SPREAD OF BEET NECROTIC YELLOW VEIN VIRUS IN INFECTED SEEDLINGS AND PLANTS OF SUGAR-BEET (BETA-VULGARIS)

Infection of sugar beet roots by beet necrotic yellow vein virus (BNYV V) was investigated with transmission electron microscopy, immunogold labelling and enzyme linked immune sorbent assay (ELISA). Here we show that infection of sugar beet roots is very fast, occurring during ger mination. Seedlings grown directly in infected soil showed higher BNYV V infection than plants transplanted into infected soil after seven da ys of initial growth in sterilized soil. The earlier the initial infec tion, the Easter was its spread. The study showed that a few different iated cells of the cortex and of the xylem parenchyma were the preferr ed sites of viral multiplication. The spread of viral infection was sl ow through differentiated tissues. Intact virions were frequently foun d in undifferentiated and mature vessel elements and xylem parenchyma, whereas they were rare in sieve elements. Virus particle number in th e differentiating tracheary elements was high, suggesting that infecti on of the vessel elements preceded their differentiation. This would e xplain increased infection after early inoculation. Even the xylem tis sue of the primary root was highly infected, the seedlings lacked viru s particles in their hypocotyls and leaves.