Apple Mosaic Virus (ApMV)

Electron micrograph of Apple mosaic virus, Bromoviridae by R. W. Fulton

Virion Properties:-
Apple mosaic virus (ApMV) is the plant pathogenic virus of the family Bromoviridae and the genus is Ilarvirus subgroup 3.
Morphology:-
Virions consist of a capsid. Virus capsid is not enveloped. Capsid is round to elongate with icosahedral symmetry. The capsid is isometric and has a diameter of 25 and 29 nm (and probably a third size). Capsids appear round (and pleomorphic). The capsomer arrangement is not obvious. Virus preparations contain more than one particle component.
Nucleic Acid:-
The Mr of the genome constitutes 16% of the virion by weight (all components). The genome is segmented; tripartite, segments are distribute among 3 particle types of different size; consists of four segments of linear positive-sense, single-stranded RNA. The encapsidated nucleic acid is mainly of genomic origin, but virions may also contain subgenomic RNA, that is mRNA derived from genomic RNA-3, is partially sequenced. RNA-4 is subgenomic. Subgenomic RNA-4 is an mRNA derived from RNA-3 negative strand template

Description:-
Virus particles are isometric 25 and 29 nm in diameter (and probably a third size). Virus particles contain 16 % nucleic acid and 84 % protein. ApMV has three genomic RNA (RNA 1, RNA 2 and RNA 3) and one sub-genomic RNA (RNA 4 species).
Transmission:-
Natural vector of ApMV is unknown. Virus is transmitted by mechanical inoculation and root grafting. It is also transmitted by seed and pollen of hazelnut. ApMV is usually transmitted with difficulty by mechanical inoculation of sap from woody plants to several herbaceous species in vitro.
Proteins:-
Proteins constitute about 84% of the particle weight. The viral genome encodes structural proteins and non-structural proteins. Virions consist of 1 structural protein(s) located in the capsid. Structural Proteins: Capsid protein is involved in viral encapsidation and involved in protein movement.
Genome Organization and Replication:-
By itself, genomic nucleic acid is not infectious (coat protein, a successful infection by the virus requires the coat protein specifically associated with RNA 3'-terminal sequences for replicase recognition.
Transcription: Sub-genomic RNA is present in infected cells; encoding the coat protein

Table: Apple mosaic virus genome information

APPLE MOSAIC VIRUS :-

Occurrence and importance:
It is the most wide-spread virus of the apple. It infects all kinds of apple in commerce. It appears sporadically but frequently. The virus spreads by vegetative propulage. We are not familiar with its vector. The damage it causes should not be underestimated from economic point of view. The presence of the virus may considerably influence the amount of the crop. In serious case it can cause a 25% decrease in crop. The virus is present in the whole country.

Symptoms and process of the disease:
The typical symptom of the infection is the change in the color of the leaf. It is chlorotic. It occurs in the form of irregular circle-shaped spots that are yellow or almost white and can be easily defined. In serious cases the infection may cause broad stripes along the veins as well as big chlorotic spots that later turn into necrotic ones. Leaves like that fall prematurely off the tree.
Pale cream-colored spots may appear on the fruits. The spots are particularly prominent on apples with red cover color. The infected crop may become little, even deformed.

Disease cycle:
Strain of the virus appear, that is the 'serious mosaic', the 'mild vein stripes mosaic' and the 'mild mosaic'. It is localized and does not spread by either insects or pollen.
Control:
As the virus spreads by propulage - we are not familiar with its vector - we can protect our trees by using virus immune propulage. The production of virus immune propulage and the verification of the virological condition of it towards the consumer are the duty of the tree nurseries. The M9 stock may get infected from roots systematically because of its susceptibility.
Natural Host Range:
ApMV can experimentally or naturally infect over 65 species in 19 different families. Natural hosts of ApMV include apple, rose, hazelnut, horse chestnut, raspberry, birch, hops, stone fruits, blackberry and strawberry.