turn brown, grayish brown or black and the portion above the infected node may die and breakdown as the xylem and phloem vessel of plant blocked which affects the nutrient and water supply to the portion above the infection point (Neupane & Bhusal, 2021) as shown the Figure 5 below. ...
... The spores undergoing overwintering when infects the collar of the flag leaf, produce symptoms which are collar rot (TeBeest et al., 2007). At initial stage infection starts at the base of the flag leaf near the leaf sheath (Neupane & Bhusal, 2021). At later stage, infection proceeds upward to the leaf that girdles the flag leaf which turned brown, dry and fall off (TeBeest et al., 2007). ...
Rice (Oryza sativa L.) is the most important staple cereal crop which is consumed by more than 50% of world population. It contributes 23% and 50% of total calories consumed by world and Nepalese population respectively. Among various abiotic factors affecting rice, rice blast is the most disastrous, causing 70-80% yield loss. This disease was originated in China around 7000 years ago. In Nepal, it was first reported in Thimi, Bhaktapur in 1966. It is caused by a filamentous ascomycete fungus Magnaporthe oryzae (Anaemorphic form-Pyricularia oryzae). It infects all the developmental stage of plant and produce symptoms on the leaf, collar, neck, panicle and even in the glumes. It decreases the rice production by an amount, enough to feed 60 million people every year. Cloudy weather, high relative humidity (93-99%), low night temperature (15-20°C), longer duration of dew is the most favorable condition for the outbreak of disease. The most usual approaches for the management of rice blast diseases are management in nutrient fertilizer and irrigation, application of fungicides and plantation of resistant cultivars. Besides, the use of extracts of C. arabica are reported to have an inhibitory effect on the disease. Seed treatment with Trichoderma viridae @ 5ml/lit of water have also been found effective. The chemical means of controlling blast disease shall be reduced, instead eco-friendly measures like biocontrol agents, resistant varieties, plant extracts can be practiced for disease control. Different forecasting model can be used in order to predict the disease prevalence.
... MT) is achieved. Of all the biotic and abiotic factors that impact the yield, leaf blast disease caused by Pyricularia oryzae is of significant importance which can scale down the yield with 80% losses depending on the crop stage it's going to affect (Neupane & Kiran Bhusal, 2021) [9] . It is polycylic, hemibiotrophic foliar pathogen, prevalent globally in humid areas where the rice is being cultivated (Neelakanth et al., 2017) [7] . ...
... MT) is achieved. Of all the biotic and abiotic factors that impact the yield, leaf blast disease caused by Pyricularia oryzae is of significant importance which can scale down the yield with 80% losses depending on the crop stage it's going to affect (Neupane & Kiran Bhusal, 2021) [9] . It is polycylic, hemibiotrophic foliar pathogen, prevalent globally in humid areas where the rice is being cultivated (Neelakanth et al., 2017) [7] . ...
Rice blast disease caused by Pyricularia oryzae is a major threat to the farmers as the disease severity may lead up to 80% crop loss in severe conditions. A laboratory experiment was conducted at Department of Plant Pathology, Acharya N.G. Ranga Agricultural University, Agricultural College, for testing the efficacy of eight different single and combination fungicides adopting poisoned food method against the pathogen Pyricularia oryzae causing rice blast disease. The experiment was carried out in a completely randomized design with eight treatments including control following 3 replications of each. Three concentrations (R-recommended dose; R/2 and 2R) each of different fungicides viz., Beam (Tricyclazole 75% WP @ 0.06%), Amistar (Azoxystrobin 25% SC @ 0.10%), Fujione (Isoprothiolane 5% EC @ 0.15%), Kasugamycin @ 0.25%, Folicur (Tebuconazole 25% EC @ 0.15%), Nativo 75% WG (Trifloxystrobin 50% + Tebuconazole 25% WG @ 0.08%), Custodia (Azoxystobin + Tebuconazole @ 0.15%) and Filia (Propiconazole + Tricyclazole @ 0.10%) were evaluated against the radial growth of pathogen. Results showed that except two fungicides viz., Kasugamycin and Azoxystrobin rest all the fungicides fully inhibited (100% inhibition) the mycelial growth of the pathogen at all the three different concentrations compared to control.
... Symptoms of leaf blast typically consist of elongated diamond-shaped lesions with grey or whitish centers and brown or reddish brown margin . Later the small spots collapse together, becomes eye-shaped in mature stage and give blistering appearance (Neupane & Bhusal, 2021). Lesion reduces the net photosynthetic rate and impaired the transport of water or nutrients or both and consequently affect the leaf tissues situated near the lesions (Bastiaans, 1991). ...
... When the node of plant is affected, node portion of the culms turn brown, grayish brown or black and the portion above the infected node may die and breakdown as the xylem and phloem vessel of plant blocked which affects the nutrient and water supply to the portion above the infection point (Neupane & Bhusal, 2021) ...
... The spores undergoing overwintering when infects the collar of the flag leaf, produce symptoms which are collar rot (TeBeest et al., 2007). At initial stage infection starts at the base of the flag leaf near the leaf sheath (Neupane & Bhusal, 2021). At later stage, infection proceeds upward to the leaf that girdles the flag leaf which turned brown, dry and fall off (TeBeest et al., 2007). ...
Rice (Oryza Sativa L.) is the most important staple cereal crop which is consumed by more than 50% of the world population. It contributes 23% and 50% of total calories consumed by the world and Nepalese populations respectively. Among various abiotic factors affecting rice, rice blast is the most disastrous, causing 70-80% yield loss. This disease was originated in China around 7000 years ago. In Nepal, it was first reported in Thimi, Bhaktapur in 1966. It is caused by a filamentous ascomycete fungus Magnaporthe oryzae (Anaemorphic form-Pyricularia oryzae). It infects all the developmental stage of plant and produce symptoms on the leaf, collar, neck, panicle, and even in the glumes. It decreases the rice production by an amount, enough to feed 60 million people every year. Cloudy weather, high relative humidity (93-99%), low night temperature (15-20°C), longer duration of dew is the most favorable condition for the outbreak of disease. The most usual approaches for the management of rice blast diseases are management in nutrient fertilizer and irrigation, application of fungicides, and plantation of resistant cultivars. Besides, the use of extracts of C. arabica is reported to have an inhibitory effect on the disease. Seed treatment with Trichoderma viridae @ 5ml/lit of water has also been found effective. The chemical means of controlling blast disease shall be reduced, instead, eco-friendly measures like biocontrol agents, resistant varieties, plant extracts can be practiced for disease control. Different forecasting models can be used in order to predict disease prevalence.
