Question

Which one of the following are biotrophic fungi?
(A) Albugo
(B) Puccinia
(C) Glomus
(D) Blumeria
Choose the correct answer from the options given below:

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

Hint:

Obligate biotrophs cannot be cultured on artificial synthetic agar media in the laboratory.
They can only be maintained and propagated on living host plants or tissue cultures.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Biotrophic organisms are obligate biotrophic parasites or mutualists that must live in close association with living host cells to obtain nutrients and complete their life cycles.
Unlike necrotrophs, they do not kill their host cells, but instead establish specialized structures to absorb nutrients without triggering immediate host cell death.

Step 2: Detailed Explanation:
Let us analyze each of the listed organisms to evaluate their biotrophic nature:
(A) Albugo:
This is an oomycete genus (commonly grouped with fungi-like pathogens) that causes white rust on crucifers and other hosts.
It is an obligate biotroph that derives nutrients from living plant tissue via specialized haustoria.
Thus, (A) is biotrophic.
(B) Puccinia:
This is a genus of basidiomycete rust fungi (e.g., Puccinia graminis causing black stem rust of wheat).
All rust fungi are obligate biotrophic pathogens that depend on living host tissues to survive and reproduce.
Thus, (B) is biotrophic.
(C) Glomus:
This is a genus of arbuscular mycorrhizal (AM) fungi.
These fungi form mutualistic, symbiotic relationships with the roots of most terrestrial plants, deriving carbon and energy directly from the living plant cells while helping them absorb phosphorus and water.
As obligate mutualistic biotrophs, they cannot complete their life cycle without a living host.
Thus, (C) is biotrophic.
(D) Blumeria:
This is an ascomycete genus (e.g., Blumeria graminis causing powdery mildew on cereals).
Like rusts, powdery mildews are obligate biotrophic pathogens that feed on living epidermal cells.
Thus, (D) is biotrophic.
Since all four organisms are obligate biotrophs, they are all correctly matched.

Step 3: Final Answer:
All the listed organisms (A, B, C, and D) are biotrophic.
This corresponds to Option (D).