Main Symptoms

The characteristic symptoms of alfalfa mosaic virus (AMV) in tobacco consist of bright yellowing of leaf areas. The yellowing first appears on veins and surrounding tissues, on large tissue areas, forming broad rings and mosaic patterns (figures 1-3). Then the affected tissue may turn necrotic.

The young leaves are sometimes distorted. More or less important enations are formed occasionally on the underside of the lamina (figure 4).

Some of the information on the worldwide distribution of the disease is obtained from surveys conducted by CORESTA (Cooperation Centre for Scientific Research Relative to Tobacco). The reliability of the information is not confirmed in all countries.