What plant disorder is associated with Agrobacterium sp.?

The plant disorder associated with Agrobacterium sp. is crown gall. This particular disease is caused by the bacterium Agrobacterium tumefaciens, which infects a wide range of plants, leading to the formation of tumor-like growths known as galls. These galls typically develop at or near the crown of the plant, which is the area where the stem transitions into the roots.

The process begins when Agrobacterium enters the plant through wounds or injuries. Once inside, it transfers a part of its DNA (called T-DNA) into the plant’s cells, causing the plant to produce hormones that stimulate rapid cell division and growth. This abnormal growth manifests as galls, which can interfere with the plant’s normal nutrient and water uptake, ultimately affecting its health and productivity.

In contrast, the other disorders listed are caused by different pathogens or agents and do not relate to Agrobacterium sp. For example, black rot is caused by a fungal pathogen, Pierce's disease is linked to a bacterium transmitted by insects, and almond leaf scorch is associated with a vascular pathogen, none of which involve Agrobacterium. Thus, crown gall stands out as the clear answer in relation to this specific bacterium