Genetic Diversity Evaluation of Two Loach Fishes and their Artificial Hybrid Population Based on 19 Polymorphic Microsatellite Loci

Sinibotia superciliaris and S. reevesae are two economically important loaches in the middle and upper reaches of Yangtze River. Recently, wild populations of them have dropped sharply due to anthropogenic and environmental threats. There is an increasing need to implement captive propagation programs to protect their populations. Here, we firstly carried out artificial breeding of S. superciliaris and S. reevesae, and hybrid combinations were designed as S. superciliaris & FEMALE; x S. reevesae a, and S. superciliaris a x S. reevesae & FEMALE;. Secondly, 19 microsatellite loci were used to evaluate genetic diversity between hybrid offspring and their parents. The mean polymorphic information content (PIC) among groups ranged from 0.685 to 0.818, implying high polymorphism in all of the four groups (PIC > 0.5). The mean observed heterozygosity ranged from 0.779 to 0.887, and the hybrid combination of S. superciliaris & FEMALE; x S. reevesae a obtained the highest observed heterozygosity, while S. reevesae had the lowest. The high heterozygosity was helpful for protecting the genetic resources and preventing the genetic decline, which could reduce the risk of inbreeding due to loss of heterozygosity. Thus, we recommend the hybrid strategy of S. superciliaris & FEMALE; x S. reevesae a as the potential germplasm resources for further artificial reproduction. Population structure analysis and UPGMA tree indicated S. superciliaris and S. superciliaris & FEMALE; x S. reevesae a were clustered together that comprised of clade I, and S. reevesae and S. superciliaris a x S. reevesae & FEMALE; were clustered together that comprised of clade II, suggesting the close genetic relationship between the offspring and their female parents. This study provides reasonable comparison of genetic diversity and potential application of hybrid strategy of S. superciliaris and S. reevesae, and the population genetic information supplied here will provide valuable resources for breeding, germplasm resources preservation and conservation genetics of these two loaches.