Question

After karyogamy followed by meiosis, exogenous spore formation is observed in

• A. Neurospora
• B. Alternaria
• C. Agaricus
• D. Saccharomyces

Answer 1

The correct option is C Agaricus

In fungi, sexual as well as asexual reproduction occurs through spore formation.
"Endogenous spore formation" is the formation of spores within the body in a special spore producing cell called "Sporangia". "Exogenous spore formation" is when spores are formed outside the body in specialised fruiting bodies.


Sexual reproduction occurs through oospores, ascospores and basidiospores. The spores are produced through structures called "fruiting bodies".

The sexual cycle involves the following steps.
1. Plasmogamy - the protoplasms of the 2 gametes fuse together
2. Karyogamy - the nuclei of the 2 gametes fuse together
3. Meiosis in Zygote - the zygote undergoes meiosis to give rise to haploid spores

So the question refers to sexual spores produced exogenously.

Neurospora and Saccharomyces belong to Ascomycetes. In Ascomycetes, the sexual spores called ascospores are produced endogenously. Hence, incorrect.

Alternaria belongs to Deuteromycetes. Deuteromycetes produce only asexual spores. Hence, incorrect.

Organisms belonging to Basidiomycetes produce sexual spores called basidiospores which are formed exogenously. Agaricus belongs to Basidiomycetes, hence correct.