Morphological and microsatellite DNA diversity of Djallonké sheep in Guinea-Bissau

Abstract

Background: The present study aimed at characterizing the Djallonké Sheep (DS), the only local sheep breed raised in Guinea-Bissau. A total of 200 animals were sampled from four regions (Bafatá, Gabú, Oio and Cacheu) and described using 7 visual criteria and 8 measurements. These parameters have been studied by principal components analysis. The genetic diversity and population structure of 92 unrelated animals were studied using 12 microsatellite markers.

Results: The values of quantitative characters in the Bafatá region were significantly higher than those obtained in the other three regions. A phenotypic diversity of the DS population was observed and three genetic types distinguished: animals with "large traits" in the region of Bafatá, animals with "intermediate traits" in the regions of Gabú and Oio and animals with "small traits" in the Cacheu region. The hair coat colors are dominated by the white color, the shape of the facial head profile is mainly convex and the ears "erected horizontally". Most of the morphobiometric characteristics were significantly influenced by the "region" and "sex of animals". The average Polymorphism Information Content (PIC) of 0.65 ± 0.11 supports the use of markers in genetic characterization. Gabú subpopulation had the highest genetic diversity measures (He = 0.716 ± 0.089) while Cacheu DS subpopulation presented the smallest (He = 0.651 ± 0.157). Only Gabú and Bafatá subpopulations presented significant heterozygote deficiency across all loci indicating possible significant inbreeding. Mean values for F_IT, F_ST, F_IS and G_ST statistics across all loci were 0.09, 0.029, 0.063 and 0.043 respectively. The overall genetic differentiation observed between the four DS subpopulations studied was low. Bafatá and Gabú are the most closely related subpopulations (D_S = 0.04, genetic identity = 0.96) while Bafatá and Cacheu were the most genetically distant subpopulations (D_S = 0.14, genetic identity = 0.87). Using Bayesian approach, the number of K groups that best fit the data is detected between 2 and 3, which is consistent with the morphological analysis and the factorial analysis of correspondence.

Conclusions: The molecular results on DS population of Guinea-Bissau confirmed the ones obtained with morphological analysis. The three genetic types observed phenotypically might be due to a combination of the agro-ecological differences and the management of breeding rather than genetic factors.

Keywords: Guinea-Bissau; Microsatellite DNA; Morphological diversity; Population structure; Sheep.

Fig. 1

Principal components analysis to study the population structure

Fig. 2

a Uniform black with tan belly; b Spotted/pied; c Patchy white-black with badger face; d Uniform white (PROGEVAL, 2017)

Fig. 3

Unrooted neighbor-joining tree depicting the relationship of four subpopulations of Djallonké Sheep of Guinea-Bissau using Nei’s (1978) genetic distances

Fig. 4

Factorial correspondence analysis. Yellow: Bafatá; Blue: Cacheu; White: Gabu; Grey: Oio. Axis 1 isolated Gabú – Bafatá and Oio from Cacheu while Axis 2 delimited Oio and Cacheu

Fig. 5

Plots for detecting the number of K groups that best fit the data (Assumption: No Admixture Model and Independent Alleles frequencies)

Fig. 6

Population structure assessed by Structure software. Each individual is represented by a vertical bar, often partitioned into colored segments with the length of each segment representing the proportion of the individual’s genome from K = 2 to 3 ancestral populations (Animals for which more than 2 loci were not amplified were removed from this analysis)