Causal Agent of Whip Smut of Sugarcane:

✅Explanation:
Whip smut of sugarcane is caused by the fungus Ustilago scitaminea. The disease is characterized by the formation of a black, whip-like structure (composed of fungal spores) at the tip of the sugarcane shoots. This disease leads to reduced sugar yield and stunted growth of the crop.

📌Other Options Explanations:
-Flag smut of wheat is caused by Urocystis agropyri and results in blackened flag leaves.
-Loose smut of wheat is caused by Ustilago tritici and infects the wheat kernels, replacing them with dark, powdery spores.
-Covered smut of barley is caused by Ustilago hordei and manifests as black, enclosed smut balls within the barley kernels.

🔑Key Points:
-The disease is caused by the fungus Ustilago tritici which survives as dormant mycelium in the embryo of infected grain.
-The major symptom of loose smut is the "smutted" grain heads, which contain masses of black or brown spores.
-After spores disperse, only a bare rachis remains with a few fragments of glumes or awns.
-These spores, in turn, infect other wheat plants at flowering, causing seed infection.