Deuteromycetes (Imperfect Fungi): Only Asexual Reproduction Known
Biology · Biological Classification · NEET
Deuteromycetes are called "imperfect fungi" because scientists have only found their asexual (or vegetative) phase, not their sexual phase. They reproduce only by asexual spores called conidia, and their mycelium is septate and branched. Memory hook: "Deutero = Doubtful sex life" — the sexual stage is missing, so it is an incomplete or imperfect group.
Deuteromycetes reproduce only by asexual conidia produced exogenously on conidiophores, growing from a septate, branched mycelium. The sexual stage is unknown, so they are called imperfect fungi.
Your doubts, answered
Why are Deuteromycetes called imperfect fungi?
Because only their asexual or vegetative phase is known. In fungi, the sexual ("perfect") stage is the complete reproductive stage. In Deuteromycetes, scientists could never find this sexual stage, so the fungus looks reproductively incomplete or "imperfect." That is why they are placed in a temporary group called Deuteromycetes (also called Fungi Imperfecti).
What spores do Deuteromycetes reproduce by?
They reproduce ONLY by asexual spores called conidia. Conidia are produced exogenously (on the outside, on stalks called conidiophores). There are no sexual spores like ascospores or basidiospores here, because the sexual stage is unknown. Remember: Deuteromycetes = conidia only.
Is the mycelium of Deuteromycetes septate or coenocytic?
The mycelium is SEPTATE (has cross-walls) and branched. This is an easy NEET fact. Do not confuse it with Phycomycetes, whose mycelium is coenocytic (no cross-walls). Septate mycelium is shared by Ascomycetes, Basidiomycetes, and Deuteromycetes.
Is Deuteromycetes a real natural class or just a temporary dumping ground?
It is a temporary or artificial group, not a natural class. When a fungus was known only by its asexual stage, it was placed here. Later, when its sexual (perfect) stage was discovered, the fungus was moved to its correct class, usually Ascomycetes or Basidiomycetes. So Deuteromycetes is like a waiting room, not a permanent home.
What is the role of Deuteromycetes in nature?
Some are saprophytes (feed on dead matter) and some are parasites (feed on living hosts). But a large number are decomposers of litter, which means they break down dead leaves and help in mineral cycling in the soil. This ecological role is often asked in NEET.
What are the examples of Deuteromycetes I must remember?
NCERT gives three: Alternaria, Colletotrichum, and Trichoderma. A memory trick: "ACT" = Alternaria, Colletotrichum, Trichoderma. Note that Alternaria is a common NEET distractor in fungal-class matching questions.
⚠️ The NEET trap ✗ Deuteromycetes reproduce by both asexual and sexual spores. ✓ Deuteromycetes reproduce ONLY by asexual spores called conidia; the sexual stage is unknown, which is exactly why they are called imperfect fungi. 🧠 If the sexual stage were known, the fungus would be moved out of Deuteromycetes. "Imperfect" = no known sexual stage = no sexual spores.
Real NEET questions
NEET 2018
After karyogamy followed by meiosis, spores are produced exogenously in
A · Agaricus ✓
B · Alternaria
C · Neurospora
D · Saccharomyces
Solution: Agaricus is a basidiomycete: karyogamy and meiosis happen in the basidium, producing basidiospores borne exogenously. Alternaria is a Deuteromycete that forms only asexual conidia (no karyogamy/meiosis, so it is wrong here). Neurospora and Saccharomyces are ascomycetes with endogenous ascospores. This question is a good reminder that Alternaria (a deuteromycete) has NO known sexual stage.
NEET 2019 / 2021 / ReNEET 2026
Which of the following statements is incorrect?
A · Morels and truffles are edible delicacies.
B · Claviceps is a source of many alkaloids and LSD.
C · Conidia are produced exogenously and ascospores endogenously.
D · Yeasts have filamentous bodies with long thread-like hyphae. ✓
Solution: D is incorrect because yeasts are unicellular, not filamentous. Statement C is important for this concept: conidia (the asexual spores of Deuteromycetes and some Ascomycetes) are produced exogenously, while ascospores are produced endogenously (inside an ascus). Knowing that conidia are exogenous is a repeated NEET point.
NEET 2022
Identify the asexual reproductive structure associated with Penicillium:
A · Zoospores
B · Conidia ✓
C · Gemmules
D · Buds
Solution: Penicillium reproduces asexually by conidia produced exogenously on conidiophores. Conidia are the same asexual spores that define Deuteromycetes. Zoospores belong to Phycomycetes, gemmules to sponges, and buds to yeast. This shows conidia are a key concept to link with the imperfect fungi.
Solved Biological Classification NEET PYQs
Try the real previous-year questions from this chapter — each with the answer and a full solution.
They are also called Fungi Imperfecti or imperfect fungi, because only the asexual (imperfect) stage is known.
Why do fungi get moved out of Deuteromycetes?
Once the sexual (perfect) stage of a fungus is discovered, it is moved to its correct class, usually Ascomycetes or Basidiomycetes, based on the type of sexual spores it forms.
Do Deuteromycetes form ascospores or basidiospores?
No. They form neither, because their sexual stage is unknown. They form only asexual conidia. If ascospores or basidiospores were found, the fungus would no longer be a deuteromycete.
Is Alternaria a deuteromycete?
Yes. Alternaria, Colletotrichum, and Trichoderma are the three NCERT examples of Deuteromycetes. Alternaria is often used as a trap option in NEET class-matching questions.
What is the ecological importance of Deuteromycetes?
Many are decomposers of litter, breaking down dead plant material and helping in mineral cycling in the soil. Some are saprophytes and some are parasites of plants.
