Principles of Genetics and Breeding

8.1.3.3 Application of gynogenesis in aquaculture

• In female homogametic species all will be females.
• 50 to 100% inbred individuals can be produced in a single generation.
• Purdom (1983) is of the opinion that one generation of gynogenesis was equivalent to seven generations of full sibmating and that induced diploid gynogenesis was a potential method in the production of inbred lines of fish which can subsequently be crossed to produce hybrid vigour or heterosis.
• Streisinger et al. (1981) found that hybrids between inbred lines showed increased vigour and that more vigorous lines could be produced by further selection.
• The ability to map genes relative to their centromeres in fish after retention of the second polarbody.
• Generation of homozygous lines by applying a second cycle of gynogenesis to the homozygous fish produced initially by gynogenesis involving suppression of the first cleavage division. This may be useful for the production of female or monosex exotic species for release into the natural environment without risk of reproduction.
• Combining gynogenesis and sex reversal it is possible to produce males with female genotype. These males with homogametic female enable to produce monosex female population. Some of the newly hatched larvae may be treated with androgens (17- a Methyltestosterone) to produce XX males which upon reach sexual maturity can be crossed with normal females to produce all female fish. By this means, production of all female stock can be maintained for monosex culture. All female grows faster than the male (commoncarp, silver barb, etc.) or when the female has a better meat quality than the male (rainbow trout) or when the roe is a delicacy.
• All female common carp were produced in Israel, by sex reversing XX gynogenetic females to males and using these XX males for breeding. All female seed released to commercial farms resulted in 10-15% yield improvement over existing commercial stocks.
• In Hungary,gynogenetically produced lines of common carp are used as brood stock for crossbreeding.
• The reason for the use of all-female monosex seed in Chinook salmon (O. tshawystscha) and coho salmon (O. kisutch) are to prevent losses arising from early maturation of males, and because the roe has become valuable and thus all-female populations are desirable.
• Monosex (all-female)strains of Oncorhynchus species are being produce by gynogenesis and by the use of Y chromosomal DNA markers.

Gynogenesis although a recent development is now seemed well established in aquaculture for practical use in inbreeding,production of inbred lines and monosex populations particularly female population for breeding purposes. Each individual gynogenetic fish will be inbred in the sense that it will be homozygous at many loci, due to the inheritance of replicate genes from the female parent.