What are the symptoms of viral disease in Brassica napus (rapeseed)?

(Agricultural Wealth Network) The symptoms of viral disease in Brassica napus are systemic necrotic spots; older leaves show symptoms early and prominently, which then spread to newly grown leaves. At the initial stage of disease, transparent spots the size of a needle tip appear, which later expand into nearly round 2 to 4 mm yellow spots, with a dark brown necrotic spot in the center, and the necrotic spots are surrounded by an oily-water-soaked appearance. On the stems and bolts, purple-black spindle-shaped to elongated lesions appear, and they spread from the middle and lower parts toward the branches and fruit stalks; in the later stage, the lesions on the stems mostly split longitudinally or transversely, and the flowers and pods tend to wilt or die. The siliques produce black necrotic spots and are mostly deformed.