Genetic diversity, population structure, and gene flow analysis of lowland bamboo [ Oxytenanthera abyssinica (A. Rich.) Munro] in Ethiopia

Abstract

Bamboo, a member of subfamily Bambusoideae in the grass family (Poaceae), is one of the most important nontimber forest resources and a potential alternative to wood and wood products. Ethiopian lowland bamboo (Oxytenanthera abyssinica) is an economically and ecologically important species which accounts about 85% of total bamboo coverage in the country. This species is experiencing population decline due to a number of anthropogenic factors. As a foundation step, genetic diversity, population structure, and gene flow analysis of various O. abyssinica populations found in Ethiopia are studied using inter-simple sequence repeat markers. One hundred and thirty isolates of bamboo belonging to 13 geographically diverse populations were collected for DNA extraction and analysis. Heterozygosity, level of polymorphism, marker efficiency, Nei's gene diversity (H), and Shannon's information index (I) analysis, analysis of molecular variance (AMOVA), analysis for cluster, principal coordinates (PCoA), and admixture analyses were performed based on the markers banding pattern. The results indicated high genetic variation (84.48%) at species level. The H, I, observed and effective number of alleles at the species level were 0.2702, 0.4061, 1.8448, and 1.4744, respectively, suggesting a relatively high level of genetic diversity. However, genetic differentiation at the population level was relatively low. Using grouped populations, AMOVA revealed that most (61.05%) of the diversity was distributed within the populations with F _ST = 0.38949, F _SC = 0.10486, and F _CT = 0.31797. Cluster analysis grouped the populations into markedly distinct clusters, suggesting confined propagation in distinct geographic regions. STRUCTURE analyses showed K = 2 for all populations and K = 11 excluding Gambella population. Using these markers, we found strong evidence that the genetic diversity of the lowland bamboo is associated with distinct geographic regions and that isolates of Gambella Region, with their unique genetic origin, are quite different from other bamboos found in the country.

Keywords: ISSR primers; Oxytenanthera abyssinica; bamboo; genetic differentiation; population structure.

Figure 1

Maps showing sample collection area: (a) Ethiopia's bamboo cover map in the Finer Resolution Observation and Monitoring‐Global Land Cover (FROM‐GLC) classification scheme with other land cover classes; (b) Map of Ethiopia showing sample collection area; and (c) Clipped map showing sample collection area

Figure 2

A representative of ISSR‐PCR electrophoresis profile of 13 populations of O. abyssinica using (a) UBC‐834, (b) UBC‐845, and (c) UBC‐888

Figure 3

Dendrogram depicting clustering patterns for thirteen (13) populations of O. abyssinica based on Jaccard's similarity coefficient. (a) Dinucleotide also 3′ anchored, (b) Tri‐nucleotide, (c) Tetra‐nucleotide, (d) Penta‐nucleotide, (e) 5′ anchored, (f) 3′ and 5′ anchored and (g) Unanchored ISSR primers

Figure 4

UPGMA‐based dendrogram for thirteen O. abyssinica populations based on Jaccard's similarity coefficient using 19 ISSR primers

Figure 5

NJ analysis of 130 individuals based on Jaccard's similarity coefficient. Samples encircled inside the bigger circles represent a single population and bigger circle represent Zonal samples

Figure 6

Three‐dimensional representation of a principal coordinate analysis of genetic relationships among 130 individuals of 13 populations of O. abyssinica inferred from a similarity matrix using (a) the Jaccard's index at STATISTICA and (b) Pearson PCoA method using XLSTAT