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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

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
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
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

slide24

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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