Diseases of Rice: Fungal Diseases Quiz

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Questions and Answers

What is the primary pathogen responsible for Brown Spot disease in crops?

Cochliobolus miyabeanus

Helminthosporium oryzae (correct)

Bipolaris oryzae (correct)

Trichoderma viride

Which chemical is NOT recommended for spraying in the nursery to combat the Brown Spot fungus?

Iprobenphos (correct)

Carbendazim

Edifenphos

Tricyclazole

How do the conidia of the pathogen associated with Brown Spot appear?

Round and spiky

Straight and colorless

Flat and leaf-like

Curved with a bulged center and tapered ends (correct)

What effect does ophiobolin A have on plant cells?

It disrupts the integrity of the cell wall Signup and view all the answers

In which temperature range is the development of Brown Spot disease most favorable?

25-30˚C Signup and view all the answers

What is a visible symptom of Brown Spot disease on affected plants?

Cylindrical or oval dark brown spots Signup and view all the answers

What is the sexual stage of the fungus that causes Brown Spot?

Cochliobolus miyabeanus Signup and view all the answers

Which of the following conditions enhance the severity of Brown Spot disease?

Excess nitrogen Signup and view all the answers

What is the primary pathogen responsible for the blast disease in rice?

Pyricularia oryzae Signup and view all the answers

Which symptom is specifically associated with neck blast in rice?

Brownish-black lesions on the peduncle Signup and view all the answers

What is the impact of the blast disease on rice yields depending on the stage of infection?

Yield losses vary between 30-61 percent Signup and view all the answers

What is the appearance of conidia produced by Pyricularia oryzae?

Pyriform to ellipsoid, hyaline to pale olive green Signup and view all the answers

Which environmental condition is NOT favorable for the development of blast disease?

Sunny weather with occasional rain Signup and view all the answers

What type of lesions appear on the leaves affected by leaf blast?

Spindle shaped spots with grey centers and dark brown margins Signup and view all the answers

Which part of the rice plant does nodal blast affect most significantly?

Nodes Signup and view all the answers

What is the perfect state of Pyricularia oryzae called?

Perithecia Signup and view all the answers

What is the primary mechanism by which the fungus causing false smut spreads?

Air-borne ascospores Signup and view all the answers

Which of the following conditions favor the growth of the pathogen responsible for poorly filled grain?

High relative humidity and high temperature Signup and view all the answers

How long can the pathogen survive in dry soil?

About 20 months Signup and view all the answers

Which management practice is recommended to control the pathogen effectively?

Applying organic amendments Signup and view all the answers

What are the visible symptoms caused by the fungus Ustilaginoidea virens?

Greenish spore balls on the grains Signup and view all the answers

Which of the following is NOT a recommended practice for managing the pathogen?

Allowing irrigation from infected fields Signup and view all the answers

What is the primary secondary source of infection for the false smut pathogen?

Chlamydospores Signup and view all the answers

Which variety of plants is recommended for resistance against the pathogen affecting grain filling?

Mansarovar Signup and view all the answers

What are the visible symptoms of Udbatta disease on ear heads?

Black spike-like structures with matted spikelets Signup and view all the answers

What type of treatment is effective against the Udbatta disease pathogen?

Removal of collateral hosts and hot water treatment at 45˚C Signup and view all the answers

Which pathogen is associated with Stackburn disease?

Trichoconis padwickii Signup and view all the answers

What characteristic symptom appears on leaves affected by Stackburn disease?

Circular to oval spots with dark brown margins Signup and view all the answers

What effective method can control Kernel Smut disease?

Seed treatment with Captan Signup and view all the answers

What visible condition do grains exhibit due to Kernel Smut infection?

Partially replaced by black spores Signup and view all the answers

What is a common management practice for controlling Stackburn disease?

Burning stubbles and straw in the field Signup and view all the answers

What is the shape and structure of conidia related to Stackburn disease?

Elongated with a long beak, thick-walled Signup and view all the answers

What types of conidia are produced by the fungus associated with grain discoloration?

Both macroconidia and microconidia Signup and view all the answers

Which of the following phytotoxins is produced by the pathogenic fungus causing grain discoloration?

Fusaric acid Signup and view all the answers

What is the recommended treatment for seeds to manage the fungal infection?

Treatment with Thiram or Captan Signup and view all the answers

What color discoloration might grains exhibit due to infection before or after harvesting?

Red, yellow, orange, pink or black Signup and view all the answers

What environmental conditions favor the spread of fungal disease in grains?

High humidity and cloudy weather Signup and view all the answers

Which of the following grains is primarily affected by the pathogens mentioned in the document?

Rice Signup and view all the answers

During which growth stage should crops be sprayed to prevent grain discoloration?

Boot leaf stage and flowering stage Signup and view all the answers

What moisture content is ideal for storing grains to prevent fungal infections?

13.5-14% Signup and view all the answers

Study Notes

Fungal Diseases of Rice

Blast - Pyricularia oryzae

Affects rice at all growth stages, causing lesions on leaves, nodes, rachis, and glumes.
Leaf symptoms include spindle-shaped spots with grey centers and dark brown margins.
Severe infections lead to brown-black lesions on nodes (nodal blast) and neck rot during flowering.
Yield losses range from 30% to 61% depending on infection timing.
Favourable conditions: High humidity (93-99%), low temperatures (15-20˚C).
Management includes fungicides like carbendazim and tricyclazole.

Brown Spot - Helminthosporium oryzae

Attacks from seedling to milky stages with spots on leaf blade, sheath, and glume.
Dark brown spots with yellow halos eventually coalesce, causing leaf dieback.
Leads to reduced grain quality and diminished germination.
Favourable conditions: 25-30˚C temperature and over 80% humidity.
Manages via resistant varieties and organic amendments.

False Smut - Ustilaginoidea virens

Transforms grains into greenish spore balls, affecting only some spikelets in a panicle.
Spherical, warty chlamydospores form as spore balls.
Depends on grassy alternate hosts for its life cycle.
Favoured by rainfall and cloudy weather during flowering.

Udbatta Disease - Ephelis oryzae

Symptoms appear at panicle emergence, causing black spike-like structures.
Spikelets get reduced in size, cemented by fungal mycelium and covered by greyish stroma.
Management through hot water seed treatment at 45˚C for 10 minutes.

Stackburn Disease - Trichoconis padwickii

Affects leaves and ripening grains with circular to oval spots with dark margins.
Glumes show reddish-brown spots; kernels shrivel and become brittle.
Conidia are elongated, thick-walled, and septate.
Management includes seed treatment with fungicides and hot water treatment.

Bunt or Kernel Smut - Tilletia barclayana

Characterized by black pustules or streaks forming on grains, which burst at ripening.
Fungal spores can replace grains partly or wholly.
Both macroconidia and microconidia are produced, with the fungus releasing non-host-specific phytotoxins.
Management via seed treatment with fungicides.

Grain Discoloration - Various Pathogens

Various fungi cause grain discoloration, leading to quality losses.
Symptoms include dark brown or black spots; discoloration can vary in color.
Favourable conditions include high humidity and cloudy weather during heading.
Prevention methods include timely spraying and moisture control in grain storage.

Bacterial Diseases of Rice

Bacterial Leaf Blight - Xanthomonas oryzae pv. oryzae

Symptoms generally occur at heading but can emerge earlier.
Initial lesions are water-soaked, leading to yellowing and drying of leaf tips.

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Description

Test your knowledge on the fungal diseases affecting rice, particularly focusing on Blast caused by Pyricularia oryzae. This quiz covers symptoms, stages of infection, and the impact on crop growth. Understand the significance of detection and management for better yields.