6.2 Plant virus transmission and host range

Plant viruses are sneaky invaders that use clever tricks to spread and infect crops. They hitch rides on insects, contaminate seeds, and exploit our farming practices to move between plants. Some viruses are picky eaters, while others will infect almost anything.

Understanding how plant viruses travel and choose their victims is crucial for protecting our food supply. By learning their transmission modes and host preferences, we can develop better strategies to stop these microscopic menaces from ruining harvests.

Plant virus transmission modes

Vector-mediated and mechanical transmission

Top images from around the web for Vector-mediated and mechanical transmission

• 

  Frontiers | RNA Viral Vectors for Accelerating Plant Synthetic Biology | Plant Science View original

  Is this image relevant?

• 

  Figures and data in Exosomes mediate horizontal transmission of viral pathogens from insect ... View original

  Is this image relevant?

• 

  Frontiers | The Use of Engineered Plant Viruses in a Trans-Kingdom Silencing Strategy Against ... View original

  Is this image relevant?

• 

  Frontiers | RNA Viral Vectors for Accelerating Plant Synthetic Biology | Plant Science View original

  Is this image relevant?

• 

  Figures and data in Exosomes mediate horizontal transmission of viral pathogens from insect ... View original

  Is this image relevant?

1 of 3

Top images from around the web for Vector-mediated and mechanical transmission

• 

  Frontiers | RNA Viral Vectors for Accelerating Plant Synthetic Biology | Plant Science View original

  Is this image relevant?

• 

  Figures and data in Exosomes mediate horizontal transmission of viral pathogens from insect ... View original

  Is this image relevant?

• 

  Frontiers | The Use of Engineered Plant Viruses in a Trans-Kingdom Silencing Strategy Against ... View original

  Is this image relevant?

• 

  Frontiers | RNA Viral Vectors for Accelerating Plant Synthetic Biology | Plant Science View original

  Is this image relevant?

• 

  Figures and data in Exosomes mediate horizontal transmission of viral pathogens from insect ... View original

  Is this image relevant?

1 of 3

• Vector-mediated transmission involves biological agents (insects, nematodes, fungi) carrying viruses externally or internally
• Insect vectors (aphids, whiteflies, leafhoppers, thrips) efficiently spread many plant viruses between hosts
• Mechanical transmission occurs through physical contact and wounding
  • Facilitated by agricultural practices (pruning, harvesting)
  • Plant-to-plant contact in dense crop stands
  • Contaminated tools and equipment spread viruses between plants
• Soil-borne transmission enabled by viruses persisting in soil and infecting roots
  • Often facilitated by vector organisms (fungi, nematodes)

Seed and vegetative transmission

• Seed transmission passes viruses from infected parents to offspring
  • Leads to widespread dissemination in new plantings (lettuce mosaic virus)
• Vegetative propagation methods spread viruses
  • Grafting of infected plant material
  • Use of virus-containing cuttings for propagation
  • Particularly important in horticulture/agriculture (potato viruses)
• Efficiency and prevalence of transmission modes vary among virus species
  • Influences virus epidemiology and control strategies
  • Some viruses rely primarily on one mode, others use multiple (tobacco mosaic virus)

Insect vectors in virus spread

Transmission modes and mechanisms

• Insect vector transmission categorized into distinct modes:
  • Non-persistent: Rapid acquisition/inoculation within seconds to minutes
    • Stylet-borne viruses on mouthparts (cucumber mosaic virus)
  • Semi-persistent: Intermediate retention time of hours to days
    • Viruses bind to foregut (cauliflower mosaic virus)
  • Persistent: Longer acquisition periods, virus circulates through insect body
    • May replicate in vector (propagative transmission)
    • Examples: Tomato yellow leaf curl virus, rice tungro virus
• Specific molecular interactions evolve between viruses and vectors
  • Enhances transmission efficiency and specificity
  • Viral coat proteins often involved in vector binding

Vector ecology and management

• Vector feeding behavior influences virus spread
  • Probing activity of aphids spreads non-persistent viruses
  • Extended phloem feeding transmits persistent viruses
• Population dynamics affect disease pressure
  • Seasonal fluctuations in vector numbers impact transmission rates
• Migration patterns of vectors
  • Long-distance movement spreads viruses to new areas (whitefly-transmitted geminiviruses)
• Management of vector populations key for virus control
  • Insecticides reduce vector numbers
  • Cultural practices like reflective mulches repel vectors
  • Resistant plant varieties deter vector feeding

Host range of plant viruses

Viral and host factors

• Viral genetic factors determine host specificity
  • Presence of specific genes or protein domains
  • Ability to overcome plant resistance mechanisms
• Plant cellular factors essential for infection
  • Appropriate receptors for virus attachment
  • Susceptibility genes supporting viral replication
• Compatibility between viral and host proteins crucial
  • Interactions required for replication and movement
  • Host translation factors needed for viral protein synthesis
• Co-evolution shapes virus-host relationships
  • Plants develop resistance mechanisms
  • Viruses adapt to overcome plant defenses
  • Results in varying host ranges (narrow vs broad)

Environmental and ecological influences

• Environmental conditions affect infection and replication
  • Temperature impacts viral replication rates
  • Humidity influences vector activity and plant susceptibility
  • Light levels alter plant defense responses
• Presence and abundance of vectors indirectly affect host range
  • Determines likelihood of transmission to different plant species
  • Absence of vectors limits spread to potential hosts
• Ecosystem diversity influences host availability
  • Monocultures increase risk of host-adapted viruses
  • Diverse plant communities may limit virus spread

Virus movement within the host

Intracellular and cell-to-cell movement

• Intracellular movement transports viral genomes
  • From replication sites to cell periphery
  • Utilizes host cytoskeleton (microtubules, actin filaments)
  • Endomembrane system aids transport (endoplasmic reticulum)
• Cell-to-cell movement occurs through modified plasmodesmata
  • Viral movement proteins increase size exclusion limit
  • Allows passage of viral nucleoprotein complexes
  • Some viruses form tubular structures through plasmodesmata
    • Enables entire virion passage (cauliflower mosaic virus)

Systemic spread and factors affecting movement

• Long-distance movement through phloem enables systemic spread
  • Specific viral proteins required for vascular entry/exit
  • Phloem-limited viruses restricted to vascular tissue (luteoviruses)
• Movement speed and efficiency varies
  • Depends on virus species, host plant, and environment
  • Influences symptom development and disease progression
• Plant developmental stage affects viral movement
  • Some tissues more permissive at different growth stages
  • Mature plant resistance can limit systemic spread
• Environmental factors impact movement
  • Temperature affects protein function and plasmodesmata structure
  • Water stress alters phloem transport dynamics