| The Pelteobagrus vachelli is the largest individual species in Pelteobagrus.It is most economically valuable species in Pelteobagrus,along with P.fulvidraco.It has great potential in genetic breeding due to its advantages of fast growth and strong disease resistance.As the male parent of a new aquatic species hybrid yellow catfish"Huangyou 1"（GS-02-001-2018）examined and approved by the National Committee for Examination and Approval of Original Breeding and Good Breeding,the study on germplasm improvement is obviously lagging behind that of female parent P.fulvidraco.At the same time,the rapidly expanded breeding scale of P.vachelli has resulted in many breeding problems,such as poor hypoxia tolerance,gender dimorphism and degradation of growth traits,which have severely restricted the culture sustainable development.Therefore,in this study,a high-density genetic map of P.vachelli was constructed based on dd RAD-seq technology.The QTLs and candidate genes for growth,sex and hypoxia tolerance were mapped and verified.This thesis provides the genetic basis for the molecular marker assisted breeding of this fish,which is also a prerequisite for the sustainable development of the breeding industry of P.vachelli and hybrid yellow catfish"Huangyou-1".The research results of this paper are mainly divided into four parts:1.Construction of high-density genetic linkage map of P.vachelliIn this study,a high-resolution genetic map of P.vachelli was constructed by sequencing 200 F1 individuals from the same parents and the parents themselves using the dd RAD-seq technology.The map contains 5059 isolated SNP markers,located on26 LGs（consistent with chromosome numbers of P.vachelli）,with a total length of44047.01 c M and an average marker interval of 0.11 c M.A comparative genomics analysis with the closely related species of P.fulvidraco showed that 3879（76.7%）markers were mapped to the P.fulvidraco reference genome,and there was a nearly 1:1 relationship with the reference genome of the P.fulvidraco,indicating that the map is highly reliable.2.QTL mapping of growth,sex and hypoxic tolerance in P.vachelliBased on the constructed genetic map,the QTLs of growth,sex and hypoxic tolerance were mapped.A total of 47 growth correlations QTLs were identified,including 11 proportional character-related QTLs（1 GW QTL and 10 CW QTLs）and36 phenotypic character-related QTLs（4 GW QTLs and 32 CW QTLs）.There are 18QTLs（4 GW QTLs and 14 CW QTLs）located on LG3 and LG14,indicating that these two LGs may be the main growth regulation chromosomes.In the gender QTL mapping,a total of 6 gender-related QTLs were located,including 2 GW QTLs and 4 CW QTLs,distributed on LG14,LG21 and LG24.In the hypoxization-related QTL mapping,a total of 11 hypoxization-related QTLs were located,including 1 GW QTL and 10 CW QTLs,which were distributed on 7 LGs（LG4,LG5,LG10,LG12,LG19,LG21 and LG23）.3.Identification and validation of candidate genes for growth and hypoxic tolerance in P.vachelliThe candidate genes in the GW QTLs region were identified and verified by collinea analysis with the P.fulvidraco reference genome.The expression of the growth candidate genes sipa1 and hsd11b2 in the liver and brain tissues of the rapidly-growing P.vachelli was significantly higher than that of the slow-growing P.vachelli（P<0.05）.In muscle tissue,the expression of sipa1 in slow-growing individuals was significantly lower than that in fast-growing and moderate-growing individuals（P<0.05）.In brain and liver tissues of P.vachelli,m RNA levels of hypoxic-resistant candidate sema7a significantly changed in the hypoxia and reoxygenation stages（P<0.05）,and peaked in both liver and brain 1.5 hours after hypoxia,and maintained a high level in the whole recovery process.4.Verification of SNPs in QTL intervals for growth,sex and hypoxia tolerance traits in P.vachelliTo evaluate the accuracy of QTLs positioning in this paper,a total of 8 SNP markers were selected from 4 growth-related GW QTLs and 1 hypoxic-resistant GW QTL for KASP validation in 200 full-sibling populations,and the results showed that these sites were significantly correlated with their corresponding traits（P<0.05）.12SNP markers（2 hkxhk types,6 lmxll types and 4 nnxnp types）were selected from 2gender-related GW QTLs and verified in 200 full-sib family and 48 wild groups.The results showed that hkxhk type and nnxnp type markers were significantly correlated with gender,while lmxll type markers were not.Moreover,the validation of all markers in the wild population were lower than that in the 200 full-sib family,indicating that the gender-related markers in the map were applicable to the mapping family,but their applicability to other families may decrease. |
PDF Full Text Request