Beet necrotic yellow vein virus

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Beet necrotic yellow vein virus symptoms on Beta vulgaris (click on image to enlarge it)
Source: Institut Technique de la Betterave Archive, France - IPM Images

Beet necrotic yellow vein virus (BNYVV)

The virus causes rhizomania, an important disease of sugar beet and is transmitted by the soil-inhabiting fungal-like organism Polymyxa betae. It may also infect Swiss chard, spinach and some weed species. Severe infections lead to a reduction in root yield of 50 % or more, with low sugar content.

The symptoms include a proliferation of the small rootlets, giving the root a beard-like appearance. The main root is reduced in size, deformed and shows internal yellowish or brownish vascular discolorations. The above-ground parts of the plant show stunting, chlorosis of the leaves, yellow veining, necrosis of leaf veins and wilting. Infected fields show distinct yellow patches of beet plants. The virus mainly spreads through the persistent spores of its vector.

Vernacular names
• Deutsch: Rizomania der Zuckerrübe
Wurzelbärtigkeit der Rübe
• English: rhizomania of sugar beet
beet rhizomania
• Español: rizomania de la remolacha azucarera
• Français: rhizomanie de la betterave

In the past, control has involved mainly resistant cultivars, carrying the Rz1 gene. However, aggressive virus strains have appeared since 2005 which overcome this resistance. Other management options include placing infected fields under quarantine to prevent the movement of contaminated soil and good drainage to reduce the spread of the disease.

The virus is the type species of the genus Benyvirus. It has 4 or 5 particles which are straight and tubular, between 80 and 380 nm long and about 20 nm wide. Each particle contains a single stranded RNA molecule, named RNA1 to RNA5. RNA5 may be missing in some strains.