Which of the following is a common symptom of plant pathogen infection?

Leaf discoloration is a common symptom of plant pathogen infection. This can occur due to various factors related to the pathogen's impact on the plant's physiological processes. For example, when a plant is infected by a virus, fungus, or bacterium, the pathogen can interfere with the plant's ability to produce chlorophyll, the green pigment crucial for photosynthesis. This interference can lead to yellowing, browning, or other changes in leaf color, which are key indicators of infection.

Additionally, leaf discoloration can be accompanied by other symptoms such as wilting, spots, or lesions, which further suggest the presence of a disease. Recognizing such symptoms is vital for early detection and management of plant diseases, allowing for more effective intervention strategies.

In contrast, root growth, flower production, and seed formation are normal physiological processes of the plant and are not indicative of pathogen infection. While these processes may be affected indirectly by a disease, they are not themselves symptoms of infection. Focusing on symptoms like leaf discoloration helps in diagnosing plant health issues related to pathogens.