Fusarium Stalk Rot in Maize Quiz

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Questions and Answers

What types of pathogens are responsible for stalk rot in maize?

Viruses and Protozoa

Fungi and Bacteria (correct)

Fungi and Algae

Bacteria and Viruses

In which climate conditions are Fusarium spp. particularly severe?

Wet and humid

Cold and arid

Dry and warm (correct)

Tropical and moist

What are the visual symptoms of Fusarium stalk rot when the crop enters senescence?

Shredded pith and brown streaks (correct)

Bright yellow stems and vibrant leaves

Healthy stalks with no signs of wilting

Green foliage and healthy roots

Which pathogen is responsible for bacterial stalk rot in maize?

Erwinia chrysanthemi pv. Zeae Signup and view all the answers

What is the shape of sporangia produced by the sporangiophores?

Hyaline oblong or ovoid Signup and view all the answers

What happens to the plants affected by Fusarium stalk rot under high plant populations?

The disease severity intensifies Signup and view all the answers

Under which conditions do oospores germinate in the soil?

Low temperatures and high humidity Signup and view all the answers

What color might the shredded pith of plants with Fusarium stalk rot appear?

Whitish-pink to salmon Signup and view all the answers

How is Fusarium moniliforme primarily spread in maize crops?

Seed infection Signup and view all the answers

What is the primary source of infection for the disease discussed?

Oospores in soil Signup and view all the answers

What symptom appears within 3 days of infection?

Chlorotic specks and streaks Signup and view all the answers

What condition is typically associated with Fusarium stalk rot in maize plants?

Permanent wilting of leaves Signup and view all the answers

What is the primary management strategy for controlling the disease mentioned?

Host-plant resistance Signup and view all the answers

How long can oospores survive in nature?

Up to 10 years Signup and view all the answers

Which of the following inbred lines is noted for its resistance to the disease?

CM 202 Signup and view all the answers

During what time do sporangiophores emerge from stomata?

During the night Signup and view all the answers

What cultural practice can suppress pathogen infection?

Organic manure amendment Signup and view all the answers

Which part of the maize plant is primarily infected by the germ tube?

The underground sections Signup and view all the answers

Which antibiotic was mentioned as effective against Erwinia species?

Streptomycin Signup and view all the answers

What are the characteristics of the symptoms caused by the pathogen?

Extensive chlorosis and stunted growth Signup and view all the answers

What is a characteristic symptom of Downy mildew?

Chlorotic streaks on the leaves Signup and view all the answers

Which chemical practice significantly inhibits pathogen growth?

Bleaching powder application Signup and view all the answers

What is the name of the pathogen responsible for Downy mildew?

Sclerophthora macrospora Signup and view all the answers

What is a common appearance of plants affected by Downy mildew?

Stunted and bushy appearance Signup and view all the answers

What color change occurs in the rind during the early stages of bacterial stalk rot infection?

Pale straw color Signup and view all the answers

Which bacterium is responsible for causing bacterial stalk rot?

Erwinia chrysanthemi Signup and view all the answers

What is primarily responsible for the degradation of plant cell walls during bacterial stalk rot?

Pectinases Signup and view all the answers

What environmental conditions favor the infection and development of bacterial stalk rot?

High temperatures and high humidity Signup and view all the answers

How does Erwinia chrysanthemi enter its host plant?

Through stomata or wounded areas Signup and view all the answers

Which of the following best describes the morphology of Erwinia chrysanthemi?

Rod-shaped with peritrichous flagella Signup and view all the answers

What is the duration of survival of the pathogen in soil and plant debris?

About nine months Signup and view all the answers

Which of the following conditions is NOT favorable for the survival of Erwinia chrysanthemi?

Dry and sandy soil Signup and view all the answers

What is the primary method of controlling the brown leaf spot disease of maize?

Using resistant varieties and hybrids Signup and view all the answers

Which stage of the maize plant is most affected by the brown leaf spot disease?

Lower leaves Signup and view all the answers

What is the pathogen responsible for brown leaf spot in maize?

Physoderma zeae maydis Signup and view all the answers

What environmental conditions favor the development of brown leaf spot disease in maize?

High temperature and abundant moisture Signup and view all the answers

What type of reproduction do the resting spores of the fungus use to survive between seasons?

Asexual reproduction through spores Signup and view all the answers

Which of the following describes the appearance of a leaf affected by brown leaf spot disease?

Oval-shaped yellow or light green lesions Signup and view all the answers

What is the function of treating seeds with Metalaxyl?

To prevent seed rot and fungal infection Signup and view all the answers

How do sporangia spread the brown leaf spot disease to healthy maize plants?

By air currents, insects, and water Signup and view all the answers

What is the primary mechanism by which zoospores of P.maydis penetrate corn tissue?

Using fine infection hyphae Signup and view all the answers

During which part of the day does P.maydis typically infect corn tissue?

Certain hours based on a diurnal cycle Signup and view all the answers

What is the time frame for the development of symptoms after P.maydis infection?

6 to 20 days Signup and view all the answers

Which of the following is NOT an effective management strategy for P.maydis?

Using higher fertilizer concentrations Signup and view all the answers

What type of structures do zoospores form after infecting corn cells?

Mycelium Signup and view all the answers

Which fungicide is mentioned as effective for managing P.maydis?

Captan 50 WP Signup and view all the answers

Which of the following varieties has been found resistant to P.maydis?

GE 440 Signup and view all the answers

The alternating bands of infected and healthy leaf tissue during P.maydis infection are a result of which phenomenon?

Diel cycle of infection Signup and view all the answers

Study Notes

Diseases of Maize

Maize is susceptible to various diseases including stalk rot, bacterial stalk rot, and Fusarium stalk rot.
Stalk rot is caused by fungi such as Fusarium, Macrophomina, and Cephalosporium.
Bacterial stalk rot is caused by Erwinia chrysanthemi pv. Zeae and Erwinia dissolvans pv. Zeae and Pseudomonas syringe pv. lapsa.
Bacterial stalk rot is more prevalent in high rainfall areas and occurs in epidemic form in foothills.
Fusarium stalk rot is more severe in low and tropical areas during initial stages and later more prevalent in cooler highlands.

Fusarium Stalk Rot Symptoms

Affected plants exhibit symptoms during senescence.
Symptoms affect roots, crown, and lower internodes.
Damaged pith turns whitish-pink to salmon color.
Leaves wilt and dry.
Plants may lodge in strong winds.
Disease severity is more prominent with higher plant populations.
Brown streaks appear on lower internodes.
Stalks become spongy, crush, and easily crimp.

Pathogen/Etiology of Fusarium Stalk Rot

Fusarium moniliforme, F. graminearum, and F. semitectum pathogens are seed-borne, and infect up to 75% of planted seeds.
Pathogens overwinter as mycelium on debris in soil and can infect via roots.
Two types of conidia are produced: macroconidia (hyaline, curved near the tips) and microconidia (abundant, single-celled).
Conidiophores are unbranched with branched phialids.
Favorable conditions for disease include dry and warm climate conditions during silking, high soil temperatures during flowering stages, and high plant population. Disease incidence increases with higher soil fertility.

Bacterial Stalk Rot Symptoms

Symptoms initially appear in lower nodes extending up the stalk.
Discoloration of leaf sheaths to stalk, leaves, and eventually toppling of the plant occur.
Interior of stalk becomes discolored and soft.
Stalks break down into fragments.
A foul odor is often present.

Bacterial Stalk Rot Pathogen/Etiology

The pathogen is Erwinia chrysanthemi pv. zeae, a facultative anaerobe.
It induces various enzymes resulting in necrosis of parenchyma tissues and vascular wilt.
It is motile.
Gram-negative rod shaped bacterium that varies in size from 0.8-3.2 x 0.5-0.8 μm to 1.8 x 0.6 μm.
The bacterium produces off-white, slimy and shiny colonies on King's B Medium.

Disease Cycle of Maize Diseases

Fungi overwinter as mycelium in corn residue and seeds.
Spore spread by wind and water.
Infection may occur via roots, wounds, or leaf scars.
Disease development is more readily in warm temperatures and mid-season rain.

Management of Maize Diseases

Use of disease-resistant hybrid varieties.
Crop rotation.
Proper tillage practices.
Adequate soil testing and fertilizer recommendations to balance nitrogen and potassium.
Control diseases with appropriate fungicides.
Control insect pests.
Plant-growth stage scouting and scheduled harvesting based on grain maturity.
Other control practices include deep plowing, crop rotation using pulses, and removing infected plants.

Downy Mildew/Crazy Top Symptoms

Characterized by chlorotic streaks on leaves.
Plants are stunted and bushy with shortened internodes.
White downy growth is visible on lower leaf surfaces and bracts.
Tassel and cobs exhibit proliferation of auxiliary buds.

Downy Mildew/Crazy Top Pathogens

Sclerophthora macrospora is the pathogen causing this disease.
The fungus grows as white downy growth on both leaf surfaces composed of sporangiophores and sporangia.
Sporangiophores are short and stout and profusely branch to bear pointed sterigmata with hyaline, oblong, or ovoid sporangia.
Sporangia germinate directly to infect plant tissues.
Oospores are produced as spherical, walled structures, which are deep brown in color.

Brown Leaf Spot of Maize

The disease causes oval-shaped light-green bleached or yellow water-soaked lesions that develop on leaf blades and leaf sheaths .
Lesions darken to reddish-brown and have lighter margins.
Spots are initially small before merging to form larger ones giving the affected area a rusty-brown appearance.
Browning leads to tissue necrosis and accumulation of fungal spores.
Leaves dry, die, and prematurely.
Stem infection weakens the tissue and breaks apart at the infection point.

Brown Leaf Spot Pathogen

Physoderma zeae-maydis
It is an obligate parasite that produces coenocytic hyphae along with sporangia that are smooth and brown in color (measuring 24–26 × 22–24 µm).
Infected lesions contain many resting sporangia (resting spores).

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Description

Test your knowledge on Fusarium stalk rot in maize with this quiz. Explore the types of pathogens, their effects on crops, and effective management strategies. Understand the symptoms and environmental conditions that influence the severity of this disease.