Assessment of parental contribution to fast- and slow-growth progenies in the blunt snout bream (Megalobrama amblycephala) based on parentage assignment

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Blunt snout bream (Megalobrama amblycephala) is a native freshwater fish species that is economically important for aquaculture in the Chinese freshwater polyculture system. In the present study, nine microsatellite markers were employed to analyze the genetic structure of three wild populations (Yuni-YN Lake, Poyang-PY Lake and Liangzi-LZ Lake) and conduct parentage assignment to assess breeders' contributions to the fast- and slow-growth progeny groups. The number of alleles (Na) per locus were from 6.33 (YN) to 9.56 (PY) and the average observed heterozygosity (HO) for each population was 0.68 (PY), 0.63 (LZ) and 0.66 (YN), respectively. The highest individual inbreeding coefficient (FIS) was found in YN (0. 21) and the lowest in PY (0.01) populations. The offspring were artificially produced using the breeders from three populations through complete diallel crossing and then communally reared in the same pond. In a sample of 468 offspring at 20months old, 96.37% of individuals could be unambiguously assigned to their putative parents. The FST value was 0.024 (P<0.05) between the fast- and slow-growing progeny groups, implying significant genetic differences between the two groups. The pedigree results showed an unequal contribution of breeders to the fast- and slow-growth progenies. In total, 15 breeders (6 females and 9 males) contributed significantly more to the fast-growth progenies, while 11 (4 females and 7 males) contributed significantly more to the slow-growth progenies. These high-efficiency breeders could be used to establish families as a core selection group for use in mass production of fry with good growth performance. The findings are therefore of use in the effort to improve the selective breeding program of M. amblycephala. Statement of relevanceThe results obtained in this study would be useful for establishment of good growth performance families in breeding program of blunt snout bream. The methods used here could be applied in other commercial aquaculture species to identify the good broodstock.