Symptoms

Symptoms of Wheat spindle streak mosaic virus (WSSMV) consist of light green to yellow streaks or dashes that are parallel to the veins and usually are tapered, giving the appearance of spindles. WSSMV causes a slight stunting. Symptoms of WSSMV do not appear on new growth but may persist on older leaves.

WSSMV cause a mosaic on leaves characterised by chlorotic to nerotic spindle-shaped streaks, dashes and spots that may coalesce. Chlorosis is light yellow-green to bright yellow to orange and more pronounced on developing leaves. Chlorotic spindle-shaped streaks may have green centres. Necrosis is orange brown to brown and more pronounced on mature leaves. Fewer tillers are produced, plant height and the size and number of grain heads are reduced. Within a crop, groups of infected plants appear as light green to yellow patches. When the average temperature remains at or above 15°C, symptoms become hidden by new leaves that are asymptomatic.

Organism

Bymovirus potyviridae

Host range

Wheat

Method of spread

Vector – Polymyxa graminis – soil-borne fungus like organism. The virus is spread with motile zoospores in saturated soils which then penetrate and infect plant roots.

Conditions favouring disease

WSSMV is favoured by cooler temperatures.

Confused with?

Other viruses and plant nutritional deficiencies.

Where?

Limited information regarding spread, however, the virus is present in Europe and the USA.