ASSESSMENT OF GENETIC DIVERSITY IN CHICKEN POPULATIONS USING GENOME MARKERS
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Date
2006-06
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SRI VENKATESWARA VETERINARY UNIVERSITY TIRUPATI - 517 502. (A.P.) INDIA
Abstract
ABSTRACT:
A total of 155 birds representing eight populations, two layer strains of White
Leghorn (WLH-IWD and WLH-IWF). two dual-purpose breeds (Dahlem Red and Rhode
Island Red), a commercial layer (Babcock), a commercial broiler (Vencobb), a native
breed (Aseel) and Non-descript (Desi) chicken were genotyped with twenty (mono, di
and tri nucleotide repeats) microsatellite markers to assess the genetic diversity, genetic
variation and phylogenetic relationships. All the microsatellite loci utilized for the
analysis were polymorphic with a reasonable informativeness ranging from moderate to
high. The total number of alleles obtained across all the populations was 285 with a size
range from 76 for MCWO51 to 256 for MCWOOS locus. The total number of alleles per
locus ranged from 7 at MCW001 to 26 at MCWOOS with an overall mean of 14.25 alleles
per locus. The mean number of alleles across the loci and among the populations ranged
from 3.50 (ADL158) to 8.63 (ADL176 and MCWOOS) and 4.70 (WLH-IWD) to 6.75
(Non-descript). The mean effective number of alleles am-ng the loci and the populations
varied between 1.96 for ADL158 and 4.4 1 for ADL267 and 2.69 in Dahlem Red and
4.15 in Non-descript. A total of 103 alleles were unique to population/strain in various
chicken populations. The frequency of most of these alleles was very less. Only 30 per
cent of the alleles had frequency of more than 10 per cent. The mean Polymorphism Information Content (PIC) values ranged from 0.39 for ADL158 to 0.71 for MCWOOS and ADL267 across the loci and 0.55 (Dahlem Red) to
0.71 (Non-descript) among the populations. The expected heterozygosity estimates
ranged from 0.63 (Dahlem Red) to 0.77 (Non-descript) with an overall mean of 0.68. The
observed heterozygosity estimates were the highest in Babcock (0.73) and the least in
Dahlem Red (0.55) among the populations studied.
The overall mean inbreeding coefficients (FIs) varied between -0.05 (Babcock)
and 0.16 (Rhode lsland Red). Babcock, a commercial layer had negative Fls value (-0.05)
indicating high genetic variation and outbreeding effects.
The genetic distance was least between WLH-IWD and WLH-IWF (0.30) and
highest between Dahlem Red and Babcock (0.80). The WLH-IWD and WLH-IWF
strains were closer with maximum genetic identity index of 0.75 among all the
populations and Dahlem Red and Babcock were wider apart with least identity index
value of 0.45 indicating their high genetic divergence. Phylogenetic analysis revealed that the eight populations were grouped in to two main clusters, one cluster representing Dahlem Red and Rhode Island Red, the pure
breeds and the other cluster representing the remaining six populations/strains (two
commercial, two synthetic strains and two native chickens). The second group was
divided into three sub clusters i.e., Aseel and Non-descript; Babcock and Vencobb;
WLH-IWD and WLH-IWF. All the loci departed from the equilibrium frequency in at
least two of the eight populations studied. It may be concluded that the chicken populations studied were in the state of mild to moderate inbreeding except commercial birds. A planned breeding is suggested for
purebreds to revive their genetic potential. High genetic diversity exists in Non-descript
birds, which can be tapped to improve the birds suitable for backyard poultry.
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