OVERVIEW OF PLANT VIROLOGY

Satish GunjalMsc 1

Roll no 11

Need for the study

India Agricultural country

Economy of India depends on agriculture

Important to study plant diseases

INTRODUCTION

TULIPOMANIA

Virus - filterable infectious agent

“in this village , It looks as if frosting continuously , For the plant I saw In the field of summer The colour of the leaves were yellowing”

HISTORY • Prehistory 752 AD plant virus in Japanese poem , tulipomania by Carolus clusius

• Recognition 1886 Meyer & iwanowski experiment on TMV 1898 bejernick viruses as an entity

• Biological age 1900- 1935 descriptions of many viruses

• Biophysical / biochemical age 1935 purification of TMV 1956 virus particle made up of identical

protein subunit 1962 structure of isometric particle 1983 structure of TBSV to 2.9 A ̊

• . Molecular age 1980 Sequence of CaMV DNA genome1984 Infectious transcipts of multicomponent BMV1986 Transgenic Protection of plants Against TMV

Classification of plant viruses

Plant viruses

dna

Ss ds

rna

Ss+ Ss-

ds

• dS DNA : Caulimoviridae , Badnavirus, Tungrovirus

• SS DNA :Geminiviridae

• SS RNA (+) : Bromoviridae , Commaviridae

• SS RNA (- ) : Rhabdoviridae , Bunyaviridae

• ds RNA : Reovaridae

Plant virus groups and families

Virus transmission

• Through insects • Mechanical • Seed • Grafting

scion

stock

Aphids White flies

TRANSMISSION OF PLANT VIRUSES

MECHANICAL TRANSMISSION 

  

The procedure and equipments required for experimental transmission by sap inoculation

Symptoms

• MACROSCOPIC : Leaf rolling , mosaic pattern yellow disease ring spot

• CYTOLOGICAL : changes in nuclei , cytoplasm & chloroplast

    

•  

• Leaf rolling induced by BLRV in broad bean (Vicia

faba)

•Distortion of the leaf, funnel shaped outgrowth and

complete reduction of leaf blade at vein on top. (Nicotinia glutinosa)

Leaf rolling

Mosaic 

Vein clearing in Physalis floridana by PVY

 

 Chlorotic streaks of MSV in maize. Streaks parallel to venation

Ringspotting: 

     

Systemic ringspotting caused by TMV in Nicotiana clevelandii

ringspots- spreading and fusing with one another

 

Symptoms of PRSV on the fruits of papaya.

Some of the dark green ringspots are turning necrotic

Viral entry & uncoating

Virus initial entry (wound)

Uncoating

Transcription

Translation of mRNA

Replication of genome in cytoplasm ,(NEPO, BROMO) in nucleus :(potex ,caulimo,gem) chloroplast: (tymo)

Assembly

Release & (transfer trough plasmodesmata)

Control

• Remove source of infection • Vector control Insecticide• Virus free seeds• Agronomic technique, (insect trapping)

• Conventional control: (Alteration of crops , burning neem leaves )

Uses of plant viruses

• Genetic enginering • viral genome use as Vector • Vaccine production

Thank you !