The key difference between primary and secondary mycelium is that primary mycelium develops from fungal spores when they mature and form germ tubes while secondary mycelium forms from sexually compatible hyphae when they conjugate during the sexual reproduction.
Basidiomycetes are a major group of fungi. The mycelium of basidiomycete fungi undergoes several development changes such as primary, secondary and tertiary stages. Primary mycelium appears during the primary stage while secondary mycelium appears during the secondary stage of their life cycles. Primary mycelium develops from basidiospores. Spores mature and form ag erm tube and develop into the primary mycelium. During sexual reproduction, sexually compatible two types of hyphae conjugate with each other and form the secondary mycelium.
CONTENTS
1. Overview and Key Difference
2. What is Primary Mycelium
3. What is Secondary Mycelium
4. Similarities Between Primary and Secondary Mycelium
5. Side by Side Comparison – Primary vs Secondary Mycelium in Tabular Form
6. Summary
What is Primary Mycelium?
Primary mycelium is the collection of hyphae formed from the germination of haploid basidiospores. Therefore, primary mycelium is generated after the germination of basidiospores of basidiomycetes.
Figure 01: Basidiospore Germination
Primary mycelium consists of monokaryotic hyphae. Hence, mycelium contains one haploid nucleus. Primary mycelium represents the monokaryotic phase of the life cycle. Hyphae of primary mycelia can conjugate and form secondary mycelium. In other words, mycelia of compatible mating strains can combine and form secondary mycelium. However, unlike secondary mycelium, primary mycelium does not contain clamp connections. Moreover, the life span of primary mycelium is short.
What is Secondary Mycelium?
Secondary mycelium is the mycelium that develops after the conjugation of two sexually compatible primary hyphae of basidiomycete fungi. Sexually compatible hyphae are known as plus and minus mating types mycelia.
Figure 02: Basidiomycete Life Cycle
Secondary mycelium contains two haploid nuclei, one from each parent. Therefore, secondary mycelium represents the dikaryotic phase of the living cycle of the fungus. The dikaryotic phase is not diploid. Two nuclei remain unfused until shortly before spore production. This dikaryotic stage is the dominant stage of the basidiomycete life cycle. Secondary mycelium generates a basidiocarp or the fruiting body which we call mushroom. Basidiocarp contains basidia on the gills under its cap.
What are the Similarities Between Primary and Secondary Mycelium?
- Primary and secondary mycelia are two types of mycelia seen in fungi.
- They are two development changes in the life cycle.
- When two primary mycelia conjugate, secondary mycelium is formed.
- Basidiomycetes fungi produce both primary and secondary mycelia.
What is the Difference Between Primary and Secondary Mycelium?
Primary mycelium is generated from the germination of basidiospores while secondary mycelium is developed from the conjugation of two mating types of primary mycelia. So, this is the key difference between primary and secondary mycelium. Furthermore, the primary mycelium contains one haploid nucleus. Hence, it represents the monokaryotic phase of the life cycle. In contrast, secondary mycelium contains two haploid nuclei one from each parent. It represents the dikaryotic phase of the life cycle. Moreover, it is the dominant stage of the life cycle.
The below infographic tabulates more differences between primary and secondary mycelium.
Summary – Primary vs Secondary Mycelium
Primary mycelium is the haploid or monokaryotic hyphae generated from the germination of basidiospores. Secondary mycelium is the dikaryotic hyphae formed from the conjugation of two mating types of fungi during the sexual reproduction. Therefore, primary mycelium contains one haploid nucleus while secondary mycelium contains two unfused haploid nuclei. Secondary mycelium represents the dominant stage of the life cycle, unlike primary mycelium. Moreover, secondary mycelium has a long life span compared to primary mycelium. Thus, this summarizes the difference between primary and secondary mycelium.
Reference:
1. “Biology for Majors II.” Lumen, Available here.
Image Courtesy:
1. “03 02 09 life cycle of Agaricus sp., Agaricales Basidiomycota (M. Piepenbring)” By M. Piepenbring – (CC BY-SA 3.0) via Commons Wikimedia
2. “Figure 24 02 07” By CNX OpenStax – (CC BY 4.0) via Commons Wikimedia