ABSTRACTAn experiment was conducted using a total of one hundred and ten indigenous chickens of three genotypes and their crosses, comprising of thirty from each genotype and twenty from the indigenous breeds' crosses with NAPRIx. The experiment was to determine the susceptibility or otherwise of the various genotypes and their crosses to Newcastle disease and to determine whether the Mx gene is involved in any resistance. The genetic diversity of the various genotypes was also assessed. The birds were inoculated with the Newcastle disease virus KUDU-113 strain. They were bled on days 0, 3, 7, 14, 21, 28 and the collected blood samples were used for molecular analysis in the laboratory while data from the molecular work was analyzed using the R statistical package. Geometric mean titre of Newcastle disease anti body was highest (4.7) in Normal feathered(NF) and lowest (3.1) in the naked neck (NN) while the NAPRIx “ NF had the highest titre of 1024 on day 28. Mortality and morbidity results showed that morbidity was 100% in all genotypes and mortality was highest in NF (87.5%) and lowest in NN (45%). The ELISA results showed that the naked neck (NN) had the highest percentage of antigen (21%) while the NAPRIx“FF had the least (4%). The Association of the Mx gene genotype with resistance to Newcastle disease showed that the frequency of the resistant A allele was higher than the G allele for susceptibility. Analysis of genetic diversity showed that the number of alleles ranged from 2-3 for NF; Polymorphism information content (PIC) ranged from 0.637 to 0.976. The allele number for FF ranged from 2-3 with PIC mean of 0.981. Expected (He) and observed (Ho) heterozygosity were 0.601 and 0.765 respectively. Allele number range from 2-3 for NN, mean PIC was 0.825 while Ho and He were 0.627 and 0.513, respectively. The allele number ranged from 2-3 for all crosses. Mean PIC for NAPRIx “ NF was 0.838, Ho and He 0.569 and 0.520, respectively. Mean PIC for NAPRIx “ NN was0.948 while Ho and He were 0.608 and 0.575, respectively. Mean PIC forNAPRIx“FF was 0.967 while Ho and He was 0.706 and 0.592, respectively. Analysis of molecular variance (AMOVA) showed an estimated variation of 0.142 among the populations and 0.042 among individuals while variation within individuals accounted for 98% of the total variation. The paired wise population matrix of Nei's genetic distance showed that the longest distance of 0.409 was observed between FF andNAPRIx “NF while the shortest distance (0.177) was between FF and NAPRIx“NN.Dendogram analysis also shows that the studied chicken populations formed five clusters of genetic dissimilarity. Based on this finding, it can be concluded that the indigenous chicken populations have the ability to resist Newcastle disease and that the Mx gene is involved in that resistance and that the naked neck was more resistant to the disease. It is therefore, recommended that crosses involving the indigenous chicken and other Broiler strains should be carried out with the normal feathered. Further experiments should also be carried out, involving the naked neck and its crosses to determine to what extent the Mx gene is involved.
