ABSTRACT
Sexual reproduction involves union of two compatible nuclei or sex cells or sex organs or somatic cells or somatic hyphae for the formation of new individuals. Sexual stage is perfect stage and technically called as teleomorphic stage. Sexual cycle normally occurs once in the life span of the fungus. Heterokaryosis is the main source of variation in the anamorphic fungi, which lack sexual reproduction. The presence of genetically-different nuclei in an individual is called heterokaryosis, and the organism heterokaryon. Heterokaryosis is a major factor in natural variability and sexuality. Anastomosis involves fusion of hyphae of some species, movement of one or more nuclei into one or the other of the fused cells, and the establishment of a compatible heterokaryotic state. Parasexual cycle is a process in which plasmogamy, karyogamy and haploidisation takes place in a sequence but not at specified points in the life cycle of a fungus.
