How does Plant Virus infect the plant?

Below is a run-up on how plant virus infect plant considering we talked about Ag tumefaciens under GMO and about the various viruses in our recent test. Since bacteriophages are adapted to infect bacteria and enveloped virus for animal cells (note: animal virus does not have to have an envelope), the question is really the above.

See below: taken from http://bugs.bio.usyd.edu.au/PlantPathology/infection/infection_process.html

Plant viruses are often transported and introduced into the plant via vectors such as fungi or insects.

Pathogens exploit every possible pathway to enter their host, although individual species of pathogen tend to have a preferred method. Fungal pathogens often use direct penetration of the plant surface to enter the host. This requires adhesion to the plant surface, followed by the application of pressure and then enzymatic degradation of the cuticle and cell wall, in order to overcome the physical barriers presented by the plant's surface. During the degradation of the cuticle and wall, a succession of genes are switched on and off in the pathogen, so that cutinase, followed by cellulase, then pectinase and protease are produced, attacking the cuticle, cell wall, and middle lamella in the order that they are encountered. The pressure needed for the hypha to penetrate the cell wall is achieved by first firmly attaching the appressorium to the plant surface with a proteinaceous glue. The cell wall of the apressorium then becomes impregnated with melanin, making it watertight, and capable of containing the high turgor pressure that builds up within the appressorium. The point of the appresorium that is in contact with the cuticle is called the penetration pore, and the wall is thinnest at this point. The increasing turgor pressure causes the pore to herniate, forming a penetration peg, which applies huge pressure to the host cuticle and cell wall.

The alternative pathway for pathogen entry is via a pre-existing opening in the plant surface. This can be a natural opening or a wound. Pathogenic bacteria and nematodes often enter through stomatal pores when there is a film of moisture on the leaf surface. Fungi can also penetrate open stomata without the formation of any specialised structures. Some fungi form a swollen appressorium over the stomatal aperture and a fine penetration hypha enters the airspace inside the leaf, where it forms a sub-stomatal vesicle, from which infection hyphae emerge and form haustoria in surrounding cells. Also vulnerable to pathogen invasion are hydathodes, pores at the leaf margin that are continuous with the xylem. Under particularly humid conditions, droplets of xylem fluid (guttation droplets) can emerge at the surface of the leaf where they can be exposed to pathogenic bacteria, which then enter the plant when the droplet retreats back into the hydathode as the humidity decreases. Lenticels are raised pores that allow gas exchange across the bark of woody plants. They exclude most pathogens, but some are able to enter the plant via this route. Some specialised pathogens can also use more unusual openings, such as nectaries, styles and ectodesmata. Entry through a wound does not require the formation of specialised structures, and many of the pathogens that utilise wounds to enter the plant are unable to penetrate the plant surface otherwise. Most plant viruses enter through wounds, such as those made by their insect vectors.