Genome-wide Association Analysis Of Growth Traits In Qira Black Sheep

The Qira Black sheep is a high quality lambskin sheep with high reproductive performance as its main characteristic.Year-round estrus and high reproduction rates are prominent breed characteristics.The skeleton is well developed and the body height is larger than the body length,mainly located in Qira County at the southern edge of the Great Taklamakan Desert and the northern foot of the Kunlun Mountains.However,the number of genetic resources of this population is small,and it is particularly important to design its conservation and utilization program scientifically and rationally to ensure that its high quality genes are not lost,but also serve well for realistic production development.Therefore,mining candidate genes related to growth traits about Qira Black sheep provides reference value for the molecular selection process of this breed.Experiment 1 Correlation analysis of growth traits and fat-tail characteristics of Qira Black ewesIn this study,408 ewes of Qira Black sheep aged 1.5～3 years were used to determine body weight（y）,body height（x₁）,body length（x₂）,body slope length（x₃）,chest width（x₄）,chest depth（x₅）,chest circumference（x₆）,tube circumference（x₇）,tail length（x₈）,tail width（x₉）and tail circumference(x₁₀),and to calculate tail volume(x₁₁),The differences in tail volume of Qira Black sheep ewes were analyzed,and the tail type was typed according to tail volume,and the correlation between body weight and tail fat traits and body size indexes was analyzed to construct the optimal regression equation for body weight.The results showed that the average tail volume of Qira Black sheep ewes was larger Mean tail volume（18 108.51±11868.52）cm³,and the tail types of Qira Black sheep ewes were divided into small-tailed,medium-tailed,large-tailed and fat-tailed;the number of fat-tailed Qira Black sheep models was relatively small（9）,The tail volume size of the fat-tailed type ranged from 50,388.00～97,920.00 cm³,with a mean tail volume of 63,493.11 cm³,The medium-tailed types were more numerous（223）,with tail volume sizes ranging from 12 000.00～29 988.00 cm³and a mean tail volume of 18 505.93 cm³;the body weight,body length,body slope length,chest circumference,girth,tail width and tail circumference of fat-tailed Qira Black sheep ewes were extremely The body height,body length,body slope length,chest depth,chest circumference,tube circumference,tail length,tail width and tail circumference of ewes were all positively correlated with body weight（P<0.01）;the regression equation constructed for the optimal body weight of ewes was y=0.152x₅+0.078x₆+0.146x₉+0.284x₂+6.430.This indicates that the tail trait of Qira Black sheep is closely related to body weight,revealing that the tail trait has some influence on meat production performance,and the tail trait should be paid attention to in the production performance determination and breed selection of Qira Black sheep.Experiment 2 Genome-wide association analysis of growth traits in Qira Black sheepIn this study,184 German meat Merino and Qira Black sheep were genotyped and tested for growth traits using Affymetrix 50 K SNP microarrays,The GWAS results showed that 84candidate genes were screened for growth traits,including weight candidate genes NELL1,PPARGC1A,BMPR1B,POMK,FABP5,CORT and PRL17 etc.,height candidate genes PRSS58,IGFBP7,NAB1 and MEIS1,chest candidate genes SPATA17,HSPA8,MROH2A,HEATR7B1,etc.,and body length candidate genes HSD17B3,RAD26L,EFNA5,etc.Combined with literature reports,PPARGC1A,BMPR1B,NELL1,EFNA5,FABP5and IGFBP7 genes can be further investigated as important candidate genes for growth traits and meat use traits.Experiment 3 Correlation analysis of BMPR1B and IGFBP7 genes with growth traits in Qira Black sheepFor the validation of the Qira Black sheep population,the genotypic analysis of the main effect genes（BMPR1B and IGFBP7）for growth traits in Qira Black sheep was selected in this study,and the association analysis with growth traits in Qira Black sheep was performed.In this study,90 Qira Black sheep were used for population validation.Phenotypic data such as body weight,body height,body length,body slope length,chest width,chest depth,chest circumference,tube circumference,tail length,tail width and tail circumference were measured for each sheep,and DNA was extracted and sequenced for two genes,BMPR1B and IGFBP7.The results showed that 2 SNPs loci were found in the genes BMPR1B and IGFBP7.Among them,body weight,body height,body length,body slope length,chest width,chest depth,chest circumference,tail width and tail circumference of AA genotype were significantly greater than those of AG and GG genotypes（P<0.01）in the g.431965A>G locus of BMPR1B gene in Qira Black sheep;Body weight,height,tube circumference and chest depth were significantly greater in the GG genotype than in the AA and AG genotypes at the g.35468G>A locus of the IGFBP7 gene in Qira Black sheep（P<0.05）.The results of this study are of great significance to the breeding plan of Qira Black sheep.In conclusion,this study is the first genome-wide association study in Qira Black sheep for growth traits,and it is also the first study to focus on some tail-type trait indicators and to identify master genes for growth traits in Qira Black sheep using the latest sheep genome Ovis＿aries＿v4.0 sequence information and GWAS methods.The results of the study are important for locating quantitative trait locus（QTL）and candidate genes in Qira Black sheep.It also provides an important theoretical basis and reference for exploring the functional genes of growth traits in Qira Black sheep.