Ppt on Major Diseases Of Potato: Symptoms, Causal Agents And Management Strategies

This presentation covers major diseases of potato, focusing on their symptoms, etiology, disease cycles, and management strategies. Key topics include fungal and viral pathogens, disease transmission, and integrated disease management. Understanding these diseases is essential for effective crop protection, yield improvement, and sustainable potato production. Important academic keywords: pathogen, symptoms, disease cycle, management, transmission.
Introduction to Potato Diseases
  • Potato is susceptible to various fungal and viral diseases.
  • Major diseases include early blight, late blight, black scurf, leaf roll, and mosaic viruses.
  • Effective management requires understanding pathogen biology and disease cycles.
Early Blight – Alternaria solani
Pathogen: Alternaria solani (fungus)
Symptoms:
  • Small, dark lesions with concentric rings (bull's eye) on older leaves.
  • Yellowing tissue around spots; severe cases cause foliage death.
  • Stem lesions may girdle plants near soil line.
Etiology:
  • Septate, branched, light brown mycelium; conidia borne in chains, obclavate, muriform.
Disease Cycle:
  • Primary infection from mycelium/conidia in plant debris.
  • Secondary spread by wind, water, or rain splash.
Management:
  • Use disease-free seed and crop rotation.
  • Remove and destroy infected debris.
  • Fungicide sprays: Mancozeb 0.25%, Chlorothalonil 0.2%, or Zineb 0.25% at intervals.
Late Blight – Phytophthora infestans
Pathogen: Phytophthora infestans (oomycete)
Symptoms:
  • Water-soaked, dark lesions on lower leaves, expanding rapidly in cool, moist weather.
  • Lesions not limited by veins; entire leaves may die quickly.
  • Tubers show irregular, sunken, brown to purplish areas with granular rot beneath skin.
Etiology:
  • Coenocytic, hyaline, branched mycelium; sporangia are oval/pear-shaped, germinate by zoospores.
Disease Cycle:
  • Primary infection from infected tubers and soil.
  • Airborne sporangia cause secondary spread.
Management:
  • Protective fungicide sprays (Mancozeb/Zineb 0.2%).
  • Use resistant varieties (e.g., Kufri Naveen, Kufri Jeevan).
  • Destroy foliage before harvest; avoid tuber injury during harvest.
Black Scurf – Rhizoctonia solani
Pathogen: Rhizoctonia solani (fungus)
Symptoms:
  • Necrosis at sprout tips, sunken lesions on stolons, roots, stems.
  • Black sclerotia (scurf) on tuber surface.
  • Stunted plants, purplish leaves, deformed tubers.
Etiology:
  • Basidiomycete fungus; produces sclerotia, rarely basidiospores.
  • Mycelium is septate, branched; sclerotia are dark brown to black, irregular.
Disease Cycle:
  • Primary infection from sclerotia in soil.
  • Seedlings from infected soil spread disease.
Management:
  • Plant only disease-free seed tubers.
  • Seed treatment with fungicides (e.g., mercuric chloride; safer alternatives preferred).
  • Crop rotation and shallow planting reduce severity.
Leaf Roll – Potato Leaf Roll Virus (PLRV)
Pathogen: Potato leaf roll virus (PLRV)
Symptoms:
  • Upward rolling of young leaves; leaves become dry, thick, and brittle.
  • Plants are stunted, erect, light green; tubers reduced in size and number.
  • Net necrosis may develop inside tubers.
Transmission:
  • Spread by aphids (Myzus persicae, Aphis gossypii) and infected tubers.
Management:
  • Use disease-free, certified seed tubers.
  • Rogue and bury diseased plants.
  • Control aphids with insecticides (e.g., Phorate 10G, 10 kg/ha).
Mosaic Diseases of Potato (PVX, PVY, Mixed Infections)
Mild Mosaic/Interveinal Mosaic (Potato virus X – PVX):
Symptoms:
  • Light yellow mottling, slight crinkling, interveinal necrosis, mild stunting.
Severe Mosaic (Potato virus Y – PVY):
Symptoms:
  • Chlorotic and necrotic streaks, leaf drop, interveinal and stem necrosis, stunting, leaf rugosity.
Rugose/Common Mosaic (PVX & PVY):
Symptoms:
  • Black streaks on veins/stems, shriveled and mottled leaves, dwarfing, reduced tuber size.
Transmission:
  • PVX: Mechanical (sap), seed, tools, contact.
  • PVY: Aphids (Myzus persicae, Aphis gossypii), infected tubers.
Management:
  • Use disease-free, certified seed tubers.
  • Grow resistant varieties (e.g., Chippewa, Irish Cobbler).
  • Rogue diseased plants; control aphids (Phorate 10G, 10 kg/ha).
  • Early harvesting and hygiene reduce spread.
Summary: Integrated Disease Management in Potato
  • Use certified, disease-free seed tubers for all plantings.
  • Practice crop rotation and field sanitation to reduce inoculum.
  • Apply recommended fungicides and insecticides judiciously.
  • Grow resistant varieties where available.
  • Monitor fields regularly for early detection and management.

Objective Questions

Q1. Which pathogen is responsible for early blight in potatoes?
A. Phytophthora infestans
B. Alternaria solani
C. Rhizoctonia solani
D. Potato leaf roll virus
Answer: B

Q2. What is a common symptom of late blight on potato leaves?
A. Black scurf
B. Concentric rings
C. Water-soaked spots
D. Leaf roll
Answer: C

Q3. Which management practice is recommended for controlling early blight in potatoes?
A. Use of resistant varieties
B. Spraying with chlorothalonil
C. Planting in infected soil
D. Avoiding crop rotation
Answer: B

Q4. What is the primary source of infection for late blight in potatoes?
A. Infected soil
B. Airborne sporangia
C. Aphid transmission
D. Seed tubers
Answer: D

Q5. Which symptom is associated with black scurf caused by Rhizoctonia solani?
A. Leaf roll
B. Greasy lesions
C. Sclerotia on tubers
D. Yellow chlorotic halo
Answer: C

Q6. What is a symptom of potato leaf roll virus?
A. Concentric rings on leaves
B. Upward leaf roll
C. Water-soaked spots
D. Black streaks in veins
Answer: B

Q7. Which virus is associated with severe mosaic in potatoes?
A. Potato virus X
B. Potato virus Y
C. Potato leaf roll virus
D. Phytophthora infestans
Answer: B

Q8. What is a symptom of mild mosaic in potatoes?
A. Rugosity and twisting of leaves
B. Interveinal necrosis
C. Light yellow mottling
D. Black scurf
Answer: C

Q9. Which management strategy is used for controlling potato leaf roll virus?
A. Spraying with mancozeb
B. Use of disease-free certified seed
C. Planting in infected soil
D. Avoiding aphid control
Answer: B

Q10. What is a characteristic symptom of rugose mosaic in potatoes?
A. Purplish lesions on tubers
B. Shriveled leaves hanging by a thread
C. Concentric rings on leaves
D. Upward leaf roll
Answer: B