Plant virology
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Plant Virology. The 30 minute semester with 3 examples from MT. PVY. WSMV. BYDV. Diagnosis. Symptoms Mechanical or insect transmission Immunological (ELISA) Nucleic acid (PCR). How do viruses move from plant to plant?. Insect vectors, nematodes

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Plant Virology

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Plant virology

Plant Virology

The 30 minute semester

with 3 examples from MT

PVY

WSMV

BYDV


Diagnosis

Diagnosis

  • Symptoms

  • Mechanical or insect transmission

  • Immunological (ELISA)

  • Nucleic acid (PCR)


How do viruses move from plant to plant

How do viruses move from plant to plant?

  • Insect vectors, nematodes

  • Mechanically (sap on clothing/tools/equipment)

  • Seed, tubers

  • Pollen


Virus diseases in mt

Host

Vector

Pathogen

Environment

Virus diseases in MT

  • Occur sporadically

  • Difficult to predict

  • Potato virus Y

  • Wheat streak mosaic virus

  • Barley yellow dwarf virus


Insect transmission of plant viruses the jargon

Insect transmission of plant viruses: The Jargon

  • Vector = insect (or other means) of transmitting the virus from plant to plant

  • Nonpersistant (stylet-borne)

  • Semipersistant

  • Persistant

    • Circulative, propogative

    • Circulative, nonpropogative


Insect transmission of plant viruses the jargon cont d

Insect transmission of plant viruses: The Jargon, cont’d


Control of nonpersistant vs persistant

Control of nonpersistant vs. persistant

  • Insecticides are effective against persistant, but not nonpersistant viruses

  • Plant resistance can be effective, but viruses evolve rapidly

  • Prevent introducing the virus inoculum (seed, tubers)

  • Prevent movement from volunteer plants by getting rid of volunteers before planting (green bridge)


Potato virus y pvy the host

Potato virus Y (PVY): The Host

  • Solanum tuberosum (potato)

  • Capsicum spp. (peppers)

  • Nicotiana spp. (tobacco)

  • Lycopersicon esculentum (tomato)

Primary source of inoculum = Seed potatoes


Potato virus y pvy the pathogen

125I-TEV

Potato virus Y (PVY): The Pathogen

  • Potyvirus (40% all known plant viruses)

  • Nonpersistant (stylet-borne)

  • Aphid transmitted


Nonpersistant viruses stick to the stylet

X

Nonpersistant viruses stick to the stylet

Mediated by a protein, HC-Pro

Specific relationship


Pvy the environment control

PVY: The Environment (control)

  • PVY does not spread rapidly in the absence of the aphid vector

    • Can be transmitted mechanically

  • Insecticides are not effective

  • Best option is preventing inoculum introduction

  • Some variety resistance


Pvy disease triangle

Host

Vector

Pathogen

Environment

PVY: Disease triangle

: Resistance

: Avoidance

: Exclusion – certified seed

: Scouting

: Roguing


Wheat streak mosaic virus the host

Wheat streak mosaic virus: The Host

  • Infects both winter and spring wheat

    • Symptoms in spring

  • Earlier infection = greater yield loss

  • Grassy weeds, volunteer wheat, corn, etc. can harbor both WSMV and the mite vector


Wsmv the pathogen

WSMV: The Pathogen

  • Family Potyviridae, genus Rymovirus

  • Mite-transmitted virus

  • Wheat curl mite survives on green tissue


Wsmv the environment

WSMV: The Environment

  • Warm, dry conditions favor mite reproduction


Wheat streak mosaic virus control

X

Wheat streak mosaic virus control

  • Early seeding of winter wheat favors mite and WSMV spread

  • Eliminate the green bridge

    • 3 week gap between herbicide

      and planting

  • Avoid spraying herbicide on volunteer wheat near spring wheat fields during cool, moist, windy weather

  • Do not plant wheat next to late-maturing (green) corn, which is also a mite host


Disease cycle of wsmv

Disease cycle of WSMV


Role of the predominant grassy weeds as reservoirs of wsmv

Role of the predominant grassy weeds as reservoirs of WSMV


Plant virology

Weed Host: Volunteer Wheat


Wsmv disease triangle

Host

Vector

X

Pathogen

Environment

WSMV: Disease triangle

: Resistance

: Avoidance

: Seed transmission

(don’t use seed from

heavily infected plants)

:be aware of the

weather


Barley yellow dwarf virus the host

Barley yellow dwarf virus: The Host

  • Infects barley, wheat, oats, rye, corn, triticale, rice

  • Resistance has been developed, but predicting the virus and aphid populations from year to year can be difficult


Bydv the pathogen

BYDV: The Pathogen

  • Family Luteoviridae

  • Persistant, circulative, nonpropagative

  • First classified by primary aphid vector

    MAV: Macrosiphum (Sitobion) avenae

    PAV: Rhopalosiphum padi

    RMV: Rhopalosiphum maidis

    SGV: Schizaphis graminum

    RPV: Rhopalosiphum padi


Insect transmission of plant viruses

Insect transmission of plant viruses


Plant virology

Circulative – nonpropagative

(Another very specific relationship)

Food

Salivary

Canal

Canal

Hemocoel

ASG

PSG

Midgut

Hindgut

Phloem


Bydv the environment

BYDV: The environment

  • Inoculum

    • Wild grasses, perennial grassy weeds

    • Aphid flights from other wheat-growing areas

  • Insecticides can be very effective at controlling the aphid and virus transmission, if applied early


Bydv disease triangle

Host

Vector

Pathogen

Environment

BYDV: Disease triangle

: Resistance

: Insecticide

: Control grassy weeds

: Scouting


Wheat streak mosaic virus the host1

Wheat streak mosaic virus: The Host

  • Infects both winter and spring wheat

    • Symptoms in spring

  • Earlier infection = greater yield loss

  • Grassy weeds, volunteer wheat, corn, etc. can harbor both WSMV and the mite vector


Wsmv the pathogen1

WSMV: The Pathogen

  • Family Potyviridae, genus Rymovirus

  • Mite-transmitted virus

  • Wheat curl mite survives on green tissue


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