Question

Biotrophic fungal pathogen, Puccinia graminis f. sp. tritici is a threat to agriculture
(A). Puccinia graminis f. sp. tritici enter through stomata
(B). Puccinia graminis f. sp. tritici forms haustoria in the plant cell
(C). Puccinia graminis f. sp. tritici can infect colateral weed plants in wheat fields
(D). Puccinia graminis f. sp. tritici can infect dicot plants also
Choose the correct answer from the options given below:

• A. (A), (B), (C), (D).
• B. (A), (B), (D) only.
• C. (B), (A), (C) only.
• D. (C), (B) only.

Hint:

Rust fungi are biotrophic pathogens that form feeding haustoria. Heteroecious rusts like P. graminis infect both monocots (wheat) and dicots (barberry).

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Puccinia graminis f. sp. tritici is an obligate biotrophic rust fungus that causes black stem rust in wheat.
As a biotrophic pathogen, it must obtain its nutrition from living host tissues without killing them, requiring specialized infection and feeding structures.

Step 2: Detailed Explanation:
Let us analyze each statement:
Statement (A) is correct: Unlike some fungi that directly penetrate the plant cuticle, rust urediniospores germinate to form a germ tube that locates stomatal openings.
The germ tube then develops an appressorium over the stomatal aperture, allowing the fungus to enter the host tissue through the stomata.
Statement (B) is correct: Once inside, the fungus develops intercellular hyphae and projects specialized feeding structures called haustoria into the host cells.
These haustoria invaginate the host plasma membrane (without breaking it) to absorb nutrients while keeping the host cell alive.
Statement (C) is correct: The pathogen can survive and multiply on collateral hosts, such as various wild grasses (e.g., wild wheat relatives or bromegrasses) growing in and around wheat fields.
These collateral hosts act as reservoirs of primary inoculum.
Statement (D) is correct: Puccinia graminis is a heteroecious rust fungus, meaning it requires two unrelated host species to complete its full life cycle.
The primary host is wheat (a monocot), where it produces its asexual stages.
The alternate host is barberry (Berberis vulgaris), which is a dicot plant, where the sexual stage of the fungus occurs.
Since all four statements are biologically correct, Option (A) is the correct choice.

Step 3: Final Answer:
Hence, the correct option is (A).