Genetic evaluation of South African indigenous chickens for disease resistance.
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Date
2015
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Abstract
An alternative standard disease control method would be selective breeding in order to increase
disease resistance. To set up marker assisted selection programmes, knowledge of the genetic
diversity of the chickens is required. To date, indigenous South African chicken lines have
received little scientific attention and has never been subjected to purposive selective breeding
for any particular trait. The objective of the study was to investigate genetic variation within
genes involved in innate and adaptive immune system response. The innate immune system
genes which were studied were the Toll Like Receptor-4 (TLR-4), Myeloid Differential
protein-2 (MD-2) and Solute Carrier Family 11 member A1 (SCL11A1) genes. The PCR-RFLP
method was used to detect single nucleotide polymorphisms in these genes and thereafter, the
electrophoretic patterns were analysed and used to compute population genetic analyses. The
indigenous chickens were moderately outbred at the TLR-4-Sau 96I and INOS-Alu I loci as
indicated by high observed heterozygosity figures of 0.78 and 0.51 respectively and low
fixation indices. The hypothesis of indigenous chicken population having a more genetic
variation was supported by the results that showed the high observed homozygosity in
commercial chickens at the SLC11A1-Sac I locus. The Major Histocompatibility Complex is
composed of genes responsible for the adaptive immune system response. The genetic variation
in the LEI0258 microsatellite marker within the MHC was investigated in indigenous chicken
populations in South Africa and across the 3 populations, 36 alleles were detected and of these,
11 of them were private alleles. Observed heterozygosity levels and high fixation indices
suggested a level of inbreeding at this locus. It was concluded that the sampled South African
chicken populations were moderately inbred at the MHC locus and that the inbreeding may be
due to natural selection of certain alleles in order to acclimate to the natural environment more
effectively.
Description
Master of Science in Genetics. University of KwaZulu-Natal, Westville 2015.
Keywords
Poultry--Diseases--Genetic aspects., Poultry--Genetics., Poultry--Disease resistance., Natural immunity., Major histocompatibility complex., Theses--Genetics., Poultry--Genetic evaluation., Innate immune response.