A parasexual cycle is initiated by the fusion of hyphae (anastomosis) during which nuclei and other cytoplasmic components occupy the same cell (heterokaryosis and plasmogamy).
Fusion of the unlike nuclei in the cell of the heterokaryon results in formation of a diploid nucleus (karyogamy), which is believed to be unstable and can produce segregants by recombination involving mitotic crossing-over and haploidization.
Like a sexual cycle, parasexuality gives the species the opportunity to recombine the genome and produce new genotypes in their offspring.
In both cases, unlike hyphae (or modifications thereof) may fuse (plasmogamy) and their nuclei will occupy the same cell.
[2] The potential to undergo a parasexual cycle under laboratory conditions has been demonstrated in many species of filamentous fungi, including Fusarium monoliforme,[3] Penicillium roqueforti[4] (used in making blue cheeses[5]), Verticillium dahliae,[6][7] Verticillium alboatrum,[8] Pseudocercosporella herpotrichoides,[9] Ustilago scabiosae,[10] Magnaporthe grisea,[11] Cladosporium fulvum,[12][13] and the human pathogens Candida albicans[14] and Candida tropicalis.
Its significance in nature is largely unknown and will depend on the frequency of heterokaryosis, determined by cytoplasmic incompatibility barriers and it is also useful in rDNA technology.