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What is the primary cause of rice blast in rice plants?
What is the primary cause of rice blast in rice plants?
Which part of the rice plant is commonly affected by rice blast lesions?
Which part of the rice plant is commonly affected by rice blast lesions?
Which of the following fungi is NOT associated with causing rice blast?
Which of the following fungi is NOT associated with causing rice blast?
What shape are the lesions most commonly associated with rice blast?
What shape are the lesions most commonly associated with rice blast?
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What is the significance of rice as a crop worldwide?
What is the significance of rice as a crop worldwide?
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Which of the following options correctly identifies the host plant for rice blast?
Which of the following options correctly identifies the host plant for rice blast?
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What type of crop failures does rice blast pose a threat to?
What type of crop failures does rice blast pose a threat to?
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Which part of the rice plant is least likely to show symptoms of rice blast?
Which part of the rice plant is least likely to show symptoms of rice blast?
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What is the primary structure formed from the appressorium during the infection process in rice?
What is the primary structure formed from the appressorium during the infection process in rice?
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Which environmental conditions most favor the outbreak of rice blast disease?
Which environmental conditions most favor the outbreak of rice blast disease?
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During what time period do the first visible lesions typically appear after planting rice?
During what time period do the first visible lesions typically appear after planting rice?
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What primarily contributes to the severity of rice blast disease?
What primarily contributes to the severity of rice blast disease?
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What is a common source of primary inoculum during the overwintering phase?
What is a common source of primary inoculum during the overwintering phase?
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How does rice typically grow in flooded fields?
How does rice typically grow in flooded fields?
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What happens to infested seeds left on the soil surface after mechanical planting?
What happens to infested seeds left on the soil surface after mechanical planting?
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Which practice is primarily used for planting rice in the United States?
Which practice is primarily used for planting rice in the United States?
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What structures produce the sexual spores in Magnaporthe oryzae?
What structures produce the sexual spores in Magnaporthe oryzae?
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Which mating system does Magnaporthe oryzae utilize for sexual reproduction?
Which mating system does Magnaporthe oryzae utilize for sexual reproduction?
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What is the common name for the asexual stage of Magnaporthe oryzae?
What is the common name for the asexual stage of Magnaporthe oryzae?
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What shape are the ascospores produced by Magnaporthe oryzae?
What shape are the ascospores produced by Magnaporthe oryzae?
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Under what conditions do conidia of Magnaporthe oryzae typically liberate from lesions?
Under what conditions do conidia of Magnaporthe oryzae typically liberate from lesions?
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Where are conidia formed in Magnaporthe oryzae?
Where are conidia formed in Magnaporthe oryzae?
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Which of the following rice pathogens is distinct from Magnaporthe oryzae?
Which of the following rice pathogens is distinct from Magnaporthe oryzae?
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How many septa do the conidia of Magnaporthe oryzae typically have?
How many septa do the conidia of Magnaporthe oryzae typically have?
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What condition is associated with the most severe incidence of rice blast disease?
What condition is associated with the most severe incidence of rice blast disease?
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How does the extent of rotten neck relate to yield loss in rice?
How does the extent of rotten neck relate to yield loss in rice?
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Which of the following factors does NOT influence the number of spores produced on an individual lesion?
Which of the following factors does NOT influence the number of spores produced on an individual lesion?
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What is the result of infection on the neck of the rice plant?
What is the result of infection on the neck of the rice plant?
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What is the main symptom caused by spores infecting the collar of the flag leaf?
What is the main symptom caused by spores infecting the collar of the flag leaf?
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Which of the following cultivars is considered susceptible to rice blast disease?
Which of the following cultivars is considered susceptible to rice blast disease?
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What type of discoloration is generally observed with infections of the neck and panicle?
What type of discoloration is generally observed with infections of the neck and panicle?
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What is a significant consequence of spores produced near the end of the growing season?
What is a significant consequence of spores produced near the end of the growing season?
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What is one cultural strategy recommended for managing rice blast disease?
What is one cultural strategy recommended for managing rice blast disease?
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How can overuse of nitrogen fertilizers affect rice production?
How can overuse of nitrogen fertilizers affect rice production?
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What is the primary challenge when using genetic resistance to control rice blast?
What is the primary challenge when using genetic resistance to control rice blast?
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Which practice is highly recommended to help in the prevention of rice blast disease?
Which practice is highly recommended to help in the prevention of rice blast disease?
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What happens to rice cultivars containing a single resistance gene over time?
What happens to rice cultivars containing a single resistance gene over time?
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Why is crop rotation advised as a strategy to manage rice blast?
Why is crop rotation advised as a strategy to manage rice blast?
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What is the consequence of under-irrigating rice fields?
What is the consequence of under-irrigating rice fields?
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What is one of the key reasons for utilizing high-quality, disease-free seeds in rice cultivation?
What is one of the key reasons for utilizing high-quality, disease-free seeds in rice cultivation?
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Study Notes
Rice Blast Disease
- Rice blast is a severe plant disease that affects rice (Oryza sativa), a staple food crop for millions globally.
- The disease is caused by the fungus Magnaporthe oryzae (formerly known as Pyricularia oryzae).
Symptoms and Signs
- Rice blast causes lesions on various parts of the rice plant, including leaves, stems, panicles, seeds, and even roots.
- The most common and diagnostic symptom is diamond-shaped lesions on the leaves.
- The pathogen produces sexual spores (ascospores) in structures called asci, classifying it as an ascomycete.
Sexual Reproduction
- The sexual, or teleomorphic, stage of the pathogen can be produced in the laboratory but has not been observed in the field in the United States.
- The pathogen exhibits a bipolar mating system controlled by two different alleles at a single locus, with additional genes influencing the sexual cycle.
Asexual Reproduction
- The asexual stage of Magnaporthe oryzae is represented by the Pyricularia oryzae form, the most common spore form in the USA.
- These spores, called conidia, are produced abundantly on lesions and are easily dispersed by wind.
Infection Process
- Infection occurs when conidia land on rice tissues and germinate, forming a germ tube and an appressorium.
- The appressorium, a melanized structure, develops an infection peg that penetrates the tissue, leading to rapid growth within susceptible tissues.
Disease Cycle & Epidemiology
- Rice blast thrives in moderate temperatures (24°C) and periods of high moisture, conditions commonly found in flooded rice fields.
- The overwintering sources of spores include grasses, volunteer plants, infested refuse, and infected seed on the soil surface.
- The disease severity is linked to the amount of infested material, leading to more severe disease in plots with higher amounts of primary inoculum.
Disease Management
- Rice blast management involves a comprehensive approach combining various techniques, including:
- Cultural strategies:
- Crop rotation to separate spores from seedlings
- Proper fertilization to avoid excess nitrogen
- Maintaining proper flood levels
- Using high-quality, disease-free seed
- Genetic resistance:
- Utilizing rice cultivars with genes conferring resistance to specific races of the fungus
- The challenge is the emergence of new races that overcome existing resistance genes.
- Cultural strategies:
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Description
Explore the critical information about rice blast disease, caused by the fungus Magnaporthe oryzae. This quiz covers symptoms, signs, and the reproductive stages of the pathogen. Test your knowledge on this significant disease affecting rice crops worldwide.
