GENETIC ANALYSIS OF WOOL TRAITS AND ITS ASSOCIATION WITH KERATIN GENES IN MAGRA SHEEP
Loading...
Date
2017
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Rajasthan University of Veterinary and Animal Sciences, Bikaner
Abstract
The objectives of the present study were to estimate the mean performance of wool traits along with the effect of genetic and nongenetic factors affecting them, estimation of genetic and phenotypic parameters both by sire and animal models, to identify the polymorphism of keratin genes (KIF- I and KAP 11-1 genes) in Magra sheep and to find association of keratin genes with wool traits. Data and blood samples for the present study were collected from the farm of Magra sheep, maintained at arid region campus, Central Sheep and Wool Research Institute (ICAR- CSWRI), Bikaner, Rajasthan.
The overall least-squares means were observed to be 690.50 ± 4.713, 754.83 ± 5.571 and 670.93 ± 5.386 g for greasy fleece yield at first, second and third clip, respectively. The overall least-squares mean for staple length, crimp frequency, fibre diameter, pure, hetro, hairy and medullated fibres were estimated as 6.26 ± 0.039 cm, 0.92 ± 0.010 per cm, 33.31 ± 0.131 μ, 54.74 ± 0.593 %, 33.25 ± 0.416 %, 12.01 ± 0.291 % and 45.26 ± 0.593 %, respectively. The effect of sire was observed to be highly significant (P≤ 0.01) on all the wool traits under study. The effect of period of shearing was found highly significant (P≤ 0.01) for all the wool traits except at greasy fleece yield at third clip and fibre diameter. The effect of sex was found highly significant (P≤ 0.01) on greasy fleece yield at different clips and crimp frequency; and significant (P≤ 0.05) on fibre diameter. The effect of season of birth was found highly significant (P≤ 0.01) for all the wool traits except for pure, hetro and medullation percentage. The regression of lamb’s age at shearing had highly significant (P≤ 0.01) effect on greasy fleece yield at different clips, crimp frequency and hetro fibres; and significant (P≤ 0.05) effect was found on medullation percentage.
Heritability estimates for greasy fleece yield at first, second and third clip were estimated as 0.68 ± 0.083, 0.81 ± 0.095 and 0.66 ± 0.150, respectively, using sire model and 0.25 ± 0.037, 0.24 ± 0.039 and 0.32 ± 0.075, respectively, using animal model. The estimates of heritability for staple length, crimp frequency, fibre diameter, pure, hetro, hairy and medullated fibres were estimated as 0.52 ± 0.085, 0.20 ± 0.055, 0.18 ± 0.052, 0.41 ± 0.073, 0.33 ± 0.066, 0.53 ± 0.082 and 0.44 ± 0.075, respectively, using sire model and 0.31 ± 0.046, 0.09 ± 0.033, 0.14 ± 0.035, 0.40 ± 0.046, 0.28 ± 0.044, 0.41 ± 0.045 and 0.41 ± 0.046, respectively, using animal model. Fitting six different animal models with various combinations of direct and maternal effects showed that there was no or very low evidence of the maternal genetic and maternal permanent effect for all the wool traits under study.
Using sire model, genetic correlations among different wool production traits ranged from 0.33 to 0.87, and that of wool quality traits ranged from -1.00 to 0.93; and phenotypic correlations ranged from - 0.01 to 0.09 and -1.00 to 0.89, respectively for wool production and wool quality traits, respectively. Using animal model, genetic correlations among different wool production traits ranged from 0.32 to 0.94, and that of wool quality traits ranged from -1.00 to 0.97; and phenotypic correlations ranged from 0.12 to 0.31 and -1.00 to 0.89, respectively for wool production and wool quality traits, respectively.
For the molecular aspect of the present study, genomic DNA was isolated from 162 blood samples of Magra sheep. The genotyping of KIF-I gene and KAP11-1 gene was done with the help of PCR-RFLP and PCR-SSCP, respectively.
The PCR-RFLP of KIF- I gene at locus KRT1.2 in Magra sheep generated three genotypic patterns by MspI digestion of the 480 bp amplicons as: 159, 126, 100 and 95 bp for AA genotype; 259, 126 and 95 bp for BB genotype; and 259, 159, 126, 100 and 95 bp for AB genotype. The genotypic frequencies of the genotypes AA, AB and BB were estimated as 0.49, 0.43 and 0.08, respectively. The allelic frequencies for A and B allele were estimated as 0.71 and 0.29, respectively. Greater frequencies of allele A and genotypes AA and AB suggests that selection for higher wool yield and wool quality favoured AA homozygote and AB heterozygote. The chi-square test for Hardy Weinberg equilibrium indicated non-significant differences (P>0.05) among the genotypic and gene frequencies with respect to KIF-I gene. Hence, it was inferred that Magra population was in Hardy Weinberg equilibrium with respect to KIF-I gene.
The PCR-SSCP of KAP11-1 gene in Magra sheep revealed three unique banding patterns forming three genotypes, viz. AA, AB and AC with genotypic frequencies 0.38, 0.51 and 0.11, respectively in Magra sheep. Genotypes BB, BC and CC were not observed in the
present samples. The allelic frequencies for A, B and C allele were estimated as 0.69, 0.26 and 0.05, respectively. The chi-square test for Hardy Weinberg equilibrium indicated significant differences (P≤ 0.05) among the genotypic and gene frequencies with respect to KAP11-1 gene. Hence, it was inferred that Magra population was not in Hardy Weinberg equilibrium with respect to KAP11-1 gene.
Association study of the keratin genes and wool traits revealed significant (P≤ 0.05) variation in the first greasy fleece yield, fibre diameter and hairy fibres due to the observed genotypes of KIF-I gene. Also, variation due to the three genotypes associated with KAP11-1 gene significantly (P≤ 0.05) affected second greasy fleece yield, staple length and hetro fibres in Magra sheep. It indicates that these genes may be regarded as candidate genes for marking variations in wool production and quality traits.
One of the purified PCR product for KAP11-1 gene was sequenced and the sequence was submitted in GenBank database with the accession number KX863744.
Description
Keywords
null