فيروس التفاف أوراق البطاطس

Viral Plant Diseases - Lecture 4

• Topic: Viral Plant Diseases affecting Potato
• Focus: Potato Viral Diseases
• Lecture Year: 2024-2025

Potato Virus Y (PVY)

• Abbreviation: PVY
• Genus: Potyvirus
• Morphology: Flexuous filamentous particle
• Genome: +ssRNA
• Host Range: Potato, tomato, and pepper
• Transmission Modes:
  • Sap inoculation
  • Aphids (non-persistent)
  • Seed tubers
• Symptoms:
  • Mosaic pattern or mottling
  • Crinkling
  • Rugose mosaic
  • Systemic necrotic lesions and vein necrosis
  • Potato tuber necrotic ringspot

Potato Leaf Roll Virus (PLRV)

• Abbreviation: PLRV
• Genus: Polerovirus
• Morphology: Isometric particle
• Genome: +ssRNA
• Host Range: Potato and tomato
• Transmission Modes:
  • Aphids (persistent, circulative)
  • Not sap transmissible
• Symptoms:
  • Upward rolling of leaf margins
  • Leaves may show purpling or reddening
  • Leaves become crunchy when touched
  • Brown necrotic tissue extending through vascular tissue of tuber (net necrosis)
  • Yield reduction of 50% or more

Potato Virus A (PVA)

• Abbreviation: PVA
• Genus: Potyvirus
• Morphology: Flexuous filamentous particle
• Genome: ssRNA+
• Host Range: Solanaceous plants, especially potato
• Transmission: Aphids (non-persistent); not seed-borne
• Symptoms:
  • Mild mosaic (difficult to distinguish from PVX)
  • Mottle on veins
  • Similar symptoms to PVY, PVX; resistance to PVY may often indicate resistance to PVA
  • Rugosity mosaic, marginal distortion
  • Yield loss up to 40%
  • Leaflet crinkling

Potato Virus X (PVX)

• Abbreviation: PVX
• Genus: Potexvirus
• Morphology: Filamentous
• Genome: ssRNA
• Host Range: Solanaceous plants, particularly potato
• Transmission: Primarily contact; possible transmission by the spores of _Synchytrium _endobioticum and Spongospora subterranea
• Symptoms:
  • Mild mosaic to severe necrotic streak
  • Symptoms more evident in low-light conditions
  • Minimal leaflet distortion; Rugose mosaic possible
  • Crinkling with mixed infections of PVY or PVA
  • Yield loss 15-20%, potentially negligible

Potato Mottle Virus (PMTV)

• Cause: A fungus-like organism associated with Spongospora subterranea
• Transmission: Resting spores
• Symptoms:
  • Stunting and yellowing of leaf tips
  • Cracking and malformation of tubers
  • Potential symptom overlap with PVY strains
  • Characteristic yellow chevrons

Potato Spindle Tuber Viroid (PSTVd)

• Abbreviation: PSTVd
• Genus: Pospiviroid
• Genome: Single-stranded circular RNA
• Host Range: Potato
• Transmission: Physical contamination, contaminated tools, insect vectors, pollen, and seed
• Symptoms
  • Symptoms in warm conditions, disappear in cool conditions
  • Slightly smaller leaves that droop inward
  • Sharper angles between petioles and stems
  • Severe strains show rugosity
  • Stunted plant growth
  • Tubers: elongated, pointed ends
  • Increase in tuber eyes; cracking on tuber surface
  • Potential yield loss up to 65%

Tomato Viral Diseases - Introduction

Cucumber Mosaic Virus (CMV)

• Abbreviation: CMV
• Genus: Cucumovirus
• Genome: Single-stranded RNA
• Host Range: ~800 plant species
• Transmission: Aphids (non-persistent) and mechanical inoculation; seed-borne
• Symptoms:
  • Stunted growth
  • Yellowing; leaf size reduction early on
  • Mottle
  • Strap/shoestring leaf shape/formation

Tomato Spotted Wilt Virus (TSWV)

• Abbreviation: TSWV
• Genus: Tospovirus
• Genome: Single-stranded RNA
• Host Range: Broad host range, including tomato
• Transmission: Thrips (persistent)
• Symptoms:
  • Circular, dark-colored spots on leaves
  • Dark streaks or spots on stems
  • Wilt or stunting
  • Chlorotic rings on fruit

Tomato Yellow Leaf Curl Virus (TYLCV)

• Abbreviation: TYLCV
• Genus: Geminivirus
• Genome: Single-stranded DNA
• Host Range: Tomato, pepper, cotton, watermelon, cucurbits
• Transmission: Whiteflies (persistent)
• Symptoms:
  • Stunting
  • Vertical leaves; upward curving leaf margins
  • Interveinal yellowing

Strawberry Viral Diseases - Introduction

Strawberry Vein Banding Virus (SVBV)

• Abbreviation: SVBV
• Genus: Caulimovirus
• Genome: Double-stranded DNA
• Host Range: Strawberry
• Transmission: Aphids (semi-persistent)
• Symptoms:
  • Latent to severe necrosis
  • Stunted growth
  • Interveinal yellowing
  • Reduced stem numbers
  • Delayed development

Strawberry Crinkle Virus (SCV)

• Abbreviation: SCV
• Genus: Cytorhabdovirus
• Genome: Negative-strand RNA
• Host Range: Strawberry
• Transmission: Aphids (circulative)
• Symptoms:
  • Variable; depends on strain and strawberry variety
  • Mild strains (latent virus): asymptomatic
  • Severe strains: crinkling and uneven leaf sizes
  • Yellow spots, often around veins.

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