Black rust or stem rust of wheat is caused by

✅ Explanation: Black rust or stem rust, one of the most devastating diseases of wheat, is indeed caused by the fungus Puccinia graminis f. sp. tritici. This rust fungus attacks the stems and leaves of wheat plants, leading to significant yield losses.

📌 Other Options Explanations:
-Option B: Puccinia striiformis: This fungus causes stripe rust or yellow rust of wheat.
-Option C: Puccinia recondita: This fungus is responsible for leaf rust or brown rust of wheat.
-Option D: Melampsora lini: This fungus causes rust in flax (linseed).

🔑Key Points:
-The rust of wheat is caused by the fungus – Puccinia
-Puccinia is a heteroecious fungus i.e it requires two different hosts for completion of its life cycle.
-1. Wheat,
-2. Barberry
-Puccinia is known as the rust fungi
-Three different species of Puccinia develop rust in wheat
-Puccinia graminis – Black rust or Stem rust
-Puccinia recondita – Brown rust or leaf rust
-Puccinia striiformis – Yellow rust or stripe rust