Genetic relationship between broodstocks of olive flounder, Paralichthys olivaceus (Temminck and Schlegel) using microsatellite markers

Abstract

For the ¢rst generation of a selective breeding programme, it is important to minimize the possibility of inbreeding. This mostly occurs by mating between closely related individuals, while proper mating can provide an opportunity to establish the base families with wide genetic variation from which selection for subsequent generations can be more e¡ective. Genotyping with microsatellite-based DNA markers can help us determine the genetic distances between the base populations. The genetic markers further facilitate the identi¢cation of the correct parents of the o¡spring (parentage assignments) reared together with many other families after hatching. We established a genetic analysis system with microsatellite DNA markers and analysed the genetic distances of three farmed stocks and a group of ¢sh collected from wild populations using eight microsatellite markers. The averaged heterozygosity of the farming stocks was 0.826 and that of the wild population was 0.868. The hatchery strains had an average of 8.6 alleles per marker, which was less than a wild population that carried an average of 14.3 alleles per marker. Signi¢cant Hardy^Weinberg disequilibrium (HWDE) was observed in two farming stocks (Po0.05). Despite relatively low inbreeding coe⁄ciency of the hatchery populations, the frequency of a few alleles was highly represented over others. It suggests that the hatchery stocks to some extent have experienced inbreeding or they originated from closely related individuals. We will develop a selective program using the DNA mar-kers and will widen the usage of the DNA-based genetic analysis system to other ¢sh species.

Caracterización genética de lotes de Brycon orbignyanus utilizados en programas de repoblamiento

“…El manejo reproductivo utilizado en las piscícolas puede ser un factor importante en la preservación de la diversidad genética, ya que una pérdida de la variación siempre es esperada cuando no hay un buen manejo genético de los lotes de reproductores (18), el cual es ocasionado por la utilización de sistemas reproductivos inadecuados (19) o por el cruzamiento de individuos emparentados, lo que consecuentemente, puede aumentar la homocigosis de los lotes (20). Este cruzamiento ocurre normalmente en lotes de reproductores pequeños y limitados (con bajo número efectivo de reproductores -Ne) donde después de tres generaciones (21), la variación genética tiende a disminuir (9) limitando el potencial genético, disminuyendo la supervivencia y aumentando la tasa de anormalidades (22), afectando de esta forma la productividad.…”

Population structure of the olive flounder (Paralichthys olivaceus) in Korea inferred from microsatellite marker analysis

“…Despite its importance to the fishery industry in Korea, however, genetic information on the P. olivaceus , such as the degree of genetic variation and population structure, is still scanty. Only Kang et al (2006) have reported on the utility of genetic markers to assess genetic variation within farmed P. olivaceus stock and wild populations. The geographic structure of P. olivaceus populations in Korea, however, has not been resolved.…”

Caracterización genética de tres líneas de tilapia del Nilo (Oreochromis niloticus)

“…La perdida de variabilidad genética en la piscicultura siempre es esperada cuando existe un mal manejo reproductivo, debido al cruzamiento de individuos emparentados (Moreira et al, 2007) o a la formación de lotes sin suficiente variabilidad genética (Povh et al, 2008), lo que según Kang et al (2006) consecuentemente aumenta el coeficiente de endogamia y reducirá el número efectivo de reproductores (Frost et al, 2006). Esta situación es bastante común en piscifactorías, ya que el método mas ampliamente usado en la formación de nuevos lotes es la selección de individuos con características favorables, lo que puede dar a lugar a un efecto cuello de botella (bottleneck effect) donde la variabilidad genética es reducida.…”