What is the Difference Between Aeciospores and Pycniospores

The main difference between aeciospores and pycniospores is that aeciospores are dikaryotic, whereas pycniospores are haploid.  

Aeciospores and pycniospores are two of the five types of spores produced by the rust fungi. The other three types include urediniospores, teliospores, and basidiospores.    

Key Areas Covered

1. What is Rust
– Definition, Structure, Importance
2. What are Aeciospores
– Definition, Structure, Importance
3. What are Pycniospores
– Definition, Structure, Importance
4. Similarities Between Aeciospores and Pycniospores
– Outline of Common Features
4. Difference Between Aeciospores and Pycniospores
– Comparison of Key Differences

Key Terms 

Aeciospores, Pycniospores 

Difference Between Aeciospores and Pycniospores - Comparison Summary

What is Rust

Rust is a plant disease caused by fungi. Approximately 7,000 species of fungi cause rust in plants. Puccinia is the most common genus of rust. However, rust fungi are diverse and affect many types of plants. However, each species of rust fungi has a narrow range of hosts. Therefore, it is not transmitted to the non-host plants. Also, most of the rust fungi cannot grow in pure cultures. Meanwhile, some rust fungi infect two hosts in different life cycle stages. They are the primary host and alternate host. The primary host is the host that allows the sexual maturity of the fungi. Also, it allows to reproduce and spread the infection. In comparison, the rust fungi can be sustained inside the alternate host.

Compare Aeciospores and Pycniospores

Figure 1: Rust Fungi

Furthermore, rust fungi have five different types of spores. They are pycniospores (0), aeciospores (I), urediniospores (II), teliospores (III), and basidiospores (IV). 

  • Pycniospores (Spermatia) (0): The gametes of the heterothallic rusts. They are haploid.
  • Aeciospores (I): The non-repeating, dikaryotic, asexual spores that infect the primary host.
  • Urediniospores (II): The repeating, dikaryotic vegetative spores. They form auto-infection on the primary host. Also, they are a prominent sign of infection in the primary host. The color of the urediniospores is red or orange. 
  • Teliospores (III): The dikaryotic spores that survive in unfavorable conditions. Also, they do not infect plants directly. Their germination produces basidiospores and basidia.
  • Basidiospores (IV): They form from teliospores. Importantly, they are wind-borne and infect alternate hosts.

They are morphologically and cytologically different from each other. Importantly, each spore state is very host-specific. Typically, they infect only one type of host. Moreover, rusts are obligate plant pathogens and infect living plants only. 

What are Aeciospores 

Aeciospores are one of the five types of spores produced by rust fungi. They form inside the aecium. Also, they form in chain-like formations. Importantly, aeciospores are dikaryotic. Therefore, they have two nuclei per cell. Also, aeciospores infect the primary host.

Aeciospores vs Pycniospores

Figure 2: Puccinia Life Cycle

What are Pycniospores

Pycniospores are another type of spores produced by rust fungi. They form inside the pycnidia. Pycnidia are special cup-like structures. However, pycniospores are produced asexually. Importantly, pychiospores serve as haploid gametes that occur on the heterothallic rusts. 

Similarities Between Aeciospores and Pycniospores

  • Aeciospores and pycniospores are two spore types that occur in rust fungi.
  • They occur in fruiting bodies.

Difference Between Aeciospores and Pycniospores


Aeciospores refer to one of the spores arranged within an aecium in a series like a chain. In contrast, pycniospores a type of spore in fungi, are produced in special cup-like structures called pycnia or pynidia.


Aeciospores are dikaryotic, while pycniospores are haploid.  


Aeciospores occur in aecia, while pycniospores occur in pychidia. 


Aeciospores occur in the heterothallic rusts, while pychiospores are non-repeating, asexual spores.

Primary Host

Aeciospores infect the primary host, while pychiospores do not infect the primary host.   


In brief, Aeciospores and pycniospores are two of the five types of spores that occur in rust fungi. The other three are urediniospores, teliospores, and basidiospores. Aeciospores are dikaryotic and occur in aecia in the heterothallic rusts. Also, they infect the primary host. In comparison, pycniospores are haploid spores that occur in pychidia and are non-repeating, asexual spores. Importantly, pycniospores do not infect the primary host. Therefore, the main difference between aeciospores and pycniospores is their ploidy. 

  1. Mehmood S, Sajid M, Zhao J, Huang L, Kang Z. Alternate Hosts of Puccinia striiformis sp. triticiand Their Role. Pathogens. 2020 Jun 2;9(6):434. doi: 10.3390/pathogens9060434. PMID: 32498285; PMCID: PMC7350320. 
Image Courtesy:
  1. Rust fungus – Flickr – gailhampshire” By gailhampshire from Cradley, Malvern, U.K – Own work (CC-BY 2.0) via Commons Wikimedia
  2. Life cycle of Puccinia graminis (high resolution)” By James KOLMER – Own Work (CC-BY 4.0) via Commons Wikimedia

About the Author: Lakna

Lakna, a graduate in Molecular Biology and Biochemistry, is a Molecular Biologist and has a broad and keen interest in the discovery of nature related things. She has a keen interest in writing articles regarding science.

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