Alfalfa Mosaic Virus

Alfalfa mosaic virus, or AMV, is a worldwide phytopathogen that can cause necrosis and yellow mosaics on a variety of plant species. It is the only Alfamovirus of the Bromoviradae family. Weimer J.L. was the first to report AMV in Alfalfa, in 1931. Aphids, seeds, and pollen were the main transmitters of the virus.

The virion has a coat protein but no envelope. AMV is a multipartite virus and is composed of 4 particles with a diameter of 18 nm. AMV’s genetic material consists of 3 linear single strands RNAs and a subgenomic RNA. The viral coat protein plays a role in the initiation of RNA replication.

The virus infects over 600 plant species in 70 families including potato, pea, tobacco, and tomato.

The virus can cause wilting, white flecks, malformation such as dwarfing, ringspots, mottles. Signs of infection are not consistent and may persist for a long time or disappear quickly. The virions are mainly found in the cytoplasm and chloroplast of the infected plant.
AMV has a longevity of 1-4 days although it can sometimes be much longer depending on air temperature and environmental factors. High temperatures increase the appearance of necrosis due to inactivation being reached at temperatures of around 60-65°C. Lack of light will also slow down the virus. AMV is not seen as a danger to domestic animals.

There are a few variations of AMV and they can be identified based on the different symptoms that each strand causes. Through seed-infected plants and aphids that spread the virus high levels of infection are quickly achieved. Since the virus can infect food crops and pasture crops AMV often causes important yield losses, reduces winter survival and facilitates other infections in plants. Unfortunately, insecticides against aphids do not control AMV.

In order to control AMV it is suggested to sow healthy seeds, manage weeds, and avoid crops next to adjacent to infected pasture. There is still research going on in order to create an AMV resistant plant.

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