Mosaics

Pathogen

Mosaic Viruses

  • Barley yellow mosaic virus (BaYMV)
  • Barley mild mosaic virus (BaMMV)
  • Oat mosaic virus(OMV))
  • Oat golden stripe virus(OGSV)
  • Soil-borne cereal mosaic virus (SBCMV)
  • Soil-borne wheat mosaic virus (SBWMV)

Each of these mosaic diseases is caused by a virus, transmitted by the soil-borne vector Polymyxa graminis. The viruses causing these diseases are closely related single stranded RNA (ribonucleic acid) rod or filamentous viruses belonging to the genus Furovirus orBymovirus.

Hosts

The diseases affect only wintersown crops. All cereals are affected by their own form of the virus which does not cross-infect to other cereals.

Symptoms

Affected plants can be very stunted and pale in colour. Typical symptoms are pale yellow streaks in the leaves which are most pronounced during the early spring, particularly following a prolonged cold spell. The yellow streaks may become brown or purple at the leaf tip and dark brown flecking may replace the yellow streaking.

Life Cycle

Mosaics-life-cycle.jpg

The disease often occurs in distinct patches which increase in size from one year to the next. The virus is carried in the soil by the rootinfecting organism Polymyxa graminis. Movement of the soil during cultivations will spread the disease within the field and to other areas. The virus survives within the spores of the vector so that once it is present in soil it persists even in the absence of cereal crops for many (more than 25) years.

Importance

Yield losses of 50% have been recorded in the patches on susceptible varieties. BaYMV and BaMMV are very common in the UK. SBWMV and SBCMV are present in the UK but are not yet commonly found. OMV is commonly found OGSV is usually found in association with OMV.

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