Which of the following is a common symptom of freezing injury in winter wheat?

Wilting of leaves is a common symptom of freezing injury in winter wheat because extreme cold temperatures can cause the plant cells to rupture when ice forms inside them, leading to cellular damage and loss of turgor pressure. This loss of turgor pressure manifests as wilting, as the leaves are unable to maintain their structure and firmness. Freezing temperatures can also impact the plant's ability to uptake water, contributing further to the wilting observed after frost events.

In contrast to wilting, root rot typically results from pathogens and does not directly relate to freezing injury. Delayed blooming might occur due to various stresses, but it is not a direct symptom of freezing injury. A change in leaf color can indicate various issues (nutrient deficiency, disease, etc.) but also does not specifically point to freezing injury as clearly as wilting does. Therefore, the symptom of wilting is closely tied to the immediate physical effects of freezing temperatures on the plant's physiology.