Read the below given notes to learn about homothallism, a phenomenon in those fungi which are self-fertile and self-compatible.
Homothallism is the phenomenon in those fungi which are self-fertile and self-compatible. Such fungi are known as Homothallic fungi. The thallus in these fungi is of one and single strain, thus two mycelia developing from a single spore are capable of interacting and forming diploid structures after syngamy.
These fungi are of two types:
(i) Primary Homothallic fungi:
Primary Homothallic fungi are those in which spores are uninucleate and the nucleus has only one genotype. Examples of such fungi are Allomyces javanicus, Pyronema omphalodes and Puccinia malvacearum besides many members of the order mucorales.
(ii) Secondary Homothallic fungi:
In these fungi, nuclei of compatible mating types are present in each spore. In other words, the spores of these fungi are heterothallic and therefore sexual reproduction can take place in mycelia produced from a single spore under laboratory conditions in artificial cultures.
Neurospora tetrasperma and Coprinus ephimerus are examples of secondary Homothallic fungi.
However, there are certain fungi which are neither Homothallic nor Heterothallic. Several mycologists like Korf (1952), Hartman (1956), Burnett (1956) and Esser (1963) have strongly advocated to abandon the use of these terms.
Esser (1963) urged to use the terms monoecious and dioecious for the fungi as well. According to him, monoecious fungi are those in which an individual can act as donor and recipient of nucleus.
While dioecious fungi are those in which individuals can either act as donor or recipient only. In his opinion, monoecious fungi may possess both the sex organs oh the same thallus or may have none but are capable of receiving or donating nuclei.
These may be self-fertile like Glomerella or self-sterile like Neurospora. The dioecious fungi may be morphologically and physiologically dioecious.
The morphologically dioecious fungi may bear male and female sex organs on separate thalli while physiologically dioecious species either bear sex organs which are morphologically dissimilar or the sex organs are absent. In spite of this, the terms Homothallism and Heterothallism are widely used even now.