What is a common visible symptom of sudden death syndrome in soybean plants?

The correct answer highlights that yellowing and necrosis of leaf tissues are common visible symptoms of sudden death syndrome in soybean plants. Sudden death syndrome is primarily caused by the fungal pathogen Fusarium virguliforme, which affects the plant's vascular system and leads to root and foliar symptoms. The yellowing indicates a loss of chlorophyll, which is often followed by necrosis, where the tissue becomes brown and dies. This progressive deterioration is a key indicator of the disease's impact on the plant's overall health and its ability to photosynthesize effectively.

In contrast, other symptoms listed do not typically align with sudden death syndrome. Leaf curling and stunting are more associated with other stressors or pathogens, such as insect infestations or viral infections. The rapid wilting of flowers is indicative of more immediate stress symptoms, possibly from drought or other environmental factors. Finally, brown streaks on stems may suggest other diseases, like bacterial wilt or mechanical damage. Thus, the significance of yellowing and necrosis as key indicators of sudden death syndrome underscores the importance of recognizing the correct symptoms for diagnosis and management in soybean cultivation.