N. Bierne et al., Microsatellite-associated heterosis in hatchery-propagated stocks of the shrimp Penaeus stylirostris, AQUACULTURE, 184(3-4), 2000, pp. 203-219
Correlation between DNA microsatellite heterozygosity and growth rate was i
nvestigated in two hatchery-propagated stocks of the shrimp Penaeus styliro
stris, which had been genetically isolated from wild founders for 17 genera
tions, and from each other for five more generations. presumed demographic
history of these populations suggested that they were maintained at small e
ffective population sizes. and this was confirmed by significant changes in
allelic frequencies between the two stocks. Despite a small sample size (n
= 60) and a small number of loci screened, a significant positive correlat
ion was detected between microsatellite tri-locus heterozygosity and growth
rate in one of the two stocks (r = 0.3, P = 0.02). In the other stock (n =
48), the positive correlation was not significant, but the combined test o
f single locus heterozygote advantage over the three loci was significant (
P = 0.005).
Use of DNA microsatellite markers, whose selectively neutral status is gene
rally accepted, allowed us to reject the hypothesis of direct overdominance
at marker loci as an explanation for an association of growth rate with he
terozygosity. The average depression associated with one locus in our case
is above or equivalent to the amount observed for a 10% increase of inbreed
ing in other species. These results suggest that heterozygosity at neutral
marker loci is sufficiently well correlated with individual inbreeding coef
ficients to reveal a significant residual inbreeding load for growth rate i
n Tahitian P. stylirostris stocks. Inbreeding during hatchery propagation w
as, thus, insufficient to purge the ancestral load. (C) 2000 Elsevier Scien
ce B.V. All rights reserved.