Which of the following symptoms indicates a plant is affected by mosaic disease?

The presence of green and yellow patching is a classic symptom of mosaic disease in plants. This condition is commonly caused by viral infections that disrupt the plant’s ability to produce chlorophyll uniformly. As a result, areas of the leaves may appear mottled, exhibiting a patchwork of green and yellow coloration. This symptom is particularly significant as it directly reflects the dysfunction in the plant's physiological processes due to the infection.

Other symptoms such as yellowing of leaves, abnormal swellings, and defoliation may occur in various plant diseases, but they are not specifically indicative of mosaic disease. Yellowing might be related to nutrient deficiencies or other stress factors, abnormal swellings can result from various types of infections or other agronomic factors, and defoliation often points to broader health issues that may not be linked exclusively to viral infections. Therefore, the presence of the distinct patching of colors serves as a clear identifier for mosaic disease.