Question

Which one of the following is Fungi Like Organism known to cause plant disease epidemics?

• A. Saprolegnia
• B. Phytophthora
• C. Magnaporthe
• D. Puccinia

Hint:

Remember that Oomycetes (like Phytophthora, Pythium, and downy mildews) are stramenopiles.
They differ from true fungi by having diploid nuclei in their vegetative hyphae, cell walls composed of cellulose, and producing biflagellated motile zoospores.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
In plant pathology, certain pathogens were historically classified as true fungi due to their filamentous growth and spore-bearing structures, but modern molecular phylogenetics has placed them in separate kingdoms.
These are termed "fungi-like organisms" or oomycetes, belonging to the kingdom Stramenopila (or Chromista).

Step 2: Detailed Explanation:
Let us analyze each of the given pathogens:
Saprolegnia is an oomycete, but it is primarily a saprophyte or pathogen of fish and aquatic organisms rather than a major terrestrial plant pathogen causing crop epidemics, which excludes Option (A).
Magnaporthe (specifically Magnaporthe oryzae, causing rice blast) and Puccinia (causing cereal rusts) are true fungi belonging to the phyla Ascomycota and Basidiomycota respectively, which excludes Options (C) and (D).
Phytophthora is a genus of plant-damaging oomycetes.
They are eukaryotic, non-photosynthetic organisms chemically and genetically distinct from true fungi, possessing cell walls made of cellulose rather than chitin.
The species Phytophthora infestans is the causal agent of late blight of potato, which famously triggered the devastating Great Irish Famine in the 1840s.
This historical event is a classic example of a major plant disease epidemic caused by a fungi-like oomycete pathogen.

Step 3: Final Answer:
Phytophthora is the fungi-like organism known to cause devastating plant disease epidemics.
This corresponds to Option (B).